My all time favorite is the Joe Zawinul power supply story. Joe called me in exasperation back in 1982. He was hearing this intermittent “zit-zit” noise in his Soundcraft console, and nobody could find the problem. He’d brought the power supply to Soundcraft, and then to Westlake. On the bench it always checked out OK, but as soon as he got it home and powered up the board, the noise returned. “Zit-zit. Zit-zit.” It went straight to the console outputs, making mixes nearly impossible.
At the time, Joe lived in the hills of Pasadena, near the Rose Bowl. He had a beautiful home, filled with unusual instruments and souvenirs of his world tours. (I was thrilled to meet Joe —- the guy who’d written the Jazz classic “Mercy Mercy”, played with Miles Davis, and recorded all those great solo albums, and founded Weather Report!) Joe let me in and showed me the problem. It was weird — just an odd little noise that repeated over and over again. I set up my scope and saw that the noise was on every output of the console.
At one point I powered down the console, and was surprised to see that the noise was still on the power supply outputs. It was STILL there with all the other studio equipment shut off. Well, that was a clue! If the noise was not originating in the studio gear, where was it coming from? I connected my scope to an AC power outlet and there was Joe’s noise, etched in blue on the CRT — “zit-zit. zit-zit”. Apparently, it was an AC power problem.
There were a lot of radio and TV transmitters near Joe’s house and I wondered if the noise might be originating from one of them. But in case the noise was caused by something in the house, I would start by shutting down the circuit breakers in his house, one by one. When I switched off the breaker for his living room, the “zit-zit” stopped. A clue!
I wandered into the living room and started looking around. Something plugged into one of the living room wall outlets must be causing it, but what would produce a noise that repeated over and over that way? My attention was drawn to a large tropical fish tank in a corner of the room. Looking closely, I noticed that the pump motor seemed to be sputtering a bit. When I put my ear near it I saw small blue arcs and heard a familiar sound from the motor: “Zit-zit. Zit-zit.”
When I unplugged the fish tank the console was suddenly quiet. There had never been anything wrong with it. The arcing in the motor was producing RF interference. The RFI passed through the air to the summing busses in the console, which dutifully amplified the noise and sent it to all outputs.
Joe was blown away. He had the motor replaced and the noise never returned. Over the next few years, Joe became one of my favorite clients. For service calls, he liked me to come early in the morning, and he’d often cook breakfast for me.
The moral: Analog mixers are sensitive to RF and electromagnetic interference. When planning a new studio, consider potential noise from sources such as AC wiring, circuit breaker panels, copiers, air conditioners, and other motorized machinery.