Mix matching tube brands

[PanterA333]

I have a Peavey 6505 (not plus). I have the stock Ruby 6L6 still in it and have another set of JJ 6L6. The JJ tubes have a way bigger bottom end and the Rubys have a more mid range. Would I be able to put two ruby and two JJ tubes in the power section to get a in between tone? The amp is factory biased so i don't have to bias it.

[NickC]

I don't know that circuit, or how the bias circuit is arranged. I (a rank amateur) would be concerned that the two different brands of power tubes may not bias up the same.

[Stevem]

Yes you can but for two things to go by.
1) the two same tubes need to be in the out side of the four tube sockets, or on the inside two sockets.
2) if you do not have a way to test the bias current you need to at least prove out in a dark room that when playing the amp at max volume none of the tubes red plate on you!
Also the better of the two sets of tubes may go into clipping way before the other pair which may not sound too good, if that's the case then you need to mod the amp for two separate bias feeds and adjustments.

[xtian]

I (a rank amateur)

You should have an "extreme humility" contest with Phil_S!

[Phil_S]

Maybe we should spell it Rank, with a capital R? ;-}
There is lot's I don't know. I've been dabbling in this for about 12 years now. It takes a long time to acquire knowledge, especially when the only amps you see are the ones you build. I've built a dozen or so. I stopped counting them a while back. Could be in the low teens now.

[lord preset]

I (a rank amateur)

You should have an "extreme humility" contest with Phil_S!

No,no. I have more humility than all of you combined! I have more humility than Imelda Marcos had shoes. I eat a barrel of crow for breakfast. I win!!

[lord preset]

But to answer the question, Stevem's answer is correct re where to put the tubes. Peaveys with non-adjustable fixed bias tend to be biased cold so there is not a huge chance that you will redplate even if the JJs bias hotter than the original tubes, but there is no telling whether the tone you get will be to your liking. THe only way to know is to try it.

[martin manning]

1) the two same tubes need to be in the out side of the four tube sockets, or on the inside two sockets.

Why would this be? The tubes on each side of a pp quad are typically paralleled pin-for-pin so it shouldn't make any difference, unless Peavey wired the two halves inner/outer just to be different. 5150 PCB seems to have them paired left side/right side.

[Stevem]

Sorry, a poor way to describe it at that moment!

[statorvane]

How is this amplifier biased - cathode bias? I swapped several sets of EL34s in a JMP50 clone I built a few years ago. I noticed I really needed to adjust the bias trimmers (dual fixed bias) between sets of different brands; JJ, some Chinese brand (Sino?) and Mullard RI. I liked the Mullards the best, but my son took them . Weird, when I swapped JJ 6V6 for EL34s in the same amp I barely had to adjust the bias voltage.

Not sure if this would affect your plans, but thought I'd let you know my experience.