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Old 24th December 2010, 01:56 AM   #1
jkwylde is offline jkwylde  United States
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Default DC voltage stepdown..

Need help. I am an idiot, but at least I know it and can account for it appropriately.

I want to use 12, 14.4, or 18 volts to power 9v effects pedals.

What is the best way to do this?

Will a step-down transformer on a pedal board be likely to induce noise into effects pedals(wah pedals and others use inductors that LOVE to pick up noise you dont need), or be likely to pick up noise from lighting/etc?

Would a pot and resistor be cool to use?

What is the best balance of efficiency, low noise, and reliability?

What are some suggested specs to do this?

Would it be possible to use a trim pot that is set, and upon battery drainage turn the pot to raise voltage? Probably end up with a voltage meter on it anyway...

Will powering effects off by robbing the power supply cause problems? Should I put a small cap between the 9vdc and the pedals to fix this?

I warned you I was an idiot...

In the end, there will be a VERY UNIQUE pedal board, Posted on several forums, with thanks included to all those who helped me on my way....

PS, thanks for the summing circuit yall helped me with. The car sounds better now.
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Old 24th December 2010, 06:33 AM   #2
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First I must tell you that me being the only one trying to answer your question is a very bad sign. You are probably just jerking me around but I don't have anything better to do right now anyway. If you are serious then you might want to hold off for a while and learn just a little more about general electronic theory. One more thing.
Would you mind if I ask you why you want to do that?

If you are wanting to step down dc voltage with a transformer I don't think you will have much luck.

AC on your pedal-board or unfiltered dc or poorly filtered dc on your pedal board is very likely to introduce noise. Everything is likely to pick up noise from florescent lights or from lights with dimmer switches, scanning radios and even Ford automobiles running in close proximity and many other things too.

I would say using a power supply of the proper voltage rated for as much or more current than your effects require and that is properly filtered. It is good to keep the power supply as far away from the effects as you can.

Suggested Specs? I guess what it says on your effect (s).

Quote:
Would it be possible to use a trim pot that is set, and upon battery drainage turn the pot to raise voltage? Probably end up with a voltage meter on it anyway...
????? I don't know. It might be but why you would want to use a battery in a power supply is another question.

Quote:
Will powering effects off by robbing the power supply cause problems? Should I put a small cap between the 9vdc and the pedals to fix this?
Robbing the power supply? Do you mean turning it off? It shouldn't cause problems if you turn it off other than that they will stop working until you turn it back on. Some effects will still pass a dry signal with no power and some won't. I would say no to the cap I think depending on what you mean by that.

I have to agree with you. It will be an extremely unique pedal board. Almost certainly a one of a kind. It will be incredible if it works.
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Old 24th December 2010, 09:15 AM   #3
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Simple voltage regulator will do. It'll hold whatever input (provided it's within it's ratings) to 9v output, so long as the input voltage doesn't drop below 9v.

They're cheap, and will work fine with whatever power supply you choose. Note: they only drop voltage. Unlike transformers, they won't give more current. Pick one with enough current output available, and you'll be fine.
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Old 24th December 2010, 05:31 PM   #4
jkwylde is offline jkwylde  United States
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The idea is because I have used power supplies and wall warts, one-spots, and daisy chains, only to arrive at the conclusion that a 9v battery sounds better in some effects, and causes no noise....

So the idea here is a rechargeable battery power. 9v rechargeable batt's suck, and are expensive, no better than they perform.

The current draw of individual effects ranges from 8mA all the way to 120mA depending on usage, settings, etc. I seldom run more than two effects at a time, but like to experiment!


So, the idea popped in my head. Get some nimh cells and build a cell with a charger....NO!

Then it happened. I want a board powered by cordless drill batteries, that plug into the board. A noiseless solution. Throw a spare on the charger. and the amp hours offered, you could play a long long time with no sag...
Put a socket in the board, and plug in.

Which presents a few probs : only older or ratty drills offered 9.6 volt batteries. So you have to buy old junk to play with...not good.
Newer ones offer 12, 14, 16, 18 volt operation, and present the problem of reducing voltage.
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Old 25th December 2010, 01:43 AM   #5
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Ok. Now it seems just a little bit more logical. Before I was saying to myself "Why would anybody want to do that?"
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Old 25th December 2010, 02:40 AM   #6
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As I understand it, you want to step-down to 9v?

Check out the 7809 datasheet
http://www.fairchildsemi.com/ds/KA%2FKA7809E.pdf

You can feed it 12VDC and get 9V regulated DC out. You will need a heatsink with it - sometimes just bolting it to the chassis (with mica/silicone washer) will do the job.

John
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