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.
Due to popular demand we have released a mastering version of the SOC-20 optical compressor. The SOC-M mastering version replaces the DRIVE and GAIN pots of the SOC-20 with stepped Elma attenuators for repeatability. We have also adjusted the RATIO’s to suit mastering tasks and all the ratio’s feature our famous “soft knee” characteristic. The SOC-M signal path utilizes our Class A discrete BE41 transistor amplifiers powered by a special low impedance power supply for vibrant sonic detail. As standard, the SOC-M is fitted with a Lundahl LL1517 output transformer providing a nice sheen to the sound. The unit is also available with a transformerless output option.
analog mid-side processing
But not only is the Buzz Audio SOC-M a stereo compressor, it also incorporates a Mid-Side (or sum and difference) encoder and decoder which is a very powerful mastering tool. When set to MS mode, signals that are common to left and right are processed by Channel A and the left to right difference signals by Channel B. Check out the SOC-20 audio samples to see how powerful this process can be. In addition, when set to MS mode, the mid and side signals are available as balanced outputs on the rear panel insert send XLR’s
side chain design
At the flick of a switch, a 12dB/octave high pass filter at 170Hz reduces the compressor sensitivity to low frequencies for more bass punch. We have also included a fully balanced side chain insert point so you can add additional equalisation to the compressor characteristic. The side chain monitor function allows you to hear what is returning into the insert point (the side chain) and you can also monitor the mid or side signals when the compressor is used in MS mode.
stereo optical compressor
dynamic range control
The 5 ratio settings feature a soft knee characteristic whereby the selected ratio is only actually acheived at 10dB of gain reduction. Therefore very gentle compression is available when using 2:1 and 3:1 and even 10:1 is usable for material that needs stronger dynamic control. The unique differential side chain circuit of the SOC-M splits the audio into positive and negative waveform and processes it separately (attack and release parameters) with the resulting balanced signal controlling the Buzz Audio BE45 electro-optical attenuator. There are 5 compressor attack settings and 6 release settings that cover a wide range of response possibilities. In addition, our clever auto modes produce very musical results. The auto attack adapts to incoming audio rise time, and the auto release will decay quickly from short impulses but longer from sustained or low frequency signals.
controls and functions
DRIVE – 24 position Elma switch that sets the amount of compression.
OUTPUT dB – 24 position Elma switch 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, 3:1, 4:1, 6:1 and 10:1 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.