[sdiy] Vactrols & Lopass Gates

[Peter Grenader]

The 7211 I've used, when wired with their suggested jumper configuration
allows for three separate poles to connect to the wiper.    Possibly there
are other jumper configurations possible that I'm not aware of.  My question
to that in this instance though it that there is no indication on the print
on this adaptation.

The amplitude drop you speak of is a real issue, but I've been able to
compensated for by putzing with the value the 15K divider that's switched on
the top half.  

I'm going to try one of these CK's in there.  It's actually a NKK 2024, but
it's the same thing, about half the $$ with a little rougher action. I'm
curious about this.  Thanks for the tip.

- P



> a C&K 7211 doesn't have a third contact, the middle position leaves one
> throw of each pole connected. In the 292B the middle position leaves the
> resistor and the cap connected, or "both". In the 292c the input
> resistor makes the gain greater, so the gain is lower for 2 of the 3
> positions, just like the 292c. Without this, the lopass gate will work,
> it will just be louder in the middle position than in the other 2.
> 
> Mark
> 
> Peter Grenader wrote:
> 
>> Mark -
>> 
>> Have a look at the Buchla's schematic B2420B.  It's the one from the CBS
>> system.  Note the switch symbol - two contacts -- dual switch.  The top one
>> shorts out the filter, the bottom one kills the feedback.  There is no
>> connection shown for a third center position.  The off (center) keeps the
>> filter going but kills the feedback thru the FET.  There is a marketable
>> sonic difference between the center and down (LP) positions.
>> 
>> Try it with a standard double pole triple throw.
>> 
>> 
>> mark verbos wrote:
>> 
>> 
>>> The Buchla 292B uses a C&K 7211 On-ON-ON switch. I am sorry, but it's a
>>> fact. I have built them all as well.
>> 
>> 
>>