Categories: Technical

A Simple One-Tube Compressor Circuit c.1953

Reader Bill W recently sent us a few interesting ancient DIY audio projects that we had not seen before.  Today’s post is from RADIO-ELECTRONIC ENGINEERING and was written by one Ed C. Miller.

DOWNLOAD THE COMPLETE ARTICLE:Constant Output Broadcast Amplifier

The article details the operation and construction of the above-illustrated broadcast-remote mixer/amp, which includes a limiter.  While the overall unit is probably not something you’d want to ‘F’ with, the limiter component could be added to a DIY tube mic preamp (perhaps with a true-bypass switch).  One caveat: as the article warns, there are apparently ‘thumping’ artifacts inherent to this circuit, which was acceptable in its intended operation since it was designed for voice-frequency.

Anyhow, might be a fun project for a rainy day – build a pair of these into box with cheap 1:1 input transformers and simple line output stages?  Crush some room mics?  Anyone?

chris

View Comments

    • Hi. It's possible, but it would be ill advised. I would recommend putting at least one voltage-gain stage ahead of it, and an interstate volume control as well. c.

  • So, what makes this different than a simple single stage tube amp? Is it the configuration of the capacitors that cause the compression?

    • I am not sure exactly how it works but it sounds awful and i don't recommend that anyone build it, total waste of time.

      • hey...i know it's an old thread but could you tell my your experience more why is it awful? Mine sounding pretty awesome...cheers!

        • I found this thread a few months ago, I find very easy to give a try, did you use 6SL7? what voltage did you apply?
          Is strange 470K for plate, did you try lower resistance? I will like a clean sound.

  • Hi, what type of transformers do you recommend for mic input and line output? I have no experience with this type of circuit. What voltage did you apply? Thanks a lot!

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