[sdiy] Pearl Syncussion VCO

[Ben Barwise]

Thanks, that helped. I suspected that, but didnt know if it was that
or if it was a trick to tie up a unused inverter. but the thing is
that it it has a proper GND , the negative voltage is the one that is
forced- see below

http://www.gearslutz.com/board/attachments/electronic-music-instruments-electronic-music-production/234092d1305016042-another-syncussion-thread-pearl_syncussion_sy-1_schematic.jpg

Maybee the VCO inverters are not across the whole supply but rather
GND to +V? it has a 1u Cap on its output so I guess that means it must
be floating between GND and +V and thus they needed a reference.

Cheers!!

-Ben



On 5 October 2011 20:47, Magnus Danielson <magnus at rubidium.dyndns.org> wrote:
> On 04/10/11 18:15, Ben Barwise wrote:
>>
>> Hey,
>>
>> I have been exploring lots of drum synthesizer schematics and I am
>> currently looking at the Pearl syncussion. I was wondering if someone
>> could give me a few tips on certain parts I am finding confusing in
>> the VCO.
>>
>>
>> I understand the integrator and schmitt trigger and then sort of get
>> the CV input but I am just completely lost what is happening with that
>> inverter stuck on the side of that PNP pair at the top - is that just
>> a good way to tie up unused pins? does this schematic seem a bit
>> bonkers? because I have traced it from that well known scan hanging
>> around the internet (why do people bother scanning schematics you cant
>> read! ) the inverters are guessed as 4069's they may not be.
>>
>> it is an interesting design anyway,
>>
>> http://img88.imageshack.us/img88/1884/pearlsyncussionvco.jpg
>
> It's a bias voltage source... "buffered" if you so like.
>
> Cheers,
> Magnus
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