Help Biasing my Vox ac50 cph

[willyeti]

I am trying to learn how to bias my own amp and I was wondering what the Plate Current should be set to.

Details:
The amp is a Vox AC50 CPH and I just put 2 EL34 groove tubes in it.
here is the signal flow chart


I am new to this and don't really know what I am talking about so i probably sound like an idiot but if you could please help me it would be greatly appreciated.

[6267]

Do you know the plate voltage and primary impedance? That can help...I would guess starting around maximum negative and reducing toward 0 until crossover distortion is no longer detected. That's the "easy" way, but it's not always the best. It's a bit of reading, but head over to valve wizard (just google valve wizard, it'll come up quick) and read about pentode power stages. Much of the stuff over there builds on the triode stuff, so maybe start reading that. There's a lot to be said for just using your ears & other senses...the original designer already set the impedances & plate v, so the ideal current is going to be wherever plate volts intersects the load line.

[tubeswell]

Check out the Tube Amp FAQ here for how to bias

http://www.geofex.com/

You'll see that EL34s in Class AB1 take between 35-40mA plate current per tube

For the output transformer shunt method, you have to measure the voltage at the plate and divide it by the DC resistance on the relevant half of the OT primary that that tube is connected to, in order to get the idle plate current. The plate dissipation with be the plate voltage x the plate current. You want to be around 70% of the tubes maximum recommended plate dissipation for fixed bias amps.

BTW measuring high voltages is dangerous