12 volt outputs on power supply(s)

[Phend]

Hello,
On some power supplies I see 12 volt and 9 volt outputs.
What are the 12 v ones for ?
I have built a few fuzzes using a 23A 12v battery, it works.
Can most any 9v effect use 12v ?
Thanks for any discussion.

[antonis]

On some power supplies I see 12 volt and 9 volt outputs.
What are the 12 v ones for ?

Could you plz post some schematics..??
('cause 12V might serve from battery charging to relay driving... )

P.S.
Almost any effect working on 9V could use 12V - the vast majority of them without any items modification..)

[ElectricDruid]

"It depends" is the accurate answer, as so often. More loosely, yes, many pedals can run on 12V with no modifications, and in some cases you even get a little bit more headroom into the bargain. This is particularly the case with op-amp based stuff, like a lot of modern overdrives.

Things that use BBDs will have a headroom limit because of the BBD, and anything digital will have internal regulation for the digital part and the "headroom" depends on the processing, not the voltage, so you won't see any benefit in these cases. I'd be very cautious about running anything like that on more voltage than specified.

The best reason I can see for running a pedal at 12V would be to make use of some specialised analog chip that requires that much voltage to run. The AS3320 filter for example needs a minimum supply of -4/+9V, so you'd need a 13V supply as a minimum, and 15V would be more sensible.

[Phend]

No schematic of psu, but for example..



The fuzz effects are a Muff Fuzz and Fuzz Face. Standard si and ge builds. That I used a 23A battery.

[ElectricDruid]

On that example, it's got "12V ACA" outputs designed to run Boss pedals that use an old ACA adaptor. That adaptor wasn't regulated and outputs roughly 12V, which the pedal then filters and smooths down to 9V internally. If you use them with a "normal" 9V supply (like the later Boss PCA adaptor) the internal voltage is too low and they often don't work correctly or just sound rubbish.
Most Boss stuff since the mid-80s has used the now-standard PCA 9V regulated adaptor, and everything since 1991 is PCA.

[R.G.]

The 12V outputs are there because (1) some things need 12V as described, and (2) some pedal users think that running a 9V pedal on 12V makes it sound different and better somehow.
Item 2 may or may not be true, depending on personal taste. A fuzz face or other transistor-only effect, for instance, might sound different in a good way because the bias point and other internal conditions shift.
Item 2 can be a problem in some limited circumstances. As mentioned, some ICs have hard limits on voltages; generally these have internal regulators, but sometimes the designers may have done a cheap and dirty design based on "only 9V ever comes in". And there is another voltage limit issue that's more common with commercial pedals - electrolytic capacitor voltage ratings.
Electro caps only come in fixed standard voltages. These are 4V, 6.3V, 10V, 16V, 25V, 35V, 50V... Yes, a few caps can be had in voltages other than these, but they're unusual and therefore more expensive. Commercial pedals - Boss and Ibanez come to mind, but there are others - sometimes use 10V caps. Probably the rated 10V caps would survive 12V, but sometimes not. Sometimes higher voltage just makes the cap dry out faster, sometimes it changes the effective capacitance, usually downward.
The company I design for insists on 25V caps. We used to use 16V, but went to 25 specifically for the trend of users deciding that running 9V effects on 12V - and in a few cases, 18V, doubled 9V - so the effects would keep running. It decreases the failure rate.
Not a huge issue, but one of those subtleties.

[Kevin Mitchell]

IIRC, those Voodoo supplies specify "L6" for the 12 volt supply in the manual - as an example really.
L6 = Line 6 modeler pedals. The power input is reverse and they usually give you a black->red cable to use with em'.

edit: yeah it's in the manual. The 12v ACA (unregulated) is specific to the L6 pedals. Polarity is probably still backwards though since most pedals are center negative.
https://voodoolab.com/wp-content/uploads/2022/08/pedal_power_mondo_manual.pdf

[Lino22]

Also, 12+12 is 24. Some univibe clones run on 24vdc.

[Rob Strand]

When you use a daisy-chained power supply with a Boss ACA pedal (9V unreg, 12V no load) and the signal chain has at least one pedal other non Boss ACA pedal you don't need to supply the ACA pedal with 12V.  The ACA works perfectly well with a common 9V supply and will receive 9V internally.  The other pedal(s) can be either a Boss PSA (9V reg) pedal, or most other pedals.

What happens is the daisy-chained power bypasses the Boss ACA Pedal power circuit on the 0V rail effectively converting it to a Boss PSA pedal.

The same trick doesn't work when the *power* to the ACA pedal is from an isolated power supply, or multiple wall-warts, even though the audio signal pass through each of the pedals.  The key is the daisy chained *power*.

Just to be clear the Boss ACA pedal take 9V unreg (12V no load) but the internal circuits are operating at 9V.   The ACA power circuit has a deliberate voltage drop which was used to help prevent ground loops.

[Clint Eastwood]

Be carefull, you can kill pedals that use voltage multiplier IC's. I repaired someones Klon clone, all he did was accidentally put 18 volt on it. But even 12 volt may do it. Fortunately, only the protection zener was fried, but still troublesome because some pcb tracks got fried as well.

[R.G.]

Good point Clint. The first charge pump multiplier, the icl7660, dies at 10V. Early adopters of this chip had a lot of failures. Later similar-function chips pushed this up to 12V, and a few modern ones can stand 15, even more. But the early charge pump converter ICs are not tolerant of even 12V.

[fryingpan]

Careful not to supply higher voltages than specified with CMOS stuff (eg. CMOS-based preamps and overdrives). I had this idea a few years ago, since the famous CMOS chip employed in lots of overdrives and the like exhibits very "soft" clipping characteristics, getting softer the higher you go. (You can see this in the datasheet). Problem is, those chips are not designed to be used for linear applications. If not used as a switch, basically, their power draw is huge and you fry the chip. A friend of mine hobbyist had this whole design idea around a CMOS chip at 15V for a preamp, he even mocked me when I told him he shouldn't do that, then realised when he powered it that it was getting scorching hot in seconds.