Lm386

[frenchie29]

I finished building this project

http://www.kitsrus.com/pdf/k17.pdf

It's getting signal but the quality is terrible is there another chip I could replace the LM386 with?

Also I want to replace the trimpot I taught I could use a 10k type A but I think the original trimpot is a type B.

 

[Rembrant]

The problem is the circuit not the chip. Looks more like a guitar amp than a head amp. 20 gain is too high.

Try this circuit for a good headamp with that chip.
http://www.minidisc.org/headbanger.html
I have one sitting on my desk right now for my computer. It sounds great.

 

[frenchie29]

So what's supposed to be the gain input range? I tested it with my Qbox at -50db -20db and +4 I'm surprised that I would get signal at -50db

 

[frenchie29]

Ok I know where the bad sound quality is from, the chip was toast that's good that I bought like 20 of those a few weeks ago. Now it's clean but I really need to pad down the input gain. At line level I'm at around %5 on the pot. How can I pad down the input gain?

 

[kaos]

Make sure the jumper is removed from C2. If there’s still too much gain then add a 30K (or some optimal value) resistor in series with C1.

 

[frenchie29]

How could I split the difference between with the jumper and without? Without the jumper is good for line level but too low for -50db

 

[kaos]

You could put a switch in place of the jumper at C2 for two different gain settings (just don’t switch it while the power’s on). You could also try a resistor in place of the jumper (something around 390 ohms) for an intermediate gain value.

 

[frenchie29]

The best value I found for a resistor instead of the jumper was 56ohm If I go over I don't get -50db from my tone generator, which brings me to ask what's the minimum db input that little amp can take? I know -50 is mic level which I should use a pre-amp but I can get a signal that low with the jumper on. I was thinking about a switch as well, that's a good idea, what's the reason I cannot switch it when it's on?

 

[frenchie29]

How should I wire the switch?


Both are working which is weird.


jumper switch

pin1------------------------ 1(Left)
pin2------------------------ 2(Center)
3(Right)




jumper switch
pin1-------------------------1(Left)*
|--2(Center)*
pin2-------------------------3(Right)

*pin 1&2 of the switch are together

 

[kaos]

If I understand your switch designations correctly, the first option appears to be the correct one. If you switch it with the power on you may get a thump in the speaker as C2 charges. On a low powered amp like this it may not be that bad.

 

[frenchie29]

If I understand your switch designations correctly, the first option appears to be the correct one. If you switch it with the power on you may get a thump in the speaker as C2 charges. On a low powered amp like this it may not be that bad.

That's what I taught that the first configuration is right but the thing that made me do the second one is that the 3rd pin or the pin far right has nothing attached. Is that right?