Lynxo323 wrote:
Quote:
10k Should take the bias to 9v (in theory and Tina-ti). We are interested in a good swing, so close to half is best.
I re-wired my unit.
P2P now on pcb.
Heater VReg. set to 12.3V. (input has 2200uF||0.1uF, output has 470uF)
+B is 18V (2200uF||0.1uF)
P1 is 10K
Added 100R to FET Gate
Removed 100K pot on input
pc sound card output to unit. without music playing, I hear faint white noise sound. did not hear this in p2p version.
the output of the FET at source or Test Point measures 12V. total current draw is about 430mA.
sounds very raspy. any ideas?
Ok, there are a couple of things to try,
First, make sure your sound card is ok, and try another source. I have, unfortunately, hooked up one of my amps backward and fried my sound card. The initial turn on surge (if hooked up wrong) is enough to damage the opamp in the sound card.
Next, if your computer has a three prong plug, use a cheater, or sacrifice an old EIC cord and remove the ground plug, With the PC grounded and the amp not, there is a chance for ground loop.
If that is all good, and you are using a 12au7 tube, try removing the bypass caps (c2). This action will lower the gain a bit. If all else fails try increasing the value of P1 in increments of 1000 ohms until you have a decent sound.