pro-audio products

mid side pro-audio compressor

A dual channel precision optical compressor optimized for the stereo buss with features not found on any other LDR compressor manufactured today.

buy buzz audio | US$2590 | €2295 | £2030 |

vocal tracking compressor bass tracking compressor

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design features

compressor stereo buss

audio path quality

The entire audio path of the SOC-20 optical compressor is made using our proprietary Class A discrete transistor BE41 amplifiers with a Lundahl LL1517 transformer at the output. A special low impedance power supply design is used to enhance the sound quality of the amplifiers by providing very stiff power rails. This overall combination produces a unique sound character with full bass and a vibrant top end void of any midrange harshness. Whilst the SOC-20 is not a clone of any vintage units, it's design is inspired by the use of the LA2 and LA3 by it's designer Tim Farrant.

mid-side processing power

Not only can the SOC-20 be used in dual mono or stereo mode, we have also incorporated a Mid-Side (or sum and difference) encoder and decoder. When set to MS mode, the stereo input is divided into signals that are common to left and right (called the mid) and signals that are not (called the side). The divided signals are sent to each channel of the SOC-20 then recombined at the output thereby allowing you to adjust the dynamics and width of the stereo image. This process has application on a wide range of stereo sounds including the mix buss and electronic music sub mixes. 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 found in modern music styles. The side chain monitor function allows you to hear what is returning into the insert point and also monitors the mid or side signal when the compressor is used in MS mode.

stereo optical compressor

control genius

The unique differential side chain circuit of the Buzz Audio SOC-20 splits the audio into positive and negative waveform and processes it separately to obtain a differential drive into our custom 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 intelligent auto modes allow for true "set and forget" operation. The 5 "soft knee" ratio settings allow for gentle to strong levelling, with the selected ratio only actually acheived at 10dB of gain reduction. The SOC-20 opto compressor is extremely musical - ideal for vocal and instrument recording plus it is equally at home on the stereo buss to glue your mixes together - a truly multi-purpose studio compressor now available in a mastering version.

Related products - | SOC-M mastering version | Essence 500 series optical compressor | Velox Optocompressor |

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.

user comments

bass compressor

Stuart Emerson

The Buzz SOC-20 arrived today and I'm just getting it fired up now. My first impressions are that it sounds clean but not too clean! It has a bit of attitude about it and the frequency range seems very wide from low to high with none of that veiled quality that some other comps have. It sounds expensive and classy and the auto modes are just like cheating - I wasn't expecting to like them as I'm a bit of a tweak freak. But it sounds great on everything from acoustic guitars to vocals and bass and the mix too, so I couldn't be happier. The M/S feature is stunning - very powerful. Thank you very much!
[Stuart works with Lorraine Crosby in the UK]

product review

Tape Op magazine by Steve Silverstein

New Zealand gear manufacturer Buzz Audio is best known for its REQ-2.2 mastering EQ [Tape Op#71], which some have compared to a classic Sontec. This impressive reputation made me curious enough to buy Buzz Audio's top-of-the-line compressor, which has achieved less visibility so far.

The SOC-20 sells for US$2450 street, which prices it competitively to other stereo electro- optical compressors like the Manley ELOP and the Pendulum Audio OCL-2. The Manley offers far less flexibility, and both the Manley and Pendulum use tube make-up gain behind the light cell. The SOC-20 has similar compression characteristics to these compressors; it's very transparent when hit subtly, and it can apply more drastic compression without adding artifact or exaggeration.

What stands out about the SOC-20 is its solid-state make-up gain. While I expected a relatively transparent signal path, perhaps because it includes Lundahl transformers, the SOC-20 make-up gain circuit surprised me by adding grit and character. The closest comparison would be the 1176 make-up gain; the SOC introduces a somewhat comparable color, behind a very different compression characteristic. The compression itself is very flexible, with either adjustable or fast/modern attack and release settings; five compression ratios; and even a balanced sidechain insert with a monitor switch and built-in high-pass filter.

saxophone compressor Another interesting and useful feature here is the Mid-Side functionality. When enabled, the left channel compresses the center sounds, and the right channel only affects the outside. If the sidechain is unused, it is possible to monitor only mid or side by engaging the sidechain monitor switch for the other channel, which results in monitoring silence for the center or sides.

The backlit meters look quite impressive too. For the first mixes I used the SOC-20, I had the best results on saxophone and drums. In a jazz recording where the sax did not quite have the thickness that I wanted, the SOC-20, with a low ratio setting, provided the subtle, organic compression that I'd expect from an electro-optical cell. The low-mid emphasis of the make-up gain helped to place the instrument's tonality nicely in the mix.

With drums, I wanted a bit more drastic compression to help tame an unruly cymbal in an overhead mic. The 6:1 ratio setting helped to bring down the cymbal without introducing any noticeable artifact, and the make-up gain's coloration also helped to bring a bit more impact to the toms. The SOC-20's combination of high-quality electro-optical compression, 1176-ish make-up gain, and impressive flexibility offers a distinctive feature set at a competitive price.


Maximum Input Level; +32dBu
Maximum Output Level; +27dBu
Maximum Input/Output Level; S/C Insert +22dBu
Noise; -95dBu Stereo Mode, -90dBu M/S Mode (measured with no make up gain and A Weighted).
Gain; variable from 0dB to +15dB
Frequency Response; 3Hz to 120kHz measured with +10dB gain and no gain reduction.
Harmonic Distortion; No gain reduction 0.08% @ 100Hz, 0.025% @ 1kHz, 0.02% @ 10kHz, 0.05% @ 100kHz
Harmonic Distortion; With 20dB gain reduction (Attack AUTO, Release 16) 0.1% @ 100Hz, 0.06% @ 1kHz, 0.04% @ 10kHz
Harmonic Distortion; With 20dB gain reduction (Attack AUTO, Release AUTO) 2% @ 100Hz
Standard Operating Level; +4dBu = 0 VU meter display. Size 2 Unit 19" rack mount, (482Wx88Hx250D).
Power requirements; 230V/115V selectable, IEC detachable power cable.

Specifications are typical of a production unit and are subject to change without notice. 0dBu reference = 0.775 volts RMS.

  Buzz Audio Ltd
  New Zealand
  Ph +64(0)3-577-5597

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