Groove Tubes GT57
Multi-Pattern Condenser Microphone
The GT57 is a multipattern FET condenser, designed by Aspen Pittman.
Three switches around the base of the grille allowed selection of:
- -10dB pad (which raised the max SPL to 144dB @ 1% THD)
- a high-pass filter, -12dB/octave @ 75Hz
- Polar pattern: Cardioid, Omni, Figure-8
The mic used Pittman’s disk resonator capsule. This was a 32mm, center-terminated capsule believed to be based on the Neumann K67 backplate design. A small metal disk is attached to the center termination screw to increase the capsule’s sensitivity to high-frequency sounds.
The mic’s impedance conversion circuit was built with through-hole components. It used a custom-wound output transformer with a nickel core.
The mic’s body as all brass, nickel-plated and painted black. The grille is made of stainless steel.
Permalink: Groove Tubes GT57
|Pickup Patterns||Pads & Filters|
(32 mV/Pa; 20 - 20,000 Hz)
Cardioid (32 mV/Pa; 20 - 20,000 Hz)
Bidirectional (32 mV/Pa; 20 - 20,000 Hz)
| Diaphragm diameter: 26mm
Capsule diameter: 32mm
Diaphragm gauge: 3 microns
|200 Ohms (Low)||Max SPL: 144 dB
Self-noise: 22.0 dB(A)
|n/a||19mm (0.75'')||64mm (2.52'')||
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