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Buzz Audio SOC-20


An audio compressor using light dependant resistors as the gain reduction element. It is a design extension of our original SOC-1.1 optical compressor featuring the same differential drive side chain process with additional features.

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The main signal path of the Buzz Audio SOC-20 compressor (including the mid/side processor) is made using our proprietary BE41 discrete class A amplifier with a Lundahl LL1517 transformer at the output. A special low impedance power supply design is used to enhance the sound quality of the BE41 amplifiers. The overall combination provides a sound character that is generally described by our users as “desireable”!

mid-side processing power

We have incorporated a mid-side (or sum and difference) encoder and decoder into the Buzz Audio SOC-20. When set to M/S mode, the stereo input is divided into signals that are common to left and right (mid) and signals that are not (side). The divided signals are sent to each channel of the Buzz Audio SOC-20 then recombined at the output allowing you to adjust the dynamics of the stereo image. Check out the audio samples to see how powerful this process can be.

side chain flexibility

At the flick of a switch, a high pass filter reduces the compressor sensitivity to low frequencies for more bass punch when used on program material. We have also included a fully balanced side chain insert point so you can add additional equalisation to the compressor characteristic or “key” the compressor with another source to create those pumping effects. The monitor function allows you to hear what is returning into the insert point and the mid or side signal when in that mode.

control genius

There are 5 compressor attack settings and 6 release settings that cover a wide range of response possibilties. In addition, our intelligent auto modes allow for true “set and forget” operation. The 5 ratio settings allow for gentle levelling or strong compression up to full on squash.


controls and functions

DRIVE – variable pot that sets the amount of compression.
OUTPUT dB – variable pot that adds gain at the output to correct for lost level.
ATTACK – rotary switch with 1mS, 10mS, 25mS, 50mS selections and the excellent AUTO mode.
RATIO – rotary switch with 2:1, 4:1, 6:1, 10:1 and 20:1 selections – all soft knee characteristic.
RELEASE – rotary switch with 100mS, 200mS, 400mS, 800mS 1600mS selections and our superb AUTO mode.
BYPASS – hard wire unit bypass to compare compressed and uncompressed signals.
METER – switches the VU meter between input/output levels or amount of compression.
S/C HPF – inserts a 170Hz high pass filter into the side chain for added bass punch.
S/C INSERT – engage the external side chain insert point and monitor the side chain signal.
LINK A/B – joins the side chain of each channel for stereo operation with “soft” tracking.
There is also a locking toggle to select STEREO or MID-SIDE mode and a handy POWER on/off switch.

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