Single-ended triode amps

[acg]

Mani, here is a link to the Nelson Pass stuff you mentioned in your first post.

Anthony, here's the correct link: https://passlabs.com/press/single-ended-class.

Many years ago, I owned a Pass Labs Aleph 4 amp - 100Wpc solid-state single-ended. It was a very smooth-sounding amp, but didn't have enough 'kick' with the Quads electrostatics that I was using at the time, for my liking. I remember when I sold it on eBay. The buyer came over with his girlfriend to collect it and obviously wanted to listen to it first. I put on a track with female vocals and I could see massive smiles immediately on both their faces as soon as the track started. He looked at me and asked me why I was selling such a great-sounding amp.

Back to NP's article... I wonder if his thoughts are only really valid when considering a truly mass-less speaker cone. And perhaps this is why PP amps just tend to sound so much more dynamic than SE amps? High efficiency horns certainly help...

Mani.

Thanks for clarifying the link.

That bit of your quote I have put in bold I strongly disagree with...I do not think that dynamics or lack thereof are a particular characteristic of either topology (SE or PP)...it all comes down to implementation...but doesn't everything?

[manisandher]

Yeah, I probably should have added, "... in my experience, using the speakers I have to date."

Here's more from Nelson Pass (from Aleph 4 Manual):

"There has been a failure in the attempt to use specifications to characterize the subtleties of sonic performance.  Amplifiers with similar measurements are not equal, and products with higher power, wider bandwidth, and lower distortion do not necessarily sound better. Historically, that amplifier offering the most power, or the lowest IM distortion, or the lowest THD, or the highest slew rate, or the lowest noise, has not become a classic or even been more than a modest success.

For a long time there has been faith in the technical community that eventually some objective analysis would reconcile critical listener's subjective experience with laboratory measurement. Perhaps this will occur, but in the meantime, audiophiles largely reject bench specifications as an indicator of audio quality.  This is appropriate.  Appreciation of audio is a completely subjective human experience.  We should no more let numbers define audio quality than we would let chemical analysis be the arbiter of fine wines.   Measurements can provide a measure of insight, but are no substitute for human judgment.

As in art, classic audio components are the results of individual efforts and reflect a coherent underlying philosophy.  They make a subjective and an objective statement of quality which is meant to be appreciated.  It is essential that the circuitry of an audio component reflects a philosophy which address the subjective nature of its performance first and foremost.

Lacking an ability to completely characterize performance in an objective manner, we should take a step back from the resulting waveform and take into account the process by which it has been achieved.  The history of what has been done to the music is important and must be considered a part of the result. Everything that has been done to the signal is embedded in it, however subtly.
Experience correlating what sounds good to knowledge of component design yields some general guidelines as to what will sound good and what will not:

1)  Simplicity and a minimum number of components is a key element, and is well reflected in the quality of tube designs.  The fewer pieces in series with the signal path, the better.  This often true even if adding just one more gain stage will improve the measured specs.

2)  The characteristic of gain devices and their specific use is important.  Individual variations in performance between like devices is important, as are differences in topological usage.  All signal bearing devices contribute to the degradation, but there are some different characteristics are worth attention.  Low order nonlinearities are largely additive in quality, bringing false warmth and coloration, while abrupt high order nonlinearities are additive and subtractive, adding harshness while losing information.

3)  Maximum intrinsic linearity is desired.  This is the performance of the gain stages before feedback is applied.  Experience suggests that feedback is a subtractive process; it removes information from the signal.  In many older designs, poor intrinsic linearity has been corrected out by large application of feedback, resulting in loss of warmth, space, and detail.

High idle current, or bias, is very desirable as a means of maximizing linearity, and gives an effect which is not only easily measured, but easily demonstrated:  Take a Class A or other high bias amplifier and compare the sound with full bias and with bias reduced.  (Bias adjustment is easily accomplished, as virtually every amplifier has a bias adjustment pot, but it should be done very carefully).  As an experiment it has the virtue of only changing the bias and the expectations of the experimenter.

As the bias is reduced the perception of stage depth and ambiance will generally decrease. This perception of depth is influenced by the raw quantity of bias current.  If you continue to increase the bias current far beyond the operating point, it appears that improvements are made with bias currents which are much greater than the signal level.  Typically the levels involved in most critical listening are only a few watts, but an amplifier biased for ten times that amount will generally sound better than one biased for the few watts.

For this reason, designs which operate in what has been referred to as "pure" Class A are preferred because their bias currents are much larger than the signal most of the time.  As mentioned, preamp gain stages and the front ends of power amplifiers are routinely single ended "pure" Class A, and because the signal levels are at small fractions of a watt, the efficiency of the circuit is not important.

4)  Given the assumption that every process that we perform on the signal will be heard, the finest amplifiers must employ those processes which are most natural.  There is one element in the chain which we cannot alter or improve upon, and that is the air.  Air defines sound, and serves as a natural benchmark."


Mani.

[vrao]

To modify and continue:

"Total system distortion" would be the more appropriate.

Either the "entire system" needs to be under one thought process that takes into account all possible details. Or there needs to be parameters that can be adjusted along the chain, to counteract distortions.

[Jack]

Mani
I presume someone is using the Orelo's....?
With presumably more success?
You must be gutted that the sound was not up to the looks.
Were your current speakers salvaged from the wreck of the Nautilus? Horns can be so beautifully quirky in appearance & for me, so far, sonically superior....
(Still Swingin') Jack

[manisandher]

Hi Jack, I'm waiting to hear back from the new owner of the Orelos - I really hope they're working well in his room. Initially yes, I was gutted that I never got them to work in my room. But I'm so content now with my Anima speakers, that that is no longer an issue. The amount of money I lost in selling the Orelos is still hard to stomach though (no different to any other piece of hifi bought from new for the full retail retail price, of course). Oh well, that's life - live and learn...

Mani.

[Robert]

Mani,
       Cars, boats and Hi-Fi are not investments, but if you have the money it doesn't matter.

A wealthy retired HiFi retailer in NZ bought a 1 of 20 only made F1 McLaren sports car new for 2 million(1994). I thought gosh at last a car that should maintain its value. The guy only drove it twice as we don't have good roads and he was afraid of other drivers.

He sold the car to an American collector 6 years later and got $800,000 dollars. I guess if he kept it for 30 years it may have gone up in value.

Hoping this will help with your grief Mani!!!

Robert

[manisandher]

On one of my recent work trips to Germany, I was talking to a guy there who was telling me of a certain word in German, "schadenfreude", that means taking pleasure out of other people's misfortunes. We don't seem to have an exactly equivalent word in English - the best Google translate can come up with is 'malicious joy', which, from what the guy was telling me, misses the point somewhat. In any event, I'd like to think I don't have much 'schadenfreude' inside me.

Edit: Actually, I think "gloat" is the closest we have.

Of course, if the guy in NZ had kept the F1 it'd be worth many, many millions now. It must be one of the most expensive cars in the world right now. (Perhaps Peter's got one covered up in his garage?) If the opportunity ever arose (haha), it'd be a tough choice between that and an Alfa 33 Stradale, which I consider simply the most beautiful car ever made.

Mani.