I just picked up a A-K Model 37 that has been butchered for parts. It is missing the Audio Interstage Transformers, knobs and dials and the tubes but is otherwise in decent condition. It will need the dials and some wiring replacement but that is failry straightforward. The power tranformer is good but the chokes are open.

What I am thinking about doing is changing the Audio amplifier stages to resistance coupling as the AF transformers are gone. Has anyone done this before and are there any potential pitfalls? Can I get enough gain and will the circuit be prone to oscillation?

Thanks for any help.

I supposed you could try it.

The original design used transformers for voltage amplification since the gain of the individual stages is not large.

- Leigh

If its single-ended, resistance coupling works but as mentioned you lose some gain. It may or may not be enough to matter. I did this to one stage in my RCA Radiola 18 and its got more than enough volume still. I tried it in a Day-Fan that had both transformers open and you can just about hear the thing. If this is a push-pull output, then the transformer ahead of the output tubes is most likely being used as the phase inverter. If that is missing or bad, you'll need to either replace it or wire in something to serve that purpose.