Speaker Suggestions for 300b SET Amp

@stereo5 , @jond 

Gents - Are Audio Note speakers available on-line or only brick & mortar?  Thanks.

@ghosthouse pretty sure just brick and mortar but they pop up used on here from time to time.

I am sick and tired of someone trying to promote his own amp by demoting other type if amps, specially singleended transform coupled low power high quality amps.
Eg.  Transformless push pull amps produces extream high odd order distortions and extreamly sensitive to power supply quality,while he declaires single ended amp has high ODD order distortion,which is false statement at best.

I have to chime in on this one, just to set the record straight. The text after 'Eg.' is false.

Transformerless push-pull amps (of which our are an example) do not produce 'extreme odd ordered harmonics', and in our case are actually less sensitive to power supply quality as opposed to single-ended circuits. This fact about balanced circuits is well known. This is easy to demonstrate- we can actually run one of our amps without any filter caps in the power supply of the output section and it will actually work fairly well. The topology does cancel even orders due to cancellation in the output (in our case, the cancellation occurs throughout the amp).

Because our amps are fully differential, like any fully differential amp, the primary distortion component will be the 3rd harmonic.

With single-ended circuits (tube or solid state) the primary distortion will be the 2nd harmonic.

The 2nd, 3rd and 4th harmonics are considered musical by the human ear and contribute to 'warmth', 'fulllness', 'bloom' and so on. The higher ordered (5th and above) do not. The 7th contributes to a metallic quality. The ear is far less sensitive to the lower orders. so if you are pragmatic, you design the amp so that higher ordered harmonic generation is avoided, while doing what you can to suppress the lower orders, as long as that does not hurt that lack of higher ordered content.

Our amps do generate higher ordered harmonics like any other amp does, but at a level that tends to be considerably lower than in a single-ended circuit. We suppressed the higher orders by simply keeping the signal path simple (one gain stage) and by separating the power supplies to avoid intermodulations. The idea was to get low distortion without feedback; at full power one of our amps properly set up will make about 0.5% THD, while IMD (which is highly audible) is less than 0.02% at full power. That's not bad for a zero feedback amp. 

What I have said about SETs making odd ordered content is true (although I didn't mention anything about that on this thread), but I did not say that this is **all** they do...  I've often pointed out that the distortion of SETs is primarily the 2nd harmonic, and that if you use them at low power their distortion decreases to unmeasurable (and also inaudible).

This is where the 'inner detail' of SETs derives as distortion can mask detail (and many push-pull amps actually have increased distortion at lower power levels). For this reason, you generally want a speaker for an SET that is efficient enough that the amp never makes over about 20-25% of full power; in that way you avoid the odd ordered harmonics that will show up at power levels above that (as well as higher ordered even harmonics, both of which are used by the ear to sense sound pressure). This is to maximize transparency.

When that guideline is violated and the speaker is of insufficient efficiency, the SET will appear to be very 'dynamic'. But its a false dynamic, simply occuring out of how the distortion interacts with our physiology, and transparency will suffer.

I prefer that any audio system sound like music, and that is how you go about it with SETs. If the speaker lacks the efficiency, the amp will fall right flat on its face. I have this idea that you want to honor your amplifier investment dollar as best as possible so the amp you bought can strut its stuff. I do apologize if anyone thinks that this sort of advice is intended to denigrate SETs, its not. Its just statement of fact so you can get the best out of the amp. 

One aspect missing from this type of discussion (though no fault of atmasphere) is input from talented builders of successful SET amplifiers.  Not to argue or necessarily disagree with atmasphere but to on an equal footing (As highly competent builders/designers) explain why SET can sound so "right" and pure. 

This forum lacks this SET manufacturer perspective so as a result SET attributes are left to satisfied/happy owners (such as myself) to share their listening experiences.  I can simply share what I hear versus other topologies (-subjective) but am not qualified to debate on engineering or technical grounds . 

I wish The builder of my Coincident or the builders of for example Viva,Audion,Triode Corp, Tron, Wavelength and many others would post here and explain why SET are so capable with the right speakers. For what ever reason this doesn't occur. 
Charles 

I've built 2 SET kits and am working on another that's not a kit--ground up build.  I'm not an engineer and I'm still relatively new to this, but I think the SET toplogy also has another thing going for it--the signal doesn't have to crossover. 

I think in a traditional push/pull design the signal has to be split into positive and negative because you have several tubes running one channel.  That split has to be put back into one, which leads to a distortion (arguably).  In my mind, I liken it to how digital breaks stuff up only to put it back together into an analog whole later on before it hits the listener.

The allure of SET is that it's simple, cleaner and more straightforward--arguably.  That's supposed to result in a pureness that listeners like.  

I cannot comment on whether SET v. PP produces more or less even/odd harmonics.