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Old 23rd November 2004, 09:58 PM   #1
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Default LM386 but on AC?

Is there such a thing as an amp similar to the LM386 but made to operate on AC? I'm looking for such an animal to be powered by about 6 to 13VAC. DC is almost out of the question because of AC hum. I don't want to use a diode and cap to supply DC if I don't have to. . Just thought I'd ask.
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Old 24th November 2004, 12:43 AM   #2
paulb is offline paulb  Canada
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Default Re: LM386 but on AC?

Originally posted by tubbytwo
DC is almost out of the question because of AC hum.
I don't understand what you're saying here.
I don't want to use a diode and cap to supply DC if I don't have to. . Just thought I'd ask.
One diode and one cap is a problem?

Anyway, the answer is no, you need to convert the AC supply to DC before you can amplify a signal with it.
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Old 24th November 2004, 03:42 AM   #3
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Sorry for the confusion. My original question was, is there a small chip amp SIMILAR to an LM386 that operates on AC. In my mind they have everything else so I thought there might be one with it's own built in DC "power supply" that would run on AC. "One diode and one cap is a problem" ...no, but it needs either to be isolated from the underside of this transmitter or encased in a metal can. It picks up hum. I've tried it. This is a one tube transmitter and I wanted to hide it. I guess I could put the whole thing in an IF can on top to keep with the antique theme.
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Old 24th November 2004, 05:21 AM   #4
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No such animal. I don't think there ever will be either.
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Old 25th November 2004, 02:01 PM   #5
macboy is offline macboy  Canada
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The only things that can run from AC are resistive heat makers (like heaters and filament lights and stoves), some kinds of motors, and flourescent and neon type lights. Every single other thing that you plug into an AC line has a built-in power supply to convert AC to DC. You'll need to do the same.

If you are picking up a lot of hum, use a bigger filter cap. Try using a regulator. You said you have 13 VAC, so after rectification that is about 18 VDC, which is far too high for the LM386 anyway. The regulator will significantly reduce the AC ripple on the power supply for the LM386.
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Old 27th November 2004, 06:38 PM   #6
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and if even not regulation will do the tric, then batteries will.

think you'l have a hard time finding AC in those.

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Old 29th November 2004, 12:38 AM   #7
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You can't run an amplifier directly on AC. If you did, it wouldn't work, and you would get hum in the speaker, and most likely fry the amp.

Just use a small diode bridge rectifier and a filter cap when you make your amp, so you can power your amp with AC because it gets converted to DC.

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