Onboard Active preamp for guitar?

[nopainkiller]

Oh jesus, I guess I can't read, either!

SO it's NOT the cap on the zobel network??? Or the 7th pin bypass??

How is this problem occuring. I don't understand! I'm sendning current from the battery straight to the speaker and not back???

[Robert M. Martinelli]

Ok - I guess we need to clarify some points.

First of all, measure if you have any DC voltage on the speaker's terminals.If so, go one step back and measure if you have any DC at the 386 output. The cap is there by design to emulate half of the supply voltage to allow the 386 to operate with a single voltage.

second - does your amp have a capacitor connected between pins 1 and 8 of the 386? if so, the gain is not 20, but 200, and, if so, pin 7 should be connected to GND via a bypass cap to improve stability.

Third - the 220-250 microFarad capacitor I was talking about is the one in series between the 386' s output and the speaker, not the bypass cap on pin 7.

Follow the link to the 386 datasheet Steve provided in one of the first posts, and read carefully the application notes for the 386. Check if you followed all the recommendations.

Hope this helps

Best regards

Bob

[nopainkiller]

ar gh I don't have a meter or anything. This was me dipping my feet in the waters! I was so happy it seemed so easy. Now I got this DC thingy problem I don't get. Will replacing the zobel network cap fix it? Or do I need to put a cap to ground from the 7th pin?? I do have a 10uf cap from pins 1 -8 for 200 gain. Is this my whole problem? Arrrgh! I've seen the circuit a billion times since, taken it out and changed a few things. There wasn't anything connecting that wasn't supposed to be. I don't see what this DC thing could be from! If I did get an ohmeter or whatever I'm not sure I'd know what to do with it argh! Putting a cap from 7 to ground won't decrease the amount of feedback and wailing I get, will it?

I just made a smokey external amp out of a lm386, two 47uf caps and a 1k linear pot and a pack of marlboro red shorts (small pack!). spdt on switch. No output jack. It was a bi*ch getting it all in there and getting it to fit, but I did it and it works great. only four parts compared to the little gem I got in my guitar! Just a 47uf cap from the output to speaker +. And a 47 uf cap from 7 to ground. 1k pot from 1 to 8 for gain. I guess this is actually my first succesfull fabrication!

[nopainkiller]

another build

I rebiult that amp in my guitar, and it works perfectly now. I've buitl someother 386 things since, and have had some success. This time I built a bridged 386 design, and stuck it in a lunchbox. I'm getting the same dc across the speaker problem. I have a meter. And can test for the dc like you told me to, i just still don't understand how to solve the problem!! What do I do about the dc?? How do I fix it once I find it?! Please hrkp!!!