Fjd
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On 4/7/2016 at 7:09 PM, Zim. said:On 4/7/2016 at 6:05 PM, wdecho said:
From the master,
"What this country needs is a good 5 watt amplifier" (Paul Klipsch).
Since the beginning of amplification single ended triodes have been acclaimed as the ultimate in sound reproduction. If the low 5 or 6 watt SET's are not good enough for our 100db speakers exactly what kind of speaker are they good for. The highly acclaimed SS designer Nelson Pass has devoted a considerable amount of his time trying to duplicate the single ended triode tube sound with SS devices. Audiophile reviewers worldwide still acclaim SET as the ultimate in sound reproduction and all other forms of amplification is judge on how it compares to the SET.
There are still people that believe OJ did not do it or the world is not round. It does no good to argue with them.
You have to be the judge of what sounds good to you and buy what you think is best. What I have just said is just cold hard facts. What anyone hears is not reality but our own interpretation of it. When someone works hard for their money they should be able to spend it as they choose to not by what anyone else says.
Since you bring up PWK, could you tell me some of the SET amps he used? Or for that matter any tube amps that he used later in his life when SS became a viable option to the tubes? Forgive my ignorance but I am only aware of his early favorite (modded Brooks 12A 2A3 PP of 10W. or so), and latter the various pro SS amps from Crown, BGW, etc.
On 4/7/2016 at 7:23 PM, Zim. said:I'm sure he certainly had excess to any amp. at his disposal, yet when SET amps galore were so easily available he still made the call "What this country needs is a good 5 watt amplifier". Why would he say such a thing if the SET was the ultimate circuit and at the same time so attainable? Why would he only endorse the modded Brooks and not a SET?
I think we have somehow created our own “red herrings” that we are now chasing upstream. In many of the articles where we have jumped to conclusions that Paul was promoting one type of amplifier topology over another, our conclusions appear to be incorrect and he is really expounding upon how well-engineered his Klipshorn speakers are. When it comes to amplifiers, I believe that PWK was primarily pointing out a simple mathematical relationship and facing an economic reality of the times he lived.
After reviewing a multitude of evidence for which I have outlined a few key points in more detail below, I tend to hold the view that I don't think PWK can be used as an advocate of low powered SET amplifiers any more than he can be used as an advocate for mid-power solid state amplifiers. Although, in one of the “Dope From Hope articles” he does state that “In a typical living room or small theater, our present all-horn systems offer concert-hall levels with a mere 10 watts peak input.” There again, PWK specifically stated 10 watts, not 5 watts, and I believe his statement was a tribute to the engineering of the loudspeaker in that it could reproduce concert-level SPL with fairly low power (e.g., doing the math), not an endorsement of any specific amplifiers or amplifier topologies.
The simple fact of the matter was, is, and always will be, the Klipschorn speaker efficiency allows a person to use very low-powered amplifiers if that type of amplifier meets that person’s listening requirements, regardless of whether that choice is SET, SEP, Push-Pull, solid state, or otherwise; and as I have noted in other posts, the Klipschhorn will reveal very quickly if the amplifier sucks or the source sucks or both suck.
After spending a very substantial amount of time revisiting the “Dope From Hope” articles and various other documentation (including the pages of “Klipschisms, quotes and anecdotes" attributed to PWK on the main website), I also could not substantiate that PWK explicitly voiced, or had written the quote often attributed to him that "What this country needs is a good 5 watt amplifier." Without specific credible evidence, especially given that PWK was looking for concert-level reproduction of 115dB SPL at the listening position, I'm now wondering if the quote is a type of urban legend that has proliferated over the internet, similar to the Robert Hartley situation I describe below (e.g., in PWKs situation outlined below, 5 acoustic watts = 20 amplifier watts, not 5 amplifier watts).
Jim Hunter, just where are you when we need you?
Since the written records appear to clearly show that PWK loved his push-pull 10 watt per channel Brook 12A amplifier, he may have actually been complaining that amplifiers of his time were not powerful enough, in addition to not being good enough.
The written information appears to show that, in addition to PWK liking the Brook 12A amplifier at first, he then moved to a variety of mostly solid state amplifiers in the range of approximately 60 watts per channel. I have also found references where he used a lot of different brands including Crown (D60) and BGW (model 100).
An interesting side note with the Klipschorn history in relation to the Brook amplifier is that Paul (and Brook) collaborated to squeeze more [power] from the 12A amplifier (a 2A3 push pull design) and developed modifications to address some bass deficiencies that were revealed by the Klipschorn speakers. The modification subsequently became a factory mod available to optimize the amplifier to the Klipshorn and was given the catalogue number of “12A3-KI.”
I have also found that there are many other references in his literature where he recommended 20 watts per channel amplifiers as a minimum for Klipschorns. Keeping in mind that one goal that PWK had often articulated in both verbal and written form, was that his loudspeakers were capable of reproducing concert-level sound of about 115dB at the listener's position, and here is one such reference from the "Dope From Hope" Vol. 14, No. 2 May 1974 titled "Power Ratings."
"[''What size amplifier shall I buy?" This is really the first of two questions. The answer, applied to KLIPSCH speakers, would be a maximum of 100 watts (sine wave rating) per side. If a higher power is used, precautions may be needed to prevent speaker damage. Crown suggests a one ampere fuse for each channel.
The second question, I think we can assume, is fishing for a realistic relation between sound pressure level and amplifier power. Accept the figure that 115 dB peak sound level pressure at the listener's ear will be as loud as what you would hear at a live concert. (A sound level meter would read 103 dB at "maximum" swings, because a V.U. meter has a "delay" or "lag", and instantaneous peaks are about 13 dB higher than the meter reading peaks).
In a typical 4000 cubic foot listening room, this requires 40 peak amplifier watts to feed a group of high efficiency loudspeakers: assuming this to be 2-channel stereo, 20 peak watts per channel or 10 watts average sine wave power rating per side is required. For a low efficiency speaker (of the typical so-called air suspension type) over 100 times as much amplifier power would be necessary: that makes over one kilowatt of sine-wave rated power for each channel.]"
In the "Dope From Hope" (Vol. 8, No. 1 July 11, 1967) article titled "Guarantee Void" PWK stated that, "[back in the good old days of 10 and 20 watt amplifiers it was uncommon to experience loudspeaker failures. When 75 watts became common, occasional tweeter failures began to occur. Then with the advent of large solid-state amplifiers with their 240 instantaneous power peaks, tweeter failures became epidemic and woofers began to come apart at the compliance rings and voice coils began to tear loose from cones.]"
Another misnomer that I found was that PWK often referred to “acoustic watts” and invariably magazine writers (e.g., Robert Hartley), among others would drop the “acoustic” and just state watts, which was misleading and only perpetuated inaccuracies.
The following are PWK definitions published in the "Dope From Hope" (Vo. 9, No. 2 June 1973) article titled "Definitions."
WATT
First of all a watt is a unit of power or rate of doing work, whether electrical, mechanical, thermal or acoustic. Equivalents are 0.738 foot pounds per second, 0.238 calories per second, or
w = e^2/z
Where w is watt, e^2 is electrical pressure or electromotive force in volts and z is electrical impedance in ohms.
The acoustic watt may be similarly expressed in terms of acoustic sound pressure p in dynes per square centimeter and the acoustic impedance of air which has been derived as the product of the air density times the velocity of sound p thus w = p^2/z.
When the sound pressure level is 100 dB, the sound power transmitted is 10^6 watt per square centimeter. (The 100 dB level is referred to zero dB = 0.000204 dynes per square centimeter: thus 100 dB = 20.4 dynes per square centimeter).
ACOUSTIC WATT
Translating the above numbers into something quickly useful, it turns out that a sound source radiating from a trihedral corner with a uniform polar pattern will be radiating one watt of power when the sound pressure measured at 4 feet is 118 decibels.
Essentially, it came down to PWK’s literature recommending 20 watt amplifiers as the minimum for Klipschorn loudspeakers to meet his Klipschorn design goal of producing concert-level sound of 115dB SPL at the listener position.
In my reference to Robert Hartley, I’m referring to excerpts from his book titled, "the Complete Guide to High-End Audio" where the excerpt can also be found in the article "How Much Amplifier Power Do You Need" where he writes that “loudspeaker pioneer Paul Klipsch conducted a demonstration of live vs. reproduced sound with a symphony orchestra and his Klipschorn loudspeakers. His amplifier power: 5W. The Klipschorns are so sensitive (an astounding 105dB SPL, 1W/1m) that they will produce very high volumes with very little amplifier power. Klipsch was attempting to show that his loudspeakers could closely mimic the tonal quality and loudness of a full symphony orchestra.”
If anyone has been following the various posts in the “high power amplifier” thread, I would have a hard time believing that someone could still conclude that a 5 watt amplifier would attain that type of concert level SPL in a theater where a symphony orchestra was playing.
The reference indicates that PWK talks about a symphony orchestra and 5 watts; however, he is not talking about a nominal 5 watts. I believe that PWK is actually talking about 5 "acoustic watts" as he has defined an acoustic watt in the Dope From Hope that I have excerpted above. Note that PWK has also put into print, including references in the Dope From Hope, a 20 watt per channel amplifier is suggested for full live symphonic dynamics (e.g., 115 dB at the listening position).
To achieve the 5 acoustic watts in the room that PWK is talking about, he had two Klipschorns and a Belle with each channel connected to 20 watt amplifiers. Once I crunched the math considering the definitions in the "Dope From Hope" (Vo. 9, No. 2 June 1973) for an acoustic watt, it became pretty obvious what happened in that I suspect that Hartley may not have understood the concept of an acoustic watt or just dropped the word "acoustic" in his text.
Essentially, there you have it in that it seems that PWK has outlined various situations that appear to indicate that for 2-channel stereo, 20 peak watts per channel or 10 watts average sine wave power would cover the concert level SPL THAT he had personally strived to achieve.
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Nice post, Craig, lot to agree with there. I would say that if the goal is to use your tube amp as some sort of ear-friendly compressor, then the little single ended jobs' monotonic distortion pattern beats the odd predominant pattern of pp amps. It seems to me that 2Bmusic wants more tube coloration, as opposed to your "bigger window" approach that yields less tube coloration, which seems to reflect his tube dabbling thus far.
In full disclosure I am looking for the best sound possible. The means to get there is unknown to me at this time. Maybe I have arrived. AS you know I had a P/P 25 watt EL84 mono block set up. It sound a smidgen better than the yammy 1030... but only on a very few songs. 3 days and 3 sets of ears could not tell one from the other.
1. I have no idea who else sells tubes or SS that I could try other than the Pass30.8. Six moons review of that amp simply said ( in my words here) the 30.8 is over the top good. And that was against mega buck tube and SS Power AMPS.
Like the review I linked to above, and my electronics background, prove that listening at 1 watt you need at least 20 more to pull from during dynamic passes.
I am not up to building anything. Mike Sanders of QS fame and Nelson Pass are far more accomplished than I in that realm.
There is nothing wrong with having a 30 watt SS amp playing at one 1 watt. With out question some music will dig into the 25 watt mark. That is the reason for that pass 30.8
At Best buy they have $50,000 worth of Mac amp preamp etc playing into $15,000 martin logans. Horrible compared to my khorns.
When my K horns were puiing 1 watt the ML's were pulling 75. Point is the 30.8 power wise is certainly not to much power. If I never use the last 5 or so watts, all the better. The more power you pull from any amp, the more distortion it makes. I love my horns because they address the issue of efficiency. The Folded Bass is a wonder of the universe. ( there may be others, but they will cost way WAY more than what I paid for these 20+ yr old Khorns.
I do not want or need to spend ~4 Large on a used 30.8. But if the sound is way better, then that is good. Same thing goes for tubes. I would try A&S casablancas but once you buy they are yours. NOT going to happen for me.
I would posit to say, your definition of the sound you are looking for is not specific enough. "I am looking for the best sound possible” is a purely subjective call and if you interview 15 people and ask them to specifically describe “best sound” and what it means to them, you will probably get 15 very different answers.
For example, some people look specifically to measurements as an “objective” tool to help them determine “accuracy,” which may be an important aspect of their “best sound.” However, “accurate” to what benchmark? Are we looking for accuracy when compared to the original studio session, accuracy in relation to the engineer’s mix, accuracy in reproducing “compression,” accurate in reproducing the tone or timbre of certain instruments, or accurate in that a Fender Stratocaster doesn’t sound like a poorly tuned banjo, or something else?
Also, if audio gear is “too accurate” it will reveal every flaw in the recording itself and every flaw in the audio gear chain. Given “human nature” being what it is, people then tend to jump to unfounded conclusions that it must be the “amplifier” or the “speaker” (in general, people have been notorious for blaming the Klipsch speaker for poor recordings and poor choices in audio gear), which in turn, tends to impact the sales levels of the item.
Others would claim that more bass, more punch, and more excitement from playing music is the “best sound.” Given the state of over-compression in music, the most accurate gear is not necessarily the best in playing heavily processed rock music and expecting more bass and more punch. Think of it this way, sometimes, a person just can’t make a cartoon look real by using a high resolution television.
Some claim that a nice crisp high frequency is what they look for as being instrumental in the best sound, while others believe that the crisp high frequency makes for an etched and mechanical listening experience.
In general, I believe that most manufacturers (especially those making mass-produced products) will go to extraordinary lengths to “claim” accuracy, to give consumers some level of “assurance” they are buying products that are accurate since the general consumer wouldn’t want their friends questioning them on why they bought an “inaccurate” stereo system (whatever that actually means).
Personally, I’ve put together various systems to meet different listening objectives. For example, I’ve tailored a system for the bedroom that will create a surreal, lush and romantic tonal experience for my girlfriend rather than have an “accurate” system playing poor recordings, piercing her ear drums to the point where she has a headache and killing the mood.
Another system involves my Klipschorns and is designed around a very detailed and highly resolving system of very minor details that are captured in good recordings where the criteria of very low noise and very low distortion levels using equipment with very linear circuits that need either none, or very little negative feedback. This system is my "evolution" system for experimentation where I swap various tube and solid state based components in an out of this system. My Jubilees are in another fairly resolving system that will probably also end up doing home theater duties, in addition to the two channel listening when I move to a bigger space.
These are extremes on the continuum for me, but I have also put together other more general systems that fall somewhere in the middle of my continuum for general listening, general entertaining and occasional parties.
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I have been reading everything I can find on Valve and xistor amps. These articles gives one to think tubes really really are not as good as transistors for the many reasons he says. I do not know. What do you folks think? I am not looking for feelings, more on a fact finding mission. Personally I lean strongly to tubes. When I graduated from electronics school transistors were just in their infancy. ( a hint of my youth or lack there-of)
http://sound.westhost.com/valves/valve-trans.html part 1
http://sound.westhost.com/valves/valve-trans2.html part 2
please give thoughtful answers. I need an amp for my khorns. I had an F6. It was ok, a little better than my yamaha 1030 HT amp. But not thousands better. The next step/ choice would be the Pass xa30.8 I just hate to spend that much money. At least if I get the 30.8, I can rest assured that it does not get much better.
What makes this so difficult is so many say, "this amp or that sounds just like valve amp". Heck just buy a valve amp and be done with it!
MY BIGGEST CONCERN IS that when it comes to tubes these days, good ones will be hard to come by. And the thought of having to replace every 1 to 4,000 ( one to three years) hours is damn scary!
I was thinking about trying the Quicksilver Audio Horn Mono's. They seem custom made for KHorns!
Maynard,
I much MUCH prefer the Khorns over the LaScala's. My Khorns have the back enclosed so I have more options for placement. The Big Ben sounded great on the LS. It really did.... HOWEVER, Base was completely absent when compared to the MIGHTY Khorns! I have found that the khorns really come alive with more than 4 watts. The Quicksilver Audio Horn Mono's are designed by an Electrical Engineer ( Mike) for our horn speakers. 25 watts each should do great. Since they are push-pull AB, the bass will be tight as well.
Mike also explained in technical terms how with transistors vs tubes.... that valves really are the best way to amplify audio.
Thanks to all who have contributed. I am ordering the Horn Mono-blocks today from Quicksilver audio.
HOWEVER, Base was completely absent when compared to the MIGHTY Khorns!You attributed lack of bass to the difference in speakers not the difference in amps correct? I have a Stereo 15 amp from Justin on a pair of Cornscallas and there is absolutely no lack of bass there.
lack of bass ( base) ( bass looks funny... like the bass fish...) is because LaScalas low freq cut off is around ~ 40 hz and starts at~ 50. This is because they were purposed for loudspeakers more than to be used as a means to play High Fidelity music. They sound good, don't misunderstand. BUT... When compared to Khorns.... well they don't compare in the realm of HiFi music reproduction.
Your Cornscallas will certainly have better base than LaScalas. The folded horn of the Khorn takes BASS to the next level.
Have you listened to Khorns set up with good equipment ? When I did, I could not believe my ears. Far better than the Snells of old. SNELLS were reference quality used to determine if this violin or that piano was up to speed. They were used for chamber music reproduction. That is not easy to do.
Well 2 hours later and Viola! Cold soldered joint on bias resistor to one of the EL p/p tubes.
Sounds very good. Better than my Advantage 1030.... not sure. Playing Bella Flecks Cosmic hippo, the base is so strong that I had to turn it down with equalizer on the iTunes control panel!
Yes, I like it!
I guess I do not deserve to be in your company. Why? Well, because the verdict is in. LONG LONG story short... After A/B the QS horn monos and my Aventage 1030 for 3 days about 3 to 5 hrs per day.... swapped speakers from one amp to the other...my self, my wife and another person could not tell much of a difference. They both sounded very good. Can the system ( khorns) sound better? HECK FIRE i have no idea. I have bought and returned a Emotiva XPA2, First Watt F6, and the Horn Monos. The Yammy is just that good. I hate to say it. I am very disappointed. Either my ears are worthless or the difference is not worth mentioning. I Also tried $580. interconnect cables. Maybe my Stealth DC-1 is the bottle neck. I do not know. BUT.... I do know this. The 1030 is plenty good enough. And the fact that I only paid $500 for it is even better. I would still like to try the Pass 30.8. But for that much money, it would have to be spectacularly better. I do not think it will be.
FYI... the signal path is mac book pro 2015 to Stealth DC-1 via a 12 foot $5.00 USB cable to the HT Yamaha 1030 to the Khorns via "monoprice' 16 gauge speaker cable.
I think to bring it to life ( more than what it is) I need to spin vinyl. ANY ONE HAVE Suggestions for a turn table? Can I get by with out spending the $2,100 for a VPI Scout. In other words am I throwing money away on a $600 Pro-jec type?
SIGNED....
FLUMUXED !
Nice post, Craig, lot to agree with there. I would say that if the goal is to use your tube amp as some sort of ear-friendly compressor, then the little single ended jobs' monotonic distortion pattern beats the odd predominant pattern of pp amps. It seems to me that 2Bmusic wants more tube coloration, as opposed to your "bigger window" approach that yields less tube coloration, which seems to reflect his tube dabbling thus far.
Actually, the OP has already had a single-ended amplifier (the Big Ben is based off the Shannon Parks Clementine single-ended circuit and modified for the 6L6 or KT88 series of tubes) in his system; however, from the posts above, it seems to have some trouble driving the bass below the horn cut-off on the La Scala, which I would expect once transitioning to the frequency range below the horn cut-off, but appears to be fine in the Klipschorns.
Part of what I see as problematic (and potentially leading to what appears to be frustration for the OP and others posting) with this thread is that the thread started out as a type of general critique of Rod Elliott's white papers on tubes and solid state then evolved into a tube amplifier hunt with no specific criteria or objective in mind.
For example, what makes this a very difficult situation is that I cannot find where there has been any identification of the specific negative characters of sound that the OP doesn't like with the Yamaha 1030. In many respects this is like going to the doctor and just stating "Doc, I don't feel well today, treat me." Without a specific understanding of what is currently viewed as wrong (or lacking or could be improved upon) with the sound with the Yamaha 1030, it is impossible to diagnose and make any type of recommendation that would even be remotely useful.
The aspect of having no specific goal is why I haven't directly responded to anything and only provided a few posts on various types of amplifiers and topologies where I had some direct experience. It seems that every time the kids come to me for advice, I end up asking them, "what are you trying to specifically accomplish and how do you believe these steps will be important in getting you there"?
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My wife & I when we first met.
Nice. As you approach the golden years, it may turn into this.
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I'm no expert, but here's what I have heard:
I have read that whether an amplifier will "pass" a peak without clipping depends on the duration of the peak. Briefer peaks will pass easier. I have read that the peaks being considered when writing amplifier specifications are 200 milliseconds to 2 milliseconds in duration.
I don't think "peaks" in a steady tone (the top of a sine wave) are like peaks in music. I think that RMS is 0.707 times the height of the sine wave of the steady tone. The leading edge of a musical peak can be much more powerful. Someone posted here (maybe 7 or 8 years ago?) that the intensity of a rim shot close up would beyond the capacity of any amp/speaker combination, if it were not for the brevity of the leading edge of the peak.
I would think that separate amps would have beefier power supply sections, and should be able to produce more instantaneous power above their rated power than would receivers.
My dealer measured one of my power amps at 171 watts per channel at the point where the top of the sine wave would just begin to flatten. The manufacturer (NAD) rated them at 150 w.p.c.. If the 0.707 thing is correct, they would be (0.707x171) about 120 wts RMS.
I think that doubling the distance in an anechoic environment, or outside at the top of a flagpole, causes a 6 dB loss, BUT doubling the distance in a room causes only about a 3 dB loss. In music, for just an instant, I can get 110 dB through 1 Khorn quite easily in my 4,000+ cu.ft. room @ 16 feet (no, I don't subject my ears to that for more than and instant ... the loud passages in the orchestral music I play average about 90 dB). My room is 1/3 larger than the one PWK was using for the chart. The 110 dB figure is right at the top of the needle swing ("C," "Fast"). Since this is a needle meter, the true, instantaneous peaks may be 13 dB higher than the meter reads, at more like 123 dB (according to PWK in another paper). According to the Klipsch chart, 123 dB (120 dB +3 dB, doubling the power needed) may take about 400 watts (or more, because my room is bigger), just for a split second, but I only have 171watts to "spend." I am familiar with what clipping sounds like, and I hear no clipping. But then I have a separate amp with a good sized power supply.
The .707 RMS is factored in before arriving at the max power of an amplifier (at least it should be). So if they measured 171 watts then that is what your amplifier made. Many manufacturers under rated the max power of amplifiers so they can boast better distortion numbers at full rated power.
I've read that Nakamichi PA-7 amplifiers that are rated at 200 watt RMS actually can put out 370 watts per channel, but have never measured them.
Roger
For how long? I would think a 50 millisecond peak might be possible at an even higher power out, whereas the un-flattened top of a steady tone sine wave power for 200 RMS would be about 283 watts (283 x .707 = 200 watts). In the oldest catalogs I've seen, a tube amp "peak power" is typically 2x (3 dB) the RMS power. Some modern "dynamic power" ratings are about 3 dB higher than RMS, but I've never seen the duration specified.
The other question re: RMS is, "at what frequency?" Is it at 1KHz? Or 30 Hz (PWK's suggestion)? Or with band limited pink noise, 500Hz to 2KHz? Over the desired bandwidth (e.g. 20 Hz to 20K hz)?
Someone a few years ago posted here that it is an error to talk about RMS power at all.
I was actually looking into trying to find more detailed information regarding peaks and better substantiate an average time of a peak or even a range; however, I realized that it seems mostly impossible to get enough information to remotely establish any comparability or reliability in any of the published numbers.
Here one "standard" definition of a "dynamic headroom" test that I considered in some of my responses in this thread along with gathering a few more insights into transformer and capacitor ratings used in power supplies, in addition to power calculations. I found the Myers Sound paper below meaningful.
"The EIA RS-490 (former IHF A-202) amplifier test standard includes a "dynamic headroom" test employing a 20-mS tone-burst. In an informal survey of musical recordings, power bursts were found with durations from a few milliseconds up to several hundred milliseconds, with an apparent clustering in the 80-200-mS range. Since the practical value of an amplifier depends on its ability to reproduce musical dynamics, a more useful power rating would be obtained by amending the dynamic headroom test to employ a 200-millisecond (or similar) tone-burst."
http://www.aes.org/e-lib/browse.cfm?elib=4898
Excerpt from Myers Sound.
[in the engineering community, the accepted method of generating a rating of the audio power produced by an amplifier is to connect it to a known load, apply a continuous sine wave signal to its inputs, and monitor its output behavior into the load. This is important to keep in mind as we examine the definition and measurement of “power.”
The definition of instantaneous electrical power is quite simple: P = EI, where P = instantaneous power in watts, E = potential difference in volts, and I = current in amperes. However, this definition is minimally useful to us in an audio application because audio sources are not instantaneous pulses, nor are audio loads purely resistive.
A sine wave is the building block from which real-world audio signals are built, making it a more appropriate source signal for measurement of an audio system. For a sinusoidal voltage source, power, while still measured in watts, is defined as“average power.” RMS (root mean square) is a method of calculating the voltage and current to obtain the average power.
For example, if we look at the sine wave voltage at the output terminals of a power amplifier, we will find the RMS voltage to be the peak voltage (Epeak) divided by the square root of 2. If we measure the RMS sine wave current from the amplifier, we will see that, similarly, it is the peak current (Ipeak) divided by the square root of 2.
Multiplying the two, we get:
(Epeak/(sq root 2)) * (Ipeak/(sq root 2)) = (Epeak* Ipeak)/2which is the average power for a sine wave.
When an amplifier is rated in RMS watts, this is a shorthand way of saying “average watts obtained by the RMS method.” If you use a signal other than a sine wave, you must use a meter reading ‘true’ RMS voltage to obtain the correct average power.
So what about peak power? Peak power is a special case where Ppeak = Epeak * I peak. For a sine wave, this is always twice the average power. A major problem with using this rating, however, is that many power amplifiers cannot maintain peak power for more than a few milliseconds.
The standard method of testing a power amplifier to see if the power supply can maintain continuous peak power is to connect all channels of the amplifier into load resistors, drive the amplifier’s input with a square wave and monitor the peak voltage at the outputs. Almost all power amplifiers will ‘sag’ in output power under this drive condition.
Now, having a power amplifier produce twice the continuous sine wave power is hardly necessary for music reproduction, but sometimes music signals produce short-term square wave or large sine wave-like waveforms. So how long should a power amplifier be able to maintain reproduction of a square wave or sine wave at full amplitude?]
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Here is one of somebody behind the times.
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We may be waiting for a while for a review and I'm thinking that I'll just add this one to my list of items that I'm still waiting for the AU1C review to be posted, along with the review of the VRD upgrade (wondering if he got the MagneQuest transformer upgrade). Without the reviews, it has been getting much more difficult to live vicariously through AU1C's purchases these days.
Okay its not as good as the VRD but its still is a nice integrated
I have been listening to it everyday for close to a month and have nothing negative to say about it .
I bought this new about a month ago this to use while my NBS / VRDS where getting upgraded .
Looks like they will be back next week .This is a really great sounding integrated
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Given the above, for 1W per channel for the stereo set-up, the "effective" SPL will be about 107dB SPL for the stereo application, so to get the extra 3dB for our 10dB swing from the 100dB SPL, the power would be doubled under the logarithmic formula to 2W per channel. Can the low watt SET owners now breath a sign of relief or does the analysis contain flaws?
The following assumes your 2 watt amplifier has a maximum RMS output (unclipped, undistorted) of 2 watts. It also recognizes that with KHorns at 1 watt it is already LOUD:
You are listening to a 2 watt amplifier at 1 watt average....then a 3 db peak comes along and your amplifier puts out 2 watts for the duration of the peak. And a 3 db increase of sound intensity has you say
( subjectively) 'Oh it got a little louder there for a second'.
Now you are listening to a 2 watt amplifier at 1 watt average....then a 10 dB peak comes along and your amplifier attempts to put out 10 watts and clips the waveform. Your amplifier ran out of gas. You say something like 'well that sounded a little rough perhaps I better turn it down a bit'.
To have 10 db of headroom above 1 watt you need a 10 watt amplifier.
I do not understand where you get "so to get the extra 3 db for our 10 db swing", to get a 10 dB swing you need 10 dB.
Please read post https://community.klipsch.com/index.php?/topic/163148-high-power-amplifiers-for-heritage-speakers/?p=2004025.
When I first read the Dope/Hope article, I had to pause and ask myself "why a typical 3,000 cu ft listening room?" Then it came to me. Back when PWK was designing the khorn, the ceilings were much higher than today. Furthermore, a well respected peer, RH Bolt, came up with what could be considered the best listening room layout calculations in 1946. I believe the chart is talking about 2 speakers in mono. I believe that if you measured from the critical distance of 2.23' in a 20'x15'x10' room, that 1 watts into a pair of (.5 watts each) LaScalas would result in substantially higher than 104 db. Moving the mic further would reduce the measured db by inverse sq law based on the critical position measurement. I cited an audio blogger claiming 20db or higher gains from the CLP, but I don't know the calculations and other caveats for instance frequencies.
What I think is that in order to see what PWK is talking about, we have to consider a 20x15x10 room. We have to calculate how .2 watts shared into a pair of 104db efficient speakers can yield 100db.
I hope someone will dust off their slide rule and give that a go.
I'm finding that there is a rational basis for most everything that PWK has written, but it seems to take a lot of searching and background reading to discern exactly what he was looking at. Although, I just happen to know where we can find a slide rule.
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All this technical talk is good for those that like to read these things all I truly know is that the "Little Sweetie" of Maynard's with it's 1.3 watts of SET power sounds plenty loud enough with my LaScala's. Much like when I asked an employee of mine years ago the difference of being drunk and high. His answer was "when you're drunk you're drunk and when you're high you're high. More educated responses would be many more words on the subject.
It has been a good mental exercise and now I think I finally did a better job of outlining the math in the post below as to why the low power SET amplifiers can drive Klipschorn, La Scala and Belle speakers to reference-type levels simulating the live event for certain types of music without clipping the amplifier. All I can say is, "Klipsch Heritage – so much more than the sum of the parts."
Given the above, for 1W per channel for the stereo set-up, the "effective" SPL will be about 107dB SPL for the stereo application, so to get the extra 3dB for our 10dB swing from the 100dB SPL, the power would be doubled under the logarithmic formula to 2W per channel. Can the low watt SET owners now breath a sign of relief or does the analysis contain flaws?The following assumes your 2 watt amplifier has a maximum RMS output (unclipped, undistorted) of 2 watts. It also recognizes that with KHorns at 1 watt it is already LOUD:
You are listening to a 2 watt amplifier at 1 watt average....then a 3 db peak comes along and your amplifier puts out 2 watts for the duration of the peak. And a 3 db increase of sound intensity has you say
( subjectively) 'Oh it got a little louder there for a second'.
Now you are listening to a 2 watt amplifier at 1 watt average....then a 10 dB peak comes along and your amplifier attempts to put out 10 watts and clips the waveform. Your amplifier ran out of gas. You say something like 'well that sounded a little rough perhaps I better turn it down a bit'.
To have 10 db of headroom above 1 watt you need a 10 watt amplifier.
I do not understand where you get "so to get the extra 3 db for our 10 db swing", to get a 10 dB swing you need 10 dB.
It's basically a trick question as I’m probably mixing terminology on you somewhat and looking more at the “dynamic range” of a piece of music (e.g., difference between the softest passage and the loudest) in the context of a type of “peak to average capability” of the “in room” amplifier and loudspeaker combination thinking about acoustic SPL output that can be measured with a simple Radio Shack SPL meter rather than something like an amplifier test of “dynamic headroom” regarding how many watts were generated or needed before clipping to cover a 10dB peak over RMS power output using an 80-200 millisecond (or similar) tone-burst.
For example, while it may be slightly unrealistic, I’m assuming that the 104dB sensitivity of the Klipschorn before any room gain and one watt of amplifier power will give me 104dB of sound electrically; however, I will probably have 3dB of room gain for SPL output that I “hear” from placing the loudspeaker in a room where the corners, walls, ceiling, and floor of a room all reinforce the loudspeaker’s output.
There would be an additional 3dB output that I “hear” that is due to having two Klipschorn loudspeakers in the room rather than one loudspeaker and I was careful to keep considering the odd aspect of “loudness” in relation to “decibels” where one loudspeaker is producing a level of 104dB SPL at one watt of power, adding a second loudspeaker playing at the same level using one watt of power only increases the overall “loudness” by 3dB SPL (e.g., loudness does not double with two loudspeakers). Essentially, the two Klipschorn loudspeakers in stereo produce a “loudness” level of 107dB SPL in the room with each being driven by one watt amplifiers. Of course, I realize that I have technically doubled my power from one watt by now using a total of two watts for the two loudspeakers combined.
Now rather than a 10dB tone-burst, I want to produce a “realistic” peak sound level for some type of music that I’m familiar with. For example, let’s say that I’m picking from a solo grand piano playing crescendos that can reach peak levels of 109dB SPL, I believe that a full orchestra in a concert hall measures peak levels of about 106dB SPL, and a rock group may have peak levels around 120dB SPL.
Of course, I fully realize that my Klipschorn loudspeakers with a 2 watt per channel stereo amplifier, even factoring in the “room gain” doesn’t stand a snowball’s chance on a hot day in San Antonio of surviving realistic peaks of a rock concert and that is why I have other amplifiers. However, it seems that I should be fine with the 106 dB peaks in relation to a full orchestra in a concert hall electrically and acoustically; and maybe I can experience the feeling of 109dB peak level of the grand piano crescendo with my Klipschorn loudspeakers and 2 watt per channel SET amplifier.
I fully realize that my 2 watt per channel amplifier will only electrically drive the Klipschorn loudspeakers to 107dB (104dB plus 3dB for doubling the power from one watt per channel to two watts per channel) and most likely any attempt above the 107dB will result in clipping assuming that my amplifier does not have any “head room” of power to handle a very short 20 or 30 millisecond burst of 2dB in excess of the rated power; however, that 107dB should still give me the “perceived” loudness of the 109dB I wanted to experience in the room given the aspects of room gain that I have outlined above.
Circuit Overview
The PA-7 delivers 200 watts per channel, uses no overall negative feedback (a Pass trademark), and boasts the Stasis section, which consists of a low-power voltage amplifier coupled to the current mirror bootstrap output stage to do all the heavy lifting required for high-power output.
Back in 1989, when Stereo Review featured the PA-7, writer Julian Hirsch measured the PA-7’s output at 253 watts into an 8-ohm load, 400 watts into a 4-ohm load, and 650 watts into two ohms. A quick look under the hood reveals why. A large 700 VA toroidal transformer and a bank of power supply capacitors totaling 132,000 µf proves the PA-7 means business. Such a setup made the PA-7 a perfect choice for demanding loudspeakers and, like the Threshold Stasis amplifiers, it ended up in many systems based around electrostatic speakers or Magnepans.
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Nelson Pass at his best.
Nelson Pass sure has developed a nice legacy of amplifiers over the years and it doesn't matter whether we are talking about flea-watt power or gigantic brute force power, he certainly has done it all. One of my early experiences was with using his white paper from 1981 for the mosfet modification to the old Harman Kardon Citation 12 amplifier and I was hooked. I liked it so much that I also have a second mosfet modified Citation 12 that now has a complete restoration internally and cosmetically. In addition, it sure seems like the Sony VFET part 2 project is coming close to fruition.
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I'm no expert, but here's what I have heard:
I have read that whether an amplifier will "pass" a peak without clipping depends on the duration of the peak. Briefer peaks will pass easier. I have read that the peaks being considered when writing amplifier specifications are 200 milliseconds to 2 milliseconds in duration.
I don't think "peaks" in a steady tone (the top of a sine wave) are like peaks in music. I think that RMS is 0.707 times the height of the sine wave of the steady tone. The leading edge of a musical peak can be much more powerful. Someone posted here (maybe 7 or 8 years ago?) that the intensity of a rim shot close up would beyond the capacity of any amp/speaker combination, if it were not for the brevity of the leading edge of the peak.
I would think that separate amps would have beefier power supply sections, and should be able to produce more instantaneous power above their rated power than would receivers.
My dealer measured one of my power amps at 171 watts per channel at the point where the top of the sine wave would just begin to flatten. The manufacturer (NAD) rated them at 150 w.p.c.. If the 0.707 thing is correct, they would be (0.707x171) about 120 wts RMS.
I think that doubling the distance in an anechoic environment, or outside at the top of a flagpole, causes a 6 dB loss, BUT doubling the distance in a room causes only about a 3 dB loss. In music, for just an instant, I can get 110 dB through 1 Khorn quite easily in my 4,000+ cu.ft. room @ 16 feet (no, I don't subject my ears to that for more than and instant ... the loud passages in the orchestral music I play average about 90 dB). My room is 1/3 larger than the one PWK was using for the chart. The 110 dB figure is right at the top of the needle swing ("C," "Fast"). Since this is a needle meter, the true, instantaneous peaks may be 13 dB higher than the meter reads, at more like 123 dB (according to PWK in another paper). According to the Klipsch chart, 123 dB (120 dB +3 dB, doubling the power needed) may take about 400 watts (or more, because my room is bigger), just for a split second, but I only have 171watts to "spend." I am familiar with what clipping sounds like, and I hear no clipping. But then I have a separate amp with a good sized power supply.
The .707 RMS is factored in before arriving at the max power of an amplifier (at least it should be). So if they measured 171 watts then that is what your amplifier made. Many manufacturers under rated the max power of amplifiers so they can boast better distortion numbers at full rated power.
I've read that Nakamichi PA-7 amplifiers that are rated at 200 watt RMS actually can put out 370 watts per channel, but have never measured them.
Roger
The Nakamichi sure has turned into one of the classics that seems to have no problems with a 2 ohm load. The following is from Tone Audio Publications.
Circuit Overview
The PA-7 delivers 200 watts per channel, uses no overall negative feedback (a Pass trademark), and boasts the Stasis section, which consists of a low-power voltage amplifier coupled to the current mirror bootstrap output stage to do all the heavy lifting required for high-power output.
Back in 1989, when Stereo Review featured the PA-7, writer Julian Hirsch measured the PA-7’s output at 253 watts into an 8-ohm load, 400 watts into a 4-ohm load, and 650 watts into two ohms. A quick look under the hood reveals why. A large 700 VA toroidal transformer and a bank of power supply capacitors totaling 132,000 µf proves the PA-7 means business. Such a setup made the PA-7 a perfect choice for demanding loudspeakers and, like the Threshold Stasis amplifiers, it ended up in many systems based around electrostatic speakers or Magnepans.
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tell me does anybody know down to what frequency do Klipsch for example claim their rated efficiency to be accurate to with a fudged room gain? the mid horns and up might be good with two watts pushing them but the woofer is what sets the pace and the horns are adjusted to the efficiency of the woofer(s).
I don't know the impact of horn loading on the woofer and I suspect it may be somewhat different for the Klipschorn vs the La Scala where a chunk of the La Scala frequency response is direct radiator vs horn loading, but I seem to remember that somewhere I had seen posted that 1W is ~ 97.7 dB SPL and 2.83V is ~ 101.7 dB SPL for the woofer. Although, I don't know if it was in reference to the pre 1984 version with the lower fs or the post version with the higher fs.
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Given the above, for 1W per channel for the stereo set-up, the "effective" SPL will be about 107dB SPL for the stereo application, so to get the extra 3dB for our 10dB swing from the 100dB SPL, the power would be doubled under the logarithmic formula to 2W per channel. Can the low watt SET owners now breath a sign of relief or does the analysis contain flaws?
The following assumes your 2 watt amplifier has a maximum RMS output (unclipped, undistorted) of 2 watts. It also recognizes that with KHorns at 1 watt it is already LOUD:
You are listening to a 2 watt amplifier at 1 watt average....then a 3 db peak comes along and your amplifier puts out 2 watts for the duration of the peak. And a 3 db increase of sound intensity has you say
( subjectively) 'Oh it got a little louder there for a second'.
Now you are listening to a 2 watt amplifier at 1 watt average....then a 10 dB peak comes along and your amplifier attempts to put out 10 watts and clips the waveform. Your amplifier ran out of gas. You say something like 'well that sounded a little rough perhaps I better turn it down a bit'.
To have 10 db of headroom above 1 watt you need a 10 watt amplifier.
I do not understand where you get "so to get the extra 3 db for our 10 db swing", to get a 10 dB swing you need 10 dB.
It's basically a trick question as I’m probably mixing terminology on you somewhat and looking more at the “dynamic range” of a piece of music (e.g., difference between the softest passage and the loudest) in the context of a type of “peak to average capability” of the “in room” amplifier and loudspeaker combination thinking about acoustic SPL output that can be measured with a simple Radio Shack SPL meter rather than something like an amplifier test of “dynamic headroom” regarding how many watts were generated or needed before clipping to cover a 10dB peak over RMS power output using an 80-200 millisecond (or similar) tone-burst.
For example, while it may be slightly unrealistic, I’m assuming that the 104dB sensitivity of the Klipschorn before any room gain and one watt of amplifier power will give me 104dB of sound electrically; however, I will probably have 3dB of room gain for SPL output that I “hear” from placing the loudspeaker in a room where the corners, walls, ceiling, and floor of a room all reinforce the loudspeaker’s output.
There would be an additional 3dB output that I “hear” that is due to having two Klipschorn loudspeakers in the room rather than one loudspeaker and I was careful to keep considering the odd aspect of “loudness” in relation to “decibels” where one loudspeaker is producing a level of 104dB SPL at one watt of power, adding a second loudspeaker playing at the same level using one watt of power only increases the overall “loudness” by 3dB SPL (e.g., loudness does not double with two loudspeakers). Essentially, the two Klipschorn loudspeakers in stereo produce a “loudness” level of 107dB SPL in the room with each being driven by one watt amplifiers. Of course, I realize that I have technically doubled my power from one watt by now using a total of two watts for the two loudspeakers combined.
Now rather than a 10dB tone-burst, I want to produce a “realistic” peak sound level for some type of music that I’m familiar with. For example, let’s say that I’m picking from a solo grand piano playing crescendos that can reach peak levels of 109dB SPL, I believe that a full orchestra in a concert hall measures peak levels of about 106dB SPL, and a rock group may have peak levels around 120dB SPL.
Of course, I fully realize that my Klipschorn loudspeakers with a 2 watt per channel stereo amplifier, even factoring in the “room gain” doesn’t stand a snowball’s chance on a hot day in San Antonio of surviving realistic peaks of a rock concert and that is why I have other amplifiers. However, it seems that I should be fine with the 106 dB peaks in relation to a full orchestra in a concert hall electrically and acoustically; and maybe I can experience the feeling of 109dB peak level of the grand piano crescendo with my Klipschorn loudspeakers and 2 watt per channel SET amplifier.
I fully realize that my 2 watt per channel amplifier will only electrically drive the Klipschorn loudspeakers to 107dB (104dB plus 3dB for doubling the power from one watt per channel to two watts per channel) and most likely any attempt above the 107dB will result in clipping assuming that my amplifier does not have any “head room” of power to handle a very short 20 or 30 millisecond burst of 2dB in excess of the rated power; however, that 107dB should still give me the “perceived” loudness of the 109dB I wanted to experience in the room given the aspects of room gain that I have outlined above.
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10 db peaks you say over average? Just remember 10 db = 10X the power.
1 Watt + 10dB = 10 Watts
10 Watts + 10 dB = 100 Watts
50 Watts + 10 dB = 500 Watts
etc.....etc......
In case it wasn't clear in the earlier posts, I fully agree with the logarithmic formula that 10 db = 10X the power. Although, after giving the issue some more thought, I actually do not believe that PWK was trying to state that a 2 watt amplifier is enough for 10dB music peaks over the average listening level of 100dB. I believe that PWK was talking about how well-engineered his speakers were.
Note that in the text of the article PWK indicates that “the larger KLIPSCH Systems are all capable of reproducing the original levels of live rock music (average 100 to 115 dB SPL with peaks 10 dB higher) in a typical listening room, all with a modest amplifier of about 50 watts per channel.” PWK goes on to state that; “the loudspeaker's short-term (50 ms or less) power handling capacity is much higher (by roughly 10 to 15 dB) than its long term continuous rating.”
Therefore, I actually believe that PWK may have been referencing the "general" capabilities of his loudspeakers when he discusses the 10dB peaks before clipping.
Given the variability in amplifier ratings there is no way to determine the actual capabilities between amplifiers and how much power one amplifier can actually produce compared to another amplifier with the same general "watt output" rating. For example, amplifier power ratings are typically established by driving the device to the onset of clipping for a predetermined distortion level that is often different between manufacturers and even can be different with the same manufacturer for a given product line.
Driving an amplifier to 1% distortion levels will yield a higher rating than driving it to 0.01% distortion levels. In addition, testing an amplifier at a single mid-range frequency, or testing just one of two channels, will yield a higher rating than if it is tested throughout its intended frequency range with both channels being driven.
Why the variability in amplifier ratings you may ask? Of course, manufacturers tend to use the method that best helps it to market amplifiers full well knowing that the published maximum power output may include some amount of clipping in order to show higher numbers.
Regarding amplifiers, the primary aspect that we do know is that when an amplifier is pushed to create a signal with more power than its power supply can produce, it will amplify the signal only up to its maximum capacity, at which point the signal can be amplified no further.
Essentially, "clipping" is the “cut off” portion of the music signal that is beyond the capability of the amplifier resulting in a sine wave becoming a distorted waveform.
In power amplifiers, the signal from an amplifier operating in clipping has two characteristics that could cause damage to a connected loudspeaker; (1) because the clipped waveform has more area underneath it than the smaller maximum unclipped waveform, the amplifier produces more output power and this extra power can cause damage to loudspeaker components, including the woofer, tweeter, or crossover, via overheating; and (2) in the frequency domain, clipping produces harmonics at higher frequencies than the unclipped signal would produce where this additional high frequency energy has the potential to damage a loudspeaker via, again, overheating.
In another tangent that I took and note that this next part has nothing to do with PWK’s table, but in relation to situations where I use a 2 watt SET amplifier, I did think about an example where I would be listening to music at 100dB (SPL). My Klipschorn’s are rated at 104dB/m/W, so with two of them, the “effective” sound pressure (at 1 meter) would seem to be 107dB SPL with 1W into each channel.
Although, there would be an impact of a drop of maybe 6dB or more at the listening position, let’s not factor in that impact of the listening position, which will be some distance away from the speakers and we all fully realize that the level would be lower at the listening position vs. the measurement position.
Given the above, for 1W per channel for the stereo set-up, the "effective" SPL will be about 107dB SPL for the stereo application, so to get the extra 3dB for our 10dB swing from the 100dB SPL, the power would be doubled under the logarithmic formula to 2W per channel. Can the low watt SET owners now breath a sign of relief or does the analysis contain flaws?
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but the thing that attracted me to the MC30 was a much greater selection of "cool" tubes that can be obtained and rolled in place of the 6L6 as opposed to the selection to roll in place of the 6550. For example, there is the metal 1614, the British Genalex KT-66, the 5781A, and Tung-Sol 5881, among several others.
Is this really the case? Can the 30's support (correctly) those tubes other than the 6L6GC? Aren't some of the voltages required for those tubes different than the 6L6GC?
And if this is true, do you know if this is also the case with the MC240?
It is always good to check or know the specific voltages of the specific amplifier; however, if your circuit calls specifically for the latest version of the 6L6GC, it is probably designed to run the tube harder and you probably cannot use the earlier 6L6 models that were rated much lower. My Harman Kardon Citation V would run the 7581 tubes pretty hard and it ran the 6L6GC tubes just fine but if just plugging in something like a 5881 the tube would have a much shorter life span.
My MC30 circuit used the 1614 metal tube which is similar to the 6L6; however, if I'm remembering correctly, there may have been a circuit designed for the 6L6GC toward the end of the MC30 life. I don't have any experience with the MC240 design other than identifying the differences with the MC30 and wanting to go with the more classic tube rectification.
Edit: Brent Jessee does a good job of outlining when the various tubes can be substituted in what situation at the link below.
http://www.audiotubes.com/6l6.htm
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If you look at the curves of the 6L6 and 6550 you will find that they are very similar; however, the 6550 has more plate dissipation. Both the MC30 and MC60 seem to basically use the same circuit with the MC60 modified with an appropriate power supply for the 6550. Of course, the output transformer will be different as the MC60 will be wound to handle more power output, Now from a MC30 to MC40 there are more substantial differences as the MC40 has a solid state power supply, cathode feedback to driver stage, and a filter choke all of which are different from the MC30.
It has been a few years now since I bought mine in 2007, but the thing that attracted me to the MC30 was a much greater selection of "cool" tubes that can be obtained and rolled in place of the 6L6 as opposed to the selection to roll in place of the 6550. For example, there is the metal 1614, the British Genalex KT-66, the 5781A, and Tung-Sol 5881, among several others. Most of the 6550/KT-88 are new production or the NOS tubes are rare or priced out of range such as the solid black plate Tung-Sol 6550 or the British Genalex Gold Lion KT-88s. Of course, there is the new production EAT KT-88s for about $1,600 a quad.
If you decide upon the MC60 and the venerable 6550/KT-88 series tubes, if it were me, I would probably have just kept the VRDs and looked into this MagneQuest transformer upgrade for the VRDs.
http://magnequest.blogspot.com/2016/01/nos-valves-vrd-amplifier-with.html
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Does the chart take compression into account? You can add power and the volume increases accordingly, but every speaker has a limit, beyond which it will not play any louder, no matter how much power you send to it.
Basically, in babadono's calculation, he outlines that 10 db = 10X the power and 1 Watt + 10dB = 10 Watts and most of us are aware of that logarithmic relationship. This logarithmic relationship appears to be the same ratio in PWK's table where he outlines 2 watts to drive "average" SPL of 100dB; and 20 watts to drive "average" SPL of 110dB maintaining the logarithmic 10x ratio.
However, I asked how people believed the ratio applied to how PWK determined that a Klipschorn (104dB sensitivity) driven with a 2 watt amplifier to an "average" SPL of 100dB SPL would also be enough power to allow peaks of 10dB above the "average" SPL to pass without clipping the amplifier? I outlined the different ways that sound is measured to see if I could back into PWK's data in the chart.
If an amplifier is measured using the root mean squared (RMS) method, it is often capable of short bursts of more power output (power supply capacitors maybe?) to handle peaks where this power output will occur for very small fractions of a second but cannot be maintained as a continuous output measured as RMS, but how do you translate that power over RMS output into handling peaks in music (e.g., how did PWK determine the 2 watts RMS was sufficient for the 10dB peaks in the music as opposed to the view that many hold that 20 watts RMS would be required)?
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I just figured that there must be a precise method in how PWK defined a "peak" or did his analysis to recommend that a 2 watt amplifier had sufficient head room for music with 10dB peaks. I just haven't been able to "back" into it.
Essentially, there are three different "measurements" in relation to sound; (1) power (sound intensity level - calculated), (2) Amplitude (sound pressure level - measured), and (3) Loudness (psycho acoustic - sensed). The common mistake that I see is that people will relate the three different measurements all to the psycho acoustic or sensed loudness.
Basically, if all three were measures of psycho acoustic 'sensed' loudness, think about it this way. If you consider the typical frequency response of +/- 3dB (Khorn, Belle & La Scala +/- 4dB in literature but often more in measurements) would result in an overall swing of a 6 dB swing meaning that music could have swings of 4 times (3 dB double loudness; therefore, 6 dB would be quadruple loudness) increase in the loudness or 4 times decrease in loudness that would not be attributed to the dynamics in the music itself.
Note that the term “perceived” sound volume and the term “loudness” are both subjective terms trying to describe the strength of the ear's perception of a sound. Essentially, loudness is only a subjective feeling that is commonly confused with objective SPL measurements in decibels.
When you consider the works of psycho-acoustic researchers such as Stanley Smith Stevens and Richard M. Warren; a more accurate rule of thumb would be that a doubling of the sensed volume (loudness) is equivalent to a level change approximately between 6 dB and 10 dB.
Think of it this way in that you have three different situations. There are two objective measurements, power and amplitude; and one subjective measurement, loudness.
Here is a nice sound level comparison chart showing the various ratios the respective ratios of subjective volume (loudness), objective sound pressure (voltage), and sound intensity (acoustic power).
From the chart above:
Power (sound intensity level - calculated):
Sound power ratio 2 (two times the intensity) changes the sound power level by 3.01 dB
Amplitude (sound pressure level - measured):
Sound pressure ratio 2 (two times the pressure) changes the sound pressure level by 6.02 dB
Loudness (psycho acoustic - sensed):
Loudness ratio 2 (two times (twice) the loudness) changes the sound loudness level by 10 dB
From the chart above:
20 dB gain change should give about the ratio of 4 (four times) for sensed volume and loudness
20 dB gain change gives the ratio of 10 for measured voltage and sound pressure
20 dB gain change gives the ratio of 100 for calculated sound power and acoustic intensity
Here are a few of the resources that I've considered:
http://scitation.aip....1121/1.1912298
http://trace.wisc.ed.../2004-About-dB/
http://www.campanell...#basic_loudness
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Fjd,
All I was trying to say is if you play your KHorns at 2 watts (loud) and you want to be able to handle 10dB peaks over this(very loud) you need 20 watts.
I understand your calculation. In trying to determine why PWK indicated 2 watts instead of 20, I was trying to reconcile the two numbers. For example, one thought that I was wondering about is if PWK may have been looking at the voltage gain factor (e.g., 3.16 multiplier for a 10dB voltage gain) required to handle peaks, which would be a sound pressure ratio using an amplitude multiplier rather than the sound power gain factor measuring sound intensity outlined in your calculations.
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I'm pretty sure PWK always referred to RMS values. After all he was an electrical engineer before he invented the KHorn. All this "peak music power" and "peak power" is a bunch of fluff.
I also said I worked from the premise that he would use RMS power output; however, it still doesn't reconcile the implied inconsistency between your table and his table regarding the availability of power to handle peaks in music. I haven't figured it out, which is why I did a type of "brain storm" of thoughts to see if anyone else can help reconcile the two tables (hopefully) using plain English.
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10 db peaks you say over average? Just remember 10 db = 10X the power.
1 Watt + 10dB = 10 Watts
10 Watts + 10 dB = 100 Watts
50 Watts + 10 dB = 500 Watts
etc.....etc......
Maybe I'm missing something here and someone with more specific knowledge can clarify further; however, babadono's calculations bring up a good point I'm trying to reconcile; and a good point in that it would seem important that a person should understand how their amplifier was rated. For example, did the manufacturer use terms such as "peak," or "max" or "dynamic" and add the term "power" afterward or use acronyms such as PMP (Peak Music Power) or PMPO (Peak Music Power Output) to rate the amplifier, then I have serious doubts about 2 watts driving Klipschorns at 100dB levels and have enough left over for 10dB peaks in the way PWK's table outlines. However, if the manufacturer used true RMS (Root Mean Squared) calculations in arriving at 2 watt RMS power to drive Klipschorns at 100dB SPL with music peaks (noting that peaks are specific, extremely short bursts and not necessarily a broad-based raise of SPL across the entire spectrum) of 10dB, would we be in a position to demonstrate that PWK is not correct by using the calculations above as evidence that 2 watts is not enough (e.g., going from ~ 0.9 watts continuous to ~ 3 watts available for the peaks doesn't appear to cover the 10dB change)? Does this situation mean that people are regularly driving the 2 watt SET amplifier into clipping and adding more distortion with the amplifier in a state of clipping on a regular basis? If not, why not?
When PWK evaluated amplifiers and had shown in his table that a 2 watt amplifier used in conjunction with a Klipschorn (104dB sensitivity) would be sufficient for 100dB of average SPL (basically using less than one watt of amplifier power except for instances of the very specific short bursts) from the speaker with 10dB peaks in music, I tended to believe that PWK was a smart enough guy in that he was talking about 2 watts using the RMS calculation for power output that is typically applied to voltage or current. For example, for an AC-type music signal sine wave, I believe that the mathematical calculation would be the peak value (measured?), divided by the square root of 2 (e.g., 1.414). In addition, it would seem that in music that the entire wave form wouldn't be a peak, but something more specific like a guitar may specifically produce a transient resulting in a 5V peak, with an average level of only 500mV, which would be an example of a 10dB peak. However, when comparing RMS power to peak in this context would not necessarily seem to be thought of in the same way as the amount of power needed to drive a "peak" in the context of the speaker at 100dB average SPL (e.g., 2 watts) vs the amount of power needed to drive the speaker at 110dB average SPL (e.g., 20 watts) for which this type of 10dB difference is highlighted in PWK's table, or would it?
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Okay, after correcting a wiring mistake regarding the inputs, and help with Maynard drawing up a diagram to wire up the 10K switched pots correctly, (ear bleed circuit) I listened to the amplifier for about 2-3 hours tonight.
It's a first take, and I'll need a bit more time to write up my thoughts on sound. but initially, things sound rather good.
The bass can really pound with heavy bass content music, it's rather impressive for a little over four watts per channel.
The dog didn't seem to care...
I had a cat for almost 19 years and, when she didn't like the way an amp sounded, she ran out of the room. If she stayed on my lap I knew all was well
. So, now we'll all wait for the detailed listening report!!!Maynard
Now that is a great test to see if any amp sounds good, cat test.
Looks like another excellent build and another excellent example of Mike's top-notch wiring skills.
However, I did get a chuckle out of this one since I can't tell from the picture if the dog actually doesn't care or is actually covering its ears planning a leap for the "ear bleed control knob." .
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Okay, after correcting a wiring mistake regarding the inputs, and help with Maynard drawing up a diagram to wire up the 10K switched pots correctly, (ear bleed circuit) I listened to the amplifier for about 2-3 hours tonight.
The dog didn't seem to care...
I had a cat for almost 19 years and, when she didn't like the way an amp sounded, she ran out of the room. If she stayed on my lap I knew all was well
. So, now we'll all wait for the detailed listening report!!!Maynard
Now that is a great test to see if any amp sounds good, cat test.
I always enjoy following Mike's and Maynard's build threads and I'm not sure you can find better examples of wiring technique.
However, I did get a chuckle out of this one since from the picture I can't tell if the dog doesn't care or is actually covering its ears planning a leap for the "ear bleed control knob." .
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Plus we tend to forget that we are not just buying a speaker, we are "buying a piece of American audio history."
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Paul Klipsch had a Dope from Hope article on this subject - linked below for the entire article. These figures are based on single-speaker output into a 3000 ft^3 room while allowing peaks 10 dB above average to pass without clipping:
https://community.kl...attach_id=69980
. So, now we'll all wait for the detailed listening report!!!
maybe tubes are not that great? I do not know! HELP!
in Talkin' Tubes
Posted
Agreed, that a comparison on an "apple to apple" basis appears to make sense and stress both amplifiers in relation to how you like to listen in order to evaluate how they perform in relation to your listening habits. However, this information now begs the question regarding how precise did you match the gain of each amplifier in your comparison?
In my experience, some people tend to forget about "level matching" or "gain matching" when comparing amplifiers. Even very slight differences in gain between amplifiers can be audible as I have found that precise level matching can be more critical than most even realize. In certain situations a 1 dB difference can change a person's perception of an amplifier.
For example, in certain listening rooms that tend to allow a speaker to "bloom" with reflective surfaces and very little absorption, a person could fairly easily detect a 1 dB difference in output level between amplifiers. From another perspective, even with "gain matching" the lower powered single-ended amplifiers are working much harder where the single-ended amplifier is being run much closer to its maximum power ratings, which tends to mean that they are distorting more. The lower the power output of the amp, the more many people make them work extremely close to the amplifier limits and the more it will be distorting.
I believe that it has been fairly well documented by Nelson Pass and others that distortion of the 2nd harmonics variety, in general, tend to be very pleasing to the ear and the correlation has often been made that perhaps the listeners that love the 'blooming' midrange are actually loving the additional harmonic distortions caused by running the amp fairly hard relative to its power output.
Given the above, on a side note, as I've posted multiple times in this thread and other threads, there is nothing wrong with liking that, it is a persons personal taste after all. I don't make it a habit to judge another person's personal taste and I sure hope that readers do not jump to unfounded conclusions reading my posts. Those that take the time to read my posts and in some instances ask clarifying questions, know that I look at the music listening experience from a "situational" standpoint and try to match a system to the mood of the environment; and have run a very large variety of amplifiers and have a fairly large stable of single-ended direct heated triode and single ended pentode amplifiers too.
In addition, since you brought up scientific methods, I firmly believe that the ear (even an “untrained” ear) can detect very small differences that seem very inconsequential on the surface; and I certainly cannot find fault with those that just use their ears and go with what provides the listening experience they are looking for. However, from another perspective, my point regarding gain matching is that although the ear can detect very small differences, the brain may not exactly know what aspect of the music reproduction chain to attribute the difference.
In general, when gain levels are different, it seems that many will tend to conclude that louder music, even if it's just slightly louder, will almost always sounds better to them than the quieter music.
Now for those reading the thread that may decide to go the measurement route and do some gain matching for amplifier comparison, I would recommend using a volt meter that will measure down to 0.001 volt AC if possible.
I have gone back and forth in my mind, while playing the relevant test tones, which is the best place to measure. For example, if measuring at the output of the power amp or if the measurements should be made at the speaker terminals.
I've been thinking that maybe both places, which will allow you to understand the voltage drop for each speaker wire or channel. For example, when you measure at the amplifier, in most instances you will find it to be slightly more voltage as the speaker wire resistance is not part of the measurement. Now if you decide to measure the voltage at the speaker connections, in most cases you will find it to be slightly less voltage as compared to the measurement at amplifier connections due to a certain amount of voltage drop across the speaker wire.
Now with the test tones playing over the two signal paths, I would shoot for a level match within about 1% or a level match of about 0.1 dB difference.
Although, given what I suspect to be the perceived difficulty of the above, I cannot necessarily find fault with those that just use their ears and forego the measurements, go with what provides the listening experience they are looking for, and attribute the difference to whatever the brain tells them too.