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Buchla 111 Ring Modulator "null adjustments"
MUFF WIGGLER Forum Index -> Buchla, EMS & Serge  
Author Buchla 111 Ring Modulator "null adjustments"
The Buchla 100 system at the Library of Congress has a 111 Ring Modulator with "null adjustments" on each input. Would these potentiometers simply bring the trim pots R13 and R18 to the front panel? This configuration with the front panel pots seems to have been deemed unnecessary because most production versions of the 111 do not have them. It would be interesting to know, though!

It definitely helps on the 110 and 111 to have 1% matched resistors (match some carbon film if you're an anachronism such as myself) where things are the same on the IT122s to aid nulling and multi-turn trimmers as well. R8/12, R9/11, R14/19 (both 10k?), R15/16. Of course, stick with 5% carbon film/carbon comp if you =want= the slop of these designs.

On 110s I set the trimmers to center, 500r, before installing and it helps even further. Don't remember if that helps on the 111 but a pot would have a larger sweet spot for adjustment than would a single-turn trimpot on a PCB. On a build with matched parts where they matter and multiturn trimpots I don't see how the manual nulls would help except to allow moving out of the actual null range as desired for more noisy results.

A customer with a Fluxmonkey-based 111 module asked me the same question and I believe we determined the front-panel adjusts weren't necessary, if I remember correctly. Others might disagree and that's what DIY is all about: make it do what YOU want.
I have seen photos of 111 panels with 4 small holes, which I assumed were for screwdriver access to those trimmers. could be wrong...
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