Shin-ei Mute Box [schematic]

[modman]

Saw this on a local listing and thought it might be of interest here.

[Nocentelli]

Schematic appears to omit the actual filter section I can't see how the envelope controls the filter sweep

[tube-exorcist]

Schematic appears to omit the actual filter section I can't see how the envelope controls the filter sweep

Hmmm... maybe the led illuminates a double LDR which is symbolized by 4 dots inside a circle (in the left lower corner - in parallel to R19, R20) ?

[Addy Bart]

Schematic appears to omit the actual filter section I can't see how the envelope controls the filter sweep

Hmmm... maybe the led illuminates a double LDR which is symbolized by 4 dots inside a circle (in the left lower corner - in parallel to R19, R20) ?

I think you're right. I found a discussion about these 4 dots here, and it appears to be a dual photoconductive cell.

http://archive.ampage.org/threads/1/fxs ... III-1.html

[Nocentelli]

It seems to be a virtually the same as the Mutron III, which uses a dual LDR/single LED optocoupler - Marked with the question mark in the pic below: