On 14/06/2021 17:55, Peter Able wrote:
On 14/06/2021 16:02, Fredxx wrote:
On 14/06/2021 14:10, Dave Plowman (News) wrote:
In article ,
Â*Â*Â* 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.



Shame you can't point us to the circuits.Â* Even with your extra notes,
above, there are still many questions arising - not least if your notes
are incorrect. (It does happen!)

Most Op Amps applications are inherently PSU-ripple insensitive.

I managed to find this article, which features different power supply
decoupling and some reasoning behind the choices.
https://sound-au.com/dwopa.htm