Alter 500

FET Limiting Amplifier

The ALTER 500 is a FET compressor built in the 500 standard. The FET-type solution was used for the first its application in the legendary UREI 1176 compressor from the 70s. 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.

Till this day no better vocal compressor has been designed!

So much stuff inside!

The compressor is equipped with a relay bypass switch on the front panel. The input is balanced with a modern, low-noise op-amp and the output with an IGS Custom transformer. The circuit has two amp stages, between which is the output control. The stage amps are based on the discrete 990 circuit. The level of gain reduction is shown by a 20 point led bar.

It's so FAT. Can you believe it?

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Specification

Device type
Fet Compressor	Yes

Basic features
All stepped manipulators	Yes

Input & Output
Input Impedance (balanced)	10k ohm
Output Impedance (balanced)	600 ohm
Audio transformers	Yes, IGS Custom, UTM3556

Levels
Operating Level	+4 dBu
Max input level	+20 dBu
Max output level	+22 dBu
Noise Level	-99 dBA
Max. gain	36 dB
Max Gain Reduction	20 dB

Time constants
Attack:	20us, 400us, 800us
Ratio	1:1 to 20:1
Release:	50ms, 600ms, 1.1s

Bandwidth
Frequency response	8 Hz to 20 kHz, +/- 0.1dB

Distortion (@ 20 Hz - 20 kHz)
THD+N	0.012%

Power
Power consumption	2.5W

Packing box
Shipping weight	1kg

Files
IGS ALTER500 user manual.pdf
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