IGS S-Type 500 VU Stereo Compressor

Review of the IGS S-Type 500 VU Stereo Compressor

IGS Audio, based in Poland, design and manufacture a growing range of rack mount and 500 Series analogue processing gear, both solid state and valve based.  The S-Type 500 VU is an update of the previous S-Type 500 now featuring a very nice illuminated VU meter in place of the previous LED based metering.

With a small clue in the S-Type naming, the S-Type 500 is based on the master bus compressor first used in the SSL SL 4000 G Series Console.  So we are talking about a design based on the probably the most famous console master buss processor in history when the SL 4000 console was an almost de facto buy for any top end music recording studio back in the heady days of the ‘80s.

IGS’s design is true to the original with the use of twin VCAs, one in each channel of the main signal path and a second shared VCA in the sidechain which derives the main VCA control voltage.  The original SSL design used the classic DBX VCA, sadly no longer available, so many of modern designs, including the IGS, use the THAT chip instead which has an excellent audio performance.

The S-Type 500 VU occupies two slots in a standard 500 Series rack frame but of course provides two channel stereo I/O.  The module electronics are housed in an enclosed metal enclosure which can only be good for screening out external sources of interference.

The front panel has a similar range of functions to the original G Series compressor but with some important additions as we’ll see.

The switched attack control has the same six choices of attack speed being 0.1, 0.3, 1, 3, 10 and 30ms.

The switched release control has the five original selections, being 0.1, 0.3, 0.6, 1.2secs and auto, plus a sixth option of 2.0secs.

Threshold is adjustable from -20 to 0db using a rotary control and a further rotary provided post compression makeup gain of 0 to +20dB, both controls have detents to make resetting easier.

Ratio selection is switched and offers the same three ratios as the SSL original, so 2:1, 4:1 and 10:1.

In addition to the front panel ¼” jack socket which allows an external sidechain signal to be inserted (just like the original), the S-Type 500 provides its own sidechain low-cut filter switchable between ‘ext’, ‘off’, ‘60’, ‘90’ and ‘120Hz’.  This allows you to control how much the compressor is affected by low frequency elements of the mix, especially the kick drum.

A major addition is the provision of parallel compression which allows the compressed and uncompressed signal to be mixed from 100% dry (no compressor contribution) to 100% wet (all compressor contribution).  In this way it’s possible to push the S-Type 500 into fairly heavy compression and then blend a proportion of this ‘bottom up compression’ into the clean mix.  This is a common way to add body to certain types of sources and is particularly useful when used across the stereo drum buss, which is one of the main ways I use this compressor during mixdown.  You can read more about parallel compression here.

The unit also has a switch for true relay based bypass so you can easily compare the in/out impact of the unit within the mix.

Maximum input and output levels are a respectable +20dBu and +21dBu respectively and distortion is quoted at 0.012% at 0dBu.  The noise spec is very good at -102dBA so it is well up to working within a high spec environment.

For any situation where you prefer VCA based stereo compression, then the S-Type 500 VU is a strong contender.  It has that SSL G Series sound within a very affordable 500 series package.  Although I use my unit as part of my stereo drum buss chain, it is great across the two buss and I see no reason why it wouldn’t be a good addition to any mastering facility.