Would BOSS FX, GT-100, ME70 etc work on 12volts ?

erky32

Most popular battery amps seem to work off 12 volt DC input (eg Vox mini5, Fender passport mini etc) ....does anybody know if BOSS effects or pedalboards which normally demand a 9v supply,  would equally work off 12v, with some kind of internal voltage limiter/reducer, - or would it be necessary to reduce that 12v externally first?
I'm thinking of a small busking rig with a 12v lead acid battery.

ICBM

Most will take 12V. I don't know of any which would be damaged by it, but some of the newer ones seem to have some sophisticated protection circuitry which will shut them down if the voltage is too high.

If you're worried or it doesn't work, you could step the voltage down very easily with a little external unit someone could make for you - at the most basic, all you really need is a 3V Zener diode with a power rating high enough for the maximum current your pedals draw, but if you want to do it properly then a 7809 regulator would do the job - if it's coming off a battery you won't even need filter caps.

erky32

cheers @ICBM ;, again !, ....always a reliable helping hand! Yes, I actually have a 9v step-down "block" which I could put in line, it probably is an encapsulated regulator. I just wondered if there was built-in regl'n for my convenience (and error protection!). I'll probably play it safe, insert the 9v reg' and put a flag on it !!) - thanks.

Funkfingers

Roland/BOSS covers its own arse by printing the mains transformer input voltage and current requirements somewhere on the case of every unit. Exceed at your own risk!

erky32

Funkfingers said:

Roland/BOSS covers its own arse by printing the mains transformer input voltage and current requirements somewhere on the case of every unit. Exceed at your own risk!

But dont you think that info is for user guidance (and yes, their name protection) , but I would have thought most pedals/boards are direct semiconductor input without transformers, and a built in overvoltage limiter or cut-out & X-polarity is an easy low cost inclusion ? Trouble is you never get to see the schematics so I dont know how you get to the bottom of this, the PCBs are difficult/impossible for me to follow.

ICBM

erky32 said:

I would have thought most pedals/boards are direct semiconductor input without transformers, and a built in overvoltage limiter or cut-out & X-polarity is an easy low cost inclusion?

It is, but rarely done. The best you get in most pedals is a crude reverse-polarity shunt diode, and components rated for enough voltage to allow for an unregulated power supply of the ‘right’ voltage.

This means that if a reverse-polarity power supply is used, the diode often shorts meaning the pedal is dead until it’s replaced - or much worse, modern high-current single power supplies can be capable of supplying enough current into the shorted diode to burn it away, which then leaves the pedal fully exposed to the reverse voltage, and often destroys it.

At least the lack of voltage protection means that a standard 9V pedal should be able to take up to 13V (the peak voltage of an unloaded unregulated 9V supply) without damage - most do use 16V caps and ICs will normally take up to 18V, so you’re normally safe at 12V, if it’s fully regulated.

erky32

ah, ....interesting! - so if you connect reverse volts by accident, the chances are, at the least, a burntout shunt diode - the protection doesn't normally have enough capacity to absorb the fault?
Furthermore, your thoughts on overvoltage might suggest that using a 12v battery as opposed to PSU might be within the tolerance of the electronics (I wont hold you responsible to that, but its good to know about!)
Great information - thanks again.

ICBM

erky32 said:

ah, ....interesting! - so if you connect reverse volts by accident, the chances are, at the least, a burntout shunt diode - the protection doesn't normally have enough capacity to absorb the fault?

Yes. The idea came about when power supplies had very little current capability and would either shut themselves down or self-limit if run into a short, and the rating of the diode was big enough that it wouldn't burn out. As supply capacity got larger, burnt-out diodes became common.

erky32 said:

Furthermore, your thoughts on overvoltage might suggest that using a 12v battery as opposed to PSU might be within the tolerance of the electronics (I wont hold you responsible to that, but its good to know about!)

Yes, because a battery is a fixed voltage - a 12V car battery is actually about 12.6V, and if it's not on charge it won't rise above that no matter how small the current draw.

I'm almost certain that no standard Boss pedal would be damaged by that, but I can't guarantee it!