[Boatanchors] FS: P&H AFC-2 Audio Compressor
petef at sprynet.com
Fri Feb 17 18:12:33 EST 2012
I'm selling the P&H AFC-2 Audio Compression Amplifier. I used it for about fifteen years from the late 70's through the early 90's, mostly on AM. P&H Electronics was located in Lafayette, Indiana and besides this made linear amplifiers and transverters.
One of the issues with many of the old compressors is they don't really compress sufficiently to be useful but this one does. Designed in 1959, it uses two inverse feedback networks through the stages to reduce distortion. The cleverest part is the use of a 7B8 pentagrid tube as the compression control stage. The microphone audio input is fed to grid #4. A portion of the output, taken from the anode, is rectified and fed to grids #1 and 2. I would never have thought of that! It's not a limiter and it's not a clipper.
It has a broad/medium/sharp bandwidth control, the low cutoff being 90Hz, the highs 6000/3500/2000Hx. There's a gain control that is a pot tied to the grid of the last output stage. The unit has high (1 meg on input) and low input and high/low output connectors and output is from an output transformer. It's also relatively small at 7" X 5" X7" HWD.
This is perfect for anyone who wants a good example of "tube sound" Of course if you replace the electrolytics you will get less of the "tube sound". This unit has all the original electrolytics installed, and I'm pretty sure the Planet Lyticaps' one year warranty has expired. I'd put in new caps immediately.
I've made a 2 minute mp3 audio demo, which you can download (1.5 megabytes) or listen to at:
If you'd like to see the manual, it's on BAMA:
And a photo I took is at:
I actually have two of these for sale. In 1980 I replaced most of the small caps in one with orange drops or silver micas, but it made absolutely no difference and they sound alike. The first buyer will be rewarded for promptness with the new caps version. The other one, someone replaced the Amphenol single button connector with a 1/4" TRS jack.
Price for these is $150 each plus shipping, as-is of course. The original manual will be included. My shipping preference is FedEx Ground but can do it some other way if you like. Or you may pick it up in the Milwaukee - Chicago area.
petef at sprynet.com
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