Biasing a Peavey C30??

[nemp]

Do Peavey Classic 30s need biasing? How hard is this?

 

[John Phillips]

No. They're cathode (self) biased.

(well strictly, yes you could change the bias if you wanted to, but that would entail replacing the cathode resistor, and there is probably no point anyway - they seem to work reliably with most types of EL84s)

 

[Troy Baer]

Originally posted by unquiet
No. They're cathode (self) biased.

I used to think that too, until I looked at a schematic for one (http://www1.korksoft.com/~schem/newamps/peavey_classic30.pdf), which sure looks fixed bias to me. Am I reading it wrong?

 

[John Phillips]

OOPS! Yes, Troy is absolutely right. It's fixed bias.

I have worked on these amps too (admittedly as rarely as I can, they're a complete pain to get into), and I really was sure they were cathode-biased...

You could adjust it, although you'd have to change a fixed resistor (R63 or R64, which are the voltage-divider network for it).

I never have though - I've replaced tubes on these many times too. But that just proves what Randall Smith says, and I agree with - a well-designed amp (which I think the Peavey is, circuit-wise, even though I'm not impressed by the build quality) does not need adjustable bias. Looking at the circuit the bias appears to be -14V, which is quite a conservative (cool) setting at a plate voltage of 332V. I have certainly never had trouble with any type of tubes from the cheapest junk to NOS Mullards.

 

[JamesPeters]

Originally posted by unquiet

But that just proves what Randall Smith says, and I agree with - a well-designed amp (which I think the Peavey is, circuit-wise, even though I'm not impressed by the build quality) does not need adjustable bias.

As long as you don't mind crossover distortion, I agree with you. And FWIW, I'm not even being sarcastic...a lot of people don't realize how much of their amp's distortion is crossover distortion until they get it modded for a bias pot and have it adjusted.

When it comes to the Classic 30--I haven't heard one yet that hasn't sounded good enough to me the way it was.

 

[nemp]

So that means I have to bias it? When and how do I do this? What if I don't do it will I have problems?

 

[nemp]

Thanks John, and Troy. Glad to hear that as I don't know what the hell I'm doing when it comes to amp mantainence.

 

[aleclee]

Originally posted by CUTTER
I'm pretty sure most folks on here bro are biased AGAINST anythying Peavey!!!!!!!!!

Maybe most Peavey products but a lot of folks (myself included) have a soft spot in their hearts for teh Classic series.

 

[nemp]

Well its either Peavey C or a Crate TV 60. Help me decide