SET vs OTL

Aarif,

It is true that there are studies indicating that a 'natural spectrum' of harmonics - which includes even-ordered components - sounds better/more natural to our sound processing systems (brains) than the same signal with only the odd-ordered components - despite the fact that THD is obviously higher in the former case.

Re: "As for SETs, the problem is (correct me pls) that even order dynamics can be accentuated by the tube's interaction with the transformer, making the sound more lush/"pleasing" but less natural/neutral." I've never heard that.

I would say that good SETs on the appropriate speakers do *not* sound 'lush' - ever. They sound crystal-clear, just right, completely natural, etc. That's how a 45 sounds, for example. Or a good 211. Other tubes probably do have some intrinsic 'character'.

Of course, good push-pull OTL tube amps sound a lot like that too. They sound even leaner, or 'whitish', as I would describe it.

What's closer to reality might be impossible to say.

The harmonic structure of a good OTL will be the 3rd harmonic, which the only harmonic that the ear considers musical and thus does not object to. SETs have that and the 2nd harmonic.

Paul, what happens with these harmonics is not that they are not audible! It is that they are not **objectionable**. When GE did their experiments in this regard, they found that people will not *object* to nearly 40% of even-ordered content. That is not the same as 'you can't hear it', you certainly can, and audiophiles have terms for the presence of even orders (just like they do for odd orders) in small amounts. From small amounts to larger amounts: Warm, lush, rich, bloom, thick, murky, woolly, muddy. FWIW these terms refer to even ordered harmonics that are in greater supply than the terms that apply to odd ordered harmonics: hard, harsh, brittle, clinical, etc., where the odd-ordered enhancement may well be less than .001%.

With regards to the phase splitter- some OTLs that is an issue, others it is not. In our amps, there is no 'phase splitter' as a stand-alone circuit- that function is integrated into the single gain stage that exists in our amps.

Most SETs have more than one stage of gain- its my contention that if they were able to have only one, they would be a lot closer to the neutrality that our amps routinely express. I've got a 45 SET and a 2A3 SET- they sound great within their dynamic limitations, but they also sound veiled compared even to amps we were making 10 years ago, despite using the best parts available. As far as I have been able to experience, transformers always limit bandwidth, add distortion and rob the music of detail.

Given the example of the speaker above, I would recommend something with more power than the Graaf, or any SET for that matter. The speaker is simply too inefficient for an SET to strut its stuff. You would really need at least 10 more db for that. There are OTLs that can easily drive that load though. IMO 15 watts would not be enough power, unless you listen near-field and at moderate volumes.

I do listen near-field and at moderate volumes and am looking to maximise neutrality.
It seems your advice Atmasphere would be to either get an SET with a single gain stage (who makes these pls??), or an OTL.
Thanks!

... and here is the famous SET that generates 150w per channel and a bandwidth of 20Hz-100,000 kHz. Too bad it costs $350,000...
The Wavac SH-833 :
http://stereophile.com/tubepoweramps/704wavac/