The CP554 is a transformer coupled diode bridge compressor based on the design of legendary British consoles, adapted to the 500 series format.

It is the ticket to immediate access to the classic, harmonics-rich sound of the seventies.

The CP554 adds some features to the original such as a variable attack time, one additional 12:1 ratio or a high-pass filter in the side chain with three frequencies.

Highlights

• Three Carnhill transformers in the audio path,
• Same output stage as in the MP573 preamp,
• Variable attack time,
• Additional ratio of 12:1 makes a limiter,
• Side chain EQ with 3 high-pass frequencies,
• External side chain input,
• All stepped controls,
• Analog gain reduction meter,
• High grade electronic components throughout,
• High grade four layers PCB,
• Available assembled or as a full kit (everything included).

1: STEREO Connects two compressors in stereo. Whichever unit receives the loudest signal at any moment, controls the sidechain

2: Meter displays the gain reduction in DB.

3: THRESHOLD Rotary switch that sets the input level at which compression begins, from -21 to +12 dBu.

4: RATIO Rotary switch that sets the compression ratio from 1.5 to 12.

5: ATTACK Rotary switch that sets the attack time from 0.5 to 16 milliseconds.

6: 50-100-200 Hz Inserts a 50, 100 or 200 Hz high-pass filter in the side-chain. Produces a Fat sound and eliminates bass driven pumping.

7: BYPASS Hardware bypass by relay (when button is released).

8: MAKEUP Rotary switch that restores the signal level after being compressed.

9: RECOVERY Rotary switch that sets the release time from 100ms to 1.5 second. The A1 and A2 positions set 2 automatic release times which are program dependent (fast on isolated peaks but slower for the average level).

10: SIDE CHAIN Controls the source for the side chain. It can be INT: internal, OFF: No compression, EXT: the side chain comes from the second input (the module is 2 units wide)

What's in the kit?

Absolutely everything!

• 3 Transformers,
• Passive components (resistors, capacitors),
• Active components (diodes, transistors, IC's),
• Front panel elements (switches, potentiometers, analog meter, knobs),
• Connectors, relays,
• PCB's,
• Front panel and side panels,
• All hardware.

You bring the solder (use good quality solder, 1mm diameter max) and the Lunchbox.

Difficulty level

The CP554 kit is a medium difficulty kit. Nothing difficult but a large number of components.

The setup is simple but requires using a good quality digital multimeter.