Peavey Tube Amps

[XXX1989]

Hi, I have a bit of a situation I believe...I have a Peavey Triple XXX and I recently installed New EL34's in and biased everything up with my bias probe, been playing playing it for a while now and thought I would go through and check the bias to make sure everything was still good and didn't creep to a reading other than what I biased at....the first time I biased the amp the inside and outside pairs were only 3-4mA apart and now they are 10-12mA apart is this OK? If not is there anyone familiar with this issue and how to resolve it?....I don't know why Peavey didn't just make it so you can bias each pair individually instead of all 4 at once...I have noticed that Peavey amps in general bias readings are always roughly 3-5mA apart from inside and outside pairs my father has a 5150II and a 6505+ and both are this way but not 10-12mA...Thank you in advance for any and all help.

[xtian]

What is your per-tube idle current? 30 or 40 mA? Anyway, a 10 or 12mA mismatch isn't terrible, and as long as you're not hearing any hum from the mismatch, don't worry about it.

[XXX1989]

What is your per-tube idle current? 30 or 40 mA? Anyway, a 10 or 12mA mismatch isn't terrible, and as long as you're not hearing any hum from the mismatch, don't worry about it.

I am not sure the per tube Idle as I only Have a Probe that has 2(A&B) sockets with a switch to bounce back and forth one socket I place on one outside tube and the other on one inside tube I wish I had one with 4 sockets they are a little costly but someday, I was told by eurotubes to just bias the hottest pair and not worry about the other but that was when it was only a few mA difference...I have the Bias @41mA on the Hottest pair(outside) but the other pair(inside) bounce back and forth between 29-31mA...There is no hum That I notice just thought this is a pretty big gap between the pairs bias wise.

[Stevem]

Peavey could have made the amp with a bias test set control for each output tube , but that would add a likley 200 bucks to the cost of the amp.
A amp with matching bias output tubes from idle on up to cranked can be loud, but also sound sterile!

If you have a voltmeter you can cheaply add a 1 ohm 1% 3 watt resistor on each output tube socket in series from pin 8 to ground and then when you hook up your meter across the resistor set for D.C. Volts you can read the current directly.

[xtian]

The point of matching idle bias current between tubes is A) avoid unwanted hum normally canceled by common mode rejection, and B) avoid harmonic distortion. Since this is a guitar amp we're talking about, distortion is a good thing. So if there's no hum, and your tubes aren't in danger of redplating, then no worries.

[Littlewyan]

I've heard it's best to have the valves DC Current matched at least for the Output Transformer's sake. I don't think Merlin believes in matched valves but I can see here that R.G. Keen does.

https://www.premierguitar.com/articles/ ... d-or-not-1

[XXX1989]

Thank you to everyone for the help and info....The amp has been playing fine with no issues so far......I am fairly new with repairs and mods of amps, pedals and such (been doing it for a few years now) and think I am better off leaving well alone so I don't cause problems that are not there now...as the saying goes "Don't Fix What Ain't Broke"...but thank you again everyone all your help and info is greatly appreciated.