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RE: GRAAF GM 200

Johnty,

I have to disagree with this... the GM200, when the bias is set correctly, does not run particularly hot, even with all of those tubes. I did some temperature measurements directly on the power tubes themselves and they were around 60-65 degrees Celsius, which is really not that hot for a 200W power amp - even solid state amps of this power will start to get to those figures.

The major determining factor in heat dissipation is the bias setting. Graff originally specified that they get set to quite a high bias current to wring the utmost audio performance out of them, using highly matched power tubes. Graff has since recommended that the bias current be reduced quite a bit for two reasons:
1) it makes very little difference to the sound of these amps
2) 16 x 2 sets of very closely matched power tubes are pretty difficult to get hold of these days


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  • RE: GRAAF GM 200 - Mark S Allen 22:15:55 08/14/15 (0)

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