IGS Audio Alter FET comp (like 1176), transformer coupled 500 series

The ALTER is a single-channel unit with stepped input and output controls. The Ratio switch has six positions, including two additional to the original 1176 1:1 and 2:1 settings. Slam Mode can be turned on with a separate switch, working regardless of the Ratio settings. Attack and release times can be set to Fast / Mid / Slow with 3-pole switches. The compressor is equipped with a relay bypass, achieved on the front panel. The input is balanced with a modern, low-noise op amp and the output with a Carnhill transformer. The circuit has two amp stages, between which is the output control. The stage amps are based on the discreet API2520 circuit. The level of gain reduction is shown by a 20 point led bar. Front panel 1. Input - Input level and compression depth 2. Output - Output Level 3. Attack - Variable Attack - 3 ranges: 0.02, 0.2 and 0.8 ms. 4. Release - Amp recovery time to the value of 0.85 max. Range: 50ms, 600ms, 1.1 sec. 5. Ratio - compression ratio over the threshold response. 6. Ratio ranges: from 1:1 (line amp), through 4:1 (compressor) to 20:1 (limiter) 7. SLAM - allows the enabling of All-Buttons-On - the "secret weapon" of any studio engineers ;) 8. COMP IN / OUT - Enable Bypass relay device 9. GR - very fast LED indicator showing the compression level in the range from 0 to 20dB.