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Author Topic: 0528/6414 Input tube compatibility?  (Read 2260 times)

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Offline blstrek

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0528/6414 Input tube compatibility?
« on: January 11, 2013, 05:57:10 PM »
I've come across a pair of these oddball tubes. A quick Google search revealed they are basically computer grade 12AV7s with triple-mica construction with the same pinout as 12AX7 and 12AU7s. But, I am told they draw higher heater current and put out nearly 3 times the Mu. This leads me to ask; Are these guys compatible with my Speedball upgraded Crack?

Thanks,
Dave

Offline Paul Birkeland

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Re: 0528/6414 Input tube compatibility?
« Reply #1 on: January 11, 2013, 06:08:28 PM »
Eh, the tube will work in the Crack, but I think the plate voltage will creep up to the point where it will mess up the biasing on the 6080.

If you have the Speedball, you could change the R1 resistors on the small boards to 1K resistors and remove the LED's on the 9 pin socket, replacing them with 1K resistors also.

That would get you in the ballpark to try these.

FWIW, the 6414 is a cool tube, but it has much more gain than you'd need for this application.
Paul "PB" Birkeland

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Offline blstrek

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Re: 0528/6414 Input tube compatibility?
« Reply #2 on: January 12, 2013, 09:50:57 AM »
Thanks, that's exactly the concern I had. And I wasn't sure it would be a good match without modification. I do have the Speedball upgrade installed. Right now, I'm running an Amperex 6085-PQ (ECC80) and a Chatham/Tung-Sol 5998. Can't imagine anything being much better than that........Dave

Offline Paul Birkeland

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Re: 0528/6414 Input tube compatibility?
« Reply #3 on: January 12, 2013, 11:16:07 AM »
Yeah, I'd stick with the E80CC (the ECC80 is a very different and incompatible tube).

Higher gain in the Crack circuit is not particularly desirable, and lower gain tubes tend to need more plate current than you'd want to deal with.

-PB
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline blstrek

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Re: 0528/6414 Input tube compatibility?
« Reply #4 on: January 13, 2013, 10:50:54 AM »
Right you are, E80CC.