Ever tried mixing diff.brand-same type power tubes?

Goran Lorencin

New Member
Feb 27, 2021
Ljubljana, SLOVENIA
A few days ago I put in a TAD 6L6 higher/top getter tube with the original Ruby 6L6GC, lower/side getter tube for an hour or so ... and I THINK the sound was different in a good way (if my mind did not play tricks on me, as it many times happens that we hear what we think we should). They were 10mV apart when I measured to set the bias, so I set one to 25 and the other to 35mV, and there are also some preamp tubes that were replaced, I have a Mullard 12ax7, a TAD 5751 and a JJ ECC83 in there also, but that does not matter as much, except for the lower overall gain, as it was all about the power tubes this time.

Any thoughts?
I remember buying my old Super Reverb 20-something years ago, a early 60s blackface model. It had a mismatch of RCA and Sylvania power tubes, along with GE, National, and I think one RCA pre tubes. It sounded fantastic! I didn’t (and don’t) have a means of matching tubes, so I used those for a while with good results. When the old, original paper caps went out not long after buying the amp, I retubed it with a matched set just to have everything fresh. Sounded even better, but that’ll happen when you replace caps and tubes that are as much as 40 years old!

I use matched brand sets because I have no way to match single tubes together. But I don’t worry about matching power to pre brands, etc. I wouldn’t hesitate to try a pair or quad of mixed-brand, matched tubes and I’d sure use them if they sounded good!
Mixing different brands of the same spec power tubes (i.e., two totally different 6L6GC) is perfectly fine as long as the bias is closely matched. I wouldn’t want to run one too hot or too cold.

Preamp tubes don’t need to be matched.
I had a few amps that were serviced back in the old days (80's & 90's) and when I got them back there was at least one power tube that was a different brand. I didn't have as discerning an ear back then, but couldn't tell a difference. This was before most power tubes were sold in matched sets and Techs set the bias using an input signal and adjusting out the crossover distortion with an oscilloscope. I don't believe using matched sets is necessary as long as the crossover distortion is adjusted out. Might sound better or worse. I do know matched sets are easier to either just pop in, in the case of cathode bias, or set bias by idle current. Many claim using matched sets sounds better. Maybe I'll put a pair of different branded tubes in one of my amps, set the bias with a scope and see how it sounds...