Soul sister question

fitz · 1660

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Offline fitz

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on: April 22, 2020, 11:23:28 AM
Would like to build a Soul Sister pre from the Valve magazine(vol.5 issue 4) to go with my Paraglows. Would like to use the 5670 tube that calls for a B7-15k transformer, would a B7-10k work ok ?   



Offline Paul Birkeland

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Reply #1 on: April 22, 2020, 12:40:36 PM
That particular schematic I think got revised at some point.

For a 5670, 9.5mA of current and 150V on the plate would be 1.5V of bias and a cathode resistor of about 160 ohms.  You could use an HLMP-6000 diode here for this.

With 3.2V of bias and 9.5mA of current, you'll have more like 225V of B+.  That's OK too if you want.

In either spot, rp is about 6K, so the 15K output transformer makes a lot more sense than a 10K output transformer.

There are a great many other 15K:600 output transformers available, many of which are still in production.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man