antilog

[Jim Patchell]

    Depending on what you want to do, in general, a Look Up Table is a lot
simpler, and faster, to implement in a micro.  One possible solution would be to
have LUT values for all the semitones, and then linear interpolate between this.

    Another posible advantage to an LUT is that if you want a pathagorean scale
or just intonation, all you have to do is change your look up table.  That is
pretty hard to do with an analog exponential converter (which gives you the
equally out of tune, tempered, scale).

    I have used the PCM56 (from Burr Brown) in various projects.  It seems to
have pretty good DC stability.  Although, I think that part is becoming
obsolete.

    -Jim

Paul Perry wrote:

> At 11:51 AM 10/08/00 +0100, Paul Maddox wrote:
>
> > Am I correct in assuming that when we use 'log convertors' on VCOs what we
> >actually do is use an 'ANTI-LOG' function?
> >
> yeah, this is the 'exponential' cell.
>
> I've been interested for a while in the possibility of making an exponential
> convertor
> using a micro, and multiplexing it, so that all the problems of stability in
> the
> expo cells would be a thing of the past.
> But, i'm not a programmer.
> I know 12 bits would be enough, though 16 bit serial D to A convertors are
> cheapest.
> (Though not guaranteed for DC, I have never had trouble with them).
>
> paul perry melbourne australia