DIY power supplies

[blueband]

I've been looking around for ideas for a DIY power supply for stompboxes and found a couple of older threads on this forum. I've been a bit put off by the thought of needing a transformer with multiple secondaries, so was wondering about using a single "master" DC supply, with a higher voltage than 9V, and then using isolated DC-DC converters to provide the separate 9V feeds to the stompboxes. Converters such as Tracopower TME 0509S look quite cheap and claim to isolate the DC output from the input. That seems to be rated at 9V, 110mA output. I would obviously need one converter per stompbox.

I was also wondering about using something like an old laptop PSU as the master supply to all the converters, as I've got several of these knocking around and it would avoid mucking around with mains voltages in my own circuit.

Has anyone tried this approach or have any ideas about whether it would work?

Thanks

Steve

[induction]

Here's what I use:





The schematic is just an adaptation of this:


The vero is easily modified to use through-hole components only, and/or to give other voltage options (-9V, etc.) Look here and here for more discussion.

[R.G.]

Your first question to answer is whether you really need isolated supplies per pedal. There are some situations where this is an advantage, but the vast majority of pedalboard setups do not need isolation.

If you don't actually NEED isolated grounds, consider carefully whether making one yourself is worth the time and money. There are really good 9V pedal power supplies in the $20 range that can power all the 9V pedals you're likely to want.

If you do need isolation for explicit reasons, you can use multiple small mains transformers. See the "spyder" article at geofex.com.

If you use one DC source and then multiple regulators, this approach helps with noise and isolation on the +V line, but does nothing for ground noise. Of course, ground noise is only an issue for pedals that have grounding issues themselves, or do not play well with others, usually high-current digital pedals. Sometimes it makes sense to give a $300 digital pedal its own $20 power supply.

If you use one DC source and multiple DC-DC converters, you may well run into noise issues from the DC-DC converters. Each of these is a switching power supply in its own right, and they may cause clocking noise issues themselves. Or not. No way to tell until you hook them up.

[amptramp]

Another vote against multiple DC-DC converters.  Even if the converter oscillation frequency is well above audio, say 100 KHz, if one converter operates at 100 KHz and another at 101 KHz, you may get an audio beat note at 1 KHz that is well within the audio range.  Besides, anything with switching frequencies above 9 KHz may run afoul of FCC radiated and conducted emissions regulations, so you could build it and use it but you could not sell it.

[antonis]

Another vote against multiple DC-DC converters.

You may well count on me, too...

[blueband]

Many thanks for the replies.

Currently I use a power supply with a simple daisy-chain connector between pedals. There is a certain amount of noise from the pedalboard, which I had attributed (maybe wrongly) to the ground loop created by the power ground connections and signal ground connections between boxes.  I understood that the isolated outputs of products such as the "Fuel Tank" power supplies were intended to solve this kind of problem and I was looking for a low cost alternative...

.... but I get the points several of you are making about the undesirability of DC-DC converters -- particularly the possibility of audio-range difference frequencies between oscillators.

Oh well, at least this is one idea I can chuck in the bin before I've spent any money on it

Thanks again.

[Mark Hammer]

I only recently started sticking some of my pedals on pedalboards.  As it happens, the "pedalboards" are wooden tiles I picked up from the dollar store, along with Velcro for adhering things, for a total of about $7.50 per pedalboard (taxes included).  Depending on the particular pedals, I can fit 6 or 7 on one, such that I have 4 different such "clusters" that can be self-contained (i.e., enough pedals to deliver up a wide range of sounds and moods) or employed as a loop in conjunction with other clusters.  I whipped up a couple of dual loop-selectors with order-flip switches, such that the clusters could be in reconfigurable series, or even nested within each other.

But that's secondary to my post.  I made myself some power distribution boxes: little black plastic boxes with five paralleled 2.1mm jacks, an extra 1000uf smoothing cap and a status LED.  A wallwart can plug into any of the jacks, and extensions run out from any of the jacks, to pedals, or yet another identical box.

As RG rightly notes, many scenarios do not require isolation and individual regulation of each output.  As it happens, unless all your pedals are of one brand or form-factor (e.g., all 1590B-sized), daisy-chaining may not necessarily work for you, physically.  So, even if individual isolation and regulation is not required, being able to run custom-length power cables to a pedal with an oddball shape or the jack mounted in a different location, from a separate output jack, is a real convenience; especially if it lets you position that pedal where you need it to be, rather than where a power cable forces it to be.

Distribution boxes like this do not need to be used on their own, but could be used in tandem with a power brick of some kind.  So, for instance, a regulated 100ma (or higher) output goes to the distribution box, and finds its way from there to a quartet of low-current analog fuzzes and overdrives.  The box becomes an extender for the brick, where physical convenience is the priority, not regulation.

[TejfolvonDanone]

I've made a supply with a two 9V output mains transformer, four 9V regulators with the regular filtering and protections and each regulator has two outputs. Each secondary of the mains transformer have one rectifier one 1000uF smoothing cap, each regulator has both on its input and output a 100nF (polymer) cap and a 100uF cap on the output as wall as a reverse polarity protection diode across the out and in. It's basically the datasheet recommended for the regulator. Each regulator (in theory) can put out 300mA current at the same time. I'm planning to fit in an indicator LED also.

I can't really tell if it is the case but don't confuse DC-DC converters with regulators (like the 7809).

With at least 23V adapter you can create a +/-9V adapter with 2 regulators (either two 7809 or one 7809 and a 7909). The regulators need a higher voltage input than their output. It wouldn't be ground isolated though. It would be a good recycle for the old adapters. Laptop DC adapters often have good regulation and high current capability.

If you really have ground loops i don't think there is an easy way beside the regular mains transformer route.

[blueband]

Hi Mark

Thanks for the reply. Yes, when I spoke of my "pedalboard", this was maybe a bit of a grandiose description. The board is made from a few plywood offcuts, with the stompboxes vecroed onto it. In my case, the pedals are all currently (voltagely??) standard 9volt stompboxes. Nothing exotic: just a tuner, clean boost and a couple of overdrives. Anything else and the rest of the band would probably look at me like I had started playing the bagpipes.

Cheers

Steve

[stonerbox]

Sorry for the hijack! How clean are these kinds of power supplies VS a "real-transformer+filter" power supply?

Happy 4/20. 

[LightSoundGeometry]

what is the difference between a 7660C and a 7660S?

http://www.ti.com/lit/ds/symlink/tl7660.pdf

I will guess they are both switching voltage converters? and would a max1044 be a good substitute or is there something else to consider?

https://datasheets.maximintegrated.com/en/ds/ICL7660-MAX1044.pdf

probably just answered my own questions , lol ..looks like a 1044=7660 but like to hear from the folks who know for sure, dont want to burn the house down lol

looks like th ranges differ

range from1.5Vto10V on the 7660 and -5 to +5 on the 1044

[Groovenut]

what is the difference between a 7660C and a 7660S?

http://www.ti.com/lit/ds/symlink/tl7660.pdf

I will guess they are both switching voltage converters? and would a max1044 be a good substitute or is there something else to consider?

https://datasheets.maximintegrated.com/en/ds/ICL7660-MAX1044.pdf

probably just answered my own questions , lol ..looks like a 1044=7660 but like to hear from the folks who know for sure, dont want to burn the house down lol

looks like th ranges differ

range from1.5Vto10V on the 7660 and -5 to +5 on the 1044

I believe the difference between the MAX1044 and the ICL7660 is the maximum input voltage, 10 vs 13. The 7660S has a frequency boost function when pins 1 and 8 are connected placing the switching frequency out of the audio range (35KHz).

[LightSoundGeometry]

what is the difference between a 7660C and a 7660S?

http://www.ti.com/lit/ds/symlink/tl7660.pdf

I will guess they are both switching voltage converters? and would a max1044 be a good substitute or is there something else to consider?

https://datasheets.maximintegrated.com/en/ds/ICL7660-MAX1044.pdf

probably just answered my own questions , lol ..looks like a 1044=7660 but like to hear from the folks who know for sure, dont want to burn the house down lol

looks like th ranges differ

range from1.5Vto10V on the 7660 and -5 to +5 on the 1044

I believe the difference between the MAX1044 and the ICL7660 is the maximum input voltage, 10 vs 13. The 7660S has a frequency boost function when pins 1 and 8 are connected placing the switching frequency out of the audio range (35KHz).

cool! i am going to build me a power supply just to learn more, especially full wave rectifying, filtering and transformers. Will never throw away my Trutone/Visual One Spot but to build is to learn plus I may need more volts for example the tube boosts like to see 12 volts even they run off of 9

[Mark Hammer]

Hi Mark

Thanks for the reply. Yes, when I spoke of my "pedalboard", this was maybe a bit of a grandiose description. The board is made from a few plywood offcuts, with the stompboxes vecroed onto it. In my case, the pedals are all currently (voltagely??) standard 9volt stompboxes. Nothing exotic: just a tuner, clean boost and a couple of overdrives. Anything else and the rest of the band would probably look at me like I had started playing the bagpipes.

Cheers

Steve

Here's one of mine.  The distribution box is in the upper right-hand corner, although the power cables aren't installed, and the box needs to be rotated 180 degrees.

[antonis]

I presume that something interesting is hidding inside Mark's BIG enclosure for EA Tremolo... 

[Elijah-Baley]

How much I searched something like that!


I don't know if someone needs, but I was looking this PSU in the last day: http://diy.thcustom.com/pedal-power/.

[Mark Hammer]

I presume that something interesting is hidding inside Mark's BIG enclosure for EA Tremolo... 

Yes.  Space for a battery and an oversized layout.  I bought about 20 of those plastic Pac-Tec chassis from a surplus place we used to have in town.  They were a dollar apiece, so I couldn't refuse, even if they were a little bigger than I'd like.  I make the end-pieces from copper board, and for shielding use a piece of copper shim material cut out to fit the underside of the top half of the board, with holes popped out for the controls and switch.  Surprisingly sturdy and rigid, and VERY light.  I put together a pedalboard a while back with 8 different pedals built into these boxes.  When the batteries were removed, the entire thing - pedalboard included - must have weighed less than 3 pounds.  The light weight of the pedals meant that I could use what was essentially a plastic boot tray as the "pedalboard".

[Elijah-Baley]

I presume that something interesting is hidding inside Mark's BIG enclosure for EA Tremolo... 

Or the EA Tremolo is used to move the suspects from the tiny FY-2.

[duck_arse]

the ea trem is the trabant on his board of cadillacs.
[/white_noise]