amp bias question

[famous beagle]

Hey y'all,

How can you tell whether an amp is cathode biased (self biased) or fixed bias?

Thanks

 

[commanda]

At the risk of stating the obvious..................

By looking at the circuit.

Cathode bias will always have a resistor from the Cathode to ground. And a pull-down resistor from the Grid to ground.

Fixed bias will usually have the Cathode going straight to ground, and the grid pull-down resistor going to a negative supply rail.

Most amplifiers have been reverse engineered and their circuits posted on the web if you're proficient at getting results out of Google.

HTH

Amanda

 

[dementedchord]

hey beagle... whatcha got?? we'll look it up and tell you... first i'm assuming it's around 25 wts??? if ya want much more than that you need a bias source...

 

[famous beagle]

Thanks y'all.

Actually, I'm building my first amp --- a Marshall 18 watt clone (model 1974). I already know it's cathode biased (because I was told it was), but I just wanted to know how to determine that.

Thanks much!