Stereo to mono converter

My TV camera generates stereo audio, like most cameras do. However, my local ATV repeater only supports mono audio. So to transmit a nice audio signal with my TV pictures, I needed a way to convert the stereo signal to mono.

Circuit

Searching the web for a simple solution I found this circuit, published by Peter N. Petersen:

The circuit is a traditional opamp based mixer. The opamp suggested here is a TL072, unfortunately that chip was out of stock here. I found a nice replacement in my junk box: the LF356, although it has a different pin layout. Most opamp’s with FET inputs will probably do the job.

Part list:

R1   47k
R2   47k
R3   27k
R4   10k
R5   10k
C1   1uF / 16V
C2   1uF / 16V
C3   3.3uF / 16V
C4   10uF / 50V
U1   TL072, OP27, LF356, etc... (check the pin layout of the selected opamp)

Check out Peter‘s website for more details.

Pictures

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