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I built the following circuit:
I tested the power supply voltages plugged it in and i could hear audio for about 1 second then it started to distort then it just started buzzing i think its the tube but i don't know what could have broken it. Any ideas?
Hi
Never yet seen 12V powering filament windings on any 12 series tube, the norm is 6.3V. Yes I know what the specs say but look through all your guitar tube amp designs, all are 6.3V.
Do your tubes still glow? If not it may be your filament windings that have blown.
You might want to register on Hoffman Amplifiers, Tube amplifier parts, tube amps, tubes and log into their forum to get their opinion. Bunch of tube guru's around on that one.
Cheers
Andrew
Make sure the grid leak bias resistor is actually 100k ohms. The grid leakage current across this resistor is what generates the required negative grid bias for the tube.
Now don't bust a vessel.There is no grid leakage current - and the grid resistor has no effect on anode current in any method of biasing.
There are essentially two methods:
1) You provide a negative voltage to the grid, and ground the cathode.
2) You connect the grid to ground via a resistor (as in this circuti), and place a resistor in the cathode. The voltage dropped across the cathode resistor is the negative bias voltage for the grid. This is called auto-biasing.
This circuit runs the valve absolutely flat out at all times, not good - and I've NEVER seen it done - or using a low signal triode as an output valve.
It's really, absolutely, terribly, horrible - don't consider it for a moment
Does anybody know of a really simple 12ax7 vacuum tube circuit?