Using the PreComp™

The following page describes how to get up and running with the PreComp in minutes! For more detailed information, we invite you to download the full manual by clicking on the icon to the left.

Getting ready

Before making any connections, make sure the power on your 500 series power rack is turned off and volume levels turned off. This eliminates power-on transients from damaging more sensitive components such as tweeters. Carefully mount the PreComp into your power rack. Make sure you screw it in. Do not over-tighten the screws. These need merely be snug to prevent the module from being dislodged when in use.

Most 500 series power racks are equipped with rear mounted XLRs. Once mounted, the PreComp will automatically route the connections via the 15 pin card edge connector. Connect your microphone to the XLR female input and use the XLR male output to feed your recording system. If you are using a condenser mic, turn on the 48V phantom power. This is recessed to prevent accidental turn on or off.

Set the controls to the 'start position' as follows:


  • Gain at 7 o'clock
  • Polarity reverse out (0°)
  • High pass filter – off (out)
  • Threshold to 2 o'clock
  • Ratio to 7 o'clock
  • Gain to 12 o'clock
  • Speed to slow (out)
  • Compressor – bypassed (out with LED off)
Click to enlarge

Turn on your recording system and monitors and slowly increase the volume. Always test at a low volume. Start speaking into the microphone and slowly turn up the PreComp's gain control. Once you have confirmed it is working well, try depressing the 180° polarity reverse and the high pass filter (HPF) to familiarize yourself with how they work. Reversing the polarity will likely change the tone in the bottom end, depending on where you are sitting in your room. Activating the HPF will cut low bass to reduce resonance. This can be very helpful when recording as it will reduce bass clutter and help clean up your recording so that the instruments cut through with less modulation.

Adding compression

Activate the compressor by depressing the IN switch. If you are new to recording, we suggest you test the compressor using a dynamic cardioid microphone as this type of mic is much less sensitive to feedback.

  • Threshold
    This control is used to set the 'tipping point' where compression will occur. Lowering the threshold by turning the control counter-clockwise will cause the compression to occur more rapidly or at a lower amplitude. Increasing the ratio control will increase the audible effect.
  • Ratio
    The ratio is used to set the amount of compression you may apply. This VCA (voltage controlled amplifier) compressor lets you adjust how much output voltage will be produced based on how much input voltage you put in. When set at 1:1 - for every volt you put in, you will get one volt out (essentially off). By increasing the ratio to 3:1, for each volt you send into the PreComp, only 1/3 of a volt will be produced. A 10:1 ratio or more is often used to 'limit' the track to prevent overload distortion as only 1 volt will be produced for every 10 volts you send in.
  • Gain
    As you increase compression, less signal will be produced. The gain make-up control is used to compensate for the reduced output. You simply adjust the gain make-up to bring the output level back to where it was. Try comparing the gain of the pre and post compressed effect by using the in/out switch.
  • Speed
    The PreComp's speed control is used to set the reaction time of the compression circuit. When set to slow, the compressor will allow the initial transient to pass before the compression effect kicks in. This is often used with percussion to allow the crack of a snare drum to pass through before the drum itself is compressed. Setting the PreComp to fast will cause the compression to occur instantaneously. This could be used on a vocal track to make sure the voice does not jump into the red.