Some help with understanding tube matching

[nightlight]

I need to buy some new power tubes: two pairs of KT88s and one quad of 6L6 tubes.

The 6L6s I am looking at actually look like two matched pairs to me, with writing on the stickers of 50 and 51. Is that close enough to use in an amp as a quad of tubes? Or should the values be closer together?

Hoping for some quick help on this one, thanks in advance.

 

[nightlight]

Found the info I needed at this RT thread. Thanks anyway, cheers.

Thread 'Power tubes, matched quad or 2 matched pairs ok?'

Apr 18, 2022

Trying to confirm this... In an amp with 4 power tubes and only one bias adjust knob do you absolutely need to have a matched quad? Or will using two matched pairs be fine as long as it's balanced properly?

• MadAsAHatter
• Replies: 13
• Forum: Rig-Talk

 

[Racerxrated]

I'll just mention that, I've never noticed a tonal improvement when I match (within 1-2ma of each other) vs a quad of, lets say 30ma on the low side to 40ma on the high side. In fact, those quads for some reason sound better in my amps.

 

[baron55]

I'll just mention that, I've never noticed a tonal improvement when I match (within 1-2ma of each other) vs a quad of, lets say 30ma on the low side to 40ma on the high side. In fact, those quads for some reason sound better in my amps.

Tube matching to close tolerances comes from the Hi-Fi world and has been severely overstated by tube dealers to up charge everyone. And isn't necessary in guitar amps.

In push - pull circuits, the tighter the matching the more even order harmonics are canceled out. In Hi Fi amps, you want a clean sterile output, not necessarily in guitar amps.

No one matched tubes in guitar amps in the 1940s - the late 70's until tube resellers started pushing it. Yes, tubes were in the "ballpark" but not even close to what they are done today.

 

[SQUAREHEAD]

I’ll guarantee the incredible classic Van Halen - Hendrix - Priest - Page tones we’ve all grown up loving were achieved with completely unmatched tubes.
I have to agree with Rx that some of the BEST tones I’ve ever gotten had tubes that were no where near matched.

I have many matched quads of nos tubes, but some of my old Marshalls have original healthy Mullards / Siemens that are like 28-35-31-39…
They sound incredible.

 

[thegame]

In push - pull circuits, the tighter the matching the more even order harmonics are canceled out. In Hi Fi amps, you want a clean sterile output, not necessarily in guitar amps.

I always thought the closer the matching, the more even order harmonics. And conversely the further apart, the more odd order harmonics. Please correct me if I'm wrong.

 

[harddriver]

I'll just mention that, I've never noticed a tonal improvement when I match (within 1-2ma of each other) vs a quad of, lets say 30ma on the low side to 40ma on the high side. In fact, those quads for some reason sound better in my amps.

I’ll guarantee the incredible classic Van Halen - Hendrix - Priest - Page tones we’ve all grown up loving were achieved with completely unmatched tubes.
I have to agree with Rx that some of the BEST tones I’ve ever gotten had tubes that were no where near matched.

I have many matched quads of nos tubes, but some of my old Marshalls have original healthy Mullards / Siemens that are like 28-35-31-39…
They sound incredible.

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
I finally stopped obsessing over perfectly matched Quads years ago, I have Quads that run with 5-10ma spread or a bit more and I never expect any MATCHED QUAD from a tube seller to be 1-2 ma because that is darn near impossible to get it that exact.

I would imagine back in the day EVH was just throwing in whatever tubes he had when they blew and cranking up the bias according to Friedman and just letting it fly, Output transformers be damned.

 

[Ben Waylin]

Matched output tubes is snake oil BS

 

[mnemonic]

I recently replaced a pair of Ruby kt88’s in an amp that had drifted quite a lot, one tube drawing twice the current of the other. I had one tube biased quite cold, the other on the ‘slightly warm’ side.

New pair of TAD redbase kt88 (matched within 1ma, at least currently) I want to say sounded slightly more aggressive, a little bit less wooly, but not a massive night-and-day difference. Also they are physically different tubes (both Chinese as far as I can tell, but the TAD redbase is psvane, and the Ruby’s are shuguang).

 

[Racerxrated]

I’ll guarantee the incredible classic Van Halen - Hendrix - Priest - Page tones we’ve all grown up loving were achieved with completely unmatched tubes.
I have to agree with Rx that some of the BEST tones I’ve ever gotten had tubes that were no where near matched.

I have many matched quads of nos tubes, but some of my old Marshalls have original healthy Mullards / Siemens that are like 28-35-31-39…
They sound incredible.

My 72 Trem came to me from England in 2020; seller said he got it from the original owner and the Siemens 34s/Tungsram pres were all original to the amp. They bias in at about what your numbers ^^ are and it sounds so good, I'd hate to mess with success so to speak and try a better matched quad.

 

[Kōbra]

Tube like socks... no need match to do same job.

Goodluck

 

[psychodave]

I like matched tubes.... not tight matched though. I've never really paid attention to it, but I've read tubes really far apart will hum more.

 

[harddriver]

If I have a set of tubes that have a large spread 10-12 ma in a 100 watt amp I do group the two tube closest together in ma reading in pairs and arrange them in the sockets for the A/B push pull circuit of the power tubes so the push pull of the circuit is somewhat balanced. I seem to remember reading that recommendation in one of tube amp books.

Back in the day most techs would install quads and just adjust the bias with an oscilloscope so the sine wave would just notch with a tad of crossover distortion on Marshalls and they would not even check what the current draws of each tube was.

 

[M@tt C]

Funny, just had this conversation with the amp guy who's putting a PPIMV in my 1987x.

Doesn't really matter that much according to him, and he got that from Bruce Egnator.

 

[nightlight]

That's very interesting, guys. Thanks for the inputs. I need to revalve all my tube amps, I think.

It's kind of like my guitar string story, i.e. I just never changed them and thought everything was fine. And this was like keeping on the same set of strings for years until one of them broke and then I would buy a new set - usually heavy gauge so that it wouldn't break again - and thought everything was hunky dory. Shame on me.

Anyway, after coming to the realisation that I need to maintain my instruments if I want the best tone out of them, I figured I should give the amps the same treatment. I've literally owned some of them for over 8 years and just never bothered to change the power tubes.

Right now, I'm about to retube my Engl Savage 120 and Engl Fireball 100, so one duet of KT88s and one quad of 6LCGCs were necessary. I didn't really break the bank on the purchases, because I read somewhere that if you're not really cranking your amps to get power amp distortion, the tubes don't really matter that much.

And since I'm usually running into my PS-2 as a load box, which doesn't have a control to lower the DI output to my interface or whatever processor I am using to get a cab sound, I really don't need to crank the amps that much either, because it just overloads the input and sounds like mush.

My Marshall came to me with good tubes, so I think I can keep those in for a while. I also want to retube my Rectifier Stereo 2:100 power amp, but that's like eight 6L6s, so I'll do that slowly.

In addition, I have a mystery amp in mind that I bought a pair of KT88s for. May work out, may not, but it'll be handy to keep a pair as backup.

Hate the fact that I'll have to take the amps to a tech to bias. Just adds to the cost, and I wish I had learnt how to do this myself a long time ago.