Here we have a classic optical compressor, made by Demeter. It is known to offer smooth tone, feel, and action which you would expect from an optical design. In practice it sounds quite transparent but there is something going on with the mids. Definitely some type of bump there but not in an overly colored sort of way.
Controls are simple — just two dials on top (and a little dial on the side of the pedal).
The Compress dial controls the amount of gain reduction to the input circuit. It's essentially a ratio control. It goes from something pretty low to pretty squishy. In fact, I found it to really start clamping down on basses with preamps by about 10:00 on the dial. At noon it really felt like the life was being sucked out of my playing.
The Volume dial is there to bring back the volume lost from compression. There is plenty of gain on hand.
The trimpot recessed into the left side of the pedal that sets the overall gain of the Compulator. Turning it clockwise brings a lot of volume. In practice, it's a lot like setting the gain stage of the preamplifier.
A higher output bass though will definitely clip the circuit. If you experience this, you will want to turn down the trimpot dial (turn counter clockwise).
My Sadowsky basses were capable of clipping the circuit even with the trimpot all the way counterclockwise. Turning the trimpot fully counter clockwise provides 30dB of gain reduction (depending on input gain)
There are no independent controls for attack and release and I found the auto attack and release to be very fast. Too fast for my taste. Turning the Compress dial up to 9:00 or 10:00 and my attack was softened substantially. If you like "grabby" compressors you would probably like the Compulator. There is no real dip-and-swell action.
The Demeter Compulator would make for a fine limiter. I'd prefer it for that function than as a compressor.
Pedal quality is excellent. The enclosure is very solid and the dials turn with authority. Seems like it could withstand several tumbles down a flight of stairs with ease.
It will operate on a 9 volt battery which you access by opening the enclosure. My test unit took at 3.5mm jack plug style DC connection. Newer units will take a standard Boss style barrel connector.
Input and output jacks are on the side as is the power input. There is a blue LED that illuminates when pedal is activated with the footswitch (which is not true bypass).
There is no LED meter to indicate the amount of gain reduction. However, your ear will easily be able to notice when compression is taking place.
Overall, I find the Demeter Compulator to have an inherent warm and smooth quality. It will work well as a limiter. It is not a great compressor for offering subtle compression and it is not a "tone magic" device. You must also be content with fast attack and fast release to accept the Compulator. EQ is relatively flat and I didn't notice much (if any) loss of highs or lows. It is relatively quiet, but not one of the quietest compressors out there. However, noise level would likely not be an issue for most and is really most noticeable at higher compression and volume levels.
Demeter is certainly a reputable brand and the Compulator is a classic compressor. But I think there are much better options on the market these days. For simple "two dial" compressors I prefer the Tsakalis Zipper, Rothwell Lovesqueeze, Becos CompIQ Mini One Pro, or Union Tube & Transistor Lab.
Pros
Smooth
Quality
Warm and organic
Good limiter
Inherent attack and release (if that is your thing)
Cons
Inherent attack and release (if that is not your thing)
Possible to clip input with strong signals (like basses with 18-volt preamps)
Not highly versatile
No LED metering for gain reduction indication
Retail price: $229