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Topic: help with LM386 audio amp. (Read 2 times) previous topic - next topic

uberdanzik

Hi, I'm trying to find the appropriate component values and wiring for a LM386 audio amplifier.  I've found other examples on the internet but nothing is working.  I've gotten it to work halfway, but every example I find uses different power sources or inputs, and I think they're just not calibrated for a guitar signal and arduino. I have no experience with how to determine component ratings or values. I'm at my wits end and need somebody to build me a simple schematic with the correct value components.

I'm essentially creating an LED light that pulses based on the guitar input's strum patterns.

1. The guitar signal is AC at around 1.5 volts max, and it will be running into the LM386.

2. The output of the LM386 should be amplified up to a max of 5v and it will still be A/C (I assume) so I need to use a rectifying diode setup to convert it to DC.

3. Then once it's in DC I'm pretty sure I need to put a small capacitor and resistor to help me find the peak voltages.  Otherwise I'm still going to get zero values in between each wave of the signal.  I could probably figure these compnent values out with trial and error, but guidance would be nice.

Also, I've heard there is an electrical engineering software program out there that will simulate electronics so you can build your circuit on the computer without having to buy parts and try them out.  This would be immensely helpful. Anybody know what the program is called so maybe I could help myself?

Thanks for any help.
Dan

Osgeld

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1. The guitar signal is AC at around 1.5 volts max, and it will be running into the LM386.


I am no where near anywhere an expert with amps, but I know the 386 is garbage with big inputs ... you need to increase the values of the voltage divider going into the input

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2. The output of the LM386 should be amplified up to a max of 5v and it will still be A/C (I assume) so I need to use a rectifying diode setup to convert it to DC.


yes, like a Light Emitting Diode, it will be fine without adding extra diodes

justjed


Also, I've heard there is an electrical engineering software program out there that will simulate electronics so you can build your circuit on the computer without having to buy parts and try them out.  This would be immensely helpful. Anybody know what the program is called so maybe I could help myself?


You might be thinking of Spice. There are some free clones out there, or sorta-clones. One is Gnucap. Here's a list of others.
... it is poor civic hygiene to install technologies that could someday
facilitate a police state. -- Bruce Schneier

westfw

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I'm essentially creating an LED light that pulses based on the guitar input's strum patterns.

Is there some reason that you've decided to use the lm386?  It is essentially a "speaker amp", designed to convert typical audio "line" levels to the power levels needed by small speakers.  For general voltage-level conversion, you'd probably be better off with a general purpose "op amp" (or two) that is designed to be highly configurable in its behavior (gain, offset, etc.)

uberdanzik

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Is there some reason that you've decided to use the lm386?


I just saw other people using the LM386 it and though I'd give it a try out of frustration.

I'd love to try an opamp, but finding one that ran on the arduino's 5v power proved difficult.  Every example I found wanted me to use a power supply that had negative voltage or ran on 9-18 volts.

If you can recommend an appropriate opamp that will run on the arduino's 5v and will handle the guitar's input, I'm more than willing to order it.

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