Power Supply with Isolated Outputs

[phillip]

I was wondering if there was a way to use a prexisting wallwart power supply, in this case one of the Visual Sound One Spot supplies that supplies 1A and 9V, and then create a circuit that will allow the single supply to feed voltage to about 5 pedals, but have each voltage output isolated to prevent ground loops.  Since the voltage is already well regulated and filtered, it wouldn't need the bridge rectifiers, regulators, or filtering capacitors as seen in supplies that have an internal 120V step-down transformer.

Has anyone seen anything like this?

TIA
Phillip

[D Wagner]

I was wondering if there was a way to use a prexisting wallwart power supply, in this case one of the Visual Sound One Spot supplies that supplies 1A and 9V, and then create a circuit that will allow the single supply to feed voltage to about 5 pedals, but have each voltage output isolated to prevent ground loops.  Since the voltage is already well regulated and filtered, it wouldn't need the bridge rectifiers, regulators, or filtering capacitors as seen in supplies that have an internal 120V step-down transformer.

Has anyone seen anything like this?

TIA
Phillip

Phillip,

Check out this thread.  
http://www.diystompboxes.com/sboxforum/viewtopic.php?t=18557  
We are working on the same objective.  I am trying to finalize the schematic for a bipolar supply.  I am still need some of R.G.'s wise guidance to ensure a quiet circuit.  Then I'll work on a PCB and layout.  

I believe R.G. wants to do something similar, which will be posted on his site http://www.geofex.com.  That is a DIY site that is definitely worth checking out.  Navigation isn't that easy, but it is a goldmine for guitar effect information.

Derek

[phillip]

I was just wondering if it would be possible to use simple 1:1 transformers to isolate the grounds, which would break the ground loop.  

If it would be possible to incorporate X number of transformers (depending on how many outputs you want) into a voltage splitter box of some sort that's being powered by a wall-wart, then it would be a simpler (and cheaper) setup for breaking ground loops without worrying about messing with 120VAC.

Phillip

[niftydog]

I was just wondering if it would be possible to use simple 1:1 transformers to isolate the grounds, which would break the ground loop.

Transformers only work for AC.  If you were going to buy that many transformers, you'd be best off buying 110VAC to about 6 to 8VAC.  Then you just bus all the primary sides together and have completely separate rectifiers and regulators for each transformer.

You only need quite low rated transformers.  The most power hungry of my boss pedals takes something like 140mA DC.

I re-wound an old TV transformer.  It's about 7inches square, weighs a ton, has eleven separate windings... but boy it does a good job!

[phillip]

So how about a single step-down transformer, going from 120VAC then stepping down to about 24VAC.  Then run the AC traces to 8 seperate rectifier setups for 8 seperate outputs.  Would using a single transformer like that have the same result as using 8 seperate transformers?  It would certainly cut down on the total cost (and weight) of the power supply.

Using 24VAC means that I could also have one or two 18VDC outputs, along with six 9VDC outputs.

Phillip

[niftydog]

Would using a single transformer like that have the same result as using 8 seperate transformers?

nope, there's still potential for ground loops.  The idea of using multiple transformers is to remove the physical connection between the mains earth and your power supplys ground as well as the connection between each rectifier/regulator circuit.