OKC

One-Knob Compressor

"Awesome! Meant to say f**kin’ awesome! The one knob is insanely useable! I’m a compressor nut and this one is a real trick! It behaves so well, attack/decay is spot on with the three basses I tried it on, no premature crushing/pumping, it just works with such aplomb and, like the distiller circuits buffers the signal so nicely.

There are a ton of compressors out there by big manufacturers but nothing as adept and easy as this one. I’m liking yours hands down simply for its ability to seamlessly translate my playing into its most obvious state WITH ONE KNOB!"

– James LoMenzo
(Megadeth, Firstborne, formerly with John Fogerty, Black Label Society, David Lee Roth & White Lion)

JTEX OKC might be the only onboard-ready bass/guitar compressor on the market. I just can't seem to find another one (please correct me if I'm wrong). Why? I don't know! Maybe because it's tough to design one that's easy to adjust while playing, sounds great, and somehow still gets long battery life?

OKC does not compromise on sonic quality in order to be a viable onboard effect. Small and power-efficient as it may be, it's a modern offspring of the classic dbx 163 "One Knob Squeezer" half-rack studio compressor.

over 300 hours of play on a 9V battery. Longer than some much simpler onboard EQs!
fits inside just about any bass
works with both active and passive pickups
single knob simultaneously adjusts compression ratio, threshold and make-up gain
automatic, signal-dependent attack and release times
VCA gain control with true RMS level detection (similar to how the ear perceives loudness)
inconspicuous soft knee compression characteristic
low noise and low distortion
internal subsonic filter protects speakers against harmful rumble and thumps
built to last, with a long life potentiometer rated at 1 million turns

Easy to use, hard to misuse!

Specifications (First Edition)

Input impedance: 1 MegaOhm
Output impedance: 100 Ohms
Supply voltage: 9V (recommended), 18V also supported
Current draw: 1.5mA (!!)
Battery life (alkaline): 300 hours
S/N ratio: 94dB @ min | 70dB maxed out
THD: typ. <0.1% at any setting
Maximum input level: +12dBu (8.7Vpp)
High pass filter: -3dB @ 25Hz, 12dB/octave slope
Board size: 38x27mm (1.5" x 1-1/16"),
Potentiometer: Long life, 6mm solid round shaft, 3/8" by 3/8" bushing (10mmx10mm)

Here's a graph of what OKC does.

When fully couterclockwise, it doesn't compress at all (acts as a unity buffer) unless the signal gets quite loud. At that point it will start squeezing it more and more the louder it gets (the straight line gets more and more curved). With a hot 0dBu input (0.775 Volts), there is only a small amount of gain reduction (3dB). With a super hot 10dBu input (2.5 Volts rms!), the output is pulled down to 2dBu (8dB of gain reduction).

At the other extreme, fully clockwise, you'll notice that the compression starts at a much lower threshold (the straight line starts curving much earlier). Make-up gain is applied (line shifted up), so that the average output level does not drop due to the large gain reduction that occurs at high input. At the top of the curve (loudest input), the output gets almost flat (going into limiting).

There is a point on the graph (the CAL point, or the nominal operating level) where the output level is the same as the input at any position of the knob. You should calibrate OKC to your bass and playing style using the CAL trimmer, so that when playing steadily at a typical level, turning the knob up and down does not significantly change the overall output level -- only the amount of dynamic range squeezing.