[sdiy] Low voltage synthesis?

Tom Wiltshire tom at electricdruid.net
Thu Jan 13 20:13:45 CET 2022


MCP6002 might be a modern op-amp, but the specs read like a 741. It's designed for rail-to-rail use at 5V, but I don't think they had audio in mind!

Not that I'm criticising your choice. I've used it too in similar situations for the same reasons.

> On 13 Jan 2022, at 18:42, Chris McDowell via Synth-diy <synth-diy at synth-diy.org> wrote:
> 
> I have dug into this some. 
> 
> I built a VCO, VCF, and VCA from LM13700s running at 3.3V. While it was what I'd call "a little bit noisy", they sound "old" which to me often equates to "good" 
> 
> I'd say build something and determine if it is too noisy. I used MCP6002 op amps and LM13700. 
> 
>> On Jan 13, 2022, at 10:20 AM, cheater cheater via Synth-diy <synth-diy at synth-diy.org> wrote:
>> 
>> Synths generally run off 15V or 12V power rails, which among others
>> helps with SNR. However, it creates a bunch of power dissipation, plus
>> you can't use some of the tiniest components. Does it make sense to
>> build synthesizer circuits that run on much lower voltages than that?
>> Say, 1.5V rails? Are there techniques of suppressing noise that are
>> better than just ramping up the voltage rails? Have the parts
>> progressed enough nowadays that we can do this?
>> 
>> Never mind stuff like interfacing with existing modular synthesizer
>> parts etc. Let's say you're building a modern 8-voice polysynth with 4
>> VCO, VCF, VCA, ENV, LFO per voice. Obviously that would generate loads
>> of heat and possibly tuning issues given the constraints of a
>> keyboard, plus it would be huge, especially given the size of
>> capacitors vs their rated voltage.
>> 
>> Where would noise creep in first if you started lowering rail voltage
>> in your synthesizer designs? What other disadvantages in terms of
>> signal integrity come from using low voltage rails for synths?
>> 
>> Thanks
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> 
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