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Hi Stan,

All that was ever installed for an R-4B here in the lab were a few PD-4 product detectors. The AMP-4 needs a good 12 to 14 volt supply at several hundred mA that doesn't exist in an R-4B. While the AGC attack distortion was much less with the PD-4, the audio distortion was still there with the audio output tube. The tube amp wasn't as distortion free as I expected.

Let’s see if the updated Gerber files make it to Colorado and go from there. There are some parts for all the kits that have become harder to source from new old stock. I would of course be more than happy to see someone run a new batch of boards.

Attached is a PDF for installing a PD-4 in an R-4B. As to coming up with 12 volts, could a voltage doubler be used off the filament line? It might be worth considering use of a less power hungry LM-380 instead of my LM-383 circuit for the R-4C. 100 mW of power is pretty loud into an MS-4 or MS-7 speaker.



Rob, NC0B