[sdiy] Low voltage synthesis?

Mike Bryant mbryant at futurehorizons.com
Fri Jan 14 11:58:15 CET 2022


And the 10x cost !!


-----Original Message-----
From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On Behalf Of rburnett at richieburnett.co.uk
Sent: 14 January 2022 10:45
To: Tom Wiltshire
Cc: synth-diy
Subject: Re: [sdiy] Low voltage synthesis?

The MCP6022 has a much better spec if you can afford the milliamps.

-Richie,



On 2022-01-13 19:13, Tom Wiltshire wrote:
> 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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