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Home Forums Technical Discussion DC power adaptors: voltage too high – sorry about the typo’s – iPhone!

This topic contains 4 replies, has 3 voices, and was last updated by  rustyfingers 7 years, 4 months ago.

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    Does anyone use DC power adaptors on their ac circuit fed from an inverter? I know in most cases it’s more power efficient to supply DC devices direct from the DC from your batteries but I’m a musician and have a bunch of equipment that runs on DC which I take into studios etc where I have to use grid ac obviously. So I find it more convenient to just plug my rig into my ac from the inverter when I’m at home rather than have plug in a load of different leads.

    I’m having a bit of trouble with the DC power supplies though… They seem to be giving too much voltage!

    I have two battery banks each with a seperate inverter. One inverter gives 231-233vac as measured at the outlet (which is normal for my country!), which I would expect as it’s a ups made by apc and designed for running of’s in the evnt of a power outage. The other inverter reads 215vac – I.e a bit low, and it’s a modified sine cheap unit from a discount store…

    But… My “9 volt” DC power adaptor which I use to power my sampler (a box with flashing lights that makes funny noises!), shows around 12 volts on the “quality” sine wave inverter, I.e too high but shows it’s proper 9 volts on the crappy modified inverter!!

    I suppose the most logical conclusion is a fault with the DC adaptor itself so I have tried other power supplies but they all display the same phenomenon to varying degrees.

    I have yet to do any tests on grid power.

    What I’m wondering is this: can the use of a modified sine wave inverter have an adverse effect on a dc power supply’s ability to give accurate DC voltage… And is this what’s happened to my DC power supplies?

    Not so sure about that though as I’ve just died a practically unused 12v DC adaptor and it’s reading 15vdc output at 230vac input

    So in short…. Why are all my DC power supplies giving higher dcvoltage than they should when I give them a stable pure sine ac signal at 230volts?!



    2nd to last paragraph… I “tried” not died a 12 v power etc…



    Typical DC “wall wart” power cube/supplies are not regulated, or at least not regulated well. Most ofthe ones I have when tested not plugged into a device they are intended to power will read that high.

    IE a placarded 12 volt suppy may read 15 volts, or higher. It is nothing to do with it being modified sine wave inverter.

    However, Some power adapters, and a lot of chinese,let me rephrase that, poorly designed low cost “things” will fry in short time on a modified sine inverter.

    I have purchased items that worked fine and I have also purchased items that fried in the matter of hours on a modified sine inverter.

    I finally last week bit the bullet and retired my trace DR2412(modified sine wave) after +12 years(I lost track of how long I have had it). Replaced it with a Magnum Sine 2800.

    II ran just about everything on that DR2412, some stuff was noisy electric motors especially but I never blew up anything expensive with it. It always seemed to be the <$10 wall wart devices that fried.


    marshall, il



    Thanks Bob that’s set my mind at rest a bit I guess I,m just dealing with some fairly crappy power adaptor… Find me one that isn’t made in china these days!

    Makes me wanna go out and buy a proper bench supply… But then I can’t see me lugging it around to gigs!

    I will test my adaptors when I’m at rehearsal next week on grid power… That may shed a bit more light on the situation.



    Theres an off-grid recording studio in Scotland which runs all of their equipment direct DC without any problems & I have hooked up my Zoom 707II guitar pedal, at 9v, directly to my batt-bank through an DC to DC reducer before & it still works just fine. Maybe making yourself up a secondary set of power cables for this stuff, just for low-voltage use would be benificial

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