SET vs OTL

P.P.S

The French company might have been Jadis or Audioaero, both of which build good amps.

BTW, both on OTLs and on SETs low capacitance speaker cables are clearly preferable, think Shindo or similar

I have used a Graaf Gm20 for about 10 years before upgrading to a Wavac Ec300b some 10 years ago. In short, there is no going back: while the Graaf had twice the stated output power, making that power useful was challenging: using autoformers to ideally match speaker impedance as well as pretty regular rebiasing, neither of which is required by the Wavac. If anything, the Wavac is faster than the Graaf despite its transformers and the bass is substantially more solid. Botj amps are classics in their line of design

My speakers are Duevel Bella Lunas with 6 ohms impedance and 93db efficiency. To run the Graaf I used Paul Speltz Autoformers to step them up. I used Bybee Golden Goddess Speaker Bullets in both instances and Auditorium23 speaker cable. 

@audition_audio,

the higher the impedance, the better for OTLs. On the Graaf, the autoformers gave a marked improvement to going without. Old speakers used to be 16 ohms which would be ideal for OTls, however most modern designs have impedance dips under 4 Ohms with which OTLs have a hard time The Duevels in this regard are relatively benign and an easy load.

P.S. Push pull designs and SETs are very different, The overtone characteristics of SETs make for a much more nuanced and colourful sound. The differences tend to be most pronounced via horn designs. Obviously pp is higher output.

👌 on the DeVores!

@pani,

touché: your description is dead-on. That said all but the best SETs suffer from their transformers: it usually sounds like there has been a cushion put on the music; yes, the flow is there but it somewhat sounds muffled and damped. Other than my Wavac I have only heard Kondo, top end Audionote and Reimyo not severely affected by this problem and none of them are cheap. Transformer design is the real differentiating factors on SETs.

@atmasphere,

there were two factors that made me move from Graaf +Autoformers to Wavac:
Comparing bass performance, the Wavac was more tuneful and ‘dry’ whereas the Graaf was ‘fruity’ and more wallowing
In terms of attack on individual instruments the Wavac got woodwinds and cello right in terms of ‘reediness’, bow attack and reverb whereas the Graaf sounded beautiful but blooming and ebbing off.
The latter is probably why the Wavac seemed to me the faster amp.
Finally the Wavac can be better finetuned by changing rectifier and power tubes, choices for the Graaf were much more limited.
Thanks for your comments, I find them highly educational

@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