basher

Hi i've just bought a dsl401 sounds amazing but i thought i would check bias so pulled out chasis bias read at pins on amp .620Mv according to various sources like marshall they recommend more like 1.3v so i rebiased to 950 at pins so was my bias really the far out and still net set higher any ideas also the stock tubes are in but amp sounds great they have jj tesla on power tubes any ideas what works well when i need to revalve it regards all great forum

JohnH

If its post august 2003, they re-designed the bias circuitry and the newer ones are biased in the factory at about 0.55 to 0.6V, as mine was. I get a slightly better, warmer sound at 0.8V, which is where I set mine. 1.375 v was actually hotter then the spec limits for EL84 tubes.

John

JohnH

Further on above - I made some tests recording the sound of the amp with a range of bias settings. This is the same few licks, stepping the bias in the order 0.9V, 0.75V, 0.6V 0.45V and 0.3V.

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i was playing as consistently as I could, on the OD1 channel - and you can hear the sound diminish at the lower settings.

The amp was miced from a seperate cab for the recordings, since it's own speaker would not have sounded good with all the amp guts hanging out to tweak the bias!

John

basher

Wow!!! thanks for replies i thought it was odd amp sounded good at .600mv when manufacturer recomended about 1.300v it was manufactered about 4 months ago i think i'll set it back to maybe .800mv if i dont like i'll put it back to originals settings .600mv many thanks all this amp is a one to keep been well impressed with it so far...