Bassist Compressor


Compressor and Limiting Amplifier

Studio Quality – Small and Simple

Keeley Engineered for Bass

SKU: KBass Categories: ,

Product Description


The Keeley Bassist Compressor provides true high-fidelity compression and limiting. Be heard and felt using performance compression by Keeley Engineering.

The Bassist Compressor is built around the exotic and extremely high fidelity THAT Corp. 4320.  Think of it as very affordable studio-grade compressor in stomp box format!  It uses high performance Voltage Controlled Amplifiers, on board true-RMS detector, and ultra high performance op-amps to bring you the very best quality. VCA compressors give you precise control.  Therefore they are directly suited to bass guitars. The Keeley Bassist Compressor is both musical and very transparent.  Where our older compressors were based on the CA3080 or the LM13700 and are perfect for single coil guitars, the new Keeley Bassist Compressor has no problems with active pre-amps and line level input signals!  Not only can the Keeley Bassist handle astonishingly large signals, it has an incredible bandwidth of over 20 KHz and incredibly low noise.  No detail in your bass guitar’s tone will be lost.  The Keeley Bassist will be a sound investment in your tone, you now have rack-mount quality at your feet.

Compression and Threshold

When bass players use the Keeley Bassist Compressor they will be greeted with a sound that is more easily amplified and heard.  Using the effect as a limiting amplifier saves your speakers from clipping and distortion.  Set the Threshold to look for peaks in your signal and limit distortion from your amplifier or damage to your speakers.  Simply watch the Threshold Indicator light to see what type of playing you want to limit, it’s that easy!  Next set the Compression Ratio Control to determine how much squash you want when the signal is above Threshold.  Set Compression all of the way down for no  (1:1) compression and use the Gain control as a boost!  Set Compression all of the way up for an above-Threshold hard-knee limiter.

A typical soft compressor setting would be 2:1 above threshold.  A good starting ratio for the Compression control may be 4:1 as it generally sounds good with bass guitar.  A ratio of 5:1 or 6:1 will sound great for slap or funk-style playing.  For synth-bass try 10:1 Compression.

Attack and Release

There is a certain figure that just sounds good as far as compression goes; and that’s 125 dB/second.  With feed forward compressors that use this type of true-RMS detector you use a single time constant parameter.  The timing capacitor gives you attack and release times that are adaptive to your playing level or the signal input to the compressor.  Bottom line: Attack and Release times vary on program content.  Attack times are generally speaking, about 100 times faster than release times.

Attack Time: typically 15ms for 10dB, 5ms for 20dB, 3ms for 30dB

Release Time: typically 8ms for 1dB, 40ms for 5dB, 80ms for 10dB, 160ms for 20dB, 240ms for 30dB


Voltage Input: 9V

Current Draw: 50mA

Input Impedance 1 Meg ohm

Output Impedance: 100 ohm

Output Voltage Gain: +30dB Boost

Bandwidth > 20kHz

Total Harmonic Distortion: 0.1%

Noise: -95dBV

Threshold Indicator: Dual LED


All Keeley pedals include a one year parts and labor warranty!

For all repairs you must complete the Repair Ticket Form below before you return a pedal for repair. We only repair pedals that have been made or modded by us, or pedals that are going to receive our mod while they are getting repaired.

There may be repair fees for pedals that will be receiving mods or pedals that have malfunctioned from user error like plugging in wrong power supply, running over it with a truck, etc… Thank you for your cooperation!

Go to our Warranty Page to fill out a Repair Ticket Form.

Product Manuals


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Super easy to dial in. No noticeable tone coloration or sustain issues.

If you have one, let me know.

… in the lab using my Precision bass…
BTW, the compressor sounds terrific and I have enjoyed getting to spend some time with it.

Best regards,

Joe Lemanski
Applications Engineering Manager

THAT Corporation
45 Sumner Street
Milford, MA 01757 – USA

Compressor Pro on BASS GUITAR!!!

When the Compressor Pro is in AUTO MODE ON and HARD KNEE, it reduces to the Bassist!

David Caraccio ladies and gentlemen!

Premier Guitar Magazine has a VERY useful demo and instruction video! Thanks Steve Cook, you nailed it!

The main difference between our two styles of compressors, one being the older 2 and 4 knob compressors, and the new style compressors GC-2 and Bassist is that the older ones are Compressor/Sustainers and the new ones are Compressor/Limiters.

The Keeley Compressor C2 and C4 – Adds Sustain – …when you are below threshold. Also, this leads to noise when you aren’t playing at all. The compressor attempts to add “sustain” or volume when your notes are ringing softly. Almost all effect pedal compressors are this way.

The Keeley Bassist and GC-2 Compressor/Limiter is different. These sounds incredibly transparent and natural. They do not add sustain but don’t add noise either, when below threshold!

Both can give you a squashed country sound if high levels of compression or sustain are selected. The old style compressors will give you added sustain. The new compressors simply don’t do anything to your tone when below threshold, SUPER transparent and low noise.

How about a couple of great questions from customers?
Hi there, I am a Bassplayer and was about to purchase a 4 knob Keeley compressor when I saw the advert on your website for the new Bassist limiting pedal, Please could you advise me as a bass player should I switch my purchase to the new pedal and is this the same type of effects pedal as your 2 knob and 4 knob compressors but specifically for bass as opposed to being for guitar/bass?

And also is there much difference in how they work and produce their effects

Looking forward to hearing from you – so I can get my order in ! 🙂


Dave P

Hello sir!
Both compressors would work with bass, however the Bassist compressor is probably the best option. The Bassist is a limiter and compressor, it is designed to give you maximum signal without distorting the amplifier or gear you are plugged into. It is designed to give you a nice polished sound and output volume. The older version of the compressor is designed to be a compressor/sustainer. It will add volume (and sometimes noise) when you play softly or stop playing. For lead guitar players this is great as it adds volume and sustain as a note decays. Most bass players never have a problem with sustain and need a compressor as a limiter/compressor so they can protect volume spikes and can do things like slap/funk bass etc. Also the new Bassist can handle active pickups and any other high output pedals you may have in front of the pedal.
Thanks sir!
Robert Keeley

Hey Craighton, I’m hoping I’m not overstepping the rules of life by reaching out but I feel like you might be a good person to answer my questions. I have a couple of them and don’t exactly know who would be able to answer them.

So I have a couple of the original Keeley Compressors. A 2 knob and a couple 4 knob models. I am wondering if it doesn’t make sense to run one of those compressors before I use the new
GC-2. I feel like the old compressor gives a different set of parameters to control such as sustain and I don’t think that it would step on the toes of the GC-2. If anything, the GC-2 would be better suited to play with the signal the old compressor would put out cranked up a bit.

I’m sure the answer would be the one I’d give, which is that there is no right or wrong and that I should just check it out and see how it sounds but if you have time and could maybe give me your thoughts, I’d love to get some input from the people who understand these effects better than me.

Which leads me to my actual question…

I bought the GC-2 and the bassist version. I also own dozens of synths and will be playing with them and these pedals together as well.

I’m curious what the actual difference is between the GC-2 and the bassist version. If the bassist version is ‘tuned for bass’ then I’m curious what that means because of the wide range of sounds the synth pumps out.

Sorry for the long winded email. If I’m asking too much then don’t bother responding. I just mainly want to know the difference between the two compressors.

Jon C

Howdy sir!
The older compressors are great for adding sustain to things, they do have an expander/sustainer. The other compressors GC-2 and Bassist are compressor/limiters only. The difference being the limiters have super low noise when under threshold and completely transparent…but they don’t add sustain.

The Bassist is best to use for keyboards as it is designed to respond better when any super low frequency is involved.
I hope that help sir!

Robert Keeley

ps gimme a call if you have any more questions!


I’m still thinking that I may end up using both the original compressor and these new limiting amplifiers together.

I may also use the bassist compressor with my guitar signal because I use some old mutron effects such as the octave divider and mutron III which add some very low frequencies into the mix.

I use the old compressors first in my signal chain but am imagining the new compressors closer to the end of the chain.

Thanks again for your input and info.

I can’t wait to see what comes out next.

You read my mind sir,
I envision people using the new Keeley Limiters in a variety of spots since they can be set for limiting with high compression ratios at the end of the chain and when you set the Threshold rather high, the unit will never make any additional noise or alter your tone.
I also imagine people will enjoy the Classic Keeley Compressors for sustain and as a great boutique stomp box compressor at the beginning of their chain. Then possibly add the Limiting Compressor at the end for a final production type of sound and response.

Keeley Bassist Limiter Compressor Instructions

Keeley Bassist Limiter Compressor Instructions

Keeley Bassist Limiter Compressor Instructions

Keeley Bassist Limiter Compressor Instructions


Width (Not Counting Jacks) – 2.35″
Height (Not Counting Jacks) – 4.41″

Input / Output Jack Location – Side
DC Jack Location – Top

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