yea so i am attempting to construct a headphone amplifier, reallll simple and basic circuit using the LM386 audio amplifier IC. but im not sure how to connect the 1/4" input jack to the input of the LM386, ive tried wiring it up, but it just ceases to work. Im almost positive the rest of the circuit is correct. Whenever i measure the input voltage i get 0V and hence i get no output, so it has to be a wiring problem with the input jack. Can someone give me some tips/guidelines? thanks alot.

did you ground from the sleeve of the input jack? Are you building a clone of another mini amp?

I forgot to mention I had a similiar problem. I built a marshall guv'nor clone the other day and got it all done and it didn't work.. I starting messing with the board and heard it kick on and had no voltage on the meter.. Come to find out I missed a resisitor to ground.. Now it works and sounds better then the original.

Funny I didn't use a real board.. I cut up a clear cd sleeve printed the layout on boxing tape then stuck it on the clear plastic sleeve.
This way I could solder point to point seeing both sides... I used a drywall screw to neatly make the holes. hey it sounds great and I didn't feel like etching aboard at the time.

Have you ever seen a see through board

here's a pic of the inside

way thats reall cool what u did, very innovative!

im like now starting out with these guitar electronics stuff so im still figuring stuff out. i havent done any etching or anything, still in the prototyping stage using a solderless breadboard.

so i built the circuit on a breadboard, and no its not a clone, its just the LM386 in its basic amplifier configuration which should be enough to only drive headphones which is what im goin for.

and yea i did ground the sleeve of the input jack, so im really not sure what im doin wrong...oh btw, im using a mono jack, should i be using stereo?

It could be anything and I can't say since I can't see it.. A mono jack should be fine.

Double check to make sure all the ground points are grounded!

hmm well i have a schematic that i would like to show you, but im not entirely sure how i upload images here..

send it as an attachment to contact@theguitarfiles.com we will post it!

alright cool i sent it there.

Here's the schematic you sent... The grey lines are all grounds! Make sure all the grounds are connected together. Next make sure you have the opt amp facing the correct way. Also make sure you have the positive side + of the 2 capacitors facing the correct way. I highlighted them in grey!

I agree!

1. make sure all grounds are connected
2. make sure the opt amp is facing the right direction
3. make sure the Electrolytic Caps have the + side in the right direction
4. make sure you have the right wires going to the sleeve,ring,tip etc.....
5. make sure all the parts your using work!

I moved thos topic to our new froum DIY Guitar Effects!

hey thanks guys for all the help much appreciated!

well i scraped everyhting this morning and built it over from scratch.
and guess what? same problem! lol. its sooo frustrating and im basically 100% sure that i did all those things you told me to.
should my circuit even work to begin with?
i know the IC is working because there is a small ouput voltage which is about 200 times that of whatever input voltage. the input voltage is seems to be receviing is just like noise. no actual voltage signal from the guitar and i was sure the guitar volume was up and everything...so i really am stumped here.
but thanks again for the help, if you guys have anything to add u can post it!

are you getting any sound at all? One common mistake is having the opt amp in backwards..

did you make this circuit yourself?

I aslo take it you have the right wires go to ring and sleeve on the 2 mono jacks right

yea well i kinda did this by myself, well i saw a schematic for a headphone amp, and well from that i got the idea to do this circuit, simple amplifier, and yea the op amp is in the correct position.

and well as for the wires, the middle prong of the jack is the sleeve right? and the other prong can be the tip. i tried either sides of the sleeve as the tip and no success either.
maybe it really is a problem with the actual circuit
but at least i should be getting a voltage at the input of the IC. i.e. the votage drop across the 100k which goes to the + input of the IC.

yep sounds like you have the jacks wired correctly... There's so many things that could be wrong. If I was there I could see and debug the problem in a matter of seconds. Try other IC and see what happens!

This is the headphone amp I built as a headphone distribution system to record a band. It worked excellent and you can just build half of it if mono is OK for you. Or at least look at it to compare it to your build.



[Edited on 5/17/2007 by oldrockerguitarist]

[Edited on 5/17/2007 by oldrockerguitarist]

Thanks for the pics and info!

You're welcome Brian. What's nice about using this as a headphone distribution system is each musician gets to have his own amp to adjust the volume. Those are cigarette cases you can get at any smoke shop. They have belt clips built in and the cigarette lighter compartment is perfect for the 9 volt battery. They show it using a recharge setup for the battery but I just eliminated that and used a standard 9 volt.
Below is how I used it with personal guitar amp (Ruby) that has a Muff Fuzz circuit.
The logmonster pics are of the headphone amps before installing the cicuit boards.
http://www.logmonster.com/images/full/?pic=hp11_1165646049- 422-14347.jpg
http://www.logmonster.com/images/full/?pic=hp8_1165573042-4 22-14345.jpg


[Edited on 5/18/2007 by oldrockerguitarist]