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CardioidAKG Acoustics SolidTube

Cardioid Tube Condenser Microphone

The AKG SolidTube is a large-diaphragm vacuum tube condenser with fixed Cardioid polar pattern. It was one of the first ‘affordable’ tube condensers for the project studio market, with an MSRP of $1500.

The mic uses a commonly available tube, the 12AX7/ECC83, selected for being “readily available from musical instrument dealers carrying spare parts for guitar amps,” according to AKG.

The mic’s frequency response is nominally flat from 20 - 20KHz with a presence peak at 4kHz and 10kHz. Its self-noise is 20dBA, moderate for a large-diaphragm tube mic.

Surprisingly, the SolidTube’s edge-terminated capsule is a prepolarized or electret type, rather than a true (externally-polarized) condenser capsule. Given its ~9V polarization voltage, a capsule swap to a true CK12-style capsule is not possible without more-extensive circuit modifications.

Mix 1998
I had a chance to compare Solidtube with a C12VR. In the cardioid setting, the C12VR has tight pattern control, while Solidtube’s cardioid pattern gets progressively wider in the upper midrange, becoming nearly omnidirectional above 4 kHz.

Sound On Sound 1998
I was surprised to note that in direct comparison with microphones that I know are good studio performers, the SolidTube sounded less honky or nasal, even though these were characteristics I’d never have associated with the other mics without this direct comparison.

The mic ships with a shockmount (AKG p/n H-Solid), power supply and cable, a foam windscreen (p/n W-Solid), and an aluminum carrying case.

Permalink: AKG Acoustics SolidTube

The mic was released in 1997.


Pickup Patterns Pads & Filters
Cardioid (20 mV/Pa; 20 - 20,000 Hz)
  • Pad: -20dB (Via Switch)
  • Filter: HPF: 12dB/Octave @ 100 Hz (Via Switch)
Capsule Dimensions Impedance SPL/Noise
Diameter n/a
200 Ohms (Low) Max SPL: 145 dB
Self-noise: 20.0 dB(A)
Weight Length Max Diameter Interface(s)
920g (32.45oz) 219mm (8.62'') 63mm (2.48'')
  • 3-pin XLR male (1)
Power Specifications
  • Includes tube power supply

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