26 Nov '10 23:031 edit

Originally posted by RevRSleeker
Very nice indeed...did the 'thump' sound eminate soley from the speakers ? Certainly an oscillation of some kind, no doubt you got it checked even if it appeared to have settled. Turning on a self build valve amp for the first time is unnerving at best lol.
http://www.stereophile.com/tubepoweramps/805quad/
I have the Quad II and ESL speakers pictured.

Thump never went away and it didn't matter what the volume level was set. The way you turn on a self made amp for the first time is to get yourself a variac, which allows you to adjust the incoming AC down to a volt or so, up to past normal. So you start out at say 10 volts and see if there is smoke. If there is, the voltage is low enough to stop it from burning itself out. Sometimes you have direct AC shorts and don't see it till you power up. You can hear a low voltage short, the variac complains! Go back to square one, find and fix the short and then run the voltage up higher till the tubes glow and you see it running. The best way to monitor things is to get an AC ammeter in line with the power leads ( the output of the variac) and just watch the meter. If at ten volts AC in you are getting 10 amps, you know for sure you are in trouble but you won't damage much at that voltage. Fix the short, fire it up again hopefully to be rewarded with a normal looking current draw, then run the voltage up, watching the ammeter, like 100 watt amp running from 110 volts AC would be 1 amp plus inefficiencies in the circuitry. So maybe running full power you draw 2 amps, which would be an overall efficiency of 50%, that would be ok. So you see you are running normal currents and everything is fine, then turn stuff off, take out the variac and run power straight to the amp and it should be fine from then on.

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