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kris

ac current from dc

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hello

would anybody have an idea how to get 9v ac from a 12v dc current

id appreciate any ideas thanks

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There are many ways, depending on what you are really doing, and how much current you need..

The more information you give, the better your answers will be.

Since you gave very little information, I'll offer a few ideas off the top of my head:

You can: Buy an automotive power inverter, which will convert 12volts (actually closer to 14.5) into 120 AC, then use a wallwart power supply to get whatever you want.

You can: Build a 555 timer in astable mode to get a 12 volt square wave, then feed that into a transformer to step it up by about 50% to 9 volts AC. Depending on the requirements of the transformer, you might need to amplify the output of the 555 somewhat.

You can: get a transformer that will step down 12VAC to 9VAC, and connect the primary directly to the 12 volt DC battery, then switch the leads real fast 50 or 60 times a second.

Use off the shelf DC to DC convertes to create + and - 10 volt supplies, then use bipolar transistors and a function generator to create the desired output.

What did you have in mind?

:-)

LyleHaze

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Also, do you really need to do this? Is it for power supply anywhere near a mains outlet? If it is for a vehicle/mobile supply, I would think the inverter suggestion is definitely worth looking into. These can be really affordable. Unless of course you want the design experience with a DIY project.

Lyle, just curious about your suggestions for driving a transformer with a switched wave; do you use a capacitor before the transformer? I wondered if there may be issues with a DC component presented with a low impedance from the transformer primary. Not sure if that would be the case.

Cheers

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hello thanks for the replys

sorry i didnt give enough imformation

I bought a little reverb an alesis microverb which i really like the sound of with my didj

Theres no problem when i use it near the mains i have the power supply which is rated at

    input 240v 50Hz 10w

  output 9v AC 7VA  (i dont really understand 7VA)

The problem arises as i want to use this with my busking festival setup(away from mains) which is a    battery amp, i use a loop pedal and an echo pedal in this setup that i have no problem powering from the amps 12v battery as they draw dc currents.

if theres a neat simple solution to this ill keep the reverb if not il have to look for another reverb that runs off dc

  thanks very much

  regards kris

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Madox:

Yeah, that might create a problem.

Kris:

Thanks.. the numbers help to give a clearer picture.

There is little doubt that the Microverb runs on DC internally, but the question now is

whether it is running a single supply or bipolar (positive and negative) supply inside.

Single Supply:

Even if it only needs a positive voltage to operate, many manufacturers include a bridge

rectifier and capacitor at the power input jack, as _some_ protection from getting the wrong

power pack plugged in. SO if you plug in a DC plug with the leads swapped, or even an AC plug,

it all gets rectified into the proper polarity. This is "responsible design".

Now, once that is done, the manufacturer is free to supply AC power supplies, which may be

a  bit cheaper than DC supplies, if both are transformer based. (With the newer switching supplies,

DC would be cheaper, but may not be more desirable for audio stuff)

Bipolar supply:

If the device needs positive and negative voltages, an AC input would be the easiest way to get it.

If you were to plug a DC supply in to this type, you would get only a single voltage, and if you got any sound at all, it would be distorted.

What to do now:

I did a quick web search, there are many MicroVerb types. (original, 2,3,4..) Which do you have?

If I could find schematics or a service manual for your microverb, I might be able to tell you more, but without that I'm just guessing.

The amount of power your device uses is a pretty light load. Looking into a DC to AC inverter might be a cheap solution. These commonly let you use small electronics while in your car. All of the ones I could quote are 120Volts AC, your area would have something different. With that you could just use the power supply you have already for 9 volts AC.

Finally, if it were me, I would TRY connecting 12 volts DC directly to the Microverb, just to see if it works. but I cannot be responsible if it does bad things.

Maybe someone else here has better advice to offer...

Good Luck,

LyleHaze

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output 9v AC 7VA  (i dont really understand 7VA)

7VA: 7 V*A = 7 Volts * Amperes

7 Volts * Amperes / 9 Volts = 0.77 Amperes

So your PSU supplies a max. of 0.77 Amperes at 9V

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thanks for the replies

  nils      thank you very much for that now i understand

lylehaze  Its the original microverb. I already have a large inverter(pure sine wave, ) id rather not use one in this situation because a)its more weight to carry in a portable rig b)they are very ineffcient, i power this set up with a small solar cell array.

i might have to look for another reverb which is a shame as this one sounds good ill think about just putting 12v dc into it, i wouldnt want to damage it though it really is a good bit of kit

kind regards kris

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Is it an analog synth? In my limited experience I've found that inverters can make soem alaogs sound bad (because they aren't getting a propper sine wave from the inverter ???)

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I can't help you with your DC/AC woes, but if you're in the market for a new reverb I can recommend the Line6 Verbzilla, provided your setup allows you to use guitar effects. I picked one up a while back off a friend who was selling his music gear off and as far as I'm concerned it's the most versatile reverb I've ever used. Plus, it runs off 9VDC the same as pretty much every other guitar pedal - even a 9V battery.

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thanks for that ill look out for one if i cant get this to run off 12v dc

regards kris

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