Category Archives: Circuits

Stereo Amplifier

My second attempt at mastering the LM386 Audio Amp IC (still sounds terrible).P1020890


Here’s the data sheet for the LM386 IC with some example circuits:

Instructables has a simple how-to:

The schematic used in my project is a variation of this one from:
The only difference is that I added a 100nF from pin 7 to ground.  I think it helps keep the noise down.  There’s also two of everything except R1 and C1.


P1020902 P1020916
P1020911 P1020905
P1020904 P1020914

Wow, my wires are all way too long.  It makes it very hard to get into a tiny box, but it works!

Arduino to TV Adapter

You can send all kinds of fun stuff to a TV from an Arduino using the TVout Library. All you need is an RCA cable and two resistors (470 & 1k).

TV Ground to Arduino Ground
TV Signal to 470 to pin 7
TV Signal to 1k to pin 9
(Audio to pin 11)

Here is the one I built to experiment with:

P1020845P1020846  P1020847

It works!  When I get another long RCA I’ll add audio support.

Here’s some code that makes this using a Line In Adapter:

or use this code for this result:

audio is Trash 80

or use this code for this result:

audio is B.L. Underwood (no relation)

and you can do what with what!!!


OPP: DSP (Digital Signal Processing)

What a wonderful resource for Arduino signal processing:

I found this post very useful when I was learning how to send various audio signals in to the Arduino (see Arduino Audio Input Module):

One of his projects is a musical note recognition device.  I wonder if it could be used to transcribe simple songs, like old arcade game soundtracks and the like.