Rockman's AutoClean

[Vivek]

What really is the AutoClean feature found on some Rockman products ?

What does it do ?

How does it do that ?

If it's a must have feature, how come it appears no other vendor offers anything close.

[Rob Strand]

This is from rockman document,

Optocouplers are used in one specific case: the complex
Autoclean circuit that allows controlling the distortion rate
from the guitar pot, without loss of volume, nor tone
response alteration. The Autoclean certainly gave a hard
time to Tom Scholz, if we compare the first release, in the
Sustainor 100, and the last ones, in recent Sustainor 200's
and Distortion Generators. The most recent items have an
Autoclean that really works great, while the first ones are
far from perfection.

You might find more info in the patents.

[GFR]

I believe you can try an overdrive followed by a compressor. Compressor after the overdrive, not the usual order. When you play softer or roll the volume down, the tone "cleans" but the compressor tries to keep it at a constant volume.

[Vivek]

This is from rockman document,
You might find more info in the patents.

I found a Sustainor Schematic that you had uploaded here many years ago : http://www.geocities.ws/diygescorp/schematics.html

I will enter it into SPICE and study it (eventually)

Would you happen to know which Patent number refers to the AutoClean ?

[Vivek]

I believe you can try an overdrive followed by a compressor. Compressor after the overdrive, not the usual order. When you play softer or roll the volume down, the tone "cleans" but the compressor tries to keep it at a constant volume.

https://varietyofsound.wordpress.com/2011/01/19/compressor-gate-and-expander/

"upward compression "

[Vivek]

https://patents.google.com/patent/US4752960A/en

https://rockman-gearup.com/rockman.fr/Legal/4752960.pdf

US Patent 4752960 for AutoClean


Very interesting !!!

[Vivek]

Oh, It's a very smart way of trying to detect the peak level of guitar signal

Then on the assumption that lower peak levels mean that the guitar has low settings of volume control, the treble and volume are boosted,

and if the peak levels are high, it is assumed that the guitar volume control is high and then the treble and volume are reduced.

Nett result : when the guitar cleans up with lower volume settings, the normally expected lower final Amp volume and loss of treble do not happen !! You get fairly consistent volume levels and tonal characteristic even if you lower the guitar volume to get cleaner sounds !!!

Smart !!!

[Rob Strand]

I found a Sustainor Schematic that you had uploaded here many years ago : http://www.geocities.ws/diygescorp/schematics.html

I can't claim much to that.   I may have helped check the schematic or checked it against the PCB in some ancient thread.

According to the quote I gave earlier, which came from this document,
https://idoc.pub/documents/rockman-design-1d47jwmxe7

The later Autoclean circuits work better.  I can only assume the patent shows the older version.
A quick scan over those schematics shows some differences to the patent.

Oh, It's a very smart way of trying to detect the peak level of guitar signal

Then on the assumption that lower peak levels mean that the guitar has low settings of volume control, the treble and volume are boosted,

and if the peak levels are high, it is assumed that the guitar volume control is high and then the treble and volume are reduced.

Nett result : when the guitar cleans up with lower volume settings, the normally expected lower final Amp volume and loss of treble do not happen !! You get fairly consistent volume levels and tonal characteristic even if you lower the guitar volume to get cleaner sounds !!!

Smart !!!

I think Mr Scholtz did well.     He clearly had a problem he wanted to solve and stuck with it until it was done.
There's a lot of RC filters and time constants to tweak on that thing.  It must have taken ages.

Anyway good thing you found the patent.