Opinions on Graaf Amps

I have had the GM20 for about 3 years now, and it has been back for repairs about 4 times. Each time the problem is the same, i.e. one chanel starts to hum and one of the capacitors needs to be changed.

My speakers are JM Lab Utopias.

Has anyone had this experience, and if so, is there a fix? Or do I just have a crappy unit?

None of the above letters seems to indicate any problems, so I'm wondering if there is something wrong with my set that needs to be fixed, apart from changing capacitors every year.

I'm very happy with the sound, but I also dont want to have to struggle with repairs every few months.

ANY help would be appreciated.

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!!!