Power needs of Heritage series speakers

[Guest thesloth]

 

Larry, gain matching is an issue with any kind of amp, and not just tubes.  One doesn't need to come even remotely close to spending $10k to get a modern, quiet, amp (I believe some forum members have said that the amps Justin sells are dead silent).  If I recall correctly, Marty said that the "Little Gem" which he built for around $250 is dead silent also.  In fact, the noisiest amps I encounter are solid state ( as one example, the guy down the road has a Krell monster which, when connected to his CWs, generates so much hiss that it's audible outside his listening room- and it is operating within spec). 

Although you seem to be speaking of noise from an amp by itself, that's not where the noise comes from.  Rather, audible noise usually comes from adverse gain-matching, as between a preamp and amplifier units.  Sure, almost any amp will be dead silent with only a speaker connected.

 

I would have to know what pre-amp, and which amplifiers with what gain, are involved.  Statements that a given amplifier is very quiet don't mean anything to me.  A particular combination of preamp and a "silent" amp can be noisy as heck. 

 

 

Most people don't need a preamp. Line level means 1-2Vrms. Most power amps are driven to max output power by line level gear like CD players, DAC's, etc......So if you are using a Preamp with 20db of gain and you input a CD player with 1Vrms out that preamp will put out a voltage of 10Vrms. Most of the time you just attenuate all that gain away and just add noise and distortion to the signal path. So an integrated amp is meant to be just hooked directly up to a CD player, no extra preamp needed.

 

IF you are plugging noisy gear into a very sensitive high gain circuit you will get noise. Some vintage tube gear will have a very high sensitivity, like being able to be driven to full output power with 10's to  hundred millivolts, plug a source with a terrible noise floor into it and it will sound terrible.

 

Other noise factors are ground loops.

Edited July 28, 2015 by thesloth

[Guest thesloth]

I agree that second order and third are not bad in small doses. Musically if you look at it second order harmonic distortion is an octave above the fundamental, so it emphasises it. Third order harmonic distortion is musical fifth which harmonizes well with the fundamental. Agreed it's the higher harmonic distortion that is unpleasant, they are very dissonant intervals musically. You can't forget that music isn't a single sine wave, it's multiple signals, especially complex music like orchestras. These extra notes we call distortion that are not part of the original fundamental caused by nonlinearities sum and difference to create intermodulation distortion which sounds like crap. A lot of single ended amps with high amounts of distoriton will make a single person singing sound spectacular with the added harmonic distortion but will fall flat on it's face and sound muddy with complex music containing several signals. Keeping distortion low is good, and even better if what is there is only second and third.

Edited July 28, 2015 by thesloth

[tube fanatic]

 

 

Larry, gain matching is an issue with any kind of amp, and not just tubes.  One doesn't need to come even remotely close to spending $10k to get a modern, quiet, amp (I believe some forum members have said that the amps Justin sells are dead silent).  If I recall correctly, Marty said that the "Little Gem" which he built for around $250 is dead silent also.  In fact, the noisiest amps I encounter are solid state ( as one example, the guy down the road has a Krell monster which, when connected to his CWs, generates so much hiss that it's audible outside his listening room- and it is operating within spec). 

Although you seem to be speaking of noise from an amp by itself, that's not where the noise comes from.  Rather, audible noise usually comes from adverse gain-matching, as between a preamp and amplifier units.  Sure, almost any amp will be dead silent with only a speaker connected.

 

I would have to know what pre-amp, and which amplifiers with what gain, are involved.  Statements that a given amplifier is very quiet don't mean anything to me.  A particular combination of preamp and a "silent" amp can be noisy as heck. 

 

 

Most people don't need a preamp. Line level means 1-2Vrms. Most power amps are driven to max output power by line level gear like CD players, DAC's, etc......So if you are using a Preamp with 20db of gain and you input a CD player with 1Vrms out that preamp will put out a voltage of 10Vrms. Most of the time you just attenuate all that gain away and just add noise and distortion to the signal path. So an integrated amp is meant to be just hooked directly up to a CD player, no extra preamp needed.

 

IF you are plugging noisy gear into a very sensitive high gain circuit you will get noise. Some vintage tube gear will have a very high sensitivity, like being able to be driven to full output power with 10's to  hundred millivolts, plug a source with a terrible noise floor into it and it will sound terrible.

 

Other noise factors are ground loops.

 

Larry, I'll add to Sloth's comments about preamps by saying that external factors may cause the preamp to be noisy.  For example, the preamp may be picking up all kinds of grunge from the powerline and amplifying it.  In addition, our environments are so full of RFI from various sources that if the preamp is poorly shielded noise can enter and be amplified that way.  Then there's the issue of interconnects which, if not well shielded, and too long, can pick up all kinds of stuff.  Also, we need to differentiate exactly what kinds of noise you are addressing.  Is it hiss, hum, tinkling, etc.  Hiss can be from the tubes themselves as the electrons flow through to the plate; hum can be internal such as circuitry picking up magnetic fields from the power transformer; tinkling can be microphonics from poorly supported internal tube structures.  So, the question is not one that's easy to answer.  One thing I will say is that I was truly impressed by Carl's Transcendent GG preamp.  It is astoundingly quiet.

Maynard

[tube fanatic]

 

One last thing, I have spoken with Maynard about this and would like to know what others think......especially the ones that do not own any tube gear and would like to. I think it would be a fun excersise to as a community design an amplifier SPECIFICALLY for Klipsch speakers.   Possible Design Goals:   1) Inexpensive 2) Quiet 3) Use readily available, current production tubes. 4) Fully ingegrated, line level input

 

This does sound like an interesting exercise, and I would be happy to keep up with the thread as it progresses.  I'm not particularly circuitry savvy, so I wouldn't be able to contribute there, but I have been in the software quality assurance field for many years, so I have that somewhat annoying tendency to question decisions, play the Devil's Advocate....and so on.  So, having said that, here's a few comments regarding your design goals above....Don't take it personally, just remember that I'm a tester at heart, and therefore a pain in the *** to designers and developers.....

 

1)  Inexpensive - As inexpensive as is reasonable while maintaining quality.  This should be quantified within specific cost parameters, $400-$800, $500-$1000, etc.

 

2) Quiet - As quiet as possible given the design.  Considering the efficiency of most Klipsch speakers, what would be the minimum/maximum THD or other data point?

 

3) Use readily available, current production tubes.- Readily available yes, "current" production.....ummm, maybe.  There are still boatloads of vintage tubes out there that are readily available, and that outperform by a wide margin "current" production tubes.  This certainly links to the cost aspect, but based on the design, may be a wash considering the quality factor...

 

4)Fully integrated, line level input - Again, this needs to be quantified as to what exactly this includes.

 

Let me add one more thought...What designs that are already in use have been shown to perform well with Klipsch speakers?  (This is a strictly rhetorical question...)  And yes, this may involve personal preference, understood, but hey, cloning a McIntosh design with good quality components might not be all bad....

 

So, again, I'm happy to jump in and be a pain whenever you would like.    

 

Jim

 

The idea of doing a dedicated, Klipsch optimized, amp is appealing.  Of course, the big question is whether one design can cover a wide range of needs.  There are guys using CWs at 110+ db, which rules out low power single ended designs.  To build a high power push-pull amp with sufficient power to cover that will be very expensive.  So, some kind of consensus has to be reached about how much power is needed, and what the majority considers a reasonable cost.

The other points raised by Jim (Jimbo):

2) it should not be difficult to come up with a quiet amp design.  The definition of "quiet" would have to be established- dead silence with an ear against the tweeter, or at 6", or 12" and so on.  THD should be "as low as possible at full output."  We need to keep in mind though that if the amp is single ended, the distortion will be higher than if it's push-pull.  This does not mean that it won't sound terrific.   

3) tubes can be chosen based on the power need and the type of circuit.  I have never used a modern tube, preferring inexpensive NOS tubes of which there are countless choices at very low price points.  Others may prefer those of current production.  Either way, tubes can be inexpensive.

4) fully integrated with a line level input is the way to go.  To keep cost down, I'd go with a single input.  If someone needs more, an inexpensive Niles switchbox will be fine.

5) as to designs which work well with Klipsch speakers, there are too many to list.  I prefer single ended amps because, in spite of their distortion characteristics (or perhaps because of them), they sound best to me with everything from Reference Series through Heritage Series speakers.  Yet, some of the guys prefer push-pull.  The only way to decide may be to build a prototype and send it on a road trip to a bunch of guys who can critique it in their own systems.  Modifications can be made based on the consensus.

So, it may come down to having a number of possibilities from which to choose.  There is also the question as to whether this should be set up for DIY (in which case we have to go with very simple designs, at least in the beginning), or whether someone has a different idea.  Personally, I think the former would be nice.  With guidance, even beginners should be able to construct a well working amp (assuming they have the basic drilling and soldering skills).  Imagine the huge level of satisfaction after building one's own amp and having it provide the best sound you have ever experienced!

Maynard

[davidt]

Yea Chad!  Yea Maynard!  Love it.  I have slowly but surely been moving away from SS to glass....although, must admit, I still like (and play), my vintage Pioneer SX receivers, and newly discovered HK-730's.

 

Tubes are, to me, a challenge, and that's what draws me to them.  Meaning, there are so many different configurations, types, etc, etc, that all of the possibilities really keep me interested.  Not to mention, they look pretty cool too....

 

Once again, thanks Maynard and Chad.  This should be fun.

 

Jim

Happy to see this section show up on this forum.  I was always under the impression that more watts = more better.  After getting my first pair of Klipsch (Forte IIs) and doing some reading online about how little power is needed to drive them and how the tubes make them sing, I have been looking into investing in a vintage Scott or Fisher to try out.  

My (very little) experience is limited to vintage SS monsters like the Pioneer SX-1050/1250 and the Marantz 2325.  I find myself listening to music at a lower levels these days, but wonder if I would be limiting myself if I went with a vintage Scott rated at 17 wpc?  Would I be happier with 30?

[garyrc]

There are guys using CWs at 110+ db, which rules out low power single ended designs.

 

Are there (relatively) high power single ended designs, e.g., 20 to 40 wpc?  At not too high a price?  According to the Klipsch chart it looks like 20 to 40 wpc would give me almost 110 db with my Khorns in my ~~~ 4,500 cu ft room.

Edited July 28, 2015 by garyrc

[tube fanatic]

David, it's a matter of how loudly you listen, the room size and characteristics, and where you sit in relation to the speakers.  The Forte IIs make a lot of sound with little power; but, if you're pushing them to ear shattering levels, then 17 watts may not even get you close (and if that's not enough, 30 won't be enough either).  If you can describe more about your listening habits, the guys can give you some good guidance.

Gary, that kind of power and a reasonable cost are mutually exclusive!!!  To go single ended at that kind of power output requires using some nice, hefty, transmitting type tubes.  And then there's the issue of having to get a custom made output transformer which can handle the plate current without saturating.  Of course, if you win the lottery, you can go after something like a Wavac!

http://www.wavac-audio.jp/sh833_e.html

Maynard

[Guest thesloth]

You can get a 25 watt single ended output transformer from Edcor for under $90, which is only $20 more than their 30 watt push pull transformers. That's a pretty good deal if you want to go reasonably high powered single ended. Edcor has good iron for great value.

 

If your argument for single ended is you like 2H, then it doesn't mean you have to go single ended. Push pull only cancels 2H that is made in that push pull stage, all the distortion from the previous stage is still there. Just design a front end with high 2H in  a push pull design for higher power and you get what you want. 12AU7 is pretty non linear and likes to make lots of 2H......take a look at the plate curves. Good NOS versions are cheap too. Heck I have a box of GE's with probably 100 in there that were made for CBS.

[LarryC]

Larry, I'll add to Sloth's comments about preamps by saying that external factors may cause the preamp to be noisy.  For example, the preamp may be picking up all kinds of grunge from the powerline and amplifying it.  In addition, our environments are so full of RFI from various sources that if the preamp is poorly shielded noise can enter and be amplified that way.  Then there's the issue of interconnects which, if not well shielded, and too long, can pick up all kinds of stuff.  Also, we need to differentiate exactly what kinds of noise you are addressing.  Is it hiss, hum, tinkling, etc.  Hiss can be from the tubes themselves as the electrons flow through to the plate; hum can be internal such as circuitry picking up magnetic fields from the power transformer; tinkling can be microphonics from poorly supported internal tube structures.  So, the question is not one that's easy to answer.  One thing I will say is that I was truly impressed by Carl's Transcendent GG preamp.  It is astoundingly quiet.

OK, that's quite a few possibilities to explain some things, but what I have actually heard over the years is usually (1) a steady thermionic noise ("hiss") that doesn't vary as someone moves around the room; (2) an irregular, sputtering sound that sometimes includes voices and music and varies as someone moves around the room (RFI); (3) low-pitched/60 Hz hum that varies in proximity to electrical current (sometimes EMI), etc.  Granting what you say about tubes and hum, I was thinking primarily of hiss due to gain mismatch, and that's at the root of many "noise" complaints.  A super quiet preamp or amplifier to me mostly represents successful gain-matching, e.g., a very low-gain preamp line stage, and very low amplifier gain for the amount of power out.  The other things you mention have been rare in my experience, in comparison.

[davidt]

David, it's a matter of how loudly you listen, the room size and characteristics, and where you sit in relation to the speakers.  The Forte IIs make a lot of sound with little power; but, if you're pushing them to ear shattering levels, then 17 watts may not even get you close (and if that's not enough, 30 won't be enough either).  If you can describe more about your listening habits, the guys can give you some good guidance.

 

Maynard,  The Forte IIs are in my split level basement apx 28' x 12', presently hooked up to my McIntosh MA6300.  It's a game room, so I may be playing Golden Tee, throwing darts or at the bar table but rarely find myself sitting at the love seat centered between the speakers to listen to music.  

I listen to mostly rock and blues from the 60's to today, mainly on vinyl.  

I mentioned in my last post that I have been listening at lower volumes lately. Ha!  I just downloaded a sound meter app and find myself listening to Nomeansno and it is averaging 100 dB. I am home alone now, so no one to disturb.  According to this app, 75-80 dB may be more the norm.  I would like the ability to disturb tho! 

[richieb]

In my experience with many SE tube amps powering every Heritage speaker it it more than just a high DB level you can push but rather the overall sound presentation. Yes a 2a3 amp at 2.5 watts will run all Heritage and rather loudly but overall sound will be "thin" when compared to amps with multiple times the power. Bass, depth of bass, controlling the woofer (particularly with Cornwall) are generally better produced with added power. I thought my SE 10 watt Dennis Had sounded great and does; I thought my SE 18 watt Almarro sounded better and it does but after many sessions my hybrid SS Valve Audio with over ten fold the power beats them all. Bass digs deeper and tighter, mid range is articulate and lightening quick and highs are smooth and crystal. Just cause you have a couple hundred watts doesn't mean you use them but the huge power supplies, caps and the like all contribute to the amps presentation. A few hundred dollars of preamp tubes hasn't hurt the effort either.

[tube fanatic]

A little while ago I got back from a visit to a local musician (aka "the guy down the road") who has been anxious to hear the "Little QT" amps which I described a few months ago with his CWs, and to compare their sound to his Rogue Stereo 90.  We didn't have time to do a perfect level match using voltage at the speaker terminals, so we used the spl meter instead (for an overall impression it is close enough).  We listened at approx. 88 db.  The speakers are 8.5 feet apart, and the listening position is 11 feet from them in a room which is about 25 feet long.  At that level, the QTs slaughtered the Rogue in terms of sound quality (the latter was fed through passive attenuators, so no preamp influence would be involved, and were in triode mode.  Set for ultralinear operation it is not a nice sounding amp).  The interesting point here is that the QTs are SEPs running about 4 watts out at clipping!!!  The bottom end, sound stage, lack of graininess, and clarity were obvious as soon as the music started playing.  And, this was evident on all the recordings we tried.  He was truly impressed (and now wants me to come up with a SEP with about triple that power output)  So, unless you really like to crank the listening level, low power can be quite sufficient.  With LSs, Belles, and K-horns even higher levels could be achieved with the same power.

 

Maynard  

[Max2]

Those CW's are sure finished nicely.

[garyrc]

 

 

There are guys using CWs at 110+ db, which rules out low power single ended designs.

 

Are there (relatively) high power single ended designs, e.g., 20 to 40 wpc?  At not too high a price?  According to the Klipsch chart it looks like 20 to 40 wpc would give me almost 110 db with my Khorns in my ~~~ 4,500 cu ft room.

 

I doubt seriously that you would listen to your speakers much at 110 db if at all. I do not have a spl meter but from my calculations checking the voltage used at speaker at the loudest I would ever listen to Money Talks AC DC I am at most 100 db. When I was younger I thought I was listening to my system louder than that but now I realize that 100 db is about my limit. Any Klipsch speaker will play as loud as most people will ever listen with 25 watts or less. Notice I said "most" people. I would rather have a good 10 watt amplifier than a mediocre amplifier with 100 watts. The 10 watts will be a more pleasant listening experience. Most listening with Klipsch speakers is done with less than a watt. It is the inefficient other speakers rated at less than 90 db 1 watt l meter that need high power, horns are made for quality low watt amplifiers. Horns filled auditoriums with 10 watts in the 50's.  

 

 

Listening to the occasional loud passage at 90 or 95 dB can, with orchestral music (classical, romantic or modern), produce brief peaks as high as 110 dB.  PWK said 115 dB.  No one would listen to music at an average level that loud, but I would want an amp to be able to produce peaks up there somewhere.  Orchestral music has a higher peak to average ratio than AC DC and the like, which may be more compressed, but intended to be played loud (see "The Loudness Wars.")  

 

I assume that peak power capability is highly correlated with rated power, even though the latter figure would be much lower on each individual amp.  Is that true with tube amps?

 

Also, are there any good, but accessible, studies about whether tubes are better than ss in producing peaks far above their rated power?  Old advertizements for tube amps commonly listed peak power as twice rated power, but I see more modest figures on most ss amps.  My ss NAD power amps were tested by my dealer as clipping at 171 wts, which, if you multiply by 0.707 gives me 121 wts RMS, but they were rated by NAD at 150 wts.  Their dynamic power was less than 3 dB above this, I think. 

 

Would a good, low power tube amp have peak power about twice as high as rated power in watts (3dB)?  Is there an industry standard as to the duration of the peaks they are looking at? 

[USNRET]

Howdy! Now as everyone here knows that I don't know squat about squat but thought I'd share my 'going to tubes' journey.

 

After my 1970 / 80s fling with the famed 901s I picked up a pair of Quartets and Chorus IIs which I lived with for about 12 years or so using various SS amps and receivers; all was good.

Along early in our new milenium I thought it wise to sell off all my 2 channel stuff and go with an AVR. About the time I did this I also started picking up Belles and sold off the Quartets and Choruii. So there I was with 7 Belles and various AVRs that all sounded like crappola now when they had not with the other speakers.

 

I started back on the road to two channel via McIntosh and then picked up a Peach pre on the forum. The Mc stuff had quelled the angry Belles but then up popped a stereo VRD on the forum; sold the Mc stuff. Now I had found what I was looking for as the VRD / Peach made smoothness thru the Belles in 2 channel.

 

I woke up more stupid than normal one day with someone wanting the VRD and I bought a pair of 500 watt SS monoblocks. Talk about ground floor, idle HISS! That little 'experiment' didn't last long and I ordered a pair of VRD monos and then later replaced the Peach with an NBS.

 

I have never rolled a tube in these amps or preamp even though I have a few goodies lying around and have only had one tube failure (an infant mortality failure of a rectifier). I check the bias about every 6 months and it never varies by any appreciable amount and it is less of a hassle to bring back spot on then prepping a used album for play. granted I get very little time to use the 2 channel with a very busy household and being early to bed and early to rise for work.

 

I enjoy the sound, looks and perplexed expressions on peoples' faces.

 

Ya'll carry on this thread. I'll be reading.

[tube fanatic]

 

 

I am intrigued about the "Little QT". It looks like a very simple amp to build. Is there a schematic available? I searched this forum but turned up no results using the engine but with google I did find a schematic but it may not be the one you are describing. I have been wanting to build a tube amp but have not settled on what to build.  

 

Thanks for asking!  Here's the link to the original discussion/schematic:  https://community.klipsch.com/index.php?/topic/157544-meet-the-little-qts/?hl=%2Bmono+%2Bsep

 

Maynard

[mike stehr]

There are guys using CWs at 110+ db, which rules out low power single ended designs

 

I've had my Cornwalls for quite some time, and I'll admit I've thrashed on them a bit...but 110 decibels plus?!

 

In my experiences with my CW's, at around 95-100 decibels the speakers (themselves) start sounding unglued...at 110 dB+, they will literally be spitting in your face.

 

Are these guys concerned about the headroom needed for musical peaks, or do they listen at 110dB+ continuously? That's akin to running a table saw with no hearing protection...

 

I had a pair of Chorus II's with a Yamaha MX-1 power amp and CX-1 preamplifier...250 watts or some such, more than enough power. In my loud and proud days, I measured 116dB peaks with a Rat shack analog SPL meter with this set-up.

 

Impressive, and really loud, but irrelevant to enjoying music.

Edited August 1, 2015 by mike stehr

[MyOwn]

Maynard would it be possible to have an online class of sorts about tube amp theory? Maybe with instructions for building and testing?

[Guest thesloth]

Maynard would it be possible to have an online class of sorts about tube amp theory? Maybe with instructions for building and testing?

 

 

I don't want to answer for Maynard but instead add my 2 cents.

 

 

I think it would be fun and educational for everyone to have a tube amp theory thread, but a background on the basics would be necessary. Maybe the prerquisite should be to have read and understood chapter one of "The Art of Electronics" by Horowitz and Hill. Tubes are active devices, first learn the passive devices like resistors, capacitors, inductors, and transformers. Then move on to diodes, tubes, transistors, etc.....

 

Certain math equations come up a lot. Ohms law is probably the most important. Understanding the Thevenin equivalent is a must.

 

But for those whom already have an understanding of these things a tube theory thread would be great!!! I am still learning everyday. One of my favorite sites for learning tube circuit theory is John Broskie's http://www.tubecad.com/

[Luv_sum_Horns]

I've been searching for the "Sound" for a long long time. With retirement coming up I really needed to get my rear in gear. First stereo was a Kenwood KR-9600 receiver and Kenwood 777-d five way "kobuki" speakers. With the help of a Pineer graphic equalizer I pretty much shredded them. 901's and lots-o-watts after that. Shopped entirely by "specification". Did the whole 7.1 video with sound thing with conventional speakers. Uninterested. Music was there but totally uncaptivating, uninvolving. Enter PWK and a pair of kg5.2 80 dollar beaters. Bing! Hey I LIKE horns.

 

Couldn't find anyone with a tube amp to borrow. Ordered a Yaquin MC84L 12W SET. Bing! That's the sound I've been looking for. Unfortunately the poor thing hit it's head on the way over from China and has a nervous left channel tick. They were totally willing to ship another but I decided it will make a good project amp challenge.

 

Ended drinking some Steve Deckert kool-aid and I am now on my second Decware amp. What caught my eye there is his page describing the Torii, that instruments produce even order harmonics. So do SET amps. PP loses some, and SS produced odd order harmonics. Either way, they sound really nice and I haven't rolled any tubes yet.

 

I guess the other important thing I learned is what loudness level I like to listen at. 75 to 85 db's is fine in my old age and what I like about the tube sound is you don't loose dynamics or imaging at lower levels. Regardless of the volume, it sounds so good that I loose hours at a time, even while trying to get chores done!

-bb