[sdiy] Cheap Midi->CV

[Bill K]

FWIW:  I once heard that musicians are capable of hearing a note being 'off' 
by as little as 2 cents during performance as well as tuning.  As a solo 
monophonic instrument, it might be fine to have a skewed version of the 
equal tempered scale, as most people are a: used to things like those 
horrible 'musical cards' (which even sometimes use a wrong note just because 
the harmonic overtones are close to the correct note - yuck!) and b): beeps 
and boops from a handheld video game.  I think some ringtones on phones are 
horribly done, as well.

But anyway, from a usability in the studio sitch, trying to match on 
multiple tracks would be a problem - and I've experienced this - where a "C 
chord" in the middle octave sounds okay, but up one octave was unusable 
because of the deviation.  Also, I use multiple boards in my composition and 
have had problems with different stretch tunings (as in a Violin and Piano 
playing together) as well as just plain 'off' pitch standards.

So anyway, it would be a problem in the studio in some cases -- heavily 
layered pieces would tend to actually benefit from it by adding some 
'chorus' like effects and adding warmth...

Just my .09 cents (as adjusted by the gas prices ;o) )

BLB


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>From: Simon Brouwer <simon.oo.o at xs4all.nl>
>To: synth-diy at dropmix.xs4all.nl
>Subject: Re: [sdiy] Cheap Midi->CV
>Date: Thu, 08 Sep 2005 22:50:23 +0200
>
>Hi Andre, all,
>
>At 00:01 8-9-2005, you wrote:
>>On 2005-09-07 00:29 +0200, Simon Brouwer wrote:
>> > Hi Michael,
>> >
>> > At 21:12 6-9-2005, you wrote:
>> > > (...)
>> > > I like the "hit the bench" mentality - it's so DIY! If you
>> > > can live with 12 bits check out Mr. Maddox and his now GPL
>> > > PolyDAC.
>> >
>> > I had thought that 12 bits would be plenty.
>> >
>> > The AD8300 that Paul uses has a maximum integral nonlinearity error of
>> > 2 LSB. Add to this a quantization error of 0.5 LSB. With a full scale
>> > of 10 V (10 octaves) that would amount to an error voltage of ca.
>> > 0.0061V, or 0.073 of a semitone interval. With a full scale of 5 or 6
>> > octaves the error voltage would be correspondingly smaller.
>> >
>> > Do you think having more pitch accuracy than that would be worthwile?
>>
>>I don't need a frequency counter to know when a guitar string is
>>7.3 cents off. So yes, probably.
>
>Sure you can hear it while tuning your instrument (if my calculation is 
>correct, at  e.g. 440Hz, a difference of 0.073 of a semitone would give a 
>beat frequency of about 2 Hz). I wonder if you would notice the difference 
>while playing, though, especially between different notes?
>
>A couple of years ago I built a MIDI2CV using an 8 bit DAC, using 4LSB 
>steps per semitone, for a range of 64 semitones (more than 5 octaves). I 
>found this quite usable, not really out of tune.
>If I remember correctly, this DAC (a ZN426) had accuracy specified at 
>better than 0.5 LSB which would be a factor 2 worse than a 12 bit DAC with 
>2 LSB accuracy if used for a range of 10 octaves.
>
>So I was feeling quite comfortable choosing a 12 bit DAC for my next 
>project. I am not so sure about that now...
>
>Would the accuracy of VCO's not be the limiting factor?
>
>
>Vriendelijke groet,
>Simon Brouwer.
>
> >>> nl.openoffice.org <<<
>