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DIYstompboxes.com  |  DIY Stompboxes  |  Building your own stompbox  |  Power Supply with Isolated Outputs 0 Members and 1 Guest are viewing this topic. « previous next »
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Author Topic: Power Supply with Isolated Outputs  (Read 799 times)
phillip
Posts: 1132



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Power Supply with Isolated Outputs
« on: February 08, 2004, 03:26:26 PM »

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
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D Wagner
Posts: 258


Re: Power Supply with Isolated Outputs
« Reply #1 on: February 08, 2004, 03:46:28 PM »

Quote from: 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


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
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phillip
Posts: 1132



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Power Supply with Isolated Outputs
« Reply #2 on: February 08, 2004, 07:46:12 PM »

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
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niftydog
Posts: 2006


Hey you're a dog, a BIG dog, a nifty-keen-type dog


Power Supply with Isolated Outputs
« Reply #3 on: February 12, 2004, 08:55:46 PM »

Quote
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!
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niftydog
Shrimp down the pants!!!
“It also sounded something like the movement of furniture, which He
hadn't even created yet, and He was not so pleased.” God (aka Tony Levin)
phillip
Posts: 1132



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Power Supply with Isolated Outputs
« Reply #4 on: February 12, 2004, 09:04:52 PM »

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
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niftydog
Posts: 2006


Hey you're a dog, a BIG dog, a nifty-keen-type dog


Power Supply with Isolated Outputs
« Reply #5 on: February 12, 2004, 10:11:44 PM »

Quote
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.
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niftydog
Shrimp down the pants!!!
“It also sounded something like the movement of furniture, which He
hadn't even created yet, and He was not so pleased.” God (aka Tony Levin)
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