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Pedal power supply using 18V tool battery


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Just to share this design from Premier Guitar, some may have seen it, I am sure it will have been done before but I couldn't find an example on here with a quick search. The Premier Guitar mag article was the first time I have come across the idea. LINK to article

I find using battery power for effects useful, as I am often only using a couple, and I can power my PJ double4 by battery, so saves having to have power supply and extra cables to get tangled up and can be mains free, so I was interested in this design enough to build myself one. I have a couple of Makita 18V power tools for use at work and a couple of batteries so it works for me 😀

Bought the bits on Ebay, £32 all in , plus a bit of wire and solder, with a couple of stomp switches and some pcb stand offs left over for other things I have planned

It works well and can power a few pedals as I used a 2A buck module, you could use a higher rated one, but you might need a bigger enclosure, the one I used was only just big enough really.

I might paint it at some point 

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Edited by Aidan63
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11 minutes ago, blisters on my fingers said:

Anybody know if it is possible to wire two 9V batteries together to get 18v.

Don't want to buy another power supply if there is a suitable bodge !

Put them in series. 

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On 10/06/2021 at 22:08, Killed_by_Death said:

 

IF you put two 9 Volts in parallel you twice the Current, but the same Voltage

two in Series = 18 Volts

 

Just a note to say that if you put batteries in parallel  for higher current capability you might want to put small resistors (say 10 Ohm) from each to a common output point. This limits the amount of current from one to the other due to differences in the individual voltages of each. Whether necessary depends on the batteries themselves and particularly their chemistry type - eg Lithium Ion / NiMH etc etc.

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On 10/06/2021 at 09:59, Happy Jack said:
Short-Circuit Protection
All 10 outputs in this unit have separate short-circuit protection, i.e. short circuit in one channel won't affect other channels' function.
 
The Donner power supply is not isolated, loke most of the sub £50 supplies they have individual short circuit protection, not true isolation.
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12 hours ago, Chienmortbb said:
Short-Circuit Protection
All 10 outputs in this unit have separate short-circuit protection, i.e. short circuit in one channel won't affect other channels' function.
 
The Donner power supply is not isolated, loke most of the sub £50 supplies they have individual short circuit protection, not true isolation.

Yes. They won't avoid "Ground Loops" and so may give rise to noise problems esp with "Digital" pedals.

It's not always obvious. Eg the Thomann "Powerplant Junior" is galvanically isolated while the larger "Powerplant" is not.

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10 hours ago, rmorris said:

Yes. They won't avoid "Ground Loops" and so may give rise to noise problems esp with "Digital" pedals.

It's not always obvious. Eg the Thomann "Powerplant Junior" is galvanically isolated while the larger "Powerplant" is not.

When you are working entirely with DC, noisy grounds are not going to be a problem. In the DC world, I'd would argue isolation doesnt really bring anything to the party.

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6 hours ago, EBS_freak said:

When you are working entirely with DC, noisy grounds are not going to be a problem. In the DC world, I'd would argue isolation doesnt really bring anything to the party.

No. In that you're never working with only DC. A "noisy ground" has AC on it by definition else it wouldn't be noisy.

One of the problems in talking about this stuff is that the term "Ground Loop" is used to describe several different, if related, scenarios.

The presence of a "Ground Loop" does not require an association with an AC Mains Supply or any connection to the planet Earth.

eg Unbalanced connections, relatively high impedances and clock signals (eg from a Digital Delay pedal) add up to a likely noise problem with power supplies that share a common "Ground".

Not my original but useful : "Ground is a concept not a voltage node".

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I was referring to the Donner power supply - if the input is 18v DC being powered off the battery which the OP is talking about, there's only one transformer or regulator in play to bring it down the 9v. I would be very surprised if you have any noise problems with that as there is no AC transformer in play. 

I get what you're saying saying though - but unbalanced runs from a pedalboard are unlikely to be a problem (and the most likely candidate would be a long cable run from your cable to the board, or board to your amp) and if you have noise leakage on a battery supplied source from a digital delay, there's a fundamental problem with the screening in the design of the pedal.

Ive yet to find a noisy pedal battery powered board - whether it's all powered from one unit... or all units individually powered. It's ok to say "it's possible" - but in reality, it's not going to be a problem.

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14 hours ago, EBS_freak said:

I was referring to the Donner power supply - if the input is 18v DC being powered off the battery which the OP is talking about, there's only one transformer or regulator in play to bring it down the 9v. I would be very surprised if you have any noise problems with that as there is no AC transformer in play. 

I get what you're saying saying though - but unbalanced runs from a pedalboard are unlikely to be a problem (and the most likely candidate would be a long cable run from your cable to the board, or board to your amp) and if you have noise leakage on a battery supplied source from a digital delay, there's a fundamental problem with the screening in the design of the pedal.

Ive yet to find a noisy pedal battery powered board - whether it's all powered from one unit... or all units individually powered. It's ok to say "it's possible" - but in reality, it's not going to be a problem.

Point taken about it being powered by a battery and not AC mains via transformer. But a "ground loop" doesn't rely on there being ac or a transformer involved in powering the system.

That supply will help in that the individual outputs make the system wiring more like a 'star' topology as opposed to a 'daisy chain' (assuming one power cable pair is taken directly to one fx unit only. So the ability of the ground reference of one fx to be modulated by another is reduced. And with a typical daisy chain with 'linear analogue' pedals the results are likely fine - at least for live / rehearsal use if possibly not studio work depending on the context - we have taken mains related noise out of the equation and with typical Hi-Z instrument pickups they are the dominant source of noise. The obvious problems can come up when using fx that have clocks and/or microprocessors etc. Yes - different fx will have different characteristics here depending on the circuit and filtering (I'm considering conducted noise here) but there is always some that gets out  and particularly common mode noise.

But in addition you have the susceptibility of a loop to have noise induced into it from an external source. eg Thyristor Dimmed Lighting. Since you have two ground connections to/from each pedal - power cable 0V and the signal cable screen then you have a loop by definition. Minimising the loop cross sectional area minimises susceptibility so this points to running power connections as close to signal connections as practicable. And/or placing 'ground loop breaker' components in your patch leads but that's not the easiest thing to implement physically esp with small jack plugs and maybe not realistic at all with the flat 'pancake' jacks plugs.

I opt to make life easy and go with electrically isolated supplies.

 

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12 minutes ago, rmorris said:

Point taken about it being powered by a battery and not AC mains via transformer. But a "ground loop" doesn't rely on there being ac or a transformer involved in powering the system.

That supply will help in that the individual outputs make the system wiring more like a 'star' topology as opposed to a 'daisy chain' (assuming one power cable pair is taken directly to one fx unit only. So the ability of the ground reference of one fx to be modulated by another is reduced. And with a typical daisy chain with 'linear analogue' pedals the results are likely fine - at least for live / rehearsal use if possibly not studio work depending on the context - we have taken mains related noise out of the equation and with typical Hi-Z instrument pickups they are the dominant source of noise. The obvious problems can come up when using fx that have clocks and/or microprocessors etc. Yes - different fx will have different characteristics here depending on the circuit and filtering (I'm considering conducted noise here) but there is always some that gets out  and particularly common mode noise.

But in addition you have the susceptibility of a loop to have noise induced into it from an external source. eg Thyristor Dimmed Lighting. Since you have two ground connections to/from each pedal - power cable 0V and the signal cable screen then you have a loop by definition. Minimising the loop cross sectional area minimises susceptibility so this points to running power connections as close to signal connections as practicable. And/or placing 'ground loop breaker' components in your patch leads but that's not the easiest thing to implement physically esp with small jack plugs and maybe not realistic at all with the flat 'pancake' jacks plugs.

I opt to make life easy and go with electrically isolated supplies.

 

Exactly, the ground loop will not have mch mains hum but the noise from digital pedals still gets through,

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16 minutes ago, Chienmortbb said:

Exactly, the ground loop will not have mch mains hum but the noise from digital pedals still gets through,

Yes - but tbf wiring the power to a 'digital' pedal (not forgetting that analogue delay pedals still have clock edges) more directly back to the power source (in this case the battery) will minimise the problem by reducing the common impedance. Just don't try daisy chaining a KORG G5 !

Of course, it all depends on how critical you are with this stuff - or how critical your sound / recording engineer is. In the past I've spent a fair amount of time in pro-audio development and lots of time with instrumentation/noise/EMC issues in general so I might be more "fussy" than some ! Speaking of which I should really go and do some work 🙂

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8 minutes ago, rmorris said:

Yes - but tbf wiring the power to a 'digital' pedal (not forgetting that analogue delay pedals still have clock edges) more directly back to the power source (in this case the battery) will minimise the problem by reducing the common impedance. Just don't try daisy chaining a KORG G5 !

Of course, it all depends on how critical you are with this stuff - or how critical your sound / recording engineer is. In the past I've spent a fair amount of time in pro-audio development and lots of time with instrumentation/noise/EMC issues in general so I might be more "fussy" than some ! Speaking of which I should really go and do some work 🙂

I am not fussy, if I cannot hear noise, I do not mind. Of course careful wiring of the ground, earth, 0V will mitigayeagainst all noise but In my experience, true isolated supplies ar the only way to fully eliminate noise and hume.

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