Summary: Can't agree with the others who have reviewed here enough on the sound quality, which is extremely frustrating, since my amp has been with the engineer as much as it has been at home! Even though I use a mains conditioner and good quality cables etc, and the source and speakers are apparently well matched, it doesn't go more than 30 hours of listening before either a tube or a fuse has blown. Bias is all good and every time it goes back it is thoroughly checked and passes all the tests. I just wish it didn't sound so sweet, or I would send it back for my money back, but when it sings, it really sings!! Hoping that the engineer will find a reason for the poor reliability this time around, so hopefully I can have the amp back where it belongs, and that it will stay there for longer next time. Everyone thinks I am made for not giving up after 4 valve and 2 fuse replacements in 5 months, but you have to really listen to this amp to understand this madness.
After finally getting the amp back the left channel immediately had an unacceptable amount of noise coming from it. Given up on this amp now, I like music, not silence whilst it is being fixed! If you want an amp that works look elsewhere. I don't know whetherthis is a valve amp issue or a Graaf issue, but this is my first and last valve amp, going back to transistors, at least you get to listen to music!!!
I have a GM200 and had the same problem until I changed the brand of PL504 tube being used. Use any European or Japanese manufactured tube and the amp will become as reliable as can be (I use GE or RCA). You may also want to lower the bias current (do the usual bias voltage measurement but set the bias to 65mV rather than 75mV).
Have to agree on the sound of the amp being world class - I have not heard any other amp that comes even remotely close to it.
Mark, Thanks but I don't have the Graaf anymore, I gave up on it. I am now looking for something comparable, as I have gone back to solid state, and after about a month of that have regretted it. I would love to find another GM100 and do as you suggest. Still searching!
Summary: I have used/ auditioned to many amps in 30 years period. In search for another power - amp , Graaf GM 100 become the alternative .I can say everything is excellent with that amp especially the unusually engineering .
Sweet midrange ,enough low frequency control ( with matching speakers) Bias is automatic so you dont have to play with anything exept the on/off button
Strengths: Sweet Sound , excellent build
Weaknesses: No cage for the front tubes,
Similar Products Used: Bryston 4B SST, Krell KAV 2250, Adcom ,Marantz ,Audio Analogue etc.
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Summary: Agree with Copland.
Takes 30 mins to get all the tubes into 100% mode. Once peak is reached, the power and dynamics is untouchable for a 100wpc amp. Sound is clean, transparent, and accurate. Stage is wide and high.
Best to use a shielded & gutsy mains power cable to deliver the current to the amp. Have yet to try the balanced input, but should raise the bar another notch. The 12 PL504 gives lots of heat, so best to leave it on top of rack with free air movement. This is not pure OTL, although uses OTL circuitary. The hybrid TL output coupled with transformers in my view is a better combination than pure OTL.
Strengths: Drives any speaker, but super sweet with Seas and Scan speak drivers.
Most high end preamps (tubes) would do a good job. Joules, Conrad, Graaf, VAC, VTL, and tubed Audio Research recommended.
Weaknesses: Its heavy.... and hots when running at its peak. Not suitable with children in room. Don't touch those 12x PL504 tubes, it need biasing every 6 months to keep it 100% accurate.
Similar Products Used: Cary monoblocks - no match
Audio Research monobloacks - no match
Solid state power amps - waste of time
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Rating Reviewed by: Daniel Copland(Unregistered User)
(Audio Enthusiast)
Review Date February 19, 2003
Overall Rating 5 of 5
Value Rating 5 of 5
Used product for 1 to 3 months
Visitors rate this review 4.64 of 5,
11.00 votes
Review 4 of 4
, from Australia
Price Paid:
$4000.00
from Used
Summary: Superb looking and sweet sounding power amp. Sounds so real. This must be the best power amp in the world. Vocal is warm, sound stage big, and brings out all the details, with great transparency.
If you find one in the market, buy it.
The finishing is Ferrari quality.
A fine breed with plenty of power and finesse.
This machine "flys" if the tubes are properly balanced.
This will turn the Musical Fidelity solid state amp into a toy.
Strengths: Sound great, powerful, and beautiful to look at. The OTL engineering and archtecture is out of this world.
All tubes.
Weaknesses: Absolutely no weakness.
Although it needs a man to lift it.
Make sure the tubes are balanced.
Similar Products Used: Musical Fidelity AC3.2
Musical Fidelity A300
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