This revision covers the REV B thru E units. Most current reissues are based on this revision. Revisions C-E had a blackface front panel while the Rev B retained the silver and blue stripe panel. Changes were made to the stage and line amps so a bipolar transistor was used as the first active component. Low noise, or “LN” circuitry, was added to this and all future revisions. Like the Revision A, the input uses an O-12 transformer and the signal is attenuated at the input with a 600Ω t-pad. The output is class A, utilizing a 5002 output transformer. This is widely considered to be the most classic FET compressor sound.
The FET/500 series of analog compressors is based on the famous 2U rack compressors designed in the late 60’s. Finally, the circuit has been faithfully recreated in 500 series format maintaining its classic sound, fully discrete audio path, and adding new features. The circuit was adapted into 500 series format by Mako Natsume. Mako has years of PCB layout experience and spent six years developing the FET/500 concept.
Classic circuit without Compromise
The FET/500 is the same FET Compressor found in the MNATS rack version. The circuit is left unaltered and the full sized transformers are used. This is true classic compression without compromise.
The FET/500 features all the classic ratios including All Buttons In (SLAM) mode. It also features a 2:1 compression mode which has become our favorite.
Dual LED Metering
The dual meter circuit displays both gain reduction metering (top) and +4 output metering (bottom) with a +16dBu peak indicator. The gain reduction meter provides a far more accurate display of gain reduction, attack, and release than even the highest quality analog meters.
In addition to the classic “GR Off” which disables gain reduction but still passes the signal through the entire audio path, the FET/500 also features a true bypass switch. True bypass removes the compressor from the chain entirely.
The FET/500 features front panel stereo linking jack. Linking is achieved by connecting the 1/8″ front panel jacks on each unit with a male-male stereo 1/8″ cable. For stereo linking to work properly FETs in each unit should be closely matched.
True Linear Power Supply
Many classic circuits require a 24-30VDC supply rail for the crucial audio signal supply. The FET Compressor requires a 30VDC rail. This is problematic with 500 series which operates on a +/- 16VDC supply. Previous designs use a voltage converter to double the +16VDC rail to create the 30V DC rail. This is also problematic as voltage converters are VERY noisy. The FET/500 uses a different approach. Mako created a PCB that uses the -16VDC rail as audio ground, creating the required voltage rail without any compromise. The DC/DC conversion is left for the -10VDC rail where it is filtered and used for non-audio purposes.