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. 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.

PA