On 14/06/2021 14:10, Dave Plowman (News) wrote:
In article ,
Fredxx wrote:
On 14/06/2021 11:07, Dave Plowman (News) wrote:
An audio circuit I found online and have been playing with has an odd
design (to me).

It's op-amp based running off a (separate) +/-15v supply.

There are on board caps across the supply, which is common enough. 10 and
0.1uF in parallel. But instead of going to ground, they are wired across
the +/-15v. Does that do the job as well? Or serves a different purpose?

I would say it is normal for 0V to be treated as ground and all supply
decoupling off that.

I can perhaps understand an instance where you might not want to impose
power supply noise/switch/ripple current on the ground rail. It depends
on the nature of the power supply.


Thanks for conflicting replies chaps. ;-)

It always "depends" on the detail. :-)

The PS shown is a conventional transformer type with a regulator for each
rail and conventional smoothing.

Are the 2 parallel caps associated with this 'conventional smoothing'?

The circuit suggests high quality op-amps and caps (on the audio side) so
I doubt it's just to save component count.

The only explanation I can thing of is the op-amps have very high power
supply rejection ratio and the idea is to minimise ground current.

Personally I would have used OV / GND as a PS common and had two caps.
There are ways of minimise the injection of PS noise currents.