Need help!

[objet]

I'm using a three way guitar splitter that uses two 9V batteries and i would like to mod the circuit to utilize a 9V ac to dc plug adapter used on most effects pedals. Is thier any way to mod a simple guitar splitter circuit without the use of batteries?

[bob91343]

Show us the schematic and we can do it.

[objet]

3-way Splitter.jpg If i can bypass the entire battery circuit that would be great!

[bob91343]

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.

[objet]

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.

[objet]

3-way Splitter.jpg Here is a better view the the splitter.

[bob91343]

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.

[objet]

Will do, i will get back to you on that by tomorrow.

[gootee]

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

[objet]

Thanks! That is exactly what I'm going to do, use two 12V wall warts with voltage regulators. Sorry for not getting back sooner i was called away for a job out of town, but do appreciate all your help.