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
Anyone.But i strong suggest you to find and try the Modena monoblock.Or place two Gm 20 in biamp connection
Yes i have had the GM 200 OTL for about 2,5 years and ive heard the GM 20 as well , i sold it off after i listened 3 months to them on my new speakers with a diamond high frequency cone .
The smooth topend what i had with the graaf tube amp and i was missing with SS was merely a tweeter problem in my case , my highs are almost as sweet with ss as with tubes (zanden exepted ).
Further very good amps, spatial/dynamic as well , i sold them merely because they need new tubes once in while , and with the 32 in the GM 200 it will not be chaep, the bass is a bitt more rounded than with the krells but also beatifull , i rank them in the top of poweramps
Replacing the entire set of 32 tubes on the GM200 costs an extremely reasonable 500 Euro for a matched set from the factory (you really want to order them from the factory as close matching is absolutely necessary). This is hardly expensive, especially when considering that these tubes have a 10,000 hour lifetime. With idle power consumption of about 1000w this is not an amp that you leave on all the time so, assuming that you use the amp for 2 hours a day, every day, the tubes will last for 14 years. Spare sets can be ordered from the new distributor, Audio Analog in Italy.

The capacitors are relatively cheap to replace but if you are worried about heat affecting the capacitors, use the tube covers that Graaf supplies. The amp is not quite as pretty with them on as it is with rows of exposed glowing tubes (although it remains a truly stunning looking amp) but Graaf is effectively doing the same thing as Porsche does with its Turbo cars - Porsche puts a thin dimpled aluminum heat shield in the 1" space between the exhaust and the very thin rear plastic bumper to stop the extremely hot exhaust from melting holes in the bumper). The tube covers protect the capacitors and transformers from heat damage in a similar way. In fact, in addition to the covers acting as a heat shield, air convection currents will pull in cold air into the bottom holes on the covers and hot air will exit through the top, cooling things down even further on the rest of the amp. A bit counter intuitive - you would think that putting the tube covers on would make things hotter but they don't.

My GM20 has just blown up for the second time this year, taking the driver of one of my Duevel Bella Lunas with it.

We're having some trouble fixing it and wondered if anyone has a service sheet with voltages and/or a circuit diagram?

I look forward to hearing from you, Zeb

PS Since it's spending more time being fixed than working these days I'm also interested in an inexpensive used amp that I could get for whilst it is being repaired. Ideally balanced, probably valve, maybe KT88s.