Any good tube amp candidates for these?

[gktamps]

Hello,

My engineer father finally decided it was time to give me his huge collection of TV and radio tubes (and some audio) - Yeah!

Trouble is, I don't have the vast experience and knowledge of most of you, so don't really have a feel for which, if any, of these tubes are good candidates. Anyone care to offer their thoughts on these for guitar amp applications?

Thanks very much,

Greg

[gingertube]

A quick squizz at the photos - my 2 cents worth
6AU6 - Good Audio pentode (mostly HiFi use)
6AV6 - 1/2 of a 12AX7 good guitar amp preamp tube

6CB6 - pentode, under rated tube, starting to see them used in HIFI as driver stages
6CG7 - 9 pin 6SN7'ish twin triode but better sounding, HIFI guys are starting to look for these.
6SN7 - often used as drivers for output tubes
6SQ7 - pentode found as 1st preamp tube in a lot of old suitcase style guitar amps
6SL7 - twin triode, mu of 70, I use these for guitar preamps instead of 12Ax7 for a "smoother" overdrive sound.
6BL7 - ??? IIRC this is a dual triode with plenty of grunt, output tube drivers or use in push pull for a low power amp.
6W6 - An power output pentode, used in a few reverb units. (very 6V6'ish)
12BR7 - A low noise pentode, use anywhere you would normally use an EF86 (e.g. a Vox preamp), not plug in compatible with the EF86
12BY7 - Video Pentode - used as an output tube driver in some HiFi Amps.
6AU5 - power output pentode - often used these days to drive big tubes like an 845 in Single End for HiFi use.
6ES8 - A variable mu version of 6DJ8/6922/ECC88, no good for HiFi, might be worth a spin in a guitar preamp. Sort of tube you might see in a compressor or a bass preamp.

These are the notably usefull tubes I spotted.
Hope this is of help,
Cheers,
Ian

[Phil_S]

Nice review by Ginger; thanks! I think 6SQ7 isn't right. That's a triode + double diode in an octal package. Mu ~ 100, so roughly equivalent to half of a 12AX7, but Ra is 85K, making this a great candidate for a tremolo oscillator, and probably a decent gain hole tube, too. I have no experience with it, so I'm guessing. I'm guessing the doides are not terribly useful, but you might find something to do with them.

[gktamps]

Wow! Thank you Ginger for an excellent review of my tubes and their potential. That is very informative and inspiring. As my experience grows, I'd really like to use some of these tubes in builds.

Thank you Phil_S for your additional info, as well.

Amazing forum here - so many talented, knowledgeable folks.

Cheers,

Greg

[Phil_S]

I didn't look carefully earlier because I was in a hurry. I see you also have:
6J5, which is a lot like half of a 12AU7 and should make a decent concertina/cathodyne when properly dressed; I imagine it might also be useful as a low power output tube, one in SE or two in PP.
6AC7, which might be used as a pentode input, dressed about the same as the 6SJ7 in the Gibson GA20.
6J6, a medium gain, low voltage dual triode might be used in place of a 12AT7 in a LTPI with some fiddling around on resistor/cap values, maybe as a reverb driver, not sure, but it seems like it ought to be useful.

I have samples of these in my bone pile, but I've never actually done anything with them.

[gktamps]

Phil_S,
I've got many, many more tubes, but had these fairly organized first (by heater voltage, mainly).
All of the obvious audio tubes have been harvested and placed in my bigass tube caddy, but I still have more to go through.
Seems a real shame not to use them, and radio guys are not as plentiful as they used to be, so it would be great to put these to good use.
Cheers,
Greg

[Herec]

What about those 6SN7GTBs?

[Phil_S]

This is the problem, as I see it. Take the 6J6. You spend time figuring out how to use it as a reverb driver. What happens when you need to retube? Maybe you have another, maybe you don't. You don't? Then what?

I think you understand that when you use these, it is strictly a hobby level endeavor. There is nothing wrong and everything right about it as long as the inherent problem is understood. No one wants surprise consequences. Inasmuch as we are a lot of tinkerers, some of us might not be bothered that we have to replace a 6J6 with a 12AT7, even though a socket change and other mods may be required.

Personally, I like the idea of having a stash of useful tubes and you'd think I wouldn't hesitate to attempt to use them in amps I build for personal use. The problem I run into is akin to a deer in the headlights. Here's an example. I've got a pair of NOS Raytheon 5755, which is a 5751 with a different pin out. Given the reputation of Raytheon tubes, I figure these have to be wonderful sounding. Yet, because I have only two and no more, I am reluctant to do anything with them. You see the dilemma? Eventually, I'll probably build something that uses one and keep the 2nd for a backup.

BTW, I see someone commented on the 6SN7GTB. I really liked the way this one turned out for a low power amp with plenty of clean headroom. (Also uses a 6AQ7, nearly the same as 6SQ7, where I only needed one triode for the concertina, but marked 6SL7 on the schematic.) http://home.comcast.net/~psymonds/6SN7amp.htm

[Structo]

Did you have many of the standard audio tubes such as 12ax7, 12ay7, 12at7, 12au7?

6V6, 6L6, KT 66, EL34, EL84, etc?

I had a buddy call me up and he was all excited.
I had just bought a trunk full of vacuum tubes for $100.

He had a pained look on his face as we went through them and only found a handful of guitar amp tubes.

Sometimes you can go to a HAM show and unload a lot of the radio tubes.

But for the TV tubes, not much call for them any longer sad to say.

[gktamps]

Phil_S - yes, I agree it makes it much more of a one-off build to use tubes with limited supply. Still, simpler builds can afford to be one-off and distinctive.

Structo - My father gave me several 6L6GCs GBs, 6V6 (many, he he), some 6k6s, which I really like (use them in my THD and would like to build an amp or two using those tubes), a couple EL84s, and many 12at7, 12au7 and 12ay7s, and a fair number of 12ax7s, but those were mostly used. I have some glorious Telefunkens and Bugle Boy Amperex tubes now, many with plenty of life remaining.

More radio and TV tubes by far, but I'm not sniveling.