Multiple LM7809 - isolated or not?

[seedlings]

I've read about RG's Spyder which uses multiple transformers, each with it's own regulator circuit.  Is one transformer feeding multiple, parallel LM7809 regulator circuits not isolated, or not isolated enough?   I have a 2000mA transformer (from an old printer), with this, I wanted to branch off 3 or 4 LM7809 circuits because the digital pedals (EHX) are troublesome whiners.

Thanks,
CHAD

[Ben N]

Have yourself a gander here.

[psychedelicfish]

Noise from digital circuits... isn't that why you see those ferrite beads on the end of laptop power supplies etc?

[seedlings]

Have yourself a gander here.

Much obliged.  Although the article doesn't specifically mention digital pedals, it does say each supply is isolated.  I'll run with that.

Re: the ferrite beads... Is this a secret trick to use a switching supply on digital pedals?? Do tell.

CHAD

[greaser_au]

The outputs of the circuit in the link are not actually isolated, because that all share a common ground, and the potential for ground loops exists just the same as a daisy chain cable. There is some 'decoupling' of the power supply because of the individual regulators (will control noise on the supply lines), but if you were to use a positive ground pedal on the board with your negative ground devices, you would still have problems.

Each of the R.G.'s Spyder supply outputs are totally isolated from one another, both ground and 'hot' sides,  whether you use individual transformers or a Weber WPDLXFMR-x (x=1 for US or x=2 for universal) as R.G. says on the Spyder page.

Remember this is mains voltage,  and it is dangerous. Get help from someone suitably qualified!

david

[Ben N]

Was gonna mention the Weber tx--that would seem to be the gold standard of isolation (as good as separate transformers, but cheaper, more compact and easier to wire). But you could try the more limited approach, tying the regulators together with jumpers, and see if it works for you, as it might. If not, remove the jumpers and go the full monte.

[seedlings]

The outputs of the circuit in the link are not actually isolated, because that all share a common ground, and the potential for ground loops exists just the same as a daisy chain cable.

And if I'd read closely, the last line says, "The power outputs share a common ground, and though it should work well with the majority of pedals, there are a few designs (mostly digital) that will require a power input with an isolated ground to avoid hum."

Full isolation will have to be the way to go.  Thanks!

CHAD

[seedlings]

Just an update on this one... I cut the patch cable shield on two cables and moved them to different positions on the pedal board.  I found that in the right location, this killed all the noise.  Now I'm able to use two power supplies: one for the Jamman Delay, and one for all the others.

CHAD