Remote Bias Pot & Oscilloscope Biasing

[The New Steve H]

Does it matter if I move the bias pot on my Bassman clone? I thought it might be nice to stick a couple of wires on it and put it in a place where it's convenient to turn it.

Also, is there any reason I can't use an oscilloscope to bias the amp? Seems like it would be pretty simple to fire it up, twang away, and twiddle the knob until the wave looks symmetrical.

[martin manning]

A case against 'scope biasing:
http://www.aikenamps.com/CrossoverNotchBiasing.html

A supporter of 'scope biasing:
http://www.duncanamps.com/technical/scopebias.html

You need a signal generator and a dummy load to use a 'scope.

There is no reason you can't relocate the bias pot to an accessible location. In my book the easiest method is to do that and put 1-Ohm 1% resistors from the power tube cathodes to ground, and install some test jacks. Use a DMM to measure the voltage across the resistors via the test jacks. The voltage you see will be the same numerical value as the cathode current in milliamps.

[selloutrr]

you can move the pot no worries
Twist the wires and run them away from other signal and power.

O'scope biasing works as well. some people like it some people talk shit to no end about it. but it does work. you don't play your guitar though you use a tone generator (sine wave). Look it up on the web for instructions on how to properly bias with a scope.

After you scope bias a few dozen times. You will probably find you get almost as good if not better (depending on your ability to fine tune with your ear and understanding of safe tube operating voltage) results with a bias probe and save a lot of time.

But yes both are fine to do.

[The New Steve H]

Thanks. I figured there might be some genius reason why these ideas were stupid.

In other news, I discovered that my last amp was humming because I used about fifty yards of filament supply wire instead of the recommended "as little as possible."