This is starting to eat at me...

[stretch2011]

I can build tube amps, tolexed cabinets, manufacture chassis, but making a .5w lm386 amplifier is kicking my a$$. I hate to say it. I've watched a bunch of videos and I know its a grounding issue but I Havnt been able to tackle it. If anyone has any advice it'd be much appreciated.

[xtian]

OMG. I had the same problem a couple of years ago. Abandoned the project!

http://www.beavisaudio.com/projects/NoisyCricket/

[stretch2011]

That makes me feel a little less stupid!

[ampgeek]

What are the symptoms and can you throw out the schematic that you are working from?

Those and a few voltage measurements ought to provide a pretty good start at the troubleshooting.

Cheers,
Dave O.

[stretch2011]

Ive messed around with the wires a lot trying to fix it. These are the schematics ive used to start out with.

When I do get sound there is a lot hum, some oscillation, and when I get it tamed somewhat it's like the volume was cut in half. I've added some caps to the power supply to reduce dc hum and it helped some. Also added a 88K resistor in series with the input to help pull signal.

I've torn it apart and started from scratch multiple times. This last time I havnt been able to get anything.

I've tried adding a darlington or another lm386 to increase volume with no good results.

I'm confused about the grounding hookup in this layout and the batteries neg. terminal.

If someone wants to try to build this I have some spares id ship at cost.

[matt h]

(deleted)

[stretch2011]

I just wanted to build one so I could jam out in between classes at college

You know what it is.....greater powers of tone keeping us from straying away from the almighty TUBE!!!

[Leo_Gnardo]

Feeling discouraged, wondered if I could "improvise" a tube amp, on the fly, with parts on my (then) bench. Yup.

Triumphantly rocked on out the pair of tube amps and never bothered again.

One of my audio "heroes" in college was an apartment mate who built his own Heathkit quad receiver, amongst other things. He's been a top astro-physicist for the past 35 years, might know what he's talking about. According to Dr. Ed, "Tubes WANT to work. Easy to design and build with them. Transistors, on the other hand, you have to prove to them there's no other choice but to work, what a hassle."

[matt h]

(deleted)

[Synchu]

Huh... good saying.
From my pedal building experience with solid state circuits, it is usually a small thing.
The last one I've corrected for a friend was scratching the remaining copper strip from a hole in a vero board that wasn't drilled properly.

Niki

[vibratoking]

Did you zap the part? Check to see if any of the pins are shorted to power or ground. Please post some voltages. When you probe for voltages make sure you probe in a way that does not enable a connection. I hope that makes sense. This looks like a very simple circuit directly off the data sheet. You have the correct pin numbering, right? You might try removing the bass boost feedback connection from pins 1 to 5. Oh, and what's hanging on the bypass pin?

That opamp is very similar to a guitar amp topology. Differential input or LTP PI. Gain stage. Push pull output. Feedback. The gain control is a little different than what you see in guitar amps.

BTW, I think transistors work easily if you understand how they work.

[ampgeek]

What schematic are you following for the DC power supply portion of the circuit?

You mention hum being one of the problems.

Consider using a battery temporarily to allow focused troubleshooting on the amplifiying portion of the circuit.

Hang in there! As others have said, it isn't all that complicated a circuit and it is probably a simple "Doh" issue that will just pop out at you when you least expect it.

Good luck,
Dave O.

[stretch2011]

Fixed it!

No sound problem:
Didn't bridge the two negatives on the bread board

Hum/oscillation:
Needed to connect the dc ripple caps neg. to the neg bar on the bread board.

Bass Boost new problem:
With it I have whisper volume. without it I was impressed to say the least!

[John_P_WI]

Few things I would look into with the schematic above...

The 10K pot to ground on the non-inverting input has a lot of loading on the pickups. Seems to be a very low input impedance.

The op-amp is running wide open with no feedback.

There is no ps decoupling on the power pin. Additionally good grounding and layout is critical there is a lot of gain here.

Pins 7 and 8 are just hanging out there... shouldn't they be tied to ground or other with caps?

EDIT: I see you got it running while I typed this... I guess disregard. Congrats

[stretch2011]

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?