Xaudia Microphone Blog: Synchron / Vega S10 Microphones

The Syncron Corporation are generally credited with launching the first transistorised capacitor microphone back in 1964 - the AU-7a, which was priced at $169.50 USD. In their own marketing, the manufacturer claimed to have built "the first microphone to successfully employ the Field Effect Transistor." At the time, competitors such as Neumann were selling microphones with tube circuits such as the KM64 and U67 which required a separate power supply. The Syncron mics ran on batteries which saved lugging around an extra box and cable. I know we all love and revere the old Neumann tube microphones, but few would argue that they take longer to set up and warm up than a solid state mic.

Syncron-Vega S10 microphons

Following the AU7a, Syncron launched their second and final microphone, which was a rather nice small diaphragm condenser known as the S-10. By this time, the brand was owned by 'Vega Electronics Corporation' and had the address on their documents had moved from Connecticut to Santa Clara in California. The price for new microphones was $260.

I was sent three S-10 microphones to clean, service and convert to phantom power for a customer. These mics were badged 'Vega'./ Like the AU7As, they were designed to run on two obsolete batteries, and so being able to run on standard +48V would be make them much more useable.

Vega S-10 original circuit and transformer,

The mics were a bit of a mess. They had been stored damp at some point and showed corrosion inside and out. I wanted to be sympathetic to the original simple circuit They are a one-transistor circuit with an output transformer, much like a Neumann KM84, and so for the phantom conversion I decided to re-build with a KM84 style circuit, keeping the original transformers.

KM84 type circuit - Russell Technology board

With a bit of improvisation I was able to rebuild the circuits using circuit boards from Russell Technologies, utilising the space freed by removing the batteries to house the phantom circuit and the transformer. The circuit boards were originally designed as an upgrade for the AKG C480B, and uses a smaller transformer than the Vega. To accommodate the larger transformer I hacked off the end of the board and wired the transformer directly.

PCB from Russell Technologies - rear

S-10 with new PCB and transformer in place.

These microphones used a 4-pin XLR output. The fourth pin was used to make a connection to the battery within the plug of the connecting cable, which means that the batteries would not go flat so long as the microphone was unplugged between sessions. I swapped these for standard 3 pin XLRs of course.

Is four better than three? No.

Although we started with three microphones, one capsule was bad and one transformer was open circuit, so we have two nice condenser microphones, which are well balanced and sound good. The sound is a little less bright and a touch warmer than a KM84. I liked these microphones and was sorry to see them go home.