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Fox Audio Research

Brian Fox began playing with electronics at ten years of age. As a child he spent endless hours in self-study and experimenting to uncover the secrets of radio technology and eventually built his own tube based amateur radio transmitter and receiver.

In parallel to his technology pursuits Brian studied guitar and, while in high school, was part of a touring choir introducing evil folk music to church congregations across Canada and parts of the Northeast USA. Five albums were recorded in the process, which lead to his interest in recording technology.

He is a graduate of the Music Industry Arts program offered at Fanshawe College, majoring in Recording Engineering. His graduating thesis was a discussion on Kunstkopf (Dummy Head) recording.

Brian spent seventeen years as a broadcast engineer, both in Radio and Television where his responsibilities required intimate knowledge of everything from microphones to 50KW transmitters and all gear in between.

He moved into the field of acoustic testing while working as a software engineer for Microtronix Systems. In recent years he is pursing his passion part-time with a home studio and in the process has applied his considerable technical knowledge and experience to improving low-cost microphones with the mission of providing quality microphones to home studios everywhere.

Mods and Repairs

Fox Audio Research

Fox Audio Research provides upgrades to inexpensive tube microphones such as the Apex 460, Nady TCM-1150, and Aurycle A5500. The modifications are patterned after three well-known vintage microphones: the AKG C12, the Telefunken Ela M 251, and the Neumann U 47.

All the FAR mods include component upgrades. For example, the C12 and 251 mods include a polystyrene input capacitor, a polypropylene output capacitor, and upgraded decoupling capacitors from Nichicon. Stock mic capsules are replaced with Peluso CEK12 or PK47. Transformers are swapped for upgraded Peluso or Cinemag units. And stock tubes are upgraded to selected 6072 or 6922.

Fox Audio Research takes these mods one step further, by implementing circuitry changes to replicate the sonic effects of the original microphones. On the C12 mod, Brian replaces the cathode bias resistor network with a Gallium Arsenide diode, effectively implementing a fixed grid bias voltage circuit. This “removes low frequency response limits and phase distortions” that can occur in the stock circuit.

In the 47 mod, Brian connects the two halves of the dual-triode tube in parallel, providing a 3dB gain in headroom and lowing the circuit’s plate resistance. This allows the tube to drive the transformer harder, and improves the mic’s low-frequency response.

The tube, transformer, and capsule selections within each modification have been rigorously tested and selected for compatibility. The Fox Audio Research website points out that certain combinations of these components can actually change a microphone’s performance for the worse, by causing significant high-frequency response anomalies.

Read more about the Fox Audio Research mods, and hear audio samples at the FAR website.

Selected Mods and Repairs