AC adaptor technical questions

[OriginalPosterLost]

I have a question for any tech-heads that may (hopefully) be reading this… Is the Boss PSA-120 AC adaptor shielded? I know its regulated, and I assume it’s shielded, but I’d like to know for sure before I lay down $20 for one.

I’m currently trying to ween my effects off of those expensive 9v batteries. I thought I had everything I needed, but my power supply is an old Radio Shack wall-wort multiadaptor I’ve had for some time. Sure it powers my pedals, but it also induces a loud, annoying hum, due to the rampant line noise that flows through my house’s electrical system. It kind of slipped my mind…

Even better, if someone who knows how could draw up a schemactic for a simple filtering circuit, that be great! I figure it wouldn’t take too much more than a capacitor or two and a resistor, but I wouldn’t know the type, rating or design. I dabble in electronics, and can read schematics, follow safety procedures, and build stuff. My theory, however, is very limited. [img]http://www.freakscene.net/ubb/confused.gif[/img]

Well, I hope someone can help me out. If anyone knows a good electronics forum that I could post this to, that’d also be very helpful. Thanks in advance… [img]http://www.freakscene.net/ubb/biggrin.gif[/img]

~Mattman

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Mattman’s post has been… uh… posted.

[This message has been edited by Mattman (edited August 13, 2000).]

[This message has been edited by Mattman (edited August 13, 2000).]

[OriginalPosterLost]

I don’t think you can shield an adapter. It’s basically a power conversion transformer. All you can do is change the shape of the magnetic field that surrounds it so it does not mess up the signal in any of the wires your signal goes trhough. And you have this power wire going into your effect where the signal is.

A filter circuit might be possible.

But the easyist solution would be to buy a couple of rechargable 9v bateries and always have a charged one handy becuase they don’t last a long as the regular batteries. Maybe in this age of powerful nicads there is an even better solution. Like you could power everything with a battery and avoid all the hum. but you may find that the hum adds to you sound.

I have been reading a book titled AMPS!. There are amp builders that seek out special transformers becuase they effect the sound of the amp. Aspen Pittmen of Groove Tubes made the Trio Preamp that J supposidly uses. It looks like it has two different powersupplys: one for a Fender sound and one for a Marshall sound.

It’s all a little too much for me. I just use a tape deck as a preamp. This hum is all part of the internal feedback that builds up. some where in there the hum turns into a scream!

If you want to learn something about electronics that is important to electric guitarists read about inductance. THAT’S YOUR HUM!

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[OriginalPosterLost]

Thanks RuBrick,

I said shielded, but I meant filtered. I was in a hurry that day. [img]http://www.freakscene.net/ubb/biggrin.gif[/img] The battery idea sounds alright, but I’m hoping to do away with batteries all together. I don’t mind a little hum, but this unfiltered AC adapter I attempted to use was rediculous.

I’ve read a bit more on this problem and have found some information saying that I need to isololate my ground lines or something (I have to go back and look at the article, it’s been a couple weeks…)

What I really need to do, though, is bone up on my theory. I took an electronics class my first year of highschool… I thought the theory stuff was really boring back then. Now I wish I had paid more attention (see my signature below about paying attention.) [img]http://www.freakscene.net/ubb/smile.gif[/img]

Thanks again,

~Mattman

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"If you can’t pay money… At least pay attention!" – My Dad

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