Pedalboard supply idea...

[yankeerob]

I have posted this in the FX section and am posting it here because it's pretty urgent (and apologise for my impatience!)



Does this look kosher?... I'm hoping it'll eliminate ground loops more than anything but I have a 50VA toroidal with two 0-15V/1.67A secondaries and this is an illustration of what I plan to do with one or both of the secondaries.

Any comments... criticisms???

Many thanks for your help,

YR

[yankeerob]

Apparently this is a bit more like it...



Advice from a guy who builds 100KV+ PSUs...

[Mick Bailey]

Many 9v regulators deliver slightly less than 9v. Each node will also reduce by 2x diode drops - maybe 1.4v, though your common-leg compensating diode will only elevate the output by 0.7v. Your pedal supply will end up being at best 8.3v. You could add another diode in series with the regulator common leg to increase the output.

Ground loops take many forms and currents can still circulate despite the isolation diodes. How effective the setup is depends on the nature of the loop and the magnitude of the current.

One concern is the ground is elevated by a diode drop for each node. This may cause you additional noise problems with some pedals, as there's no direct path to ground for AC and some pedals don't have good supply bypass caps. Though many of those are vintage designs that you may not be using off a pedalboard supply.

[yankeerob]

That's a start Mick... Thanks for your input! I'll start with a breadboard mockup of the output section and see how it goes...

Best regards,

YR

[J M Fahey]

The pedal grounds will be shorted to each other anyway by guitar cords, so all you get is having *power* grounds isolated and all grounds, power and signal, floating 1 diode above supply ground.

You complicate it in exchange of nothing.

If any, I'd wire all the regular way, and cut ground at one end of each cable.

That said, you should not have ground problems just by interconnecting pedals, since (I presume) all live together in a nice large common pedalboard inches away from each other, but, most important, current consumption is nil, so residual voltage drop across residual resistances should be very very low.

If you have a ground hum problem, maybe you should recheck the supply itself, it's the only point nearby where you have large current pulses (charging supply caps) at mains frequencies (or its multiples) .

[olddawg]

Just buy a OneSpot or a Godlyk.

[oc disorder]

Some more food for thought and a possible copyright infringement!
R.G. Keen provided a schematic way back for the Spyder although he has now removed the info.
He had provided details for winding mains transformer secondaries but in hindsight he must have reconsidered as could be lethal.

http://www.geofex.com/article_folders/spyder/spyder.htm

This project involves wiring and working with AC mains line voltage. You MUST pay strict attention to safety warnings and MUST be able to do the wiring safely. This article will not teach you to do that - you have to come prepared to do that on your own. If you don't already know how to do it safely, do not try this project.

April 10, 2015. This project has been up on geofex for fifteen years. I believe it was the origin for commercial many-output power supplies for pedalboards, and for the many dying battery simulators that are common in the DIY effects world. However, it does involve some risks. That warning is serious. In a couple of forums on the net I have seen some questions that have finally made me conclude that there are people coming into the DIY effects world that will ignore the warnings however they are worded. So, regretfully, I am removing the technical content from this article.

I would buy a transformer .. it's far to risky to mess with altering power transformers especially when 230volts!

Here's the current address for the Weber transformer mentioned in the article and a picture attached here.

WPDLXFMR-1 Transformer



Here's the article via the Wayback Machine before it was removed

http://web.archive.org/web/201402100...der/spyder.htm


Here it is re-posted .. the French version ?
http://www.techniguitare.com/projets...fex-Spyder.pdf

[yankeerob]

All comments gratefully received and noted...

Project on hold til Friday anyway... really appreciate your thoughts!!!

Wishing you all the best,

YR

[yankeerob]

A quick comment - I don't want to emulate nearly exhausted batteries or any of that old guff... I just want to power straight, 9V, neg grounded pedals with chassis isolated inputs (as in that the pedals positive is isolated physically from the pedal chassis)... the diode idea is already out of the window (from Mick and Juan's input) and the root of the circuit already works very well... produces a robust 9.5V @ 1A so effortlessly it's almost yawning... I haven't even tested a 'pedal train' with it yet but I have an odd enough assortment to get the ball rolling - likely at weekend.

Really do appreciate everyone's comments and will let you all know what we wind up with... my mate Nick's back on Friday too... Speak soon

[Mark Hammer]

Just buy a OneSpot or a Godlyk.

Though not a problem in every single case, problems can arise when two or more digital pedals share a common power source. I've experienced it, and so have many others. A digital pedal is dead quiet, when used in conjunction with a bunch of analog pedals, all daisy-chained to a PSU like those you mention. Buy/add a second digital pedal, and all of a sudden the same power arrangement that was nice and quiet, and the same pedal that was quiet on its own, turns into a hornet's nest of buzzes and whines.

The problem is that clock spikes travelling across the power lines are generally too high to be audible. But have two pedals sharing the same power line - one with a 2.001mhz clock, and the other with a 1.999mhz clock (each very very close to spec) and their difference is 2khz, which IS very audible.

Happily, more and more digital pedals are taking steps to protect against that sort of heterodyning. But for the time being, daisy-chaining PSUs across multiple digital pedals is something to be done with medium-to-low expectations. It won't break anything, but it may not sound very nice. Happily, it is resolved by using separate supplies for each digital pedal.

[yankeerob]

Though not a problem in every single case, problems can arise when two or more digital pedals share a common power source. I've experienced it, and so have many others. A digital pedal is dead quiet, when used in conjunction with a bunch of analog pedals, all daisy-chained to a PSU like those you mention. Buy/add a second digital pedal, and all of a sudden the same power arrangement that was nice and quiet, and the same pedal that was quiet on its own, turns into a hornet's nest of buzzes and whines.

The problem is that clock spikes travelling across the power lines are generally too high to be audible. But have two pedals sharing the same power line - one with a 2.001mhz clock, and the other with a 1.999mhz clock (each very very close to spec) and their difference is 2khz, which IS very audible.

Happily, more and more digital pedals are taking steps to protect against that sort of heterodyning. But for the time being, daisy-chaining PSUs across multiple digital pedals is something to be done with medium-to-low expectations. It won't break anything, but it may not sound very nice. Happily, it is resolved by using separate supplies for each digital pedal.

That's some great input Mark!... this - by virtue of having two separate 0-15V secondaries to start may accomodate two digital pedals even if this problem arrises... very interesting stuff!!

YR

[olddawg]

Though not a problem in every single case, problems can arise when two or more digital pedals share a common power source. I've experienced it, and so have many others. A digital pedal is dead quiet, when used in conjunction with a bunch of analog pedals, all daisy-chained to a PSU like those you mention. Buy/add a second digital pedal, and all of a sudden the same power arrangement that was nice and quiet, and the same pedal that was quiet on its own, turns into a hornet's nest of buzzes and whines.

The problem is that clock spikes travelling across the power lines are generally too high to be audible. But have two pedals sharing the same power line - one with a 2.001mhz clock, and the other with a 1.999mhz clock (each very very close to spec) and their difference is 2khz, which IS very audible.

Happily, more and more digital pedals are taking steps to protect against that sort of heterodyning. But for the time being, daisy-chaining PSUs across multiple digital pedals is something to be done with medium-to-low expectations. It won't break anything, but it may not sound very nice. Happily, it is resolved by using separate supplies for each digital pedal.

Yeah, I suppose it's situational. When I have had similar problems I simply ran the offending pedal on its own supply. My point was the OneSpots are so inexpensive and have such a small footprint it's worth a try before spending the time, effort, and cash to reinvent the wheel if it isn't necessary. You could still have digital noise if the grounds aren't isolated too, which usually aren't the minute you plug it into the pedal chain.