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SET amps.............


SWL

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Wow Kevin, that drawing is really old. I might change that 2uF to 1.5uF or even 1uF -- I'd have to go back and run the numbers.

With the autoformer, the impedance will be all over the place, and would probably look similar to the Klipsch curve. You probably have a good bump somewhere in your midrange response.

What would changing the 2uf to 1uf do, sound wise?

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A little less tweeter energy -- a little.

This might be a good thing. - If you do get some time, and would 'run the numbers' on my crossover, I would appreciate it. And I would gladly make it worth your while $$$ wise --- There are a lot of taps on the t2 autoformer that may or may not be an improvement in what I'm doing here. I like the idea of a simple crossover, and would like to 'set it' for what would give me the best results. - I understand that there are compromises.

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Just to add one more thing here.....any fool with an electronics circuit cookbook can build a 300W SS amp with damping factor of 400 and distortion of .01% with about 40dB of negative feedback. No listening required whatsoever. It will be a "perfect" amp for anyone whose primary goal is to make the loudest bass booms they can get from any set of speakers. And, they're cheap too! $400 bucks or so should do the trick. Yeah, that's engineering! heh, heh!

This observation can also apply in relation to the design of tube amplifiers. There's a lot of poorly designed and engineered gear out in the market place, both tube and solid state. In fact relying on manufacturer's spec sheets and unsubstantiated claims of 'unsurpassed sound quality', whether speaker or amplifier, lends itself to the advice; 'buyer beware'...

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Interesting little debate between Mark and Dean. I think we are seeing that any argument taken to extremis becomes ludicrous in the end.

Listening is a great guide to choosing a system - there is probably non better - but, if your tastes change what you once loved ....

What I find interesting is that the arguements for SET and very similar to those used for a good MC cartridge on a TT - or just a TT in fact.

I am yet to be convinced that this much loved sound (the SET sound - and I know there is no such thing but bear with me) cannot be achieved, matched or even bettered, with alternate types of amp merely adjusting the source or, even the speakers.

Noteworthy perhaps - that I have heard many systems with that magical liquid midrange - well a few anyway - sans SET.

Having said that I have heard SET amps (8 watts or more admittedly) with really rather decent bass.

I think it comes down to this for me. If SET is the only way to get the sound I WANT - then SET it will be. If, however, I see an alternative (not punitively expensive) that provides a similar quality of sound then that is more than likely the route I would go IF it offered less trade-offs in terms of power.

As for measurements - I would imagine it is more important for the manufacturer than the listener to measure. Some of these measurements must mean something - surely?

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First, EARS can't measure a d@#n thing, being only receptors - its our brain that does all the measuring and each of us uses a different standard to determine what is "GOOD".

Measurement devices allow folks to compare phenomena in a controlled environment - we can all agree on what 90dB is on a SPL meter (although we may not all agree whether that is too loud or not). The good thing about these devices is that they can measure and quantify data much better than we can and the results can be communicated in a way that all (well, most) can agree on. The problem is that these devices can only measure very specific phenomena and the criteria for which they were designed is based on an extremely focused yet incomplete science. I liken it to being in a forest on a dark night with only a flashlight. By shining the flashlight on the path, trees, leaves, etc., you can determine a lot about your surroundings BUT you haven't the time nor the battery-life left in your flashlight to view everything in the forest and you can never hope to perceive as much by the light of a flashlight than you can by the light of day.

While we don't measure and correlate specific data nearly as well as the devices designed to do just that, we can perceive and integrate sound phenomena on a grand scale and the amount of information we take in each instant compared to ALL the sound-measurement devices ever assembled is on a magnitude beyond measurement - literally off the charts.

My point is that while measurements are essential in defining and comparing specific criteria in sound equipment, we have yet to quantify but the smallest fraction of the characteristics of sound much less design anything that can measure all that we perceive.

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Max---

Of course you could achieve that "SET sound" by other means. But, it would not be as easy as you might imagine if, for example, you choose transistors and also want 500 watts of power. Maybe more to the point though, is that SET sound isn't a universal shared goal (that should be obvious to anyone by now). Thus, not that many designers WANT to achieve that sound, right? Look, what makes it a prominent feature here (Klipsch) is that it goes well with high efficiency horns. So, it gets more play here than in other audio circles, where people might babble on about other kinds of sound.

Measurements to me are guideposts, markers and reference points. They are not goals to be achieved - only the sound is a goal. Naturally, if I can improve a measurement AND retain the same sound, I'd be a fool not to do that. But, that is rarely if ever the case.

Lastly, here on the Klipsch forum, the "SET argument" per se, is actually an emotional remnant of 2001, when very bad blood was spilled on this issue. That was sort of the "Civil War Period" on these forums, and most of the emotional rhetoric you hear now is a remnant of that era. For instance, you don't hear any "anti moving coil" sentiment, or "anti subwoofer" sentiment etc.

Besides, alll dogs need a bone to chew.

Ah yes - I think I recall those bloody battles of yore. Amazing how heated an exchange of opinions on, what is actually taste in music reproduction, can be in a medium which allows for no comparison of experience other than the telling.

I do wonder about whether meaurements are merely guideposts, markers and reference points for you as a manufacturer. It would appear to me - as an impartial observer that you have gone to great lengths to make a high(ish) output of 25 wpc for your pCats. All the fun of SET without the drawbacks perhaps - but I'd guess that was a design aim - number based design aim?

Some measurements (such as simple power output) are important. I may not consider driving my amps with a 3.5 wpc amp (of any description) with a mere 91 dB sensitivity - but with 25 wpc - hey that might get an audition.

I would not buy it on the basis of the specs - but I would NOT buy it or even audition it on the basis of the specs - LOL!

(In other words I might decide not to buy something on the basis of the specs I see).

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"The acoustic output in SPL does NOT "track" to the impedance curve measured at the speaker terminals..."

No, not in magnitude, but it does follow along, and can have quite an effect on the acoustic output. The example in the following article is using a damping factor of 2.4 ("8 ohm" speaker / 3.3 ohm output resistance).

http://www.stereophile.com//features/127/index.html

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  • 2 weeks later...

My set amps

Hi Guys, I have some Sets 2A3, 300B, 45, VT-25, each with his qualities, Set class A different sound that PP is a matter of taste, I personally prefer the Set, IMHO 2A3 sound more balance on full range than 300B Not as sweet as 300B in mid-range, but more balance on high and low with good bass. VT-25 I only say WOW great sound, very balance on full range with excellent high range and bass too. 45 is a great tube with deep bass. I think 300 is very good only in mid range (female voices in jazz) . My next project 71A, Thanks and good luck (Sorry fr my bad english It isnt my mother language)

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Hi, I did not understand your question to which you are referring about the VT-25, thanks, Martin

tn_5GC95801.jpg


I was wondering when they were designed but I just found the information on the valve history site..

The VT25



The (RAF) VT25 was based on the MOV type DET25 which was a modernised version of the
landmark MOV type DET1 introduced in the later 1920s. Both types were widely used by the RAF
for aircraft transmitters in the HF band. Power output was modest (around 30 W carrier) but the valves
were economical, reliable and robust. The giant L4 base cap allowed generous insulation for RF anode
voltages in excess of 1000 V, even when damp (flying through cloud) or at high altitude.

During the 1930s and throughout WW2 the RAF bought quantities of these valves from several
manufacturers (including American). Exhibits VT25 and VT25 are both DET25's of MOV origin (but probably made at their Shaw shadow
during WW2 rather than at Hammersmith). Exhibit VT25 is of characteristic
Ediswan design but was presumably made in an Ediswan Mazda factory which in peacetime had made valves for
the domestic market under the Mazda label.


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Hostorically where does the VT25 fit in?I have seen a couple VT25 amps lately on audiogon lately. The 300B is my fave so far. I still believe preamp selection is crucial for a good SET system.

Hello all,

The VT25 is the
equivalent to the 10 which is good for about 1.6 watts according to its 1930's data sheet. Its close enough to a 45 IMO which is good for 2 watts. "I was looking at the globe one which I guess doesn't have the Thoriated filament" which is less power out!

I like 300B's I have a close friend that uses them for 7 watts with his La Scala's which use a DIY ALK crossover he also uses Western Electric 300B's and likes them very much!

As for a preamp needed I disagree.

I have a 572-10/811-10 SET amp making 10 watts with 500 millivolt sensitivity for full power used with modified Forte's. I drive my mono block amps CD direct from my variable outs from a Sony X77ES player which can drive the amps to clipping at about 2/3 plus or so depending on the recording just fine. I have no need for additional gain, I could use a linestage if I want to but I find that they get in the way for me! Its an additional gain stage or gain stages in the signal path which depending on the preamp can compress music dynamics as well lower a systems resolve, I have a huge soundscape as well as striking transparency with very,very good dynamics from just two voltage gain stages in the system.

But I'm open minded to trying a preamp out and I'm hoping SWL will be able to make a get together at my place on March 22nd to try out his Peach II as it has been a while since I have had a preamp in my system and he will be listening to a very powerful SET amp as well. It should be interesting. I might point out that I to am a major DIY designer and if I like what I hear I guess I'd have to consider designing a line stage but it would have to have considerable performance for me to consider designing and building one.

SET12

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Hostorically where does the VT25 fit in?I have seen a couple VT25 amps lately on audiogon lately. The 300B is my fave so far. I still believe preamp selection is crucial for a good SET system.

Hello all,

The VT25 is the
equivalent to the 10 which is good for about 1.6 watts according to its 1930's data sheet. Its close enough to a 45 IMO which is good for 2 watts. "I was looking at the globe one which I guess doesn't have the Thoriated filament" which is less power out!

I like 300B's I have a close friend that uses them for 7 watts with his La Scala's which use a DIY ALK crossover he also uses Western Electric 300B's and likes them very much!

As for a preamp needed I disagree.

I have a 572-10/811-10 SET amp making 10 watts with 500 millivolt sensitivity for full power used with modified Forte's. I drive my mono block amps CD direct from my variable outs from a Sony X77ES player which can drive the amps to clipping at about 2/3 plus or so depending on the recording just fine. I have no need for additional gain, I could use a linestage if I want to but I find that they get in the way for me! Its an additional gain stage or gain stages in the signal path which depending on the preamp can compress music dynamics as well lower a systems resolve, I have a huge soundscape as well as striking transparency with very,very good dynamics from just two voltage gain stages in the system.

But I'm open minded to trying a preamp out and I'm hoping SWL will be able to make a get together at my place on March 22nd to try out his Peach II as it has been a while since I have had a preamp in my system and he will be listening to a very powerful SET amp as well. It should be interesting. I might point out that I to am a major DIY designer and if I like what I hear I guess I'd have to consider designing a line stage but it would have to have considerable performance for me to consider designing and building one.

SET12

The set amps I had sounded good with some preamps but when I added the high gain George Wright preamp I found the sound was vastly improved. Is it possible that this was due to the 6SN7 tubes in the pre and not the high gain? I hadn't that about this before but the change was drastic. I'd love to hear an 811 based SET.

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Dean.

"If and when I go back to tubes, it will be 300B with a constant impedance filter."

You up to elaborating on that a little more?..........like what amp are you thinking of and what filter?

jc

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Hostorically where does the VT25 fit in?I have seen a couple VT25 amps lately on audiogon lately. The 300B is my fave so far. I still believe preamp selection is crucial for a good SET system.

Hello all,

The VT25 is the
equivalent to the 10 which is good for about 1.6 watts according to its 1930's data sheet. Its close enough to a 45 IMO which is good for 2 watts. "I was looking at the globe one which I guess doesn't have the Thoriated filament" which is less power out!

I like 300B's I have a close friend that uses them for 7 watts with his La Scala's which use a DIY ALK crossover he also uses Western Electric 300B's and likes them very much!

As for a preamp needed I disagree.

I have a 572-10/811-10 SET amp making 10 watts with 500 millivolt sensitivity for full power used with modified Forte's. I drive my mono block amps CD direct from my variable outs from a Sony X77ES player which can drive the amps to clipping at about 2/3 plus or so depending on the recording just fine. I have no need for additional gain, I could use a linestage if I want to but I find that they get in the way for me! Its an additional gain stage or gain stages in the signal path which depending on the preamp can compress music dynamics as well lower a systems resolve, I have a huge soundscape as well as striking transparency with very,very good dynamics from just two voltage gain stages in the system.

But I'm open minded to trying a preamp out and I'm hoping SWL will be able to make a get together at my place on March 22nd to try out his Peach II as it has been a while since I have had a preamp in my system and he will be listening to a very powerful SET amp as well. It should be interesting. I might point out that I to am a major DIY designer and if I like what I hear I guess I'd have to consider designing a line stage but it would have to have considerable performance for me to consider designing and building one.

SET12

The set amps I had sounded good with some preamps but when I added the high gain George Wright preamp I found the sound was vastly improved. Is it possible that this was due to the 6SN7 tubes in the pre and not the high gain? I hadn't that about this before but the change was drastic. I'd love to hear an 811 based SET.

Thank you Seti,

I have some experiance with 6SN7's several friends of mine own them a very fine sounding tube! Some of them don't like the 6SN7's microphonic tendencies but the tube is very transparent with 2 out of 3 people I know loving them. They are using Cary line stages.

I think the secret to getting by without a line stage is having
sufficient gain in a power amp and having a strong full bodied CD player.

With gain if your set up at a 2 volt input
sensitivity and I'm at 500 milli volts or .5 volts in thats 12 db difference, Theres the line stage gain!

Most of my listening is midway on my Sonys volume control this puts its output
impedance at 5k but its not an issue with short cables and a 500K input impedance of my poweramps.

Now think of this if your using a preamp with an audio taper volume control and its at a midway setting your thinking I'm at the halfway mark I must be using half of the signal coming in!

No your actually using 20% of the signal coming in! Thats 14 db
attenuation of the original signal! Which means your close to what is called unity gain meaning the signal coming in is equal to the signal coming out! And thats the part that kills me!

Some people need the flexibility in their systems I guess. And some would argue that they need the life that a line stage brings. And that maybe so for them but its not my in my case and I just as soon put the funds into the front end source componets that can drive direct the difference is not subtle for some as well!

As for the 811 the tube is very nice especially its glow one of the prettiest around! with its thoriated yellow filament glow! Its sound is very full and musical.

But the 572 is another story! Its not as pretty to look at but its job is to sing and sing it does! Since the addition of Bottle Heads C4S current source to my 6EM7 driver tube for my SET amp the differences have become greater between the 811 and the 572 with the 572 hands down the clear winner in my book! The tubes designers ment it to compete with the 845 or the 211 and I think they really have suceeded even though it is not as popular as they have hoped it would be. Its smaller than the 811 or the 211/845 tubes and I think that had an impact. but it has the capacity to make 40 watts on a 1000 volt B+ and I have as of late been thinking of raising the amps power output even though it not necessarily needed but on extremely demanding peaks its useful. The 572 has nauce capacity that the 811 only hints at. And right now they are directly inter changeable.

If you live in the midwest and you'd like a listen give me a PM

SET12

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