Well it appears that the circuit requires 18V total. If you have a wall wart with maybe 8V ac or 9V dc output we can probably use that. If it's dc output we'd need to open it and see if it has a bridge or half wave rectifier; we need it to be a single diode rectifier so we can add a reverse diode to get the opposite polarity.
Failing that, if we have one that puts out 18V or so we can devise a dc splitter to provide positive and negative 9 V, especially since the two supplies have identical loads.
Failing that, if we have one that puts out 18V or so we can devise a dc splitter to provide positive and negative 9 V, especially since the two supplies have identical loads.
I don't have a wall wart, though i would like to have one. I was thinking about using the 1Spot by www.VisualSound.net it comes with a 6 plug daisy-chain. i measured the output at 9.14V constant for all 6 plugs, whether or not that voltage is diminished under a load while powering more than one component i don't know, i do have it powering three effects pedals at once that utilize 9V each and i would like to incorporate the guitar splitter we are trying to mod off of a fourth plug if i can. Do you need me to open the 1Spot to determine what is required for the mod? I've tried to look for schematics on-line with no success.
Unless we know what we have, we won't know what modification might work.
Basically you need two supplies, one positive and one negative. So a unit that only delivers one polarity might be able to be modified to deliver the opposite polarity as well. If it has a half wave rectifier, we are in business. If a full wave bridge, no way. If a full wave center tap, we can do it.
So I guess you will have to look inside to see.
Basically you need two supplies, one positive and one negative. So a unit that only delivers one polarity might be able to be modified to deliver the opposite polarity as well. If it has a half wave rectifier, we are in business. If a full wave bridge, no way. If a full wave center tap, we can do it.
So I guess you will have to look inside to see.
Get two identical regular transformer-type 9V wall warts and connect the positive output of one to the negative output of the other. That will be your new ground. The remaining + and - leads will be your new +9v and -9v. (If I was doing it, I would probably get two 12V wall warts and then add voltage regulators to the + and - to get a nice, clean 9V.)
The wall warts must be the transformer type, and should not have three prong plugs. In the USA the properly-isolated types should say something like "Class 2 Transformer", somewhere on the outside.
You could also get an 18V wall wart and use a rail-splitter circuit, similar to the one in the LM675 datasheet that you can download from national.com . For low current/power you can just use an opamp instead of the LM675 power amp.
There are also easy ways to invert a single positive voltage (probably with a small switch-mode supply) to give you both + amd -, and there are ways to double the output amplitude of the transformer in a wall wart and then split that into + and - DC supplies. But my first suggestion is usually the easiest and fastest.
Cheers,
Tom Gootee
The wall warts must be the transformer type, and should not have three prong plugs. In the USA the properly-isolated types should say something like "Class 2 Transformer", somewhere on the outside.
You could also get an 18V wall wart and use a rail-splitter circuit, similar to the one in the LM675 datasheet that you can download from national.com . For low current/power you can just use an opamp instead of the LM675 power amp.
There are also easy ways to invert a single positive voltage (probably with a small switch-mode supply) to give you both + amd -, and there are ways to double the output amplitude of the transformer in a wall wart and then split that into + and - DC supplies. But my first suggestion is usually the easiest and fastest.
Cheers,
Tom Gootee
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