SET vs OTL

@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. 

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.

As long as we are talking about bandwidth, power, detail, THD, we are not going to meet anywhere.

@pani  You may have noticed that I've been talking about *distortion signature*, which isn't the same as THD. You can hear these things very easily- quite literally its the difference you're describing. The reason bandwidth is important is that if the amp is using little or no feedback, bandwidth is needed to preserve phase relationships. Detail is a subjective idea so probably isn't measurable, but we do know that it can be masked by louder sounds as that is one of the human hearing perceptual rules.

Regarding the above list, every. single. one. of them mix single-ended circuits with balanced (PP) outputs. This results in that 5th harmonic prominence I mentioned earlier; IOW  you're making my point.


Its simply erroneous to assume that because all the amps you've heard don't bring home the bacon that *all* PP amps won't. There are detractors of class D amps that make the same mistake- because they heard several class D amps that sounded bad to them, the assumption is that all are bad. In this case I'm making the statement that you need to compare a fully differential circuit against one that is single ended only. You've not done that yet so far as I can see.

@atmasphere

Ralph, are you able to address my comparison between Graaf GM20 and Wavac EC300b in the same way? I am not yet convinced that the issues raised by @pani aren‘t valid in the same way.

For what it‘s worth I have yet to hear a balanced connection that can compete with an optimum single ended setup and I think Ken Shindo, JC Verdier and Keith Aschenbrenner would agree…

This thread is pleasantly devoid of polemics and addressing the core issues: thank you all, this is what the forum should be

Ralph, are you able to address my comparison between Graaf GM20 and Wavac EC300b in the same way? I am not yet convinced that the issues raised by @pani aren‘t valid in the same way.

From what I can see of the Graaf front end circuit, while it is balanced it must have a fairly low CMRR; this based on the lack of a constant current source. This causes the circuit to have higher offsets, lower gain and higher distortion. This in turn muddies the water as far as the distortion product goes (mostly due to the offsets generated, which cause more 2nd harmonic to be created)- you can't say its entirely cubic insofar as its non-linearities are concerned. So I can't really comment about the comparison and certainly can't contest your findings! But of course the Graaf is one of a number of OTLs out there.

Regarding the balanced connection thing, I always encourage people to look at whether the gear doing the balanced connection supports the balanced standard or not. The reason is simple: if you don't support the standard you don't accrue the benefits either! FWIW most high end audio manufacturers don't seem to support the standard. One of the more important aspects is that in balanced mode, neither the inverted or non-inverted signal references ground- they reference each other and ground is ignored. Its this bit that makes supporting the balanced standard a bit tricky- most of the time you need an output transformer to do the job. To do that right is expensive.We patented a means to get around that problem but that simply means we're the only one doing it our way, which is direct-coupled.