A 9 watts beats Passlabs, EAR and YBA ?

Over the weekend, I have listened extensively to the following four different amplifiers and I have decided once and for all that the SET 300B, no negative feedback is the way to go.
The four amplifiers are as follows:
Passlabs X150: very neutral, powerful yet the sound almost very sterile.
EAR 834: very musical, tube mid-range yet sound the least like live music.
YBA 2 High current, Double Transformers: very musical, soft and sound very enjoyable; yet again not like live music.
Audio Note kit one: This is a killer and provided the music is limited to vocals and chamber music. Very good mid-range with good attack and the best like live music; but not very much bass.
However, this listening session made me to want more bass with the SET.
Thinking about the Cary 805, deHavilland or Atma-sphere ?
Any comment ?
Please advice
Hi Eldartford, sure. All amplifiers have what is called Propagation Delay, which is the period of time that it takes a signal to propagate from input to output. This propagation is caused by the risetimes of various internal stages and is not 'the speed of light' which is a common misconception.

In fact the propagation delay of any audio amplifier can be easily measured on any decent oscilloscope.

The propagation delay is a constant; it is not a problem unless there is negative feedback. Lower frequencies that are fed back tend to arrive much closer to the actual time that they need to be there (although the propagation delay means that they will *always* be a little late). As frequency increases, this delay has a more profound effect, essentially introducing a ringing effect.

This ringing is easy to understand if you think about a positive-going pulse of short duration being applied to the input. The amplifier responds to it and the feedback applies an inverted version of the pulse at a lower amplitude back to the input. By this time the original pulse is either gone, or nearly ended. Now the amplifier has to amplify the negative-going pulse; this process goes on as a ringing phenomena that dies out, although wider-bandwidth amplifiers often have to have filters in the feedback network to prevent this phenomena from causing oscillation, particularly if the amplifier exhibits phase shift at higher frequencies!

The result is low-level odd-order harmonic generation, usually the 5th, 7th and 9th are the greatest concern. It does not take a lot- the human ear so sensitive to odd-ordered harmonics that hundredths of a percent will audible (as a hardness or harshness) when a band of frequencies is being amplified.

Conversely, the human ear does not object so much to even-ordered harmonics. These create 'warmth' and 'lushness' but are a coloration nonetheless. Audiophiles have words to describe harmonic distortions of both types.
odd ordered descriptive terms: hard, harsh, clinical, overly-detailed, chalky or chalky-white, brittle, etc.

terms for even-ordered harmonics:
warmth, bloom, lush, fat, muddy
-as distortion increases.
Thanks for the info. You are a font of knowledge!

I understand propogation delay and the need for compensation in the feedback loop to avoid oscillation. The part I don't get is where you say "The result is low-level odd-order harmonic generation". Why that?

Feedback is not necessarily a yes/no thing. The feedback signal can be limited to low frequencies where the propogation delay is insignificant, while the higher frequencies are "zero feedback".
Unfortunately, an SET will not have the drive of the EAR 890, unless you use a very unusual speaker with it's own set of problems. One must come to know one's own predilections.
Hello, Edlertford and Atmasphere,
Special thanks to Atmasphere for given us such detailed explanation on the distortion.
Somehow, choosing the right speakers is the most important thing and in this case; I slept with Maggie.
Maggie is my life now yet SET is my destiny.
You can say that we want to have the cake and eat that too; isn't that every man wants to do that way!
Let's get serious now, someone suggests we try the latest Pass Labs XA series which itself a single-end, class A; Triode or not, I don't know.
All I know trying them is expensive; I have already paid for the X150.
Know anyone who want to buy the X150, brand new, 10 hours of listening.
May be I should give the X150 hours to burn it, right?
See how the bugs bite now.
The following link certainly describe exactly what we are:


Go figure, bye
Anyone for more information on helping me?
May be a woman can solve the problem, or even more problems?
Hi, Eldartford, the idea that you can run zero feedback at some audio frequencies and then use feedback at low frequencies suggests to me a gain non-linearity that changes with frequency. So that would take some tinkering to make that work, to say the least. To my knowledge no-one does this, as the idea behind many amps that use feedback is the concept of 'constant voltage' wherein the amp is capable of constant voltage regardless of the load impedance.

Zero feedback amps do not behave this way for the most part, usually subscribing to a different idea wherein the amp makes 'constant power' with respect to the load.

These two ideas have been in conflict in audio for the last 50-60 years, resulting in the tube/transistor debate and the subjectivist/objectivist debate, plus the general idea of component matching.

Robertwolfee, the Pass Labs amplifier is class A, but it is not tube. However it is one of the best-sounding transistor amplifiers out there. At any rate you will need some power for the Maggies, so due to the power limitations of most SETs, you won't get them to be very practical with your speakers although I am sure they they would sound fine, just at very low volume levels.