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RE: 71A schematic...

Vinnie and others -

This was a simple "on paper only" conversion of JC's 3.5 Micro to use 71A's. I've never built it myself, but am thrilled that Vinnie has (and that it worked out nicely). I'll have to follow his lead one of these days - I have lots of 71A's. I originally didn't want it posted until I was sure it would work!

The driver stage is straight from JC. It does sound very good. The two triodes are used in parallel.

JC's original 3.5 Micro (2A3) is wonderful. To quote the original article

"The Micro 3.5 W amp is as simple as it looks. It's a perfect partner for your Siren (Song Preamplifier). Built it as proposed and it will work great. Given the ultra-simple direct coupled signal path the output transformer will determine the ultimate sonic performance of the amp. Excellent iron = excellent results. Build it and enjoy!!"

The original schematic is above:

I just adapted the cathode resistor to correct the voltages to give an op point of 180v plate/20ma/-40v bias.




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