previous: Rebel420 i still recommend pulling it out, y... -- 4/24/2000 7:43 PM

Re: Measuring B+ on 12AX7 - before or after plate load resistor?

4/24/2000 8:11 PM

beto

Re: Measuring B+ on 12AX7 - before or after plate load resistor? I must be doing something wrong: I turned on the amp and let it warm up. Then I took the red probe on my multimeter and touched it to pin6 directly on the 12AX7 tube. Then I took my black probe and touched it to the chassis. It measured 85 volts. On Pin 1 it measured 105 volts. This seems way low. So either I am a complete meathead, or this is one reason this amp is so mushy with no headroom. If this means anything, this is V1, the tube that is connected to the inputs. One pair of inputs goes into the 85 volt stage and the other pair go into the 105 volt stage. Not surprisingly, the 105 volt inputs are much louder than the other pair.     IF I am measuring correctly, how to I up the voltages? Drop the plate load resister values down? Gees, may amp is giving me a college education.   Thanks

 

Replies:

Doc Many preamps are run with plate to ... -- 4/24/2000 8:47 PM jason Have you done as Rebel suggested an... -- 4/24/2000 8:48 PM