Amp-fx Keeley Compressor clone // C4 4-Knob Version // Handmade in Berlin.

Amp-fx Keeley Compressor Clone. C4 4-Knob Version.

The holy grail of guitar compressors. Improved.

Not the most expensive, but definitely one of the best guitar compressors.

Robert Keeley clones and improves the Ross compressor. Amp-fx clones and improves the Keeley compressor. The Keeley compressor is widely known as the holy grail of the guitar compressors. Rightfully so, we think. We let our customers decide what level of holiness this compressor will achieve.

We only build the 4-knob version for the highest rate of flexibility. Differing from the 2-knob version, attack and clipping can be adjusted from the outside. Attack controls the trigger time of the pedal. Clipping lessens the input signal to prevent distortion. This is useful when connected to other instruments or line level signals.

On all Amp-fx pedals we align the controls in a row. That way we can solder them directly onto the PCB. The dozen wires between the potentiometers and the circuit board are avoided. This makes the pedal less prone to unwanted interference, because the wires work like little antennas that can pick up RF noise. Another improvement is the well designed circuit board with its straight ground plane. Through this, the pedal does not generate any noise on its own.

Only the best components available reach the high expectations we have in an Amp-fx pedal. Handpicked, tone-tested parts leave your natural sound untouched. On the whole we use the same high quality parts that Keeley uses for his Ross compressor clone: Panasonic metal film capacitors and low noise metal film resistors in the audio path, expensive tantalum caps for filtering and sturdy 1/4" jacks "made in Japan". The transistors are matched to less than 1% (very important for consistent compression). The compressor is true bypass to leave your tone unaltered when switched off.

UPDATE: Customers informed us that Keeley downgraded from tantalum to cheaper electrolytic caps. The result is a more noisy pedal. Rather buy an old 2nd hand Keeley Compressor or better get yourself a new Amp-fx Compressor.

Level: Adjust the volume here. Match the bypass volume with the compressed signal. You can turn it up to overdrive your amp, or you can create a lead boost for solos if you turn the sustain all the way down, and pick your preferred overdrive level.

Sustain: Controls the compression rate. Due to the smart design of this pedal, your sustain can increase without your noise-level going up. You also will not lose your high end. It softens the loud notes and amplifies the quieter notes, and as a result, evens out your sound.

Attack: In the zero position you get the fastest attack. Turn the dial up for longer / slower attack times.

Clipping: Adjusts the input level. This is used to lessen distortion when connected to sources that have a high output level (Humbucker, booster in front of the compressor, line level signals, or other instruments).

The pedal can be powered using an internal 9V battery or an external 9V Boss style (center negative) AC adapter. The battery disconnects from the circuit when you pull the input jack. This will extend the battery lifetime. The current consumption of the pedal is low. It draws only 5 milliampere.

Historically, the best place for a compressor is right after the guitar. Nowadays it is popular to use after your main "tube sound" pedal. This way you can get a more smooth transition from a clean to distorted sound. The compressor also works well before a booster. However, it does not work well behind a booster. The internal CA3080 likes low level signals more. We do not recommend using the pedal after a delay, echo or in the effect loop of your amp.