SynthModules

Brice, yes, it does make sense - and perhaps I need a more accurate
meter to to the calibration.

gary


"Brice D. Hornback" <bdh@...> wrote:
>
> Gary, these are all the exact same PSIM-1 modules.  All the PCBs and 
> components were purchased at the same time.  All the resistors are
1%.  When 
> I calibrated the modules I've already sent you, I used a Fluke volt
meter 
> that was calibrated against a NIST certified volt meter/voltage
source.  You 
> could use one of your other PSIM-1 modules as a precision voltage
source to 
> calibrate this PSIM-1 module.  Simply output a voltage from #1 into
a VCO 
> and the same voltage from #2 into a second VCO and zero beat them by 
> adjusting the trim pot on #2.  Dave's idea of using a 440 Hz tone
generator 
> is a great idea and you could accurately calibrate all your PSIM-1
modules 
> to that source.
> 
> Also, the Atom-Pro can output an audio tone (such as 440 Hz) on the AUX 
> port.  So in effect, you can use the PSIM-1 to calibrate itself by
feeding 
> the output of the audio tone on the AUX port to an input to sample the 
> voltage and adjust the trim pot so the output matches what is being
fed into 
> it.  You could have all the LEDs get brighter to indicate when it is in 
> tune.  I started to write a program to do that at one time but never 
> finished it.  The program could even be set to automatically
calibrate (set 
> an offset variable) itself on startup.  I'm not sure how accurate
that would 
> be... but in theory it should work.
> 
> For starters, most volt meters (unless they are NIST certified) are
not all 
> that accurate.  One meter may display 10.666 volts and another
10.555 or 
> whatever.  If I were you, I'd just measure the voltage at TP1 on one
of your 
> other PSIM-1 modules and set this one to whatever your volt meter
reads and 
> see if that works.  That may be the easiest and fastest way.  So, if
your 
> volt meter reads PSIM-1 #1 at 10.555 volts... set this one to that
as well. 
> The volt meter may be off (or mine may be off)... but that way, they
will be 
> the same.  Does that make sense?
> 
> Best regards,
> Brice
> 
> ----- Original Message ----- 
> From: "djbrow54" <davebr@...>
> To: <SynthModules@yahoogroups.com>
> Sent: Thursday, November 16, 2006 12:57 AM
> Subject: [SynthModules] Re: Completed PSIM burning in....
> 
> 
> >I assume the input attenuation resistors are 1%.  In a voltage divider
> > with 10 volt input, the output could be 5 volts +/- 50 mV.  That's a
> > 100 mV difference potentially between channels.  100 mV is greater
> > than a semitone so you could be off that much in sampling.  The only
> > way to correct this would be to either trim each channel to calibrate
> > it, or figure out how much it is off and use an offset multiplication
> > in software.
> >
> > The other possibility is the 10.666 volt reference as has been
> > mentioned.  Sending a 1440, 1824, 2208, and 2592 to the 4 Dacs will
> > result in 3.75, 4.75, 5.75, and 6.75 volts.  These should correspond
> > to "A" octaves.  You can then adjust the 10.666 by beating a VCO
> > against a 440 Hz reference, which I assume would be more accurate than
> > trying to set it with a voltmeter.
> >
> > Is your software quantizing?  If so, it wil magnify the error.
> >
> > Dave
> >
> >
> >
> > --- In SynthModules@yahoogroups.com, "Gary Chang" <gchang@> wrote:
> >>
> >> After precisely calibrating the module, the new PSIM consistently
> >> outputs a sampled cv that is higher that the other PSIMs that are
> >> similarly trimmed.  I know that this is a moot point for those who
> >> have only one PSIM, and, for that matter, I can run Mike Firman's
> >> quadrature lfo program on the new one and use the older units that
> >> match for other stuff, but, I have to wonder - is there any
> > difference
> >> between the old and newer PSIMs?
> >>
> >> gary
> >>
> >> "Brice D. Hornback" <bdh@> wrote:
> >> >
> >> > Gary,
> >> >
> >> > You need to calibrate the reference voltage (there is a blue trim
> >> pot next
> >> > to U5 labeled RT1) to exactly 10.666 VDC between ground and TP1.
> > It's
> >> > labeled on the PCB next to the test point.
> >> >
> >> > Best regards,
> >> > Brice
> >> >
> >> > ----- Original Message ----- 
> >> > From: "Gary Chang" <gchang@>
> >> > To: <SynthModules@yahoogroups.com>
> >> > Sent: Wednesday, November 15, 2006 12:22 AM
> >> > Subject: [SynthModules] Completed PSIM burning in....
> >> >
> >> >
> >> > >I assembled my new PSIM tonight (with the help of disassembling
> > one
> >> > > that Brice built for me 2 years ago).  It works - but when run
> >> > > identical programs (gc-sah-sr-nq-djb.bas), the two modules
> > output two
> >> > > different pitches when sampling the exact same source.
> >> > >
> >> > > Is there a way to calibrate the modules to be identical?
> >> > >
> >> > > gary
> >> > >
> >> > > p.s.
> >> > >
> >> > > Assembly really wasn't hard - and I have the module working now.
> >> > > Those of you who don't have their modules should really consider
> > this
> >> > > option.... 8^)
> >> > >
> >> > > gc
> >> > >
> >> > >
> >> > >
> >> > >
> >> > > Be sure to check out the primary Web site at:
> >> > > http://www.SynthModules.com
> >> > >
> >> > > Yahoo! Groups Links
> >> > >
> >> > >
> >> > >
> >> > >
> >> > >
> >> >
> >>
> >
> >
> >
> >
> >
> > Be sure to check out the primary Web site at:
> > http://www.SynthModules.com
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
>