The BISON 500 is a stereo M/S matrix with a parallel dry/wet mixer in API 500 format, built by IGS Audio as a routing tool that extends the capabilities of any existing dual-mono or two mono compressors and equalizers. The BISON itself does not process audio – its function is to encode a stereo L/R signal into Mid/Side before external processors, and decode it back to stereo L/R on the return, with a Mix knob blending the processed signal against the dry input. Two stereo TRS jack connectors on the front panel serve as send and return for external inserts, a three-position toggle switch selects the operating mode, and a large Mix knob controls the parallel blend. Electrical performance: THD+N 0.001% at 0 dBu, dynamic range 100 dB, SNR –99 dBA, frequency response 20 Hz – 20 kHz ±0.1 dB.
M/S mode – how BISON 500 splits and reconstructs the stereo image
In M/S mode the module performs a complete analog encode and decode matrix in the signal path. The left insert channel carries the Mid signal (L+R sum – the centre of the stereo image), the right channel carries the Side signal (L–R difference – the stereo width information). A compressor patched into the left channel compresses only the centre – affecting vocals, bass, and central elements without touching the sides. A compressor on the right channel compresses only the sides – reducing or expanding stereo width independently of the centre. Two different processors can be used simultaneously: one compressor on Mid, a different one on Side, or an equalizer on one channel with no effect on the other. After the inserts BISON decodes the M/S matrix back to stereo L/R before the output.
Parallel and Stereo – the two remaining operating modes
Parallel mode routes the signal through the external processors and blends the result with the dry input using the Mix knob – without building a separate parallel chain on the console or in the DAW. Heavy compression at 100% wet delivers pump and density; pulling the Mix back to 30–40% restores the natural dynamic envelope while retaining the colour and weight the processor contributes. Stereo mode passes the signal through the inserts without M/S encoding – the BISON functions as a simple stereo insert send/return with a parallel blender. A 5-point LED VU display monitors signal level. Input impedance 2 kΩ, output impedance 600 Ω, maximum input level +22 dBu, maximum output level +22 dBu, power consumption 8 W.
KEY FEATURES
- Stereo M/S matrix + parallel mixer, API 500 format
- Two stereo TRS jack connectors on the front panel (send + return)
- Three-position mode switch: M/S / Parallel / Stereo
- Mix knob – continuous dry/wet blend
- Fully analog M/S matrix, encode and decode in the signal path
- Independent Mid and Side processing via external processors
- VU metering: 5-point LED
- THD+N: 0.001% at 0 dBu
- Dynamic range: 100 dB
- Stereo Link: yes
TECHNICAL SPECIFICATIONS
- Type: stereo M/S processor + parallel mixer, API 500
- Operating modes: M/S / Parallel (Dry/Wet) / Stereo
- Inserts: 2× stereo TRS jack (send + return, front panel)
- Input impedance: 2 kΩ (balanced)
- Output impedance: 600 Ω (balanced)
- Operating level: +4 dBu
- Maximum input level: +22 dBu
- Maximum output level: +22 dBu
- Dynamic range: 100 dB
- SNR: –99 dBA
- THD+N: 0.001% (0 dBu)
- Frequency response: 20 Hz – 20 kHz ±0.1 dB
- Metering: VU, 5-point LED
- Stereo Link: yes
- Power consumption: 8 W
