Power supply make or buy

[Phend]

Hello
Any comments on this topic?
Diy is probably the most satisfying.
Purchase can be cheap, but cheap is probably cheap.
Thanks

[GibsonGM]

I think it depends on what you want it for. A bench power supply for pedal testing or what have you, that can be fun to build (educational) and you can build in some functionality you might not get elsewhere.  Or for a small amp or whatever.

For running a pedal board, IMO it's easiest, most economical and reliable to just buy something. There are many companies with good reputations in this regard.

As always, YMMV!

[Phend]

In this case the power supply is for 9 volt effects.
Maybe 6 DC outputs.

[bluelagoon]

Have to recommend the Strymon Ojai. You cant make them for as cheap or as efficient, well built, functional or as pretty as the Strymon
for less than you will pay for the store bought unit. You can try!

https://www.macronmusic.com.au/strymon-ojai-r30-hi-current-power-supply

[ElectricDruid]

I've recently built a Eurorack power supply using these:

https://uk.farnell.com/mean-well/irm-30-12/power-supply-ac-dc-12v-2-5a/dp/2815509

Dead easy to use - you just feed it AC mains and it does the rest, pretty much. Quiet enough for audio. Unfortunately they don't make a 9V one, but I bet someone else does. 2.5A output is enough for 6 outputs at 400mA.

[R.G.]

There are two questions lurking here.

First, do the effects require ground isolation for technical as opposed to la-di-da internet fussy reasons? One technical reason might be positive ground versus negative ground pedals. Another might be bad-actors pedals that behave so poorly that they need a protective environment for their grounds.

Second, how much do YOU value education/fun from building versus convenient and reliable packaging and hookup? I can make a technically-better power supply than I can buy. But it will take a long time, cost more, and have clumsier packaging. Your actual use also gets into the evaluation. Are you playing only at home? Or do you lug your creations out to play gigs? Playing gigs is a big recommendation for getting a well packaged commercial supply.

GibsonGM is right: There are companies with very good reputations for effects power supplies. A little research can save you a lot of time and perhaps money.

Full disclosure: I work for Truetone; this lets me see the insides and inside-the-company way they're designed, sourced, sold, and supported. You do your own research. I suggest you look at the 1Spot line and its reputation.

[stallik]

Isolated outputs or not? Big difference in price/complexity. Some 'isolated' supplies really aren't.

My board runs quietly on a 2 output 9v/12v diy job with the 9v daisy chaining everywhere. Big dual toroidal, 2 variable power/filter boards. If not for the 12v requirement, my 1spot would do the job. So impressed with it that one of their larger units would be my first choice if I needed true isolation.

However, the GigRig has just announced a new power block for their modular system which looks interesting

Edit: RG beat me to it

[Phend]

Looking at Pin Negative (for NPN builds).
Negative Ground.
Home use only.

I found this note on this web site:
https://www.instructables.com/Build-A-Power-Supply-For-Your-Guitar-Pedals/
"IMPORTANT NOTE: Depending on what pedals you intend to use this for, you should take care to wire the DC connectors as pin-positive/ring-negative or pin-negative/ring-positive. The latter is the industry standard way of doing it, although it poses issues when building a pedal that has a metallic housing. I prefer pin-positive/ring-negative because of that issue, and I wired this supply in this way."

Issue with Pin Negative, not sure I understand unless using metal "jacks"

And Yes I have fun building one offs, plus the education.
Hammond enclosure ?
Cost, no issue.

Thanks all for the suggestions..

[Kipper4]

I got a second hand lab type power supply from a mum and pop electronics store for 20 bucks. I don't know if I just happened on it at the right time but it's a super little unit.
Voltage and current readings.

Hope you find the best solution for you.
Rich

[Rob Strand]

"IMPORTANT NOTE: Depending on what pedals you intend to use this for, you should take care to wire the DC connectors as pin-positive/ring-negative or pin-negative/ring-positive. The latter is the industry standard way of doing it, although it poses issues when building a pedal that has a metallic housing. I prefer pin-positive/ring-negative because of that issue, and I wired this supply in this way."

Issue with Pin Negative, not sure I understand unless using metal "jacks"

All it's saying is the author prefers positive tip in order that the metal jacks connect the negative to the casing.  Connecting the chassis to the incoming power isn't a good idea anyway.  IMHO it's a cop-out so the author doesn't have to deal with it.

The construction in that article is potentially dangerous:
- The transformer is exposed.  The mains windings can be damaged and exposed to the user.
   It technically needs a grounded cover.
- glued down caps inside an enclosure with mains inside, then exposed mains wiring on top of that.

You would be better off using an external wall-wart which then plugs into a box that does the regulation.   Non isolated outputs works fine in many cases. You can help isolate the supplies with small resistors in series with the -ve of each output.  Non isolated outputs aren't suitable for positive ground pedals that's where you need either isolated supplies.   Another option for positive ground pedals is to have a few negative outputs but that complicates things a bit.

[R.G.]

Good point Rob. Having a cheap, fun to build power supply isn't worth dying for.   8-|

Safe construction is part of what you pay for with  commercial power supply, and there is usually at least some effort in a commercial supply to meeting formal safety standards. Home brewed supplies often have big safety issues.

@Phend: there is quite a number of articles on power supplies and power issues at geofex.com, going back to about 2000. You might like reading through them. google "geofex power" to get started.

[Phend]

Thanks Rob and R.G. :
Yes I can work with 120 v, but to construct a safe unit, fused, switched etc and make it UL would not be worth it. Just running a 3 prong cord into it is a design project. Plus the mounting of components.
With that said I have looked at various supplies.

Truetone is an option. As is strymon ojai.
Truetone makes their Pro unit and the Truetone 1 Spot Combo which is inexpensive.

The 1 Spot could be taken a step further, don't laugh, for a cleaner distribution, purchase a Hammond box or make a wood one, and get a bag of barrel jacks. Run the 1 Spot into a jack which connects to a MC8 (inside the box) which in turn connects to a array of barrel jacks wired to jacks mounted thru the wall of said box. Getting the wiring nice and clean inside (partition is required).

[ElectricDruid]

Home brewed supplies often have big safety issues.

While I entirely agree, I'd say only if you're damn lazy, frankly. It's not hard to make something that's really, genuinely safe - it just takes a bit more effort and bothering to get the right parts (like putting heatshrink over mains connections, for example).

But a lot of people *are* pretty lazy, so you do see a lot of dodgy stuff out there. I save my laziness for situations where mains voltage is not concerned!

[R.G.]

I think the issue is more not knowing the details of what safety is than in laziness.

The fundamental mantra of safety certification is that the failure of any one component (including the worst possible one!) should not allow a thermal or electrocution hazard to happen. The ramifications of that get tricky.

For instance, what if the failing component is a layer of insulation between primary and secondary inside the power transformer? The answer to this one and the other primary wiring insulation instances is either to provide a solidly safety grounded shell, or to make two layers of primary insulation for all primary wiring. That is, either safety ground the whole thing, every single user-touchable metal part; or to put in two layers of insulation - the so-called double insulation method.

What if one of the primary wires breaks loose at one end/solder joint and slips out of its heat shrink? The answer is to mechanically secure all wires carrying hazardous voltages so that if any one wire breaks, the loose end is restrained from touching any user-accessible metal, or can only touch a safety grounded surface.

What if a voltage transient comes down the AC line and breaks over between a primary wire and a secondary wire? The answer is (1) require high-potential testing up to about 4000V with no breakover (try that one at home; I once did it with a variac and a neon sign transformer, but I still get twitchy thinking about the test setup) and (2) require enough creepage and clearance distance between primary and secondary wires to withstand that kind of transient even over a PCB dusted with greasy dust and bar funk for a few years.

All of this kind of thing is reasonable once you're exposed to it for a while, but it's not obvious to someone who hasn't been through a safety certification test program. That's what makes me think the exposure is more being new/naive than lazy.

[antonis]

That's what makes me think the exposure is more being new/naive than lazy.

Unless you make a PS for someone else, with bad intentions..

[PRR]

......high-potential testing up to about 4000V with no breakover (try that one at home; I once did it with a variac and a neon sign transformer, but I still get twitchy....

Electric fence charger. The cheapest one in Tractor Supply claims 2.8KV. The tester sold on the same aisle blips the 4KV neon even with 100 feet of damp horse-tape. (However reading close it may claim 2KV or 977V..... CYA??) 



No, pulse testing is not as strenuous as steady voltage. OTOH most KV surge around the house will be brief. Otherwise bigger stuff will arc/smoke.

And a fence charger can "give you a lesson" and you probably not die of it: these things have few warnings and the company has been in business for years, so the total jolt must be not-real-lethal.

I know that 30KV *once* cured me of working on live parts.

[stallik]

Probably the wrong way to think about it but, if my PS build electrocuted me, that would be it. In a second or two. On the other hand, if it were to short, cause a fire and burn the house down, I'd never hear the end of it.

[ElectricDruid]

I think the issue is more not knowing the details of what safety is than in laziness.

Ok, but you can *look up* the details if you don't know, and not doing that is laziness. It's not like this stuff hasn't been done a hundred times before. There's stuff out there that you can find that tells you what you need to do. You just provided a very succinct summary in four paragraphs, so it's not exactly impossible.

But yes, I agree, when you don't know what you don't know, it's easy to get yourself in a twist. In that position, you should at least know enough to stay away from mains, surely?!

[Rob Strand]

But yes, I agree, when you don't know what you don't know, it's easy to get yourself in a twist. In that position, you should at least know enough to stay away from mains, surely?!

That's pretty much it.    "Safe" viewed by experienced eyes is very different to "Safe" viewed by electronics people in general.

Using wall-warts is a good way to keep away from mains.    It also reduces the complexity and size of the project, and even the cost.  In simple terms if you can't let your children use it with electrocuting themselves or put it under your bed at night without it catching fire one day you shouldn't build it or use it!

If you just have a regulator in a box it can be pretty darn small,

[MrStab]

For what it's worth, RG's deterrence years ago forms the bedrock of my own cautiousness when it comes to mains AC.

I still use one of the PSUs I nonetheless built on a regular basis, and the one preceding that still works well after many a gig. Both fused, safety-earthed with sufficient crimping and tooth washers, live wiring isolated from chassis, firm, reliable mounting and ample spacing between pre/post rectification. Then came the DIY power amps. The safety modifications to non-compliant Chinese equipment are now second-nature. The repairs to commercial mains equipment are still undertaken very carefully. Self-doubt a must at any level of experience.

So thank you for telling me not to do it. In a counter-intuitive way, despite the fact I ignored the advice not to try any of it, it's probably why I'm still here!

Don't do it, OP. You legitimately may die in an instant. I may have done so. It's really not something anyone will want to encourage while being able to still sleep at night. But there is a whole grey area of a philosophy behind how you choose to proceed. Don't skimp on any research.