[sdiy] modern AD/DA chips?

[Jean-Pierre Desrochers]

You are completely right Dave.
I was aware of that but already had some MAX551
in my 'humble' inventory stock so.
I could swap my velocity DAC's for 8 bits one but
would need to take care of that in my CPU functions thou
.. not a big deal.
By the way this will be a MONO/POLY type MIDIdac
so in MONO mode the 6 velocity CV's will be in order
mono velocity, Pitch wheel, Mod wheel, Aftertouch, CC0 & CC1.
The 2 last are assignable types CC's by mean of on board dip switches.

JP

 On Thu 07/05/09 10:48 , Dave Kendall davekendall at ntlworld.com sent:
> Hi JP.
> 
> Just a thought - if you needed to or wanted to cut the cost down, maybe 
> cheaper DACs could be used for the 6 VELOCITY CV outs.
> The ear is not anywhere as sensitive to tiny shifts in amplitude as it 
> is in pitch. Assuming the velocity CVs will be driving VCAs, in many  
> percussive sounds, if the VCA drifts, the drift won't be heard at all  
> as the sound will be decaying in amplitude due to the action of an  
> envelope, and I'm not sure if it would be significant even in a  
> sustaining pad sound.
> 
> just a thought....
> 
> Interesting project by the way. It'll be the first 6 voice capable  
> MIDI-CV *with* velocity CV I've seen  :-)
> 
> Good luck with it!
> 
> cheers,
> Dave
> 
> 
> 
> 
> On May 7, 2009, at 13:52, Jean-Pierre Desrochers wrote:
> 
> > Some months ago I was starting a Polyphonic
> MIDIdac> project like you seam to do..
> > After several emails and suggestions from
> the> list members I finaly decided not to go
> with> the mux 4051 & s/h opamps design
> type> because of the ripple effect 'zipping'
> sound> noticable on each s/h opamp outputs at
> idle.> My MIDI dac will use one PIC16F877 and
> will> drive 6 X 1v/oct CV's,  6 X velocity CV's
> and> finaly 6 X gate outs.
> > All the CV outs will have there own MAX551
> 12bits dacs> for CV stability.. 12 overall.
> > My choice is much costly but much
> efficient> and 'hearing' pleasant as a final
> result.> I'm now wondering if my notes CV's poly
> portamento> will be generated with software porta slopes
> calculation> or using I2C 1meg digital pots in an RC
> configuration...>
> > This was my 2 cents.
> > JP
> >