recordinghacks

OmnidirectionalAvenson Audio STO-2

  MSRP: $549 Omnidirectional Condenser Microphone

Avenson Audio STO-2

Description

The STO-2 is a small diaphragm condenser with an omnidirectional pickup pattern, sold in matched pairs for use in stereo miking applications. The case is machined out of solid aluminum.

This mic started life with a TapeOp article by Joel Cameron called “How to Build a Microphone.” Over months of experiments, revisions, and improvements, Erik Wofford and Brad Avenson elaborated the original concept kit, powered by a 9V battery, into a beautiful, professional-studio-level microphone, the STO-2.

Early versions of Wofford and Avenson’s mic were called “Stapes Omnis,” and you’ll find references to these in audio forums and rec.audio.pro. The ‘STO’ in the STO-2 model number stands for STapes Omni; the ‘2’ indicates additional improvements by Brad Avenson.

The Cameron article called for an inexpensive electret omni capsule from Panasonic, the WM-66AY, although apparently this was a typo — the correct part number is WM-60AY. This capsule has since been discontinued, but the WM-61A and WM-61B are reported1, 2 to be comparable.

The same capsule powers T.H.E.’s highly regarded KP-6M Reference microphone, some of Earthworks’ mics, and the inexpensive Behringer ECM80001.

Eric Wofford

Yes, we use the same Panasonic capsules that Earthworks use in their microphones. The difference between ours and the Behringer mics, or just straight out of the box is quite substantial. We modify the capsule so that the FET is rebiased, allowing for a balanced signal, and a drastic increase in SPL limit from the Behringer. The mics are now phantom powered, which is not an easy circuit to build on a board the size of your thumbnail, and the noise is nowhere near as bad as the Behringer mic.

See this TapeOp thread for numerous praiseworthy comments about the Stapes mics.

The Avenson Audio STO-2 is also known as: Stapes Omni, STO2, STO.

Specifications

Pickup Patterns Pads & Filters
Omnidirectional (5.25 mV/Pa; 20 - 20,000 Hz)
Capsule Dimensions Impedance SPL/Noise
Diaphragm diameter: 6mm
 20 Ohms (Low) Max SPL: 145 dB
Self-noise: 28.0 dB(A)
Weight Length Max Diameter Interface(s)
100g (3.53oz) 127mm (5.00'') 25mm (0.98'')
  • 3-pin XLR male (1)
Power Specifications
  • Requires phantom power
  • Phantom voltage: 48v

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