Sterling Audio ST77 Mods
The Sterling ST77 is a high-noise FET microphone with what appears to be a variation of the ADK A-51/MXL 2001 circuit.
The mic has relatively high sensitivity, but like most Sterling mics, relatively high noise. The circuit offers insufficient and perhaps even unintentional high-frequency correction: -2dB @ 20kHZ. This results in a slightly over-bright voicing that limits the microphone's utility. The mic's grille causes a surprisingly sharp EQ effect: -2dB @ 4kHz and +0.5dB @ 8-12kHz; if you replace the capsule, we recommend replacing the grille too.
We have three modification options for the Sterling ST77:
#1: Capsule Replacement
The capsule in the ST77 appears to be a standard Chinese 32mm K67, with thin brass shims over plexiglass clamping rings. If you find the microphone to sound thin, harsh, or metallic, blame the capsule.
The RK-47 is a fine replacement/upgrade capsule for the ST77. It is better suited to the stock circuit than is the ST77's original capsule.
The RK-12 is an alternative replacement/upgrade capsule for the ST77. It has a broader, lower amplitude presence boost in the high frequencies than does the original capsule, giving it a much more balanced sound.
Both these capsules should install easily onto the Sterling mic's existing mounting post, using the "supersaddle" enclosed with the RK-47 and RK-12.
Read more about these capsule voicings.
#2: Grille Upgrade
The ST77 grille can be easily replaced and upgraded with our custom TLM49-style grille. Our design has no internal parallel surfaces, which can reduce standing-wave reflections within the acoustic cavity. Our grille has a more neutral frequency response too.
Click more info on our replacement grille for the Sterling ST77.
#3: Circuit Upgrade
We have adapted our best-selling T-84 circuit kit to fit the ST77. You'd remove the mic's existing circuit and transformer and install our parts instead. The mic will have lower noise and rich harmonics. We strongly recommend pairing this circuit with the RK-12 or RK-47 capsule.