[sdiy] Vactrols & Lopass Gates

[mark verbos]

Peter Grenader wrote:

> 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.

that's true. I assume that the assembly drawing called specifically for 
a 7211 because that's what's in there.

> 
> 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.
> 

good luck.

Mark



> - 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.
>>>
>>>
>>>
> 
>