Studio microphone Sterling Audio ST51 FET

Sterling Audio ST51

This is a cardioid condenser microphone with a field-effect transistor (FET) preamplifier with side signal pickup.

Unlike most Sterling Audio microphones, the ST51 is not a reincarnation of the Groove Tubes model. Unlike most other GT/Sterling large diaphragm microphones, the ST51 uses a 6-micron diaphragm instead of the 3-micron material typical of the ST55, ST59, and ST66.

The outer diameter of this capsule is 33 mm, with a diaphragm of 25 mm. Only the front diaphragm is metallized; the back is transparent mylar. The drilling pattern of the back plate is characteristic of the Neumann K67 model.

The ST51 FET PCB has high sensitivity (30 mV/Pa) and a transformer-coupled output signal, which is typical for other Sterling models. The impedance conversion circuit consists of a combination of through-hole and surface-mount components.

JFET — 2SK30A, which is somewhat unusual for an inexpensive microphone. (Most such microphones use 2SK170.)

The ST51 has a heavy cylindrical brass body with a grille made of painted stainless steel.

Specifications of the ST51 large diaphragm condenser microphone with field-effect transistors:

Preamplifier: class A field transistor
Polar pattern: cardioid
Frequency range: 20–20,000 Hz.
Equivalent noise: 22 dB SPL — weighted
Sensitivity: 32 mV/Pa
Maximum sound pressure level: 134–144 dB (adjustable with a pad)
Typical load resistance: > 500 Ohm
Source output resistance: isolated transformer 200 Ohm