Opinions on Graaf Amps

Just read your graaf post and I posted just before you about a year ago. My post also cited problems - take a look. My graaf also required replacement of the large capacitors (one or two as I recall), a power tube socket, a resistor, and one other thing I can not recall. However, after I purchased some Zeros - autotransformers - that stepped up the speaker input impedance - all problems went away and the sound improved dramatically. With the zeros in place, the amp had no problems for well over a year of steady use. Before I sold the amp, I had the tubes replaced and the unit fully checked out by an authorized Graaf service facility and was perfect.

My speakers are the Alon IVs with an impedance range from 8 to 3 ohms! I looked up your speakers and it looks like their impedance is 4 ohms. The amp specs say that it wants to push against no less than 8 ohms. So, I suspect that your amp may be working too hard - I recommend the autotransferms by Paul Speltz (you can search direct and there is a link on the atmasphere web page (they make OTLs also). As I understand it, OTLs are very sensitive to speaker impedance, and while tube amps (unlike ss amps) are also sensitive to speaker impedance, the lack of an output transformer makes the OTL design more vulnerable. My dealer (Stereo Unlimited in Walnut Creek, CA) knowingly and ignorantly sold me the $5K amp to drive my Alons (which they also sold me) - I do not do business with them any more.

Wonderful amplifier.

I have had the listening experence in Montreal hifi show this year. The combination of GM200 plus Bosendorfer loudspeaker VC7, and GM20 plus Bosendorfer VC2 are marvelous. Very good playback on piano and vocal. They actually hired live jazz group with female vocalist and a real Bosendorfer grand piano to do A/B comparison live!

More info can be found from link below:

http://www.enjoythemusic.com/montreal2004/rickbecker/page5.htm

I have heard enough praises of the Graaf GM20 and think it may be the time for me to physically listen to one or two (in bridged mode). I use several different loudspeakers including the high efficiency models like vintage JBL4333A difficult loading Quald ESL-57 and the modern moderate efficiency French Jean-Marie Reynaud Reference 25th Anniversary and Bosendorfer VC-7. I received a pair from the new US and Canada distributorfew weeks ago. After a few days burn in I listened the GM20 with my different loudspeakers. Switching to different loudspeakers didn't change the tonal character of the GM20, it is highly analytical yet very smooth, with very liquid mid to high and pin point localization of the sound sources. Those characters are very favorable to muscial reporduction and I like them very much. According to my experience with other high end amps, the merits are not only limited to Graaf GM20s; you can find these characters on most of the high end power amplifiers. What wonder me is I find ALL these elements perform at the same time through a samll output amplifier. What even shock me off is something which unique to the GM20s, I haven't heard that character very often before especially with all the other tonalities mentioned above from a single amplifier. Not so even on very powerful high end amps like the already very bass powerful Mark Levinson 33H. It is the power, authority and resolution in mid to low range in bass ( from app. 180 to 45Hz ). Quality and realistic bass in reproduced music becomes very rare and expensive nowaday, I expereince many super systems, including Wilson Grand Slamm, IRS and Genesis V and not many of them produced qulaity bass with speed, accuracy, resolution and QUANTITY that can move your emotion not only by the music but also by the air and vibration which is in pace with the music. I was shock by the first time I used a pair of mono bridged GM20 into my Jean-Marie Reynaud Reference 25th Anniversary speakers without hooking to my pair of highly modified Triad Gold Sub-woofers; a pair of 2 X 10" push pull highly modified very "musical sub-woofer", now I can listen to only the Jean-Marie Reynaud Reference 25th Anniversary and enjoy the sweetness, open, airly yet powerful, full range down to 25Hz bass and coherent musical experinece. I have no second thoughs after I change to the GM20s from a pair of Atma-Sphere OTL and very powerful Parasound JC-1. I am now free from hardware induced compromise and enjoying music like nothing before.

I have a set of Graafs GM20 (monoblocks) to drive the difficult Sonus Faber Eelcta Amator (first version, so without the passive radiator). This speaker especially goes down in Ohm in the lower frequencies and a single Stereo GM20, didn't pull it. But the monoblocks do!!!

I purchased a pair of Sonus Faber Guarneri's and have tested maybe 10 amps. I have kept the Graaf GM20 otl as my final choice. It is quiet, accurate, detailed warm.
I am listening to the system at low volumes in a 10x11 office so the mono route is not neccessary (but at louder volumes I find the bass control lags). This is an exceptional rare product that continues to fascinate me with musical enjoyment. I have ordered a GM200 for another system and will be recieving it soon, GRAAF makes products of high quality and refinement. Such products are becoming harder and harder to find in todays cluttered marketplace. I am glad I stumbled on this beauty.