I did this as a bit of an experiment. I want to build one and this has always been one of those that would prefer to do on a PCB, but I thought I'd still like to put a layout together to see how small I could get it using my methods and as I have I may as well put the results on here.
At 20 x 29 is may just fit in a 1590B if you aren't using a battery and have the stomp switch mounted right at the bottom, but with it having 4 pots, I think I'd probably opt for a 125B which should be a more comfortable fit.
Avoiding 19 links is another of the reasons why I would prefer a PCB :o)
Info about the great sounding original:
BJF design guitar and bass Auto Wah / Voltage Control Filter pedal
Hand-made in Finland premium quality auto wah pedal.
The SNOW WHITE AUTOWAH (SWAW) circuit is based on a 1991 BJF rack mount remote wah circuit and is tuned like a real wah.
The circuit was redesigned with envelope controls and built into small size pedal.
It has very fast tracking and accuracy rarely found on auto wahs/ envelope filters. With the four knobs you can have total control of the effect.
SWAW works both with guitar and bass and you can fine-tune the pedal to suit your instru-ment, your playing style and your taste of tone.
The pedal has a unique decay control for the filter frequency fall speed. You can set it to be fast for wah effects on every note, or slower for a more traditional auto wah sound.
Like all Mad Professor pedals SWAW is hand made in Finland using only premium compo-nents, to give years of trouble free operation with superb musical tone.
SENSITIVITY: Sets the filter trigger level, tune this carefully to fit your guitar/bass output and your playing touch.
You can further change the sensitivity from your guitar volume knob while playing.
BIAS: Controls the filter resonance frequency. When Sensitivity is turned fully off the Bias can be used as a sweepable filter.
RESONANCE: Controls the sharpness or Q-factor of the filter.
DECAY: Controls how fast the filter frequency falls back to resting point (that is set with the Bias control). This can be set fast (CW) so you get the wah effect on every note or slow for a more traditional auto wah sound.
PLAYING: Please take time to get used to the controls and as this is a voltage control filter it will react to your playing touch. The envelope control circuit is carefully designed to follow the dynamics of guitar/bass and it might take some time to master the Auto Wah playing technics.
Try also adjusting guitar volume between 8 and 10 to further expand use.
Modded version as per the improvements discussed below in the comments: