291r - build pics

some pics of a Buchla format 291r...

The old Rev 1 291r used 2 PCBs.

These aren't official build notes, just pics to help trouble shooting the build.

The cost of parts when building a 291 is very much tied up with the vactrols.
I'm using NOS VTL5C3/2. These average $20AUD each. There are chinese clones out there but I haven't used them yet. I think its better to use the original VTLs for this filter. if you can find them..

"The VTL5C3 (and VTL5C3/2) is what I refer to as the 'golden' Vactrol because of its response characteristics - I.E., the curve of its response when transitioning from dark to light and light to dark resistance. This curve, I believe through sheer serendipity, closely mimics the percussive envelope of certain natural objects. This response molds sharp transients into very 'organic' type responses. The response can range from a malleting sound, a 'thwipping' sound, or a plucking sound, depending on what's going on at the time. Interestingly, this response adapts to how *hard* or *soft* the transient is (in terms of amplitude) just as a natural object such as a string or drumhead would react when being plucked or struck softly or with more intensity." Scott Stites

This first build of mine was partly successful. I experimented with different pots on the upper and lower filters. The upper filter was most successful.

 I've seen a few suggestions:
Pot 1. Resonance Q: = 5K .... trim pot
Pot 3. Bandwidth Input:=  10K (Lin)
Pot 5. B.W. (CV) = 10K
Pot 2: FM: = 50K Lin
Pot 6. C.F. (CV) = 10K
Pot 4. Centre Freq = A10K

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I purchased  this 291r a while back which sounded great.

It was unusual as the pot choices were different to what I've used before.

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Building v2 of the 291r filter.
The BOM says:

20K LIN POT1, POT7
9MM VERTICAL 652-PTV09A-4030UB203

10-100K LIN POT3, POT4, POT5, POT6, POT9, POT10, POT11, POT12
16MM ANGLED
http://smallbear-electronics.mybigcommerce.com/alpha-single-gang-16mm-right-angle-pc-mount/

10-100K AUDIO POT2, POT8
16MM ANGLED
http://smallbear-electronics.mybigcommerce.com/alpha-single-gang-16mm-right-angle-pc-mount/

decided to stick with the  20K for the pot 1 & pot 7
and now use 100K A for pots  2 & 8 - (FM input).

we sill see how this sounds.

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