noisy cricket problems

[MellowD]

Hi,

I've been reading this old thread with great interest. Recently, I bread boarded the complete series of LM386 amps, first Smokey, then Little Gem, Ruby and finally Noisey Cricket.

Apart from correcting small wiring errors where I didn't read the schematic or tried mods incorrectly, most everything went as it should. However, when I got to the Ruby build I got distortion, regardless of the position of the Gain and Volume pots. I checked and rechecked my wiring and component values and viabiliy, all seemed well - still, distortion, regardless of settings.

So ... I went back to the LM386 datasheet and discovered the following paragraph:

"When using the LM386 with higher gains, bypassing the 1.35 kohm resistor between pins 1 and 8, it is necessary to bypass the unused input, preventing degradation of gain and possible instabilities. This is done with a 0.1 mF capacitor or a short to ground depending on the dc source resistance on the driven input."

I had jumpered pins 3 and 4 sending the jumpered pair to ground. So I took the statement literally, and removed the jumper, placing a 0.1 mF cap between pin 3 and its own ground connection. This totally cleared up the distortion (which btw, hadn't been a problem until I added the jfet into the circuit).

Curious, I fooled around a bit with the ground from pin 3. I changed to the lauded 220 mF cap between pins 3 and 6. Also worked.

Still curious, I removed all caps on pin 3, and sent that pin directly to its own ground (remember, I had jumpered it to pin 4 originally). Shocker! It worked too.

Turns out removing that one little jumper cleared up the distortion.

There's definitely something about how you ground the unused input (or perhaps just the unused +ve input, which is input 3) that makes a difference in whether you get unwanted distortion or not.

So ... based on my discovery I went ahead and wired up Noisey Cricket. Bingo! Works great!

The tone control is kind of subtle, though it does work. The grit switch is fantastic. And with the headphone output, I can practice at night without disturbing my wife's sleep.

I'm no electronics wiz, but if you're having trouble getting Noisey Cricket to respond correctly, I'd suggest fooling around with the ground from pin 3 for sure.

Hope this sheds a bit more light on the solution here that seemed to work, but remained unexplained.

Thanks all

Wayne

[Cozybuilder]

Great information, thanks for posting!

Edit:
Welcome to the forum! 

(and thanks Duck for reminding me to use some manners for a change)

[duck_arse]

this might be the answer to a lot of people's problems.

don't forget "welcome to the forum", cozy.