[sdiy] Buchla Lowpass Gate Switch

[mark verbos]

Actually, now that I look at this again, it's not that at all. What they 
did was divide the highs and lows and put different time constants on 
them. The low frequencies get a slower reaction, I assume for distortion 
reasons.  I don't know what's wrong with me today, telling lies, LIES!!!!

sorry about that. again.

Mark



mark verbos wrote:

> Incidentally, the Focusrite compounder uses a Silonex vactrol in the 
> same configuration as the Buchla for it's gate circuit. The same box 
> has a limiter based on a Vactrol that uses a complimentary schem. The 
> signal is inverted, then the so called shunt mode is used on both 
> halves, then they're re-combined. I guess this is similar to the 
> series/shunt mode. of course that's not practical in a lopass gate. a 
> balanced VCF, ha.
>
> Mark
>
>
>
> Fernando de Izuzquiza wrote:
>
>> Hi,
>>
>> In the Silonex site there is many info/examples about vactrol based 
>> VCAs and many variations and methods to get better "muting", ways of 
>> controlling the LED, etc.
>>
>> I think I will try different vactrols when I build mines (LPGs). Two 
>> 5C3, a 5C3/2 and two Silonex also. The NSL-32SR3S it's fast and 
>> selected for a tighter resistance value. I'd like to see how it works 
>> on it...
>> I assume a faster vactrol will sound less Buchla.
>>
>> I found a 3P3T on-off-on switch at RS-components, 103-5552. Is this 
>> the right one for PeterG's approach?
>>
>> Fernando
>>
>>
>>
>> > De: Peter Grenader <peter at buzzclick-music.com>
>> > Fecha: Wed, 11 Aug 2004 21:22:24 -0700
>> > Para: mark verbos <mverbos at earthlink.net>, synth diy
>> > <synth-diy at dropmix.xs4all.nl>
>> > Asunto: Re: [sdiy] Buchla Lowpass Gate Switch
>> >
>> > I might add that I didn't use single vac's on the rev Bs I've made, 
>> but
>> > opted for the same single 3/2 dual element used in the rev c. I did 
>> this
>> > for cost reason's only. As far as the performance, the sonic 
>> characteristic
>> > of the two, the only differences I can hear is slightly less gain in
>> > amplitude operation and a bit more resonance in lowpass mode, which 
>> I assume
>> > comes from the properties of the FET.
>> >
>> > In any event, the rev B's FET allowed for the additional bleed-killing
>> > inverted feedback I added, I haven't been able to do this with the 
>> rev c.
>> >
>> > - P
>> >
>> >
>> >
>> > Peter Grenader wrote:
>> >
>> >> Mark-
>> >>
>> >> I used a straight double on-off-on on my rev B's and I've got 
>> combo in the
>> >> center. I'll be happy to post an mp3 to illustrate this!
>> >>
>> >> Have a look as the schematic- the top half of the switch puts 15K 
>> across the
>> >> output of the second vactrol element, killing the filter. The Rev 
>> C does
>> >> the same thing, but does so with only 10k. The bottom half of the 
>> rev B
>> >> switch increases the cap value, (.0047), just as C does. The 
>> additional
>> >> third switch element in the rev C adds 15k to the input signal's 
>> amplifier,
>> >> increasing it's gain. Granted, the rev B doesn't do this, but this 
>> addition
>> >> does not effect the mode switching, it just ups to output of 
>> amplify-only
>> >> operation. This is why I didn't see that an on-on-on was required 
>> and as it
>> >> turns out, it seems to work fine without one.
>> >>
>> >> - P
>> >>
>> >>
>> >>
>> >>> it actually doesn't save anything because the switch the rev B 
>> used is a
>> >>> On-On-On switch, which is even more rare and pricey than the 3PDT 
>> one!
>> >>> The reason i modded the rev C was because of price. I wanted a 
>> cheap and
>> >>> simple solution. Also the wiring is easier than using multiple pole
>> >>> switches. Fewer wires, smaller switches that can be closer together,
>> >>> easier to get, cost less. Seems like an obvious choice to me, but I
>> >>> guess not for everyone...
>> >>>
>> >>> mark
>> >>
>> >
>