[sdiy] Cheap Midi->CV

[Thorsten Klose]

> The reason is...each DAC has its own gain...and they are off by just enough 
> that it is very annoying.

thats the reason, why the MBHP_AOUT module has a seperate gain control
for each DAC channel at the OP-Amp stage.

The reason, why I used a multi-DAC chip: it offers a better performance, 
once the output channels have to be multiplexed for a 64 CV interface (see
http://www.ucapps.de/mbhp/mbhp_shx8.pdf ). 64 channels can be refreshed 
in parallel to a lot of other tasks which are handled by the MCU

The timing conditions are very relaxed. The MBHP_AOUT module can not only 
be used as a trivial MIDI-CV interface, but also for modulations 
(LFO/EG/wave-sequences) which are realized in the software

Best Regards, Thorsten.

On Tuesday 06 September 2005 03:38, you wrote:
> I would recommend against doing it this way ( if 
> http://www.ucapps.de/mbhp/mbhp_aout.pdf is what you are talking about).  I 
> did a similar thing on a project I did a few years ago ( 
> http://www.oldcrows.net/~patchell/smb1/smb.html )...and in hind sight....I 
> would have not done it that way.  The reason I did do it that was was lack 
> of board real estate...but the correct way is to use a single DAC and a Mux 
> with multiple sample/holds...
> 
> The reason is...each DAC has its own gain...and they are off by just enough 
> that it is very annoying.
> 
> Here is one of the solutions I came up with :
> 
> http://www.oldcrows.net/~patchell/synthmodulesII/200-1017.pdf
> 
> Although...that 12 bit DAC that I am using costs about $20....but you get 
> more bang for your buck as opposed to the MAX525 which I recall cost me 
> about $40 each....
> 
> At 09:14 AM 9/6/2005 +0800, dougall wrote:
> >The midi box one on ucapps.de is very nice but it requires a MAX525
> >Digital-Analog-Converter which are very expensive.  Anyone on the list
> >know somewhere cheap to get these?
> >
> >There was talk a while back, of a redesign of the Analog Output board
> >to use some cheaper DAC's.
> >
> >--dougalli
> 
>          -Jim
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> http://www.oldcrows.net/~patchell
> 
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