[sdiy] minimalist resistor ladder DAC intonation

Tom Wiltshire tom at electricdruid.net
Tue Dec 18 00:48:10 CET 2012

Interesting idea. Does anyone know where you find the maths for non-binary resistor ladder DACs? Actually working it out seems a bit daft seeing as it must have been done a thousand times.
My fear would be that the kind of intervals you're talking about would only work for a few values of the DAC. Scaling the DAC outputs to semitones is at least simple...


On 17 Dec 2012, at 23:05, Jason Nanna wrote:

> Hi, I'm looking at building a minimal resistor ladder DAC as an
> experiment with a Raspberry Pi.
> I was hoping someone might have some ideas with respect to
> temperament.  What I'd like to accomplish is a direct bit-to-interval
> relationship, so for example the LSB would correspond to a semitone,
> the next-LSB would be a larger interval which could have the LSB added
> to it to achieve the third pitch, and so on.  Perhaps the LSB has to
> be a microtonal interval to 'correct' certain others.  I'd like it to
> be 8 bits.
> I don't require a general-purpose scale.  I'm looking for something
> musically useful.  The octaves do not have to be 2:1 per se, and I
> don't need a wide range of control voltage.  The GPIO pins are 3.3v,
> so I presume I'm going to have to scale the DAC output up to 4 or 5
> volts, which would be the maximum control range I'd expect.  Even 3
> octaves would be sufficient.  The music will (hopefully) suit the
> tuning, not the other way around.
> Hoping to get interesting ideas.  Perhaps someone knows of a similar
> project, but I haven't been able to find anything online to date.
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