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9 polar patternsTNC Audio ACM-1200

Multi-Pattern Tube Condenser Microphone

The ACM-1200 is a multipattern tube microphone.

ACM-1200 tube circuitACM-1200 tube circuit

Switches on the mic body provide access to a -10dB pad and a high-pass filter (frequency and slope not specified). A switch on the power supply provides access to 9 polar pickup patterns.

Under the microphone body is a two-sided circuit board with discrete components and a socketed 12AX7B tube.

The 32mm large-diaphragm capsule has two center-terminated membranes. They are protected by three layers of screening; the headbasket is constructed of two layers of medium-gauge metal mesh with a middle layer of fine-gauge wire screen sandwiched in between.

The included elastic shockmount is lightweight (195g) but surprisingly effective. The mic is held by a spring-loaded padded ring that is much faster to operate than screw-mount designs (at the possible risk of being less secure, especially over time).

The mic ships in a padded flightcase with the shockmount, foam windscreen, a vinyl storage pouch for the microphone, dedicated power supply with pattern selection switch, and a microphone cable.

TnC and Terry Manning’s Lucas Engineering have announced the availability of upgraded transformers and circuits for the ACM-1200:

  • Transformer model T14-1200 ($75) - Drop-in replacement for stock ACM-1200.

    Oliver Archut

    The 14-1200 is an upgrade for the stock electronics (aside from the changed ratio it is identical to the T14-C12). [Besides providing] higher resolution it also smooths out the high end as well making the low end a bit more robust.

  • Transformer model T14-C12 ($75) - Replacement transformer for ACM-1200, to be coupled with the custom C12-based electronics PC board upgrade (based on Oliver Archut’s design parameters for his C12VR upgrade electronics).

    T14-C12 the standard Hiller type x-former used in the very early C12 and some 250/251. Ratio 12 to 1 with a 200 Ohm output and works best with either a 12AT7 (the best is still the Telefunken ECC81, or the one and only tube to use in C12 type of mics — the ECC801s). The 6072a will work too, but the price these days is ridiculous.

  • Transformer model T47 ($85) - Replacement transformer for ACM-1200 with U47-like transformer characteristics (BV8), to be coupled with the custom “47” electronics PC board upgrade (based on a simplified 47-inspired electronics circuit).
  • Transformer model T49 ($85) - Replacement transformer for ACM-1200 with UM49-like transformer characteristics, to be coupled with the custom “49” electronics PC board upgrade (based on a simplified 49-inspired electronics circuit).
  • Transformer model T67 ($90) - Replacement transformer for ACM-1200 with U67-like transformer characteristics, to be coupled with the custom “67” electronics PC board upgrade (based on a simplified 67-inspired electronics circuit).

Terry Manning

The T14-1200 transformers are based on the Hiller T14-C12 transformer (ratio 12 to 1), as used in early C12 mics, but have the ratio of 9 to 1 as used in the stock ACM-1200.

The 47-49-67 transformers are based on a Neumann-inspired transformer. They come in the three different ratios of 6:1 for 47-styled electronics, 10:1 for 49-styled electronics, and 7:1 / with feedback winding for 67-styled electronics.

As of late July 2009, the T47 and T49 mod circuit boards are available and shipping; see the Bulldog TnC Mic Mods page. Transformers and electronics for the T67 and T14-C12 are not yet available.

The TNC Audio ACM-1200 is also known as: ACM1200.

The mic was released in 2008.


Pickup Patterns Pads & Filters
Cardioid (20 mV/Pa; n/a)
  • Pad: -10dB (Via Switch)
  • Filter: HPF (Via Switch)
Capsule Dimensions Impedance SPL/Noise
Diaphragm diameter: 25mm
Capsule diameter: 32mm
200 Ohms (Low) Max SPL: 134 dB
Weight Length Max Diameter Interface(s)
660g (23.28oz) 237mm (9.33'') 46mm (1.81'')
  • 3-pin XLR male (1)
Power Specifications
  • Includes tube power supply

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