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Topic: Which DAC should I use? (Read 4671 times) previous topic - next topic


yes, i think In the op amp section I have a 1K resistor and 10k multiturn trimpot as R1, and in the feedback R2 is 22k


I know this an old thread, but I was wondering if someone could clear this up a bit for me. I understand the importance of Resolution and Accuracy. However, I am having an issue with the design process. I am wanting to design a reasonably simple 1V/octave MIDI to AC converter.

My Design Spec:
+   be able to produce a good 61 key/ 5 octaves scale
+   a gate
+   possibly a pitch bend if it is feasible.

As mentioned, I am considering it from a designers point of view, before any components have been purchased. So how would I achieve this?

From my very basic understanding:

In a 1v/octave design, 1 step or semitone is 1/12 = 83.33mV. Therefore, if I require 5 octaves then a reference voltage of 5.0813V is required?

how is the gate and pitch considered into this ?


I don't know how much resolution you need but Adafruit offers a cheap 12-bit DAC.
If you need something better you can look HERE.
What op amp are you using ?
I would recommend THIS.
You'll need a spectrum analyzer
Music stores sell an electronic tuning DEVICE.
How many turns is the gain pot for your op amp ?


Jan 04, 2018, 08:06 pm Last Edit: Jan 04, 2018, 08:06 pm by MarkT
Pitch-bend might be another DAC whose output is scaled down and summed - you don't want
individual DAC steps to be audible doing this, so very fine steps are needed.  The other approach
would be use a 24bit DAC from the start.   

Also for bending the rate of update of the pitch bend DAC needs to be fast, beyond the range of hearing,
or you'll hear it.

Alternatively some good low-pass filtering might make it easier to pitch bend from a DAC without
having to worry about such artifacts so much, probably simpler - but you only want this low pass on
the bends, not normal note transistions, so 2 DACs still needed.   Even a small R-2R ladder might be
enough for bending with good low pass filtering.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

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