SynthModules

I chose a gain of 8 based on the maximum output of some of the
samples.  I wanted the max to be 10 v pk-pk.  As such, many of the
samples are lower output, typically 6~7 volts pk-pk.  I have enough
output level but you may want to change the gain to about 10.

I also wanted the output to be either mono or stereo selectable by
whether the right output jack was used.  The SC-7 decreases volume of
the channel as you approach balance to the center.  I didn't really
characterize this very well but I wanted the sum of left and right to
also be 10 volts pk-pk.  As such I used a mixing arrangement that had
a gain of 4 when only the left channel was used and switched to a
gain of 8 when a plug is inserted into the right jack.  This seems to
work pretty well although I get a momentary noise 'glitch' in the
left output when a jack is inserted into the right output jack. This
mixing arrangement seems to work well.

I also added a 15 volt to 9 volt regulator with a bypass resistor to
take most of the heat load off the regulator.  I added a jumper in
the +5 regulator output and also at the bypass resistor so I can run
directly from +5 volts if it is available (which I have in my
cabinet).  I don't know the total current demand but am guessing that
the +5 is around 250 mA and the +15 is probably only 10 to 20 mA.  It
did generate a lot of heat when run off of +15 only.

I also had to pull all the connectors and controls off the pcb in
order to make it fit.  This was a real challenge as many of the parts
soldered directly into back to back ground planes with no heat relief
pads.

I uploaded a scan of the schematic in the same photo directory.

Dave



--- In SynthModules@yahoogroups.com, "Brice D. Hornback"
<synthmodules@s...> wrote:
> It looks AWESOME!  Great job Dave!!!  Thanks for sharing it with
us.  By the
> way... I may be a bit interested in how you converted the output
levels if
> you wouldn't mind sharing the circuit.  I've been running my SC-7
into my
> Blacet I/O module to get the levels up.
> 
> Thanks!
> - Brice
> 
> ----- Original Message ----- 
> From: "djbrow54" <davebr@e...>
> To: <SynthModules@yahoogroups.com>
> Sent: Wednesday, June 23, 2004 10:52 PM
> Subject: [SynthModules] Companion SC-7 Sound Canvas
> 
> 
> > I've been using my PSIM MIDI out to drive a Roland SC-7 Sound
Canvas.
> > It's a nice little GM MIDI synth in a half rack.  I converted the
> > unit to a 1U MOTM format panel. The SC-7 is a GM MIDI synth with
28
> > voice polyphony, reverb, and chorus. The conversion came out
pretty
> > good although it is a large pcb that barely fits my cabinet.  I
> > converted the unit to run on +/-15 with jumperd got +5 volts if
> > available. I also converted the output levels to 10 volts pk-pk. 
It
> > came out well and is a nice companion to the PSIM.  Photos of the
> > panel and pcb in the photos section under "DJB PSIM-1 (MOTM
format)"
> >
> > Dave