This is starting to eat at me...

[stretch2011]

Here is the progress so far.

[vibratoking]

That's alright! I didn't use a pot, didn't have a 10k on me. so I used a 10k resister. Thoughts on what size pot should go with the 10 uf cap between pin 1 and 8 for a gain control? What I might want to do with pin 7?

Glad you got it working. Hopefully, by having some success, you have cleared up the nonsense that transistors don't behave as well as tubes. There are ICs with a large number of transistors, in the millions, and they all work. Now if we could clear up the analogous nonsense about PCBs.

Take a look at the data sheet. It doesn't give you an equation, but it does give examples, on page 5, with 3 different gain configurations. From that you should be able to determine a reasonable pot value.

http://www.ti.com/lit/ds/symlink/lm386.pdf

Here is a link to an analysis that someone kindly performed for you:
http://www.electrosmash.com/lm386-analysis

[stretch2011]

That's a lot of equations!

[boots]

Sounds like you cured the problem.

I built an LM386 amp in an Altoids can a few years ago as a project with my son, and it worked OK. I think we just used a basic circuit out of an electronics text book. Built it on a perf board, used a 9V battery for power.

It actually had a decent distorted guitar sound, and put out more sound than you'd expect, using a salvaged 4" speaker.

My son ended up using it as a amp for a crystal radio, so he doesn't have to use headphones.

Not a bad little project for any guitarist, although it doesn't glow in the dark....

[stretch2011]

question for you all. Why do some of the schematics on the electrosmash page such as the little cricket have the input on the neg. number 2 instead of the positive number 3? is it because of the transistor?

[vibratoking]

question for you all. Why do some of the schematics on the electrosmash page such as the little cricket have the input on the neg. number 2 instead of the positive number 3? is it because of the transistor?

There is an inverting and a non-inverting input. The function of the opamp is determined by the circuit surrounding it. There are MANY possibilities, including adders, difference amps, differential amps, inverting gain, non-inverting gain, etc...The number of possibilities have filled many books over the years. Simplistically and in general, the output is inverted or non-inverted depending on which input the signal is applied to.

[stretch2011]

Thank you for the answer!

[stretch2011]

I put a Darlington after the 220uf cap. Collector to power and emitter to the speaker. Seems like its a little louder not much, but smoother. Not so much harsh tones even with max gain

[stretch2011]

Here's to resurrecting an old thread!
I have them built finally! Here are some pics. The red one runs a 6 volt block battery and a 4 Inch speaker while the black one runs a 9v battery and a 2 1/4 speaker. They sound awesome! I can actually use my guitar volume and tone knobs to clean / dirty it up like a tune amp. What's really amazing is they both actually have good bass response, and there's a significant difference between the pick ups like there should be!

[Structo]

pics?

[stretch2011]

Sorry for the delay my phone isnt picking up the attachment? Actually it still isnt. Is there a problem ith the servo bc ive tried uploading from two different devices and still nothing.

[shoggoth]

I've got an lm386 amp (for use as an "amp microscope"), the big problem I saw is that the lm386 wants a relatively tiny input impedance. I need to add a source follower...

The output impedance is also a big deal for these chips, I recall (although the details are fuzzy, it's been a while since I messed with it)

[stretch2011]

I havnt had any troubles with mine as for as input or output impedance. but im also doing my sound tests by ear(no o-scope).

edit: I have added a 1m res. to the input and use an 8ohm speaker.