Audio AMP. will this fry my I/o lines?

Dgswaner

I was planning on using this circuit to power a speaker for audio feed back and eventually a text to speech module. I used a variation of this circuit for a guitar amp effect. and it worked great. I didn't consider it being a problem but I read a post (can't find it now) about someone who did something similar and it fried their emic module. can I get some input on this being Stamp/propeller friendly or not? should I add diodes or resistors to the i/o lines?

your input would be appreciated.

data sheet
www.nteinc.com/specs/800to899/pdf/nte823.pdf

the NTE823 is a drop in replacement for the LM386 and is what I'll actually be using.

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A complex design is the sign of an inferior designer. - Jamie Hyneman, Myth Buster

steve_b

Are you using the stamp/propellor to drive this circuit?

Not quite sure if you were going to connect a stamp to the output to monitor output....Emic output to this circuit??

The stamps can source 20mA and I think sink 35mA. There are clamping diodes in the stamp (not sure about the propellor) that will handle excess voltages fine (20Volts me thinks) but a series resistor is generally used to keep the current down to prevent killing the I/O pin.

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<FONT>Steve



What's the best thing to do in a lightning storm? "take a one iron out the bag and hold it straight up above your head, even God cant hit a one iron!"
Lee Travino after the second time being hit by lightning!

Dgswaner

this is for sound output so I'll be hooking the stamp to the input of this amp. it connects directly to a 10k pot, but I don't know if that sufficient to keep the stamp safe.

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A complex design is the sign of an inferior designer. - Jamie Hyneman, Myth Buster

JonnyMac

You'll get much nice sounds if you put an RC filter between the pin and the amp -- see FREQOUT for a schematic.

Mike Green

The problem with the EMIC module is that the speaker output connections on the EMIC can't be grounded without damaging the module and that's probably where they connected this amp (which does have a ground referenced input). The datasheet is very clear that you shouldn't do that.

With the EMIC, you have to use the AOUT output pin and that needs a series capacitor to block the DC bias on that pin. A 10uF capacitor should work fine.

Dgswaner

I breadboarded the circuit last night. it works well! and the whole thing only cost $5.00. I had a BS1 and my computer connected to it (not at the same time) worked like a champ. I don't have an E-mic yet and I understand what your saying about the speaker out. Thanks for the heads up. I think I would have found out the hard way on that one.

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A complex design is the sign of an inferior designer. - Jamie Hyneman, Myth Buster