answers to questions about matched tubes.

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crazyzeke
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Re: answers to questions about matched tubes.

Post by crazyzeke » Mon May 03, 2010 1:40 pm

Brad, how about that thing where you run the outer pair with EL34s and the inner pair with 6L6s? Is that as bad an idea as it sounds, assuming seperate bias pots for each pair?
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Re: answers to questions about matched tubes.

Post by øøøøøøø » Tue May 04, 2010 12:39 pm

Haven't ever done anything like that, so I can't say. Seems it would require separate bias pots for each tube in order to be even feasible. Have no idea how it would sound. Who did that?

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Re: answers to questions about matched tubes.

Post by crazyzeke » Wed May 05, 2010 4:43 am

øøøøøøø wrote:Haven't ever done anything like that, so I can't say. Seems it would require separate bias pots for each tube in order to be even feasible. Have no idea how it would sound. Who did that?
Bob over at Eurotubes. Personally I wouldn't trust an amp running like that, even with really tough transformers.
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Re: answers to questions about matched tubes.

Post by Jay » Wed May 05, 2010 7:10 am

I don't see why you couldn't do that given the tubes were each biased independently or the entire thing was cathode biased. If the latter you'd have to have a cathode resistor that got the bias into a range amicable for both types but it's certainly doable.

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Re: answers to questions about matched tubes.

Post by øøøøøøø » Wed May 05, 2010 10:09 am

I just wonder if there's a compelling reason to do it other than a thought experiment.

I'd reserve judgement on the concept until someone tries it. But you'd think it would've been designed into amps by now if there was a real tangible benefit-- but perhaps not.

Anyone want to try it and report back?

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Re: answers to questions about matched tubes.

Post by Jay » Wed May 05, 2010 9:01 pm

I do believe there are commercial amps available that run a variety of power tubes at the same time. The Egnater Rebel comes to mind as one but I've no idea what the circuit is actually doing.

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Re: answers to questions about matched tubes.

Post by budda12ax7 » Wed Jan 05, 2011 8:27 pm

crazyzeke wrote:Brad, how about that thing where you run the outer pair with EL34s and the inner pair with 6L6s? Is that as bad an idea as it sounds, assuming seperate bias pots for each pair?
This is the setup on the Mesa Boggie Mark 3 amps....I run two EL 34's and two 6L6s....I can also run the amp on just the EL 34's with a flip of the switch...

It sounds great...

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Re: answers to questions about matched tubes.

Post by case_dizzle » Fri Mar 04, 2011 10:00 am

I've always wanted to try a mismatched set because I've heard it can produce some lovely sounds, but I've been afraid to. I think I am going to go for it.
Who sharted?

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Re: answers to questions about matched tubes.

Post by blacktiger » Wed Mar 30, 2011 8:15 am

crazyzeke wrote:
Bill Ashton wrote:'K, then I am mistaken... :blush:
You weren't mistaken. Your original question mentioned doubt about the function of a hum balance control on a BF Fender and Jay confirmed it. Perhaps it's an aftermarket modification added by an end user?
No, there was definitely a "hum balance" control on some Fenders at some point. IIRC, it was a post-CBS thing.

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Re: answers to questions about matched tubes.

Post by 46346 » Fri Jul 13, 2012 1:24 pm

case_dizzle wrote:I've always wanted to try a mismatched set because I've heard it can produce some lovely sounds, but I've been afraid to. I think I am going to go for it.
i've had my eye out for affordable single power tubes (of good quality manufacture) in good shape for this kind of experimentation.
seems they're way cheaper than half of a matched pair.


does anyone have something of a strategy toward 'semi-matching', i.e. pairing up disparate power tubes?
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Re: answers to questions about matched tubes.

Post by jorri » Mon Sep 15, 2014 9:50 am

I heard it was still needed in cathode-biasing amps, at least for longevity ( i know little, but i just was persuaded to pay for some matched quad!), and headroom was also explained to be better.

I tried to replace w/ a matched pair on the ac30 primarily to save money knowing two were gone...i think i got the positions wrong even after switching them about a bit into their pairs-sounded awesome then the new tubes blew in 6 months. Is it still the xyyx position? it will be usefull to remember for next time.

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Re: answers to questions about matched tubes.

Post by øøøøøøø » Mon Nov 03, 2014 7:29 am

xyyx, or yxxy.

not xyxy, and definitely not xxyy

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Re: answers to questions about matched tubes.

Post by aRoseisaRoseis » Tue Jan 03, 2017 4:41 pm

Figured this might be the best thread to ask this.
I have a Vox TB35 which is running 4 6v6s.
The stock power tubes gave out and I've started looking into replacements.
Could I swap the quad 6v6s for one pair of 6L6(G)s?
The amp being cathode biased, it it a direct swap or am I missing something?

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Re: answers to questions about matched tubes.

Post by budda12ax7 » Tue Jan 10, 2017 8:03 pm

øøøøøøø wrote:xyyx, or yxxy.

not xyxy, and definitely not xxyy

Just to ask.....I am redoing my Ampeg VT-22...I could just buy two pairs of 7027a's instead of a matched quartet? AND would this run on 6l6gc's?

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Re: answers to questions about matched tubes.

Post by øøøøøøø » Thu May 18, 2017 10:54 pm

budda12ax7 wrote:
øøøøøøø wrote:xyyx, or yxxy.

not xyxy, and definitely not xxyy

Just to ask.....I am redoing my Ampeg VT-22...I could just buy two pairs of 7027a's instead of a matched quartet? AND would this run on 6l6gc's?
question 1: definitely yes
question 2: most likely yes, depending on the individual 6L6GC. I believe JJ sells a 7027a that appears to be identical to their 6L6GC. No guarantees on that info, though.

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