For those of you that aren’t familiar with a compressor, in the most basic of descriptions, it is an automated volume control. When the signal rises above a set point the compressor kicks in and turns the volume down. Compressors usually have a knob to adjust the level at which it will kick in (threshold), the amount the signal that will be turned down (ratio), and an overall volume (make-up gain). There are also other adjustments such as attack and release that are important but beyond the scope of this review. To learn more about compressors in general, check out this great link: Onvilab
The Keeley Bassist Limiting Amplifier is a brand new compressor from Robert Keeley that is specifically designed for bass players. The provided literature describes that the Keeley Bassist uses a very special IC chip: the THAT Corporation 4320. This is a high fidelity integrated circuit that provides the electronics that you would normally find in a studio grade compressor, now small enough to fit in a stomp box.
It’s housed in a sturdy metal stomp box with a black matte finish and attractive graphics. There are control knobs for setting compression, threshold, gain and a single on/off stomp button. The compressor is powered by a 9 volt battery or by a nine volt power supply (not provided). The compression can be set from 1:1 (no compression) to infinity (where it functions as a limiter). The threshold control is basically set using your eyes and ears. Turn the threshold knob counterclockwise to have compression kick in at lower levels. There is an indicator LED that will turn from green to red when entering into compression. The gain knob is used to adjust the output level. It can be used to compensate for compression reduction or turned up even higher to be used as a boost.
The Bassist is very easy to dial in for conventional use. I first set the threshold so that the indicator light is just lighting up on the loudest plucks, snaps and pops. I then dial in the compression where it is having a noticeable reduction on the volume spikes without sounding unnatural (about 4:1) and then I set the gain so that I have the same volume whether the unit is on or off. This setting works very well at taming those annoying spikes in volume that go along with slapping a bass, particularly with bright strings.
Setting up the Bassist as a hard-knee limiter was just as easy. I dialed back the threshold to where the light was only responding to the loudest plucks and then cranked the compression to the infinity setting. When properly set, the limiter function will keep you from overdriving your speaker cabinet to distortion and/or damage. The Bassist can also be used as a boost by simply turning the gain up above the unity setting.
In describing how the Bassist sounds, I’d like to first focus on what it doesn’t do. It doesn’t add noticeable tonal coloration, loss of low end or unwanted sustain. The fact that the Bassist leaves my tone alone and focuses only on taming unwanted volume spikes is just what the doctor ordered. In the old days, when bass players had fewer options, I tried using stomp box compressors that were designed for six string guitars. The results were always less than stellar – they always colored my sound and added gobs of unwanted sustain. I believe the Bassist will be a welcome addition to any bass player who is seeking to tame the transients without affecting the overall tone and natural character of the bass. Street price is currently $199.00. For more information: Keeley Bassist Compressor