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IGS Audio Alter 500

500 Series Mono FET Compressor Module

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  • Alter 500 (Front)
  • Alter 500
RRP: £610.00 (You save £38.00)
£572.00 (inc VAT) £508.33 £476.67 (exc VAT)
Usually Ships in 48 Hours
3 Years
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The classic 1176 sound - now in the 500 series

The Alter 500 from IGS Audio brings classic 1176 FET compression to your 500 series rack.

The Alter 500 is based on the original '70s UREI 1176 limiting amplifier. It inherits all of the features from the original unit, but with some added extras. The Alter includes additional 1:1 and 2:1 ratios, as well as the SLAM switch. This switch gives you the famous All-Button-In mode from the original 1176. The Slam control works independently from the Ratio setting. The other standard ratios included are 4:1, 8:1, 12:1 and 20:1.


The Alter 500 features all stepped controls, for easy recallability. The Input knob adjusts the level of the signal fed into the compressor. The Output knob controls the amount of make up gain applied to the signal after the compression has taken place.

Attack and release times can be set to Fast / Mid / Slow with 3-pole switches.

The Alter is equipped with a relay bypass, switchable 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 discrete API 2520 circuit. The level of gain reduction is shown by a 20 point led bar.


The Alter 500 is useful on almost any source. The 1176 style compressor is popular for vocals, bass, drums, percussion and more.

Team the Alter 500 up with the IGS One LA 500 for a classic compression combo of fast and slow, popular on all types of vocals and bass.


  • FET Compressor
  • All stepped controls
  • Discrete input opamps
  • Carnhill output transformer
  • Ratio: 1:1, 2:1, 4:1, 8:1, 12:1, 20:1
  • Slam (All-buttons) switch
  • Attack: Fast (20μs), Med (400μs), Slow (800μs)
  • Release: Fast (50ms), Med, (600ms), Slow (1.1s)
  • Standard 500 Series format

Pay over up to 12 months - interest free.

Deposit 6 Months 10 Months 12 Months
£115.80 (20%) £77.20 per month £46.32 per month £38.60 per month
£144.75 (25%) £72.37 per month £43.42 per month £36.18 per month
£173.70 (30%) £67.55 per month £40.53 per month £33.77 per month
£231.60 (40%) £57.90 per month £34.74 per month £28.95 per month
£289 (50%) £48.33 per month £29.00 per month £24.16 per month

SKU: alter-500

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