Has anyone tried a "12AU7 to 6SN7 Adapter"? - diyAudio
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Old 22nd August 2015, 07:59 AM   #1
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Default Has anyone tried a "12AU7 to 6SN7 Adapter"?

Has anyone tried a "12au7 to 6sn7 adapter"?
Click the image to open in full size.

I got a bunch of 12ax7 and 12au7 from my guitar amp.
How a 12au7 compares to 6SN7, with the same gain?
I read that the smaller 12au7 should hum less, half filament current, less microphonic, and less crosstalk between the two triodes.

A 12ax7 is probably too hot/gainy and will drive the grids of the power tube too early on the volume pot.
Anyway, it is nice to have an option to try a more common tube in the there.

Any experience?

Last edited by James Freeman; 22nd August 2015 at 08:04 AM.
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Old 22nd August 2015, 08:15 AM   #2
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Hi,
Absolutely no reason why it shouldn't work. According to various manufacturers the 12AU7 is the 9 pin noval equivalent of the 6SN7/7N7.
I recently built a pair of amplifiers with provision for fitting either 12AU7/6SN7/7N7. Tried all 3 types and found the the larger valves introduced more hum than the 12AU7. DC heating cured pretty well all of the hum. I "think" I preferred the larger valves but it was marginal.

John
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Old 22nd August 2015, 08:30 AM   #3
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Something I found on other board:
Quote:
The primary difference between a 6SN7 and 12AU7 would be ten years of technological evolution (6SN7 evolving into the 12AU7). If you go backwards from the 6SN7, you'll find the single bottle 6J5, then the 76, 37, etc.
One way to judge the impact of physical size is to look at how much heat one of the plates can dissipate. A 12AU7 can burn off 2.75 Watts, while earlier 6SN7's are rated to 2.5 watts (the GTB/A can do more).
It's also worth noting that the overall geometry differences between the 6SN7 and 12AU7 lead the SN7 to have more stray capacitance, which may contribute to some of the observed sonic differences.
IMO, the very best of the 12AU7 family edge out the 6SN7, but an average 6SN7 will sound a little better to me than an average 12AU7.
John Caswell,
"think" + marginal and "a little better to me" is practically the same... maybe the 6SN7 has the looks factor which effects the sound?
Basically the 12AU7 is just a newer and better tube overall, minus the larger more impressive bottle... ?

I want to hear more opinions about how the two compare.

Last edited by James Freeman; 22nd August 2015 at 08:34 AM.
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Old 22nd August 2015, 09:15 AM   #4
M Gregg is offline M Gregg  England
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I made some,

here is a pick before they were put together with epoxy putty.
Couple of valve bases with PTFE cable.

Regards
M. Gregg
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Old 22nd August 2015, 09:37 AM   #5
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The ECC83 or 12AX7 is almost the same as a 6SL7, save heater current.
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Old 22nd August 2015, 11:10 AM   #6
Ketje is online now Ketje  Belgium
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It's not always safe to replace a 6SN7 by a ECC82
For preamp's normaly no problem, but when driving output tubes and other more demanding circuits better check first.
Mona
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Old 22nd August 2015, 11:41 AM   #7
SY is offline SY  United States
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Quote:
The primary difference between a 6SN7 and 12AU7 would be ten years of technological evolution (6SN7 evolving into the 12AU7).
Not really true, if by "technological evolution" the writer means "improved quality." The tubes are different, that is true. Besides capacitances and heaters, 6SN7 has significantly lower distortion than a 12AU7 in most circuits- whether that's desirable or not depends on whether you're building something for music production or music reproduction.
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Old 22nd August 2015, 11:59 PM   #8
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I recently purchased socket converters from a Chinese manufacturer to try ECC99 and 12BH7, instead of 6SN7. After that, I got another pair to try 6CG7 and Russian 6n6p. I am a very happy customer. Their converters look exactly like the photograph you posted. I think the build quality is very good, though I've never checked internal wiring.

Those Chinese converter saved my time, and actually look much better than my makeshift DIY converters with small tube sockets residing on top of the "nest".

Yoshi
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Old 23rd August 2015, 01:50 AM   #9
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Folks, you are forgetting that the 6C4 relates to the 12AU7 the same as the 6J5 relates to the 6SN7.

SY mentioned linearity. I'll firmly state that the 12AU7 is unsatisfactory as a voltage amplifier, because of its non-linearity. If you want to use Noval socket/Octal plug adapters, wire them up for the 6CG7/6FQ7/6GU7 group. The triodes in the 6CG7/6FQ7 are "identical" to those in the 6SN7. The 6GU7 contains the same triodes as the 12BH7, which are slightly lower in mu and somewhat lower in RP than those in the 6SN7, etc. Most of the time, a 6GU7 will drop into a 6FQ7 "hole", without incident.

BTW, 12BH7s are pin compatible with 12AU7s and will work in those commercially available adapters. The triodes in a 12BH7 are linear.
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Old 23rd August 2015, 03:53 AM   #10
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I'll disagree with Eli and say that the 12AU7 can be quite nice, depending on where it is in your circuit and what sort of harmonic compliment it adds to the mix. Heath them in a Williamson configurationm in the W5 and that's a lovely-sounding amp. In terms of gain, take note that in low-current use it has the same gain as a 6SN7 but in higher-current situations it has less gain, and you will notice it. For example, in the Heath W5 design, if I substitute a 6SN7 for the input tube, there's no noticeable change in gain. But if I substitute a 6SN7 for the driver stage, there's an increase in gain. At any rate you have a choice. :-) In most situations a 12AU7 will drop in comfortably. I'm about to order a few of these adaptors so I can swap out tubes for a Williamson-style amp I'm building for a friend. He likes to have as many options as possible. ;-)
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