Noise-free decoupled power supply

[roberto]

Hi all,

during my last waiting time in the lounge in Dubai, I came out with this idea to decouple the power supply of stomp boxes in order to avoid hum-loops. I've done some sims I want to share, and ask if someone else has done something similar.

Basically from one single tap we can get:
- one main output, directly connected to the tap, for the high current requirement (around 1 A);
- as many outputs as needed decoupled by a couple of 220 uF 25 V bipolar caps, then to a regular power supply with low current requirement (I've simulates a CCS with 100 mA here).

Then of course a standard 7809 (/12/15/18) and then 100 n to the stomp box.

The sims has been done with 14 Vrms as a voltage supply.

Has enyone done something similar?

[trobbins]

The seperate supplies are galvanically seperated, but the grounds are effectively connected for hum/noise loops (assuming pedals are signal linked) due to the large coupling capacitors that let through mains frequency for each of the 'dc isolated' supplies.

[roberto]

DC decoupled, AC coupled: noise coupled
Thanks trobbins!

[Stevem]

Low impeadance is the cure ( phase cancel what is bad) ,but it doubles the parts and current draw!