SynthModules

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@earthlink.net>
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
>
>
>
>
>