• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

High gm version of 12AU7

45

Member
2008-12-18 2:29 am
UK
I should also have said the same physical size as the 12AU7!

Cheers

Ian

I would try the 6N1P-EV. It's cheap and very good. The EV version is long life. It was designed as a true low frequency voltage amplifier. It is 6.3V though with pin n.9 connected to a screen between the two halves. Amplification factor is 35 and average gm 4.5-5 ma/V at 150-180V/6-8 mA. Input capacitance is higher than 12AU7 though.
 
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The 7044 looks like a great tube until you see the plate curves, not that great looking to me. I am curious to how it sounds for audio use.

Lots of ARC amps have used them in balanced driver circuitry. Used to have bunch of Amperex ones which I unloaded when I realized what they were worth.
 
New age of insane prices on tubes

If the bottle has to be the same size as a 12AU7, then I think 5687 is going to be the best choice. Unfortunately, it looks like prices on those tubes have gone a bit crazy. They used to be a $4 tube, now it's $15 and up.

Then again, I see people selling 5814 (industrial 12AU7) for stupid crazy prices these days. So maybe the 5687 is still something of a bargain at "only" $15 each.

Possible problem is that the 5687's pinout is different, and its heater takes double the current of a 12AU7.