Manual for Bias Tool

[Andy S.]

The guy I'm doing repairs for gave me his Bias Tool (socket with leads out for a DVM) but he hasn't seen the reference manual that came with it for about 8years. I ordered one the other day but it's probably gonna take a week or so to get here.

Anyone have the info that is needed to adjust/check the bias on a Peavey Classic 30? if not, I can wait until the book gets here. But if I can get it sooner, the sooner the amp goes back to the owner.

Thanks,

Andy S.

[slidincharlie (Carlo P)]

Steve Ahola made a wonderful website full of info on Peavey amps, including bias check and adjust:
http://blueguitar.org/

[Enzo]

Please note there is no adjustment on the PV C30 for bias.

[Andy S.]

OK, First, to SlidinCharlie, thanks for the info on that site. Excellent info!!

Enzo, my bad, I have a Classic 30 of my own and when I wrote that, my brain skipped a bit to my amp, not to the one that I was asked to look at.

It's SUPPOSED to be a Classic 50. I say supposed to be since the guy hasn't brought it in yet and the shop owner tends to generalize and just use names of models that pop in his head till he sees the stuff. (makes it REAL interesting at times! )

So I guess, from just a quick perusal of the articles on that site, the Classic 50 does need to be adjusted? Or Not?

I recall, a couple of years ago when I put new tubes in my 30, corresponding with a Peavey Tech from their website, he said the 30 did NOT need adjusting. Does that translate over to the 50?

One guy at the shop insists that ANY tube amp needs re-biasing no matter what the manufacturer says. I think that may be a bit extreme, and perhaps way off base. I mean!! If the manufacturer says it, whose to argue?

I have heard talks about how some guys like the bias set one way or another, looking for a particular tone. But, it was my understanding that the bias is supposed to be set for optimal operation of the tubes....ie, more power, longer life, etc..

Anyhow, fill me in on what you know and your thoughts on that.

Thanks!!

[Enzo]

more power, longer life, etc..

Well that is the deal, what is "optimal," the long life, the more power, the cleaner tone? Up to you.

PV Classic 50 doesn't have an adjustment either.

BUT...

Customers often call their old PV Classic a "Classic 50." It puts out 50 watts, and it is called a Classic. But it is NOT a Classic 50, it is just plain old Classic. And some of the old Classics DO have an adjustment. Not only that, but there was the original Classic, then the Classic VT, and the Classic VTX. All the ones with numbers cam a lot later. And I hear guys calling their Classic 50/50 a CLassic 50. Not even remotely similar amps.

And while we are at it, the old Bandit was a 1x12 combo. But the Bandit 112 was a separate model. In fact there are more than one versions of Bandit 112. More than one Transtube Bandit 112 even.

So make sure which amp you get.

One guy at the shop insists that ANY tube amp needs re-biasing no matter what the manufacturer says. I think that may be a bit extreme, and perhaps way off base. I mean!! If the manufacturer says it, whose to argue?

Who's...

Always and Never are pretty long times. I always look NEVER over real good, and I never take ALWAYS as gospel.

SOme folks chant "bias" like a mantra. Oh dear lord, what will happen if we don't adjust it JUUUUST so. well, the same thing that happens when you don'teltdown like so many like to do is reliability. if you want to go through three sets of power tubes a year, then go for it. But a lot of people out there would buy an amp and then complain to the factory that it eats tubes. A cooler setting tends to increase tube life and make failures that less likely. Furthermore, problems are caused by people mis-adjusting the bias control - if one is provided.

Guys will fret over half a milliamp. More power to them, but will the amp really sound or perform much different if the idle current is 2ma hotter or cooler? I doubt it.

The only way to adjust the bias on the C30 is to modify the amp. Not that it is complex, but not all customers will be excited to hear, "Oh, by the way, I added an extra hour labor to modify your amp after I fixed whatever it was here for in the first place.

To demand all amps be adjusted, or made to adjust, is to buy into the it has to be EXACTLY this idle current thing.

Everyone has his preferences, and if hotter bias sounds better to someone, then make it so. But thousands of those amps are out there and they sound JUUUST fine to their owners the way they are.

[hasserl]

Please note there is no adjustment on the PV C30 for bias.

Enzo, the bias in the Classic 30 can be adjusted by changing the value of R64, right?

Always and Never are pretty long times. I always look NEVER over real good, and I never take ALWAYS as gospel.

I love it! Good stuff.

[Enzo]

Yes, changing that would alter the bias voltage. It is not at all difficult to modify, but the stock amp is set by design.