Just a thought about matched output tubes

[iknowjohnny]

Yuk ! Man, i can't for the life of me understand why this practice is still considered by most to be important. I now feel it's just one of the most detrimental things you can do to guitar tone in most cases. Most cases meaning of course there will always be exceptions. But anyways, what i'm getting at here is this. I already talked about how since making my amp dual bias i have found that mismatching tubes is a far better sounding setup if you like harmonic complexity and a thick tone w/o tinniness. But now i'm using different tubes in my 2Xoctal amp. I was using el34. Then I tried 2 different brands of them and found you could get richer better sounds whether or not you match the bias. The other day i mentioned how i tried 6L6 in my amp and loved them. But now comes the final chapter....one 6l6 and one el34 chosen for it's very opposite tone to the JJ 6l6....a winged C el34. I gotta tell you,the tone is just killing. With that and the sozos i just put in i can honestly say i have never heard or played a better high gain tone than i'm getting right now. Of course it's subjective, but i think many would agree. Anyone who likes Gary Moore's (RIP buddy, you'll be greatly missed) hi gain tones I feel would be floored by this amp, as i think it sounds that good right now, and i'm a huge fan of that tone. The sozos make a big difference, but that output trick just put it well over the edge. With el34's matched the amp sound very good. As i have it now it's scary good.

Why this isn't more common is beyond me. But try it. As long as the amp is capable try the worse mismatch you can....seems the worse the better. I mean, a 6l6 and the most opposite sounding el34 i had?! Can't get much more mismatched than that w/o damage ! This is the best tone i've ever had in 40 years. And the cleanish in between tones with the guitar on 5 are utterly fantastic too. But the hi gain tone is just insane.

[David Root]

Very interesting. What kind of circuit is this amp? In Dumble type circuits mismatching by several mA generates hum, at least in my experience.

[RJ Guitars]

I have had similar experiences but only as far as using the same designation of tubes yet different brands or styles. I've never cross pollinated a 6L6GC with an EL-34 in Push-Pull but if it works that would no doubt lead to some interesting sounds. I think Mesa Boogie has their own take on this but using "push-pull pairs" of like tubes in parallel. Also makes me wonder how your output tranny feels about this complex marriage?

I think David Root adds an important piece to the big picture. When things get too far outa whack on the bias matching, then my experience is that your gonna get hum. There is a pretty good thread on that somewhere here on TAG that explains the "why" of it all.... maybe something about "tube matching circuit"??

My thought is that with your ability to dial each tube individually you should be able to "dial the hum in and out". It would be interesting what happens to the tone as you do this? I'd be curious if you are able to hear the hum and the tone change as you dial?

rj

[iknowjohnny]

Honestly theres no hum at all. I just biased them like i would normally bias each type. I biased the 34 at about 33ma and the 6l6 about 10 higher. No hum, just killer tone. For anyone reading who isn't up on this stuff, don't get me wrong, no one is going to get gary moore tone from a amp thats no where near it. But i already had mine sounding really good and the sozos plus this make a big difference. But while it won't make a killer amp out of a mediocre one, it's probably about as big an improvment as any other single thing i've found.

[rdjones]

Even with the idle currents matched there will still be a difference in the gain of the two dissimilar types.
How much of the tone "improvement" is still there when the tubes are matched (within their normal range of capabilities) ?

This area of experimentation opens such a Pandora's Box, very intriguing.

rd

[iknowjohnny]

How much of the tone "improvement" is still there when the tubes are matched (within their normal range of capabilities) ?


rd

Well, like i said they ARE actually. When i bias the amp I use webers bias charts, and they show around 44ma for the 6l6 and i think 34-37 or thereabouts for EL34 at 70%. Don't quote me but it's somewhere around there. And we're talking about 465 plate voltage. So thats where i put them. I suppose i could try matching the currents by taking the 6l6 down to where the el34 is but wouldn't that be too cold to get nice cleans? Maybe i'll try that. But right now it just sounds so good i don't have much reason to mess with it further. I think if anyone asked my opinion (god forbid LOL!) concerning tips when deciding on what to build i'd tell them build whatever you want, but make it dual adjustable bias. I use the 1 ohm resistors off the cathodes and test points on the back panel so i can play with it all i want.

This area of experimentation opens such a Pandora's Box, very intriguing.

I know, thats why i said i don't understand why this hasn't been covered more. I see little to noting mentioned about it. But I guess it's likely because few have dual bias.

[212Mavguy]

@INJ and DR,

Bravo! Love your posts in this thread!

No herd following from you two...Signature tones come from asking questions and answering them on your own using your own toys. If nothing breaks and it sounds good for what you want, it's good...period!

With that said, please 'scuse the intrusion...my $.02 FWIW

Separate bias supplies for each socket in a 2 or 4 socket PP or SE, or each pair of sockets in 4 socket same(s) is a good thing, period. Regarding Mesa, what is "Simul class?" Mr. Smith just didn't go all the way and put in bias pots for each pair because he knew that for the 90% + of his amp buyers really not knowing where their tones come from on the amp side, lacking amp theory knowledge, would open up the "Bad" Pandora's box and folks would complain. He's a smart businessman. God bless him.

Gots one of Chris Siegmund's amps, a Midnight Blues Breaker head. Chris says that it's a good thing to mix different brands of the same tube type...you get the tones of each. My personal tube rolling sez yes, that is true. Yup.

Too much bias difference between each side is a hum maker. When mixing tube types yep, that rule still stands, settings for each tube type as well as side, but there is a lot of elasticity in what can be done before the "hum line" is crossed.

@ INJ, RE: No on balanced current for similar type power tubes...

For the distorted tones you write about, yep, no disagreement with you. Get more girthy sounds with the mismatch until the mismatch gets enough for the hum thang starting to happen.

For tones within the limits of clean headroom, well... IMHO within my experience in my Siggy, (which has a bias and bias balance pot using a shared bias supply) sustain within clean headroom limits is better with tight balance, within 1 ma provides noticeably more sustain than a 5 ma diference in clean tone...

Bias settings have significant effect on harmonic content of tones from an amp. In my C-tone 50w OTS HRM as well as my Siggy, in two "one of a kind" TST PP amps using Bendix Red Bank 6094's in one, 6384's in the other, as well as my 2/12 combo Boogie Maverick with an unusual, one of a kind adjustable cathode bias mod ( ) a hotter bias yields not only more sustain clean as well as dirty, but also more even order harmonic content, that singing sustain that we love too, as long as bias settings are within reasonable limits for the power tubes' operating limits...but you can go too hot, fry tubes, and get mud if you are not careful. Too cold and things start sounding nasty, bright and brittle.

Within the limits for the chosen tube types, it's OK and actually preferable to use your ears along with your DMM for bias settings. And that might VERY well be different for what room and volume setting is desired at a particular time.

Peace.

[M Fowler]

Matched pairs of tubes are not very well matched once their in your amp and your setting the idle.

Hence is why I think I will start putting in dual and guad bias pot arrangements from now on.

I do like a little mismatch though. Set by DMM and then take a listen.

I haven't tried different types of tubes EL34/6L6 and I think I will stay away from that but I have run two different types of EL34s in one of my amps. I didn't have enough tubes to go around.

Mark

[selloutrr]

http://eurotubes.com/euro-i.htm#9.

I've mixed and matched tubes but usually as a pair in push pull 100watt+ amps. two 6L6 or KT66 + two El34 or KT77 This sounds great in Mesa Dual and Triple Rec's.

[iknowjohnny]

Well, tonite i cranked up the MP3's and did a bit of jamming and i tried various tube pairs and it turned out that in a mix i actually preferred the pair of 6l6, and matched or not didn't matter a lot. Solo i liked the 6l6 and el34 as i said earlier, but in a mix the 6l6 proved most savory. Amazing how things change depending on the sonic melee that happens to be going on at the time. However, you know how that goes...one nite the tele is god, the next you'd throw it in the trash because the start is so much better. Spent years on stages trying to figure out why why why. You know. In any case, the sozos have not been anything but wonderful. they are the biggest surprise, and not one that will change depending on the moment. They just improve things greatly. tomorrow maybe back to the 6l6/el34....who knows. Maybe a extra socket and a switch?

[M Fowler]

Your heading in the right direction and loving your amps that is great!

I have always favored 6L6 over EL34's for some reason.

What sounds good at home doesn't always translate to what sounds good in the mix of a band, I find that out all the time.

Mark

[iknowjohnny]

So true. I can't count the number of amazing amps i sold because at the gig my mediocre amp consistently sounded better. The only thing about the 6l6 i'm finding, and it surprised me, is they are not near as bright. Thats a good thing but i may have to add some brightening to the amp. I know exactly what to do too. But i find it's always better to have an amp thats a bit dark because you can do something to remedy that, whereas a bright amp is a real tricky thing to deal with.

[rp]

Keep it coming guys, please build up the mismatch hype on the internet. I'm going to start a new boutique tube company offering intentionally mismatched tubes. They'll be graded and rated 1-10 depending on the mismatch, and I'll even offer Pot-Luck sets, expertly selected by a random number generator, at an extra premium. Anyone wanna put up the venture capital?

I just remember the days before Groove Tubes started the whole matching thing when nobody bothered with matched tubes. In fact when a power tube blew you just went out and bought one new tube and stuck it in there (and yes I do remember it sometimes humming.) It changed overnight when Groove Tubes appeared. It's funny, '50s-70s was the era of golden tone that so many people are chasing, yet so many are trying to forcibly capture it with hifi methods. All good, and experimenting is good, and of course everyone wants to engineer everything as well as possible, but still I can't help noting it.

I got a whole bunch of great NOS unmatched tubes that I haven't been using cause after 30 years I too am now indoctrinated with the matching thing. Thanks for helping me cast off my chains IKJ.

[M Fowler]

I would walk over to Radio Shack across the street from my home and buy or test old 6L6 tubes for my Fender Bassman and Tremolux.

I never used matched sets and no one I knew did either. Got a lot of my tubes from the med-tech guys at the local hospitals since they had a great stock of NOS tubes and the equipment that used them were long gone.

Then came GT

[rdjones]

I would walk over to Radio Shack across the street from my home and buy or test old 6L6 tubes for my Fender Bassman and Tremolux.

I never used matched sets and no one I knew did either. Got a lot of my tubes from the med-tech guys at the local hospitals since they had a great stock of NOS tubes and the equipment that used them were long gone.

Then came GT

I was never a fan of precise matching, either.
I treat testing and bias current readings as more of a performance verification process than a precision matching requirement.
I'm speaking of my own use here, if someone wants stuff matched within a couple tenths of a mil we can do that too.

I was a Groove Tube dealer and sold a lot of matched sets.
I think the deal at first wasn't so much that the tubes were exactly matched, but rather that they were "harder" or "softer" which had more effect on the sound than any high degree of precise current matching.
I do agree that once the idea of matched sets was out there that there was no turning back.

rd