Oops, the Curtis chip is likely a 3310, not a 3330.
--- In oberheim@yahoogroups.com , "nelsonj_sce" <nelsonj_sce@...>
wrote:

>
> Ok - I am not sure if the schematic you linked is actually an OB-SX
> board. Assuming it is, it has 2 envelope chips (the should be

Curtis

> chip likely a 3330) for both the VCA and the VCF. Check your board
> to see if it has these chips. It has slots for all the control
> voltages for ADSR shown on the left side.
>
> I own an OBX-A and have done a lot of mods and I am sure this is a
> different schematic, but I don't know if this and OBX-A or OB-SX.
>
> If your board is the same as the schematics, you just need to

provide

> the static voltages to control all of the items shown on the left.

I

> think the voltages range from -5V to 5V in most cases, but you need
> additional schematics to make sure.
>
> Also note, the board does not have an LFO, so you will have to

build

> one (these are fun to make, I added a 2nd LFO to my OB-X and it was
> not that hard to make.)
>
> This is a big project, even to make a mono-synth without memory.

The

> good news is, if you plan ahead, you can do it without making ANY
> modifications to the sound board. Nothing to loose but time and
> money, and perhaps your wife if applicable.
>
>
>
>
>
>
>
>
>
> --- In oberheim@yahoogroups.com , ogusa@ wrote:
> >
> > Each of the connections like PWM, ENV etc. are voltage control
> inputs.
> > THe voice board does not produce envelope or control voltages,
> they
> > were created by the CPU.
> >
> > You face quite a challenge YOu would have to build at leat 2
> envelope
> > generators and LFOs, as well as several static voltage

generators

> > (pots), get voltage control to the envelopes and LFOs and set up

a

> > routing matrix. Even on the classic monosynth, the architecture

is

> > "normalized" but there are switches for various CV routing otions.
> >
> > Plus much of the Oberheim "sound: came from the many control
> > possibilities (Env mod PW 1 with delay etc). If you want that
> sound,
> > you are going to have to build half of a a full modular system

to

> > support the module.
> >
> > Anyway, unless you're a analog synth designer or advanced

hobbyist

> > (like myself), you'll never get it to do what you want.
> >
> > Sorry,
> >
> > Peter
> >
> > Quoting analogback <gehayman@>:
> >
> > > thanks for the reply Jeffrey,
> > > i found schematics and voice board connector info today,
> apparently,
> > > the board was from a blue obsx which is supposed to have the

same

> > > voice card as an ob xa. but a few questions remain!
> > >
> > > i have a midi-cv converter and +15v -15v & -5v power supply
> (required
> > > voltages)
> > >
> > > there are a few connector ins/outs that are labeled but not
> > > immediately obvious to me so i will try to get more info!
> > >
> > > if anyone with knowledge of these machines would care to take a
> look
> > > at this picture, perhaps it could help me determine the less
> obvious
> > > connection points
> > >
> > > http://i133.photobucket.com/albums/q55/neonleg/obxapinout.jpg
> > >
> > > thanks!
> > >
> > >
> > >
> > >
> > > --- In oberheim@yahoogroups.com , Jeffrey Nelson <nelsonj_sce@>
> wrote:
> > >>
> > >> You will need to power it up, and then supply it with
> > >> a gate and CV. A good place to start is a Midi to CV
> > >> converter. You can get them off of Ebay around $75.
> > >>
> > >> The problem will be the power supply, you will likely
> > >> need +/- 12V and +/-5V and others perhaps.
> > >>
> > >> The other problem is that you need to provide voltages
> > >> for all of the envelopes, VCF filter and res...
> > >>
> > >> Finally, you need to build an final output stage for
> > >> overall volume control.
> > >>
> > >> In short, it can be done, but it won't be easy. Not a
> > >> simple project. Get a schematic first. Good luck.
> > >>
> > >>
> > >> --- analogback <gehayman@> wrote:
> > >>
> > >> > hello! i have an obsx voice board that i would like
> > >> > to try and modify
> > >> > in order to use it as a standalone monosynth.. does
> > >> > anyone know if
> > >> > this has been done before if its possible
> > >> > obviously the boards
> > >> > connector info would be a great help as well!
> > >> > any info appreciated as i've scoured the net to no
> > >> > avail :(
> > >> > greetz
> > >> >
> > >> >
> > >>
> > >
> > >
> > >
> > >
> > >
> > > Yahoo! Groups Links
> > >
> > >
> > >
> > >
> >
>