Little Gem amp help

[jeffz63]

Hello,
I am posting this as a new thread because all the one I found on search were old.

I hope someone will help. I have some experience with electronics though this is my first attempt at building a cicuit.
I just got done making the little gem amp and it doesnt work.
I assembled it from the diagrams here...

Little Gems

I am positive that all the components are installed correctly and there are no bridges.
When I turn it on (I added a power switch and LED) the light comes on and there is a pop sound from the speaker and if I turn down the volume pot the pop is more quiet.

I assume the chip is ok.

Any ideas? I would be eternally greatful!
Jeff

 

[audioguru]

The circuit should work fine but its output power is low. It produces a muffled sound (not bright) when its input is from a guitar magnetic pickup because its input impedance is low.
What are you using for the input signal?

 

[jeffz63]

The circuit should work fine but its output power is low. It produces a muffled sound (not bright) when its input is from a guitar magnetic pickup because its input impedance is low.
What are you using for the input signal?

I am using this as a guitar amp. The input signal is from a guitar. I was thinking, if the battery is weak would that prevent the amp from working or would there still be some output?
Thanks!

 

[audioguru]

I am using this as a guitar amp. The input signal is from a guitar. I was thinking, if the battery is weak would that prevent the amp from working or would there still be some output?

Does your guitar have a magnetic pickup?
Are the strings on the guitar suitable for a magnetic pickup?

The datasheet for the LM386 amplifier shows that its minimum supply voltage is 4V or 5V when its max output power to an 8 ohm speaker is very low at only 0.075W.

 

[jeffz63]

Yes the guitar has a magnetic pu. And yes the strings are sutible. Does the popping noise from the speaker indicate that the IC is still good?

 

[audioguru]

When power is applied to the circuit then the output capacitor quickly charges into the speaker which makes a POP sound.
Since there is no guitar sound being played then maybe the amplifier circuit or the amplifier IC is bad.

 

[jeffz63]

Ok I may have fried it in my first attempt. I will get a new chip and try again. I will let you know how it goes.
Thanks for your help AG
Jeff

 

[audioguru]

About the only way to fry the LM386 is to connect the battery backwards, to use a supply voltage higher than 9 volts or to short the speaker when it is playing..

 

[jeffz63]

Ok, It was the IC. I attempted to build this amp before with a used PCB and I guess I fried it then. I am using this as a little test amp. I build cigar box guitars and this is perfect for testing my pick up wiring.

One last question though if you dont mind....Can I run this amp with a wall adapter. Ive seen guys build this with an input for an adapter. How is this done?

I guess what I'm asking is what kind of adapter do I need to power this without frying it.

 

[audioguru]

Use a 9VDC/300mA DC to 9VDC/500mA adapter. Its output will be higher, about 12VDC when its is not working hard.
Do not connect its polarity backwards.

 

[jeffz63]

So I have a cell phone charger adapter. It rated 12voltDC output and 300mA. This will be OK?

 

[audioguru]

12VDC is too high for an LM386 IC.

 

[jeffz63]

Oh, Ok I will make sure its 9volt and I dont reverse polarity. Thanks for all your help!