Which Amp

[skeptic]

This statement ignores the fact that nearly all vacuum tube amplifiers exhibit significantly inferior performance by delivering an indistinct unclear sound and boomy colored bass with limited low end capability. (I exclude the relative handful of OTL tube amplifiers which have overcome the high output impedence exhibited by conventional designs using very high plate impedence output circuits with inefficient impedence matching transformers.) This is regarded by some audiophiles as a "warm" or "sweet" sound especially when connected to their shrill audiophile loudspeakers with limited low frequency output capability. The electrical shortcomings of these amplifiers may actually compensate for the shortcomings of the loudspeakers but that hardly justifies their other obvious limitations for example the fact that they begin to self destruct from the first second they are turned on.

The abillity of amplifiers with linear signal topology to perform up to their audible potential depends on the quality of the power supply and the nature of the load. Small amplifiers with relatively modest power supplies will sound indistinguishable from heftier designs with efficient easy to drive loads. On the other hand, the beefier designs will show their mettle when the loads are difficult and the program material is demanding. The good news it that for people more interested in the quality of the amplifier and not the quality of the brand cache, there are excellent units available at remarkably modest prices, a far cry from the market realities of 40 years ago.

The current specifications presently in use for describing and measuring amplifiers has been inherited fromt the 1930s when they showed the real differences between competing designs. They are completely obsolete and of almost no use today when comparing units. For example, frequency response is still measured at 1 watt with a resistive load. What of any practical use does that tell us?

If what you sad was true, you could pick practically any amplifier off the shelf at random and it wouldn't matter. IMO, sound systems should be engineered as a totality considering budget, type of music to be played through it, room acoustics, room size, and maximum undistorted sound levels required. Pick the loudspeakers first and then choose from amplifiers which can satisfy their drive requirements. You won't need an engineering degree to do that.

[DMK]

This statement ignores the fact that nearly all vacuum tube amplifiers exhibit significantly inferior performance by delivering an indistinct unclear sound and boomy colored bass with limited low end capability. (I exclude the relative handful of OTL tube amplifiers which have overcome the high output impedence exhibited by conventional designs using very high plate impedence output circuits with inefficient impedence matching transformers.) This is regarded by some audiophiles as a "warm" or "sweet" sound especially when connected to their shrill audiophile loudspeakers with limited low frequency output capability. The electrical shortcomings of these amplifiers may actually compensate for the shortcomings of the loudspeakers but that hardly justifies their other obvious limitations for example the fact that they begin to self destruct from the first second they are turned on.

The abillity of amplifiers with linear signal topology to perform up to their audible potential depends on the quality of the power supply and the nature of the load. Small amplifiers with relatively modest power supplies will sound indistinguishable from heftier designs with efficient easy to drive loads. On the other hand, the beefier designs will show their mettle when the loads are difficult and the program material is demanding. The good news it that for people more interested in the quality of the amplifier and not the quality of the brand cache, there are excellent units available at remarkably modest prices, a far cry from the market realities of 40 years ago.

The current specifications presently in use for describing and measuring amplifiers has been inherited fromt the 1930s when they showed the real differences between competing designs. They are completely obsolete and of almost no use today when comparing units. For example, frequency response is still measured at 1 watt with a resistive load. What of any practical use does that tell us?

If what you sad was true, you could pick practically any amplifier off the shelf at random and it wouldn't matter. IMO, sound systems should be engineered as a totality considering budget, type of music to be played through it, room acoustics, room size, and maximum undistorted sound levels required. Pick the loudspeakers first and then choose from amplifiers which can satisfy their drive requirements. You won't need an engineering degree to do that.

If you're responding to me, my statements ignore the "fact" you began with because I've never found it to be a fact. I've found tube amps outperform solid state with ease, if all we're talking about is the resultant sound and not the technical or longevity or convenience problems. If you're hearing boomy bass and especially an unclear sound, you're listening to the wrong amps! My speakers could hardly be called "shrill". No tweeter! If anything, the highs are rolled off which is ok since I can't hear anything above probably 13 khz anyway.

But I'm glad you responded because it made me remember your post regarding SS amp sound where you wrote that you knew SS amps could sound different because when you swapped one out, you had to re-calibrate your equalizer. Could you refresh this for us and perhaps Mtrycrafts could respond?

[skeptic]

First of all DMK, I was responding to Rober Czar but I will be happy to discuss the recalibraton of my equalizer when I had to swap out my blown Dynakit Stereo 120 with the comparably powered (60wpc) Mosfet 120 I built in 1993. After more than 20 years of venerable service, the Dynaco was taken out by Prokifiev's Alexander Nevsky, track 5 The Battle on the Ice DG 419 603-2. The load was the relatively efficient but not necessarily easy to drive 4 ohm Teledyne AR9s with three additional Audax tweeters per channel in parallel. I can't say if my identical vinyl recording would have been so effective at blowing up that amplifier. The Mosfet was a kind of lineal decendent of the 120 designed by Klaus and Peterson, two very respected amplifier designers. Much to my amazement, a direct swapout of the amplifiers yielded a rather different sound. For other people who haven't read any of my postings about equalization and other matters, I want my sound system to reproduce the sound of acoustical instruments as exactly as I can remember them on as many of my recordings as possible and that I haven't found the kind of measurement equipment for audiophile use including noise generators, calibrated microphones, and spectrum analyzers useful in achieving that goal. So unfortunately, I have come to resort to a long period of trial and error trying to achieve one small incremental improvement at a time and sometimes going backwards. It took me about two years to get back to where I felt I had been. Can I be absuolutely sure that the end results are exactly the same? The obvious answer is NO.

Thanks for reminding me DMK. That experience alone was enough to convince me that all amplifiers do not sound the same.

[RGA]

Good tube amplifiers that I have heard don't sound warm or sweet. most new even cheap Tube amplifiers put out under 1% total harmonic distrotion across the complete audible bandwidth - including new Single ended topoplogies - and when it does happen to distort sounds better to the ear.

I would be happy to own either a SS or a Tube so long as it sounds good - and there are pretty good and bad examples of both.

[skeptic]

As an amplifier is strictly an electrical device performing strictly an electrical function, it ought to be possible for it to be judged strictly by electrical performance criteria. It's bad enough that manufacturers of other purely electrical devices such as cables have not developed specifications, measurements, performance criteria which demonstrate the differences between their products and that of their competitors describing their unique aspect but the fact that they haven't been researched and developed by amplifier manufacturers or in other research laboratories is inexcusable. Even if these criteria weren't understandable to the average non technical consumer or had so many aspects that there are often no clearcut winners and losers, they should at least be understandable to engineers. The meager exceptions are the half hearted and far from complete efforts to describe and measure transient intermodulation distortion in the 1970s and the qualifier that harmonic distortion be described as "up to and including rated power" in the 1960s. As a result, the market for audio amplifiers has degenerated into cultism. I don't think anybody would have forseen this decades ago.

While I don't agree with Rober Czar, I sympathize with him. You could take 20 amplifiers off the shelf and to look at their specifications, every one of them should sound identical. But they don't always and not only can't you predict what their differences will be by their specifications, even when you know that they sound different, there is no rational explanation as to why. Does it have to do with the way the power supplies interact with different loudspeakers? What are the other specifications we are missing. It's maddening. Will a $4,000 Bryston power amp outperform a $400 Panasonic receiver? The industry has no difinitive way to tell us. We are left to guess, conjecture, argue, and divide in to opposing camps. Cults. If an 8 watt SET has special electrical properties which mitigate its otherwise miserable performance by outperforming the competion substantially in some critical aspect as yet unknown, there ought to be a way to prove it. And this time you can't just blame the SET manufacturers, it's an entire industry that has been lazy and indifferent. Don't look for the answers from advertising hype either. If and when answers do come, they will start out in professional journals like AES or IEEE.

[RGA]

Will a $4,000 Bryston power amp outperform a $400 Panasonic receiver? The industry has no difinitive way to tell us. We are left to guess, conjecture, argue,

Well you could also listen - if you're in the DBT rigged and goes against Validity according to psychology then listening in the same manner you would normally listen is thrown away - I have done SBT's - thanks I'll take the Bryston. And hey I owuld be happy to take the 2k CDN bryston model over the 4kUS receiver.

[skeptic]

Even if what you say is true, because we don't understand why, there is no way to predict if we would get the same results with other loudspeakers. We also have no way to know if your preference is based on an objectively better performance or your personal preferences which might be exactly the opposite were other people doing the evaluation. This is the difference between science providing understanding and validating what we hear and cultism. Not only would objective standards by which to measure and evaluate perceived differences tell us why we perceive them differently, it would tell us how far we have to go before we reach the limit of what is possible and indicate for engineers the direction they have to go in. As it is, even for engineers, it's strictly hit or miss optimizing the parameters they do know about and leaving the rest to pure chance.

[CannondaleSuperVee]

Ok, i'll come to Rober Czars' defense and anyone that wants to try and take Richard Clarks amp comparison challange and win $10000.00 is able to try, you can find out about it on carsound.com in the forum under his column, search amp challage. I got in the middle of an agument about being able to hear the diffrence between a $200 sony and a $30000 krell and R C said that if I can tell the diffrence to bring both and win an easy $10K.

[rb122]

Ok, i'll come to Rober Czars' defense and anyone that wants to try and take Richard Clarks amp comparison challange and win $10000.00 is able to try, you can find out about it on carsound.com in the forum under his column, search amp challage. I got in the middle of an agument about being able to hear the diffrence between a $200 sony and a $30000 krell and R C said that if I can tell the diffrence to bring both and win an easy $10K.

The man claims that all amps sound alike, regardless of whether they are tubed or transistored. That's a very dangerous claim for someone who is offering to pay $10K. If he kept it to transistors, he might have something.

Recently, I had the displeasure of listening to a tubed amp that exhibits some of the characteristics mentioned by Skeptic in his above post. Simply by dialing in more negative feedback, the sound worsened considerably. I'll mention this challenge to the owner of the amp. I can't imagine anyone mistaking this amp for anything else.

[skeptic]

The improper use of negative feedback is not merely deleterious, it can be an outright disaster. It can send an amplifier into spontaneous oscillation. The people who have never looked at the complex equations describing negative feedback circuits let alone solved them are playing russian roulette with their designs if they try using it. You really have to look at the phase response as a function of frequency. It really requires a lot of skill to pull it off well. Many designs are probably ho hum in this respect realizing gains in some aspects of performance and losing some in others. I'm sure there is software for the really clever EEs to just plug in their numbers and let the CPU do the crunching. There is on the othe hand real risk in not using negative feedback. Not only is harmonic distortion considerably higher, possibly by a factor of ten times or more, and not only is bandwidth more limited but negative feedback also stabalizes performance so that gain remains constant and to a degree less dependant on tube condition.

Anybody who thinks all tube amplifiers sound great should hear my old HK A500. Specs said its frequency response extended out to something like 50 or 70 khz but it had a high end rolloff to my ears, it didn't have enough power, and it didn't sound clear enough. But in those days, so did most other amplifiers because they were all tubes.