High quality pedalboard power supply

[dimi3]

Hi,

I’m new to the forum, and looking for some info and help for my project. I’m a guitarist myself and facing the problem as many others do, powering bunch of hungry pedals from one power supply on the pedal board.

What I would like to do is regulated power supply with isolated outputs to avoid ground loops, using a torodial transformer with multiple secondaries, and I want that its totally hum free and clean.

Why I want to build it? It’s only a power supply. Because what is currently on the market costs 200$ + with decent quality, and most of them are underrated with mA of current for my needs.

Then I need to pack it to very compact enclosure e.g. (6" x 3.4"x 1.75")

Specification for the supply would be something like:

Build as many outputs as you need.
9V,12V or 18V since each rail is separated this could be easily achieved.
Up to 1,5A per rail, depends on transformer selection. (Typically ordinary pedals need less then 100ma, but some also 300 and 400mA).

I searched the net for similar projects and found bunch of ideas, how to approach this. The best project I found was https://www.audioxpress.com/magsdirx/ax/addenda/media/tipton2926.pdf, but its huge rack version with ordinary transformers, and its missing some kind of DC protection circuit.

The PCB layouts are also available for this, but I thing that it could be done more compact, since I won’t putting it in the rack enclosure, I’m not really a PCB designer so I would need some help around this. If someone has some spare time to help I’m willing also to pay for the design. Basically what needs to be done is only 1 rail of power supply which is then copied as many times as many outputs somebody needs.

So my questions for all the good and experienced people on this board:

What is your opinion on the schematic regarding of hum issues DC filtering?
Do you think there is a need of adding DC protection circuit to each output?

If anyone is interested in building something like this (some guitar players on board) join the thread.

I will really appreciate all the comments on this topic.

 

[dimi3]

I did some homework and drew shcematics in Eagle. Is there someone willing to take a look? Since this is my first schematic i'm not sure if I did it correct.

Thanks,

 

[RDL2004]

It looks okay.

I've never used a bleeder resistor on an output before, but I've never had a 1000µf cap on an output either. You could probably change C4 to 100 or 220µf.

C5 is recommended to be a tantalum type if only 10µf, an aluminum electrolytic can be used but needs to be larger, say 100µf.

R3 and R4 can be combined into one if a suitable value for your desired output voltage is available, or you could use a potentiometer (variable resistor).

 

[dimi3]

Hi thanks for the input, as I said I found similar design on web (attached link in first post), i will change C5 to tantal cap I didn't quite understand your recommendation if tantal cap is used I could retain the 100nF value?

I suppose that aditional 1000uF cap on the output is because the circuit puts out verry clean power with no hum, so I suppose that this cap hepls a little.

My idea regarding R3 and R4 that I would use trimpot for fine adjustment of the output like +-2V and add a selectable output with some DIP switch for selecting 9V 12V or 18V of operation.

But unfortunate I don't know how to do that Can anybody help?

Thanks

 

[RDL2004]

What I meant was that if you use an aluminum electrolytic instead of the recommended tantalum cap for C5 then you should increase it to 100µf.

Here is a sch attached showing a way to use a dip switch for voltage selection. There are many other ways to do it, this is maybe the simplest. One problem is that you could have more than one of the individual switches in the connected position leading to unexpected voltage output. A rotary 1 of 4 (or however many) type switch would probably be better.