Mismatched Power Tubes

[FourT6and2]

So, the Chupa has independent bias for each power tube. So you can mismatched pairs and still bias them up however you want. I'm wondering if anybody has experimented with putting two different brands of power tubes in their amp? I have a bunch of tubes laying around (JJ, Ruby, SED) and was going to play around with something like one Ruby BHT and one JJ E34L.

I've also been playing with setting the amp's bias to NOT match. So, one tube at 36mv and the other colder, at 28-30mv. And it seems the amp gets more aggressive and mean when I do this. When the bias is matched perfectly for each tube, the amp sort of sounds smoother and less aggressive.

 

[Dale B]

So, the Chupa has independent bias for each power tube. So you can mismatched pairs and still bias them up however you want. I'm wondering if anybody has experimented with putting two different brands of power tubes in their amp? I have a bunch of tubes laying around (JJ, Ruby, SED) and was going to play around with something like one Ruby BHT and one JJ E34L.

I've also been playing with setting the amp's bias to NOT match. So, one tube at 36mv and the other colder, at 28-30mv. And it seems the amp gets more aggressive and mean when I do this. When the bias is matched perfectly for each tube, the amp sort of sounds smoother and less aggressive.

Technically, the power tubes are still matched if they're all within 10 mA window. If you like the way it sounds at that particular point, keep using it. Most people prefer tighter matching because it helps eliminate power tubes from drifting completely out of spec. You don't have to worry about that if you have control over each power tube.

 

[FourT6and2]

Yeah, I'm just curious about what kind of effect happens when you purposely mismatch the bias. Because I've noticed that I actually prefer the tone of mismatching the tubes. When I set them at the same exact bias point (let's say 36mv) the amp sounds sort of... tame. Smooth and sizzles. When I throw one side of the pair colder by about 6-8mv or so the amp comes alive and gets all angry and i hear all sorts of cool overtones in the midrange.

 

[londaxe]

Interesting

All my amps but one (a JTM45 clone) have properly matched power tubes...as far as I know. The thing you described with the midrange is spot on...the tubes are about 10mA apart (or they were when they were installed at least)

Not sure if it's necessarily bad for the amp, but after about two years of use, I haven't noticed a single issue with mismatched tubes mine. Not sure if they've drifted one way or another, but it sounds

Glad you're enjoying the amp.

 

[Doubleneck]

That's one of the things I love about my Egnater MOD100. I run SED 6550's in the middle and SED EL-34's on the the outside slots. I haven't tried to mismatch the bias on purpose, might be cool to try.

 

[Anolin]

Hmm, I need to try this with my Renegade. I have a quad of kt88's with the tube mix at 12 o'clock and I could bias one side a little cold and the other side a little hot and see what effect that gives off...

 

[Chris6870]

I have run mismatches before. When I was gigging regularly I would have a tube go bad and just throw in whatever was around. I never really noticed that much of a difference. I would run the tubes until they died. There where no online suppliers like there are now (early 90's) and the local shops would have some Groove Tubes but there were expensive. Now it seems like guys change tubes as often as strings.

 

[FourT6and2]

I have run mismatches before. When I was gigging regularly I would have a tube go bad and just throw in whatever was around. I never really noticed that much of a difference. I would run the tubes until they died. There where no online suppliers like there are now (early 90's) and the local shops would have some Groove Tubes but there were expensive. Now it seems like guys change tubes as often as strings.

I can definitely hear the difference between brands tubes as well as how they are biased. I have three sets of tubes laying around: JJ, Ruby and SED. And they all sound different. Is it night and day? No. But there are differences, nonetheless.

 

[Chris6870]

I'm not denying there is a difference. Just not that much of one, especially in a live situation.

 

[FourT6and2]

I'm not denying there is a difference. Just not that much of one, especially in a live situation.

WELL I DON'T PLAY LIVE I PLAY IN MY BEDROOM!!!!! Which is technically my entire apartments because I live IN A STUDIO!!!!

 

[Armitage]

Throughout the '70s and early '80s, we never matched tubes... just plugged and played.