Sterling Audio ST55 Microphone Mod

Sterling Audio ST55 Microphone Mod

sterling audio st55 mod
Sterling ST55 mod

The ST55 (aka the Groove Tube GT55) mic is a medium priced microphone which makes a fantastic donor body. These are transformer coupled mics built into a very heavy high quality body. What’s more is that the ST55 features two external switches – a 10dB pad and a Low cut filter.

Why upgrade?

The stock ST55 uses a “resonator disk” capsules which was an attempt to add some top-end to the tone. It also uses a pretty dull and boring sounding transformer. The result is a sibilant and harsh top end without a lot of warmth and color. With our mod, you get a high quality capsule, transformer and brand new circuitry using our BFM board. We can transform your ST55 into a high quality vocal or instrument microphone. See more general Information about our mic mods here.

Custom Mic Options

We can only rebuild the ST55/GT55 as a Transformer-coupled mic. Our Transformer-Coupled BFM circuit is based on the classic Neumann KM84 circuit adapted for a Large Diaphragm Capsule. The Pad and Filter switches are fully supported and work as expected. Our BFM board supports an optional internal pattern switch to select Cardioid/Omni modes. The caveat is that the ST55 is not as easy to open and re-close as most other mics so that option may not be desirable for everyone. Without the switch, the mic is fixed as Cardioid.

We typically use a high quality CineMag Transformer but there are other options as well. In general, the BFM gives us an extra bit of transformer color or mojo. There is some extra fatness in the lows and low-mids due to the harmonic distortion of the transformer as well as a subtle bit of dynamic compression on transients.

For capsules, we use a Center Terminated k47 style. The K47 gives us a harmonically rich mid-forward classic tone that you think of coming from the great Neumann microphones. Our k47 capsule is a high quality approximation of the Neumann Capsule. Never sibilant or harsh but with a wonderful clean top-end.

Choose your rebuild and options below or contact us for more information!