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Opinions on Graaf Amps

Does anybody have any expereince with Graaf OTL amps? I'm especially interested in the little GM 20 but don't have a chance to listen to it where I live. Has anybody heard it? In my search for a new amp I have listened to the Carys (572s) and found them overall too bloomy. I don't like tube amps that try to sound like solid state (i.e., Audio Research or BAT) but I also don't want the tubes to color the sound too much. I've tried the Atma-Sphere S 30 which sounded terrific in my system, open, airy and very musical, but it just runs too hot. So now I am considering the Graaf or perhaps an Air Tight. Any thoughts would be appreciated.

My system:

Joule Electra LA 100 MK-III
Merlin VSM + BAM
Audiomeca Keops as transport and Audio Logic 2400 DAC
JPS Super + speaker cables, FX interconnects, and Power Cords

Many thanks,

Dr V
drv
fosse
47 posts
 
Does anybody have the instruction for how to mono-bridge the GM20? I have just recieved the kit, and can se how to bridge it innside from your page Theo, but how do you connect it to your preamplifier and speakers?
atmasphere's avatar
atmasphere
11,794 posts
 
Monostrapping any Circlotron-based OTL is an easy thing to do. The speaker terminals are placed in parallel and so are the inputs. This will usually more than double the output on smaller OTLs like the GM20 or the Atma-Sphere S-30 (which goes from 30 watt/ch into 8 ohms to 90 watts into 8 ohms, and runs a little cooler).

So: a 'Y' adaptor on the inputs and a couple of jumpers on the output terminals are all that you need. Just pay attention to phase on the outputs- get it wrong and the amp will make no power and be very hard on the power tubes!
fosse
47 posts
 
Thanks a lot Atmasphere.
fosse
47 posts
 
Got feedback from Graaf. There should be no jumpers between output terminals and no "Y"-adaptor on the input. Everything is taken care of by the internal mono-kit.
ken1967
24 posts
 
QUOTED from Theo

.....You also have to replace the large electrolytics resting on top of the amps every other year. They last for about 3-5000 hours. Better replace them in advance in the summertime, before the listning season begins.....

Are you sure? Because it is rather expensive and gard to live with if true. Many tube amp need not change of this during its whole life....
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