According to the manual, the CPR is modelled on a certain vintage compressor. We can't tell which one, but it certainly has retro credentials, and is the ultimate in operational simplicity.
There's no messing about with attack and release settings; just set the amount of sustain you need and then adjust the output level to balance the on/off sounds.
On the version we tried, there was no decay control, but this is available (at no extra price) as a custom shop option.
Apart from the HBE's Medicine Bawl, all of the company's pedals follow roughly the same basic design traits; they are simple and sturdy, built in either small or medium die-cast boxes and powder-coated in bright, sparkly colours. They all run on either a nine-volt battery or a DC adaptor (which is not supplied).
When a pedal is this simple, it has to work straight out of the box, and we weren't at all disappointed. The CPR is designed to provide a very transparent type of compression, and at low sustain settings there are no noticeable tonal difference from the dry amp sound, apart from the obvious increase in sustain.
Pushing the Sustain knob beyond 50% seems to thicken the mid-range qualities of the tone very slightly, but there is the possibility that this could be a result of pushing the amp a little harder than normal.
Even at full sustain, the natural attack of the guitar sound seems unaffected, so you don't have to worry about unusably squashy sounds - you just benefit from bags of extra sustain.
We tried playing a few solos with the bridge pickup on a Strat, using only a tiny amount of amp overdrive, but the CPR added a wonderfully articulate feel.
The level control offers plenty of scope either for counteracting the signal boost introduced by high Sustain settings or for adding an extra level of boost altogether. With both controls at 100%, the CPR doubles as a very smooth clean boost pedal.