[sdiy] CV outputs from 3.3V and 5V uC systems

[Roman Sowa]

Hello Spiros and list,
first of all, you don't just put "any off the shelf DAC" in a decent 
MIDI2CV converter. If you want 10 octave range then too low power supply 
is the least of your challenges.

my advice is:
1. yes, this is the best way. Do nothing and have 5 octaves (or more 
like 4.5) with some usability
2. if you really want to go that way, there are full-contained power 
boosters, even making +/-15V out of 5V, in a form of small SIP device, 
or even SMD chip. Just add some additional filtering and you're done. It 
will have noisy output, but it's so easy to have whatever voltage 
converter nowdays.
3. negative CV range is useful when someone wildly twists pitchbender at 
the lowest note. But -3V seems like overkill. OTOH who told you it 
cannot be -10V to +10V. Everything has its uses, pitch CV is just one 
example. In fact you could make it switchable like +/-10, +/-5, 0..5, 
0..10, -5..10, -10..10 etc.

You don't need 100mA for that. If you think you do, search for another 
parts. I'd say more like 10mA is your goal.

Roman

W dniu 2020-09-16 o 11:29, Spiros Makris pisze:
> Hello list,
> I am working on a (predominantly) midi project, based around the Teensy 
> platform, and I'm trying to figure out the best way of adding a CV 
> output, compatible (and useful) with eurorack.
> Without any additions, I can use any off the shelf DAC to get 4 or 5 
> octaves of 1V/oct, but I would be interested in supporting the whole 
> MIDI range (~10 octaves) - which means I need some switching converters, 
> perhaps even a voltage inverter.
> The options I can think of are:
> 1. Don't do anything, have 5 octaves of range.
> 2. Use a boost converter to get a 12V rail, then have 0-10V range
> 3. Use both a boost and inverting converter, to get a pair of dual 
> voltage rails (-12/+12 or similar?), and use a (-3,8V) range.
> 
> I know the basic concepts of switching converters, but have never used 
> one myself. I assume I need less than 100mA of current (to supply 4 
> opamps and a DAC), what parts would you recommend?
> 
> Regards,
> Spiros
> 
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