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SET amp owners

I have had a number of OTL amplifier's here over the years, mainly for servicing and repair, mostly to repair, including those from Croft, Futterman, Berning and Graaf. All have a very direct sound, fast and clean, almost solid state in presentation, but ultimately they just do not have the musical and emotional involvement of a good SET amplifier. Good SET amplifiers just have the ability to draw you into the music with an emotional engagement unlike any other amplifier topology. From a circuit design point of view it is easy to understand why. Having said that, I have heard OTL's work well with Electrostatic loudspeakers because you only have one transformer between the valves (tubes) and the ESL drivers, so there is protection for the drivers incase of a fault, or a blown output valve (tube) in the amplifier. Normal valve amplifiers would have two transformers in the signal path between the output stage and the ESL driver units, so you can see the OTL has an advantage in this situation...

A little OTL story for you as its Christmas:
I remember the good old days of the Heathrow Show when I was exhibiting with Avantgarde Acoustic at the Penta/Ramada Hotel. The show was over booked so the organisers hired the Park Inn Hotel opposite. At that time I was responsible for servicing/repairing the Audio Analogue, Unison Research, Monrio, Beard and Graaf range for the UK distributor UKD. UKD had a nice room in the Park Inn hotel and when I went over to see them I couldn't help noticing there was no sound in the room plus there was a horrible smell. I soon realised why. UKD were showing 2 Graaf GM20 OTL amplifiers mono'ed to drive a pair of the top Diapason Adamantes loudspeakers. Unfortunately both OTL amps had failed and sent a shed load of DC down the speaker cables which in turn melted the voice coils in the Adamantes, rendering them useless. Replacement amplifiers and speakers were used to get music back in the room later that day, but thankfully the amplifiers were shipped back to Italy after the show so I didn't have to repair them. I suspect the GM 20s would have been a little "messi" inside... :)
 
Some 14 years or so ago I owned a pair of Cary CAD 572SE mono power amps, paired with Leema Xavier speakers.

KsdVAB7.jpeg


Full story on Hifi Pig....
https://www.hifipig.com/cary-audio-design-572se-monoblocs/

I wish I'd kept them longer, they'd have made a fascinating pairing with the MBL speakers I got a couple of years later.
 
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My experence of otl amplifiers is as described above, a great very 'direct' sound but coupled with (varing ) lack of real subtle detail depending on the amp
The one exception was a se otl my mate built using a single stc 13e1 per channel that was really nice, my experence is parallel valves are to be avoided.

I'm currently listening via 1930s globe px4 valves driven by cosser 41 mhl mesh plates also from the 30s through tribute amorphous txs.
 
jandl100 said:
Some 14 years or so ago I owned a pair of Cary CAD 572SE mono power amps, paired with Leema Xavier speakers.

KsdVAB7.jpeg


Full story on Hifi Pig....
https://www.hifipig.com/cary-audio-design-572se-monoblocs/

I wish I'd kept them longer, they'd have made a fascinating pairing with the MBL speakers I got a couple of years later.
Click to expand...

I listened to these monoblocs a few years ago with Diapason Adamantes II and I still remember that wonderful, emotional hearing, natural and superlative timbre. One of the best experiences I've had in this hobby. Together with an Audiomeca Mephisto CD player.
 
Some great jazz with Trafomatic Elysium 250 TL 70w and Cessaro Zeta heard over the weekend at friend's place in Holland




 
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