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Old 24th October 2005, 02:47 AM   #1
bradd is offline bradd  Australia
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Join Date: Oct 2005
Default Designing a simple tube opamp?

I've been interested in the idea of makinig a tube opamp suitable for stompbox use that uses 12U7 tubes for quite a while. Mostly because these tubes are happy running off a 12v wall-wart!

I've been checking out the ol' Philbrick tube opamps, but after seeing Joe Davisson's discrete transistor opamps (here & here), I'm keen to see if a much simpler alternative to the Philbrick version is possible.

Would it be possible to simply mirror Joe Davisson's Compression Opamp design by using one 12U7 as a differential pair going into another 12U7 acting as Class A stage? Would it then be possible to use the left-over half of the second 12U7 as the compression diode by omitting the grid?

Sorry if these are stupid questions!
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Old 26th October 2005, 06:24 AM   #2
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Join Date: Dec 2000
Location: Germany
Default Op Amp

If you compare tubes and transistor you see that all tubes are
n-channel devices: There is no aquivalent for a pnp transistor.

Nelson Pass has wrote an article about discrete op amps. Think there was a tube op amp in the article,

Reinhard
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