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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

Showing 2 responses by atmasphere

atmasphere's avatar
atmasphere
11,640 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!
atmasphere's avatar
atmasphere
11,640 posts
 
Zebshaw, likely the problem you are having has more to do with the power tubes than the amp.

A simple way to get greater reliability out of the tubes is, if you have a new set, put them in the amp and run it in Standby for about 2 days, and the bias up the amp and run it with either no music or very quietly for another day. This will double the life of the tubes and you will be far less likely to get premature arc-over failure!

We make fully differential balanced OTLs FWIW.
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