SET vs OTL

The one thing that clearly differentiates an SET from any Push-Pull (OTL or not) is the crossover distortion which occurs due to splitting the wave and joining it back. Once I heard and lived with an SET, that distortion was so clearly audible in Push-pull that it was no more acceptable as "right". It is a fundamental compromise.

The sound without the crossover distortion is a very continuous flow like a inner tissue connecting the whole spectrum of music. It feels like a "one" sound. Whereas Push-pull just feels disconnected pieces playing together "in comparison". It is not a triode or tube thing. I have heard the same effect even in single ended solid state amps (Sugden, Valvet).

In real life all sounds are single ended hence it is recognisable as natural when that aspect is preserved. Surprising that no one points to this.

@atmasphere, your knowledge on design is at expert level so I wont talk about that.

Whether we call it crossover distortion or "push-pull special" distortion. I have heard the exact same distortion attribute when I compared:

1. Audionote SET to Leben push-pull
2. Ayon Crossfire II SET to Triton II push-pull
3. Trafomatic Experience SET to Traformatic 6550 pushpull
4. Wavac EC-300b SET to Canary audio 300b push pull
5. Border patrol 300b SET to Border patrol 300b push pull
6. Unison research Kt88 SET to CJ Premier KT88 amps
6. The list goes on...
All of them were side by side comparison with my own music.

In every case, the attribute of "oneness" is lost in the push-pull design. It is not a issue of richness of tone. One sounds chopped, the other sounds intact. When the ear catches it, it is unmistakable after that.

Unfortunately error of commission that push-pull introduces is never discussed with the appropriate light in the Hifi community. 

As long as we are talking about bandwidth, power, detail, THD, we are not going to meet anywhere. If there is an instrument which can measure this effect (apart from our ears), I don't know it. But I am surprised it is not measured. 

My exposure to OTL was only with the Tenor OTL75 which I owned for about 6 months. Lovely amplifier but surprisingly even with 75 watts it could not control my Tannoys' bottom end like a 10 watt Wavac 300b (which I owned just prior to the Tenor). The bass was loose. In my relatively small room it was an issue. The rest of the spectrum was deliciously to my taste. It still missed the cohesion of a Single ended amp though.

@atmasphere I have not heard your amps yet and also my exposure to differentially balanced amps is very limited hence I would eagerly wait to hear them out. I would be very happy if I can find the cohesion of single ended design in a powerful balanced push pull design

I have the Tannoy Turnberry SE

You are correct @atmasphere that Tenor had the better PRAT. But it did not control my speakers as well as the 10 watt Wavac. That was wierd. It also did not sound as illuminated from within as the Wavac. I have again noted this difference between typical SET vs Push-Pull amps. SETs illuminate the entire spectrum evenly (DHTs more, non DHT) but push-pull amps have a darkness to the presentation. Can't explain it well. That is also one reason SETs sound more vibrant & energetic compared to Push-Pulls.  

There is another quality that I have clearly noticed in all SETs vs Push-pull. And this is even in systems which are super efficient and made for SETs (single drivers, Audio note speakers etc). SETs sound like "they are here" whereas push-pull sound like "we are there". At any volume and with any speaker I have heard, this is another phenomenon that was consistent

Again, I do not know how to measure this or if there is any way to measure this. SETs simply sound more direct. Instruments and voices sounds realistic, as in small, focused, dense and direct. Just the way they sound in real world. This doesn't happen on any of the Push-Pulls. In fact this is the primary sonic difference I was trying to nail between the 2 topologies. A vast majority of the amps therefore do not sound like real thing. Even a large instrument like Cello, when bowed has a very direct and focused sound, like it is speaking to you. Only SETs get this directness. Is it because it just amplifies without any further "processing" ? May be. Whether it is measurable? I don't think so, I have never seen any amps having a measurement which talks about these characteristics.

I have heard SETs with negative feedback (Unison Research) and without (Audio note, wavac, trafomatic, Allnic). The directness is there regardless of feedback and output type. Feedback does make the sound more controlled, sometimes too controlled, affecting the flow. I prefer zero feedback every time.

How about an OTL SET ?

Berning makes a ZOTL SET on request. I know Berning is not strictly OTL but from what I understand the transformer is only there to filter some very high frequency noise riding the signal.