[sdiy] Low voltage synthesis?

Steve Lenham steve at bendentech.co.uk
Thu Jan 13 18:23:57 CET 2022


On 13/01/2022 16:59, Quincas Moreira via Synth-diy wrote:
> If you use a switching supply there is very little heat dissipation 
> even at 12 or 15v.

With respect, that's not generally true. There will be less dissipation 
in the POWER SUPPLY, yes, but most of the dissipation takes place in the 
load (i.e. the actual circuitry of the synth) and that will remain the 
same regardless of how the rail is generated. Having said that, the 
benefits of a switching supply increase as the operating voltage of the 
synth (which is what this thread is about) decreases:

Example 1 - a synth that draws 1A at 15V, i.e. 15W

A 90% efficient switching regulator adds 1.7W to that, giving a total 
dissipation inside the unit of 16.7W.
A linear regulator with a realistic input voltage of 20V adds 5W, giving 
a total dissipation of 20W. Not that different.

Example 2 - a synth that draws 1A at 5V, i.e. 5W

A 90% efficient switching regulator adds 0.6W to that, giving a total 
dissipation of 5.6W.
A linear regulator with a realistic input voltage of 10V adds 5W, giving 
a total dissipation of 10W. Quite a bit higher!

And yes, I know that there are low-dropout linear regulators, but in the 
real world you will not be able to sail much closer to the dropout 
voltage when using the traditional transformer/rectifier/cap arrangement.

Cheers,

Steve L.





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