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Shin-ei Mute Box  [schematic]

Posted: 16 Jan 2018, 23:20
by Addy Bart
Saw this on a local listing and thought it might be of interest here.

Re: Shin-ei Mute Box

Posted: 17 Jan 2018, 18:22
by Nocentelli
Schematic appears to omit the actual filter section :scratch: I can't see how the envelope controls the filter sweep

Re: Shin-ei Mute Box

Posted: 18 Jan 2018, 01:03
by tube-exorcist
Nocentelli wrote:Schematic appears to omit the actual filter section :scratch: 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) ?

Re: Shin-ei Mute Box

Posted: 18 Jan 2018, 23:16
by Addy Bart
tube-exorcist wrote:
Nocentelli wrote:Schematic appears to omit the actual filter section :scratch: 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

Re: Shin-ei Mute Box

Posted: 19 Jan 2018, 14:26
by 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:

Image