This is a dual mono compressor with a stereo link switch that enables it to be used as a bus compressor with no significant movement of the stereo image. When selected to stereo, whichever compressor is performing the most gain reduction due to a peak on that side, the other channel will gain reduce by an identical amount. The control passes seamlessly from one side to the other. There is a TRS jack on the rear panel to link two or more GTC2's together.

There are three separate level control options available :-

1. Opto (the default setting)
2. FET (engaged by pressing the red FET button)
3. Combined = both paths connected in series (engaged by pressing the blue COMB button)

Additionally, these three all class A, unity gain, discrete transistor circuits can be used to "warm up" a circuit by switching off the side chain (releasing the red ON button).

Geoff Tanner had three goals with this unit :-

1. To provide the most feature packed compressor that he could.
2. To make it easy to use with colour coded knobs, illuminated switches, and clear, illuminated, VU meters.
3. To make it great sounding with custom input and output transformers and class A all discrete transistor circuitry.

Each channel of the compressor comprises of six illuminated switches and five potentiometers.

The switches select the following :-

1. (Green) = Hard Bypass off when lit. This is relay switched so that, even if the unit has the power switched off, the input and output XLR's are connected together so that it could be left in circuit without loss of signal. When the unit is in bypass mode both the VU meter and the compress sidechain are disabled so as not to give misleading readings. Releasing the switch into hard bypass is a quick way of checking the difference in sound between processed and non-processed signals.

2. (Red) = Side chain on when lit. With this button selected the compress sidechain is connected to the audio signal path. It can be disabled if it is desired to just use the channel as a unity gain "sound sweetener".

3. (Yellow) = VU meter in gain reduction mode when lit. The VU meter normally acts like a conventional VU meter measuring the output level leaving the compressor. When the yellow button is pressed the needle rises to the 0VU position and works backwards towards the -20VU region as the gain reduction increases.

4. (Red) = FET control circuit enabled when pressed. Pressing the red button disables the opto path and sends the audio through the FET gain reduction stage. Depending on settings, this path can really make guitars sound good!

5. (Green) = Automatic release option enabled. The automatic setting adjusts the release (recovery) time according to the nature of the material going through the compressor. Short repetitive beats will produce shorter release times than longer rifts that will extend the release time.

6. (Blue) = Combined control arrangement selected. Pressing the blue button cascades the two audio paths so that the signal is compressed by both the opto and the FET. This will produce greater attenuation depths than achievable with just one path and the VU meter is automatically set to the gain reduction setting in order to include the correction network to indicate the new deeper value.

There's also a green button in the center of the unit that stereo links the two mono compressor paths.

The five potentiometers are as follows :-

1. (Grey) Threshold = a 20 detented position pot calibrated for thresholds from +30dBu to -10dBu, a 40dB range. I chose the +30dBu starting point because of the huge signal levels obtainable from the D to A's of many current digital devices.

2. (Grey) Ratio = a 20 detented position pot calibrated for ratios between 1.5:1 and 10:1.

3. (Blue) Attack time = a 20 detented position pot calibrated for attack times ranging from 500uS to 5mS.

4. (Blue) Release time = a 20 detented position pot calibrated for release times from 100mS to 3 seconds.

5. (Red) Gain Make up = a non detented audio taper pot calibrated on the front panel artwork at 2dB intervals up to 10dB and broader points beyond that to correspond with the exact audio taper. The calibration points enable loss indicated on the VU in gain reduction mode to be quickly compensated for by turning the red knob to the appropriate setting.

Using the compressor is simply a matter of rotating the threshold pot clockwise with the meter set to gain reduction. When the needle starts to move you know that you are in the right kind of level region and can have great fun selecting the various functions and pot settings until you achieve the sound that you are looking for!

We had a lot of fun playing with it in our studio!