BluegrassDan

Triple triode tubes?
« on: December 22, 2018, 07:29:02 PM »
Has anyone experimented with triple triode tubes like the 6AC10? I just aquired a bunch and wondered if they could be at all useful.


Re: Triple triode tubes?
« Reply #1 on: December 22, 2018, 08:20:58 PM »
I saw some used as moving coil meter drivers in a Brennell reel to reel  I have , I forget which type they were at this stage ,I think they were just paralelled up  with the meter in the anode circuit .

Matt C

Re: Triple triode tubes?
« Reply #2 on: December 22, 2018, 08:38:29 PM »
I haven't really experimented with them but I see them all the time in old Ampeg amps I'm fixing (they used the 6K11 i believe).

abbey road d enfer

Re: Triple triode tubes?
« Reply #3 on: December 23, 2018, 07:57:25 AM »
Has anyone experimented with triple triode tubes like the 6AC10? I just aquired a bunch and wondered if they could be at all useful.
It seems to be very close to 12AT7, only 3 sections instead of 2. Not the most commonly used tube in audio applications. 12AT7 is almost exclusively used in the phase-inverter of push-pull amps. Could be used as a hefty line output stage, maybe...
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

mjrippe

Re: Triple triode tubes?
« Reply #4 on: January 09, 2019, 06:24:30 PM »
There are compactron triple triodes of many types including 12AT/U/X7 in various combinations.  Here is a link to a great PDF: https://www.dropbox.com/s/h4goh9wqj6oxvf2/Compactron_Survey_v1-06.pdf?dl=0

BluegrassDan

Re: Triple triode tubes?
« Reply #5 on: January 09, 2019, 07:18:39 PM »
There are compactron triple triodes of many types including 12AT/U/X7 in various combinations.  Here is a link to a great PDF: https://www.dropbox.com/s/h4goh9wqj6oxvf2/Compactron_Survey_v1-06.pdf?dl=0

Thanks for the link!

buildafriend

Re: Triple triode tubes?
« Reply #6 on: January 09, 2019, 07:28:10 PM »
compactrons seem to be a limiting factor for many tube testers

rackmonkey

Re: Triple triode tubes?
« Reply #7 on: January 09, 2019, 11:21:12 PM »
compactrons seem to be a limiting factor for many tube testers

Indeed. Even most of the better Hickok models require an add-on adapter unit to test them.

I once got a box of tubes with several 6EZ8s in it. One of the few non-compactron triple triodes.  The 3 triodes are identical and have electrical characteristics between a 12AU7 and a 12AV7, if I remember correctly. I played around with using it in a guitar amp with a tube tremolo circuit in it. I thought using those triple triodes might beat either having to use hard-to-find single triodes or wasting half a dual triode for the tremolo circuit. But in the end I abandoned the project because if one triode gets weak or fails, I’d have had to replace all three, regardless of their individual conditions.  Didn’t seem economical to me. I ended up settling on 6AV6s for my simple tremolo units. Plentiful and cheap as dirt.

But if you’ve got several you might consider going ahead with a project and living with the limitation above, at least until you run out of them. From there, you can always convert it to use more common tubes, I guess.  Just a thought.

« Last Edit: January 09, 2019, 11:25:20 PM by rackmonkey »
Whether you think you can or you think you can't, you're probably right.

Re: Triple triode tubes?
« Reply #8 on: January 10, 2019, 04:08:35 AM »
I was comissioned to design a phono preamp using one compactron for each channel. Not sure what more you're expecting, it's just three 12AT7 triodes in one bottle *shrug*.

abbey road d enfer

Re: Triple triode tubes?
« Reply #9 on: January 10, 2019, 04:58:29 PM »
I was comissioned to design a phono preamp using one compactron for each channel.
Seems to me like a very strange commission; no performance target, only a big constraint...
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.


mjrippe

Re: Triple triode tubes?
« Reply #10 on: January 12, 2019, 03:51:41 PM »
compactrons seem to be a limiting factor for many tube testers
Indeed. Even most of the better Hickok models require an add-on adapter unit to test them.

Yes, but this is GDIY!  I have a military TV-7 tester and I just built a compactron socket into a bud box with a rotary switch.  A multi conductor wire goes to a plug with a nine pin miniature base.  Plug in the 9 pin and set the tester for the first triode of the 12AX/T/U/whatever.  Then use the rotary switch to select triode 1, 2, or 3.
« Last Edit: January 13, 2019, 09:36:26 PM by mjrippe »

Re: Triple triode tubes?
« Reply #11 on: January 13, 2019, 12:14:12 PM »
Apart from the issue pointed out below, IE that if one valve goes weak you have to replace the valve, it's still a useful valve. The  6AC10 has high u/gain - 62, lower than a 12AT7/ECC81 but not far off a 12AX7, one 6AC10 and you have a high gain IP stage and LTP all in one, saves space, meaning the amp chassis can be compact.  If you have four or so and build an amp, two in the two as spares it'll last a good few years. Still, it means you have to buy "special" valve bases which are probably more expensive than your average B9A or octal. Am pretty sure I've seen them used in a few headphone amp design's. 

If you don't use them the prices of these have gone up like all valves, some folk love em and they can fetch a good few bob, so not a bad find.

Andy.

abbey road d enfer

Re: Triple triode tubes?
« Reply #12 on: January 13, 2019, 07:44:49 PM »
The  6AC10 has high u/gain - 62, lower than a 12AT7/ECC81 but not far off a 12AX7,
You must have your references mixed up; 12AT7, Mu=60, 12AX7, Mu=100.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

buildafriend

Re: Triple triode tubes?
« Reply #13 on: January 13, 2019, 11:41:23 PM »
I have a military TV-7 tester and I just built a compactron socket into a bud box with a rotary switch.  A multi conductor wire goes to a plug with a nine pin miniature base.  Plug in the 9 pin and set the tester for the first triode of the 12AX/T/U/whatever.  Then use the rotary switch to select triode 1, 2, or 3.

I was looking at TV 10 testers. Good idea with the DIY compactron adapter. I use a Hickok 532, but I want a mu tracer. It’s nice to be ready for anything

btw we’re both brooklynites. Let me know if you’de like to grab a drink and geek out

All the best,


 

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