noisy cricket problems

[markrocknroll]

A friend and I built a Noisy Cricket in a cigar box with a 4" alnico speaker.  We have built 4 tube amps from the ground up and four or five pedals and have never struggled like this before.  We built it on the Radio Shack board and it kind of sputtered.  We then rebuilt it on a perf board, checking every connection as we went and we still have problems.  When the Tone is turned anything past OFF it kind of sputters (same problem as before).  With the Tone all the way off it can get some good sounds.  However, there is always some noise unless you mute the strings.  With everything but the Tone all the way up, the noise gets pretty loud.  With no guitar plugged in, still some noise.  We changed out the Tone switch, cap on the Tone pot and retouched every solder joint.  We have checked continuity to ground on every ground connection and triple checked the layout.  Also the Grit works backward of what I thought.  When the switch is broken (off) the amp is louder.  We have used two different LM386s and two different transistors.  Same results.  My next move is to redo the battery clip/ac adapter grounding scheme.  Any help would be appreciated.

[GibsonGM]

Not to be a jerk, but is the pot ok?

[markrocknroll]

You're not being a jerk.  I'm hoping it's something easy I missed but have been too close to it to see.

Yes the pot is good.  I said in my post I changed the Tone switch but what I meant was I changed the Tone pot with the same results.  I also checked it (all the pots actually) with my trusty multimeter last night and it seemed to be working properly.

[acidblue]

Double check your caps and their polarity.
Did you use the exact cap values for all caps?
Sometimes I don't have the exact cap say a 4.7uF so I'll use the closest match that i have
like a 2.2uF, you can usually getaway with this but sometimes you can't.

Leave out the tone pot, so you just have just gain and volume and see if you still have the same problem.

In my experience it's usually something stupid I've done, like connect the wrong pin,
bridged some connections with solder, or using a nearly dead battery.

Good luck.

[El Heisenberg]

the lm386 amps have always given me mysterious problems after building them on perf. I had built alot of them, and could never debug the ones that didnt work. What I would do is just rebuild it exactly the same with different pots. I hate the tone pot. Its just something beavis put in there to dress up the circuit. Leave it out or put a big muff type control in. The grit mod can do weird things. But really when it's working correctly the effect isn't all that great at all.

I was never satisfied with the little amps I build from these chips until I tried a bridged design with two, running at 9-12v. I had adapted the grit mod for this design and put it in those. Sometimes it would work great. Instead of a grit thing I got a really nice treble boost. It got alot sharper and clearer. But sometimes it would just squeel unless I turned the gain down on the two lm386's (I used a dual gang pot).

Anyway my main advice is just rebuild the circuit. But if I were you I'd get rid of the FET, and just use a dual op amp, with a tone control in between the op amps into the lm386. I'd also do a bridged LM386. Forget the noisy cricket tone control, it's weak, and if you can work out the grit mod (try different caps) then keep it, but otherwise it's just a novelty. These chips can't really produce a very wide range of tones, at least not with those options.

[bigandtall]

I just built one of these had have noticed that the grit knob doesn't do much. Is there anything that can be done to make it... grittier?

[markrocknroll]

I have double checked the caps and their polarity.  I used the exact cap values.  I checked they were in the right place.  I disconnected the tone pot and still have that sputtering sound except all the time.  When the tone pot is in the circuit and turned all the way off the sputtering goes away.  Crack it open and it returns.  Tonight I scrubbed the backside of the perf board and redid the grounding with no change.  Can't find a bridged connection and the battery is good.

I also noticed a couple of other things.  With the volume at half way, tone all the way off, gain pot off and grit switch on, I get a pretty good clean sound, EXCEPT there is a quiet distortion in the background.  It's like you have two amps in parallel one clean and one distorted at half volume.  Second, most of the time (not all) when you turn the grit switch off you get a loud hum (noise) that changes in loudness and pitch with the gain knob.

[acidblue]

I suggest you re-build with a different 386 chip.
Could be bad chip.
I had a problem with an oscillator I made a few weeks back,
turned out the 10 pin was bad, took me me forever to figure it out.

Also I try El Heisenberg's idea.
Here's a link to a schematic:
http://runoffgroove.com/littlegem.html
Scroll to the bottom

[compuwade]

A friend and I built a Noisy Cricket in a cigar box with a 4" alnico speaker.  We have built 4 tube amps from the ground up and four or five pedals and have never struggled like this before.  We built it on the Radio Shack board and it kind of sputtered.  We then rebuilt it on a perf board, checking every connection as we went and we still have problems.  When the Tone is turned anything past OFF it kind of sputters (same problem as before).  With the Tone all the way off it can get some good sounds.  However, there is always some noise unless you mute the strings.  With everything but the Tone all the way up, the noise gets pretty loud.  With no guitar plugged in, still some noise.  We changed out the Tone switch, cap on the Tone pot and retouched every solder joint.  We have checked continuity to ground on every ground connection and triple checked the layout.  Also the Grit works backward of what I thought.  When the switch is broken (off) the amp is louder.  We have used two different LM386s and two different transistors.  Same results.  My next move is to redo the battery clip/ac adapter grounding scheme.  Any help would be appreciated.

I know this is going to sound very very strange. However, the Noisy cricket was my very first project and I had the exact same problems with it that you are having using the radio shack board. I tried many different IC's, different caps, resistors and even rebuilt it on a new RS board. All resulting with the same issues. When troubleshooting it for some reason I decided to connect the 220uf cap across pins 3 and 6 of the IC and this fixed the problem. I even emailed Dano from Beavis Audio and he said that it should do absolutly nothing. But it did fix the circuit. I was wondering, if you haven't figured out the problem, could you humor me and connect a 220uf cap across pins 3 and 6 and see if that clears up the problem. As I said, I know it sounds strange and shouldn't do anything but I'm curious as to why mine worked.

Thanks,
Wade

[dano12]

I hate the tone pot. Its just something beavis put in there to dress up the circuit. Leave it out or put a big muff type control in. The grit mod can do weird things. But really when it's working correctly the effect isn't all that great at all.

Forget the noisy cricket tone control, it's weak, and if you can work out the grit mod (try different caps) then keep it, but otherwise it's just a novelty.

So I take it you don't like the Noisy Cricket?   

Any help would be appreciated.

Not sure what could be wrong--looks like the usual advice has already been posted here. Almost every problem I've had personally with the NC is a bad 386 chip. I invariably use the JRC/NJM part because it just seems more reliable.

Having said that, I get about 10 emails a week about the noisy cricket project. Although hundreds of these have been built, part of the problem is my poor choice of circuit boards--that radio shack PCB is very hard to decipher and work with. I guess it is time for a Noisy Cricket Mark III and an improved build document.

[Hupla]

I hate the tone pot. Its just something beavis put in there to dress up the circuit. Leave it out or put a big muff type control in. The grit mod can do weird things. But really when it's working correctly the effect isn't all that great at all.

Forget the noisy cricket tone control, it's weak, and if you can work out the grit mod (try different caps) then keep it, but otherwise it's just a novelty.

So I take it you don't like the Noisy Cricket?   

Any help would be appreciated.

Not sure what could be wrong--looks like the usual advice has already been posted here. Almost every problem I've had personally with the NC is a bad 386 chip. I invariably use the JRC/NJM part because it just seems more reliable.

Having said that, I get about 10 emails a week about the noisy cricket project. Although hundreds of these have been built, part of the problem is my poor choice of circuit boards--that radio shack PCB is very hard to decipher and work with. I guess it is time for a Noisy Cricket Mark III and an improved build document.

Im still having problems with it too, but im also having problems with any 386 related schematic so I also suspect bad chips. Gonna order a few and see if that makes a difference.

[El Heisenberg]

Beavis you are right. Its the radioshack PCB and the ICs.

Its really easy to mess up those 386s. Ive never had the problems I have with 386s with any other IC. It drove me to use sockets for EVERY IC i used cos I thought something was wrong with the way I soldered.

As for the radioshack PCB, I never tried it. I just went straight to perf board. Back then, it seemed that there were too many ways it could go wrong. Doing it on the radioshack PCB only complicated things. Perf board also helped me learn better soldering techniques.


Anyways I left the 386 amps behind a long time ago. It's not that any of the designs are bad, it's that the chip is plain small and very limited. I don't like the tone control in the noisy crickets cos the 386 performs so bad in the first place. Everyone says the 386s are great for some reason. They mean great for being so cheap and simple.



But I gotta repeat my advice, just rebuild the entire circuit. Use a different IC and use a socket for it. Socket the FET too. If you give up on this, just try a TDA2002 or TDA2003 amp. They are even simpler builds (half component count) and 19 times (8 watts) more powerful. All you'd need is a 12v adapter or two 6v lantern flashlight batteries to power it. It'll blow you away!

[anchovie]

Can you post voltages, as per the "debugging" sticky thread?

[El Heisenberg]

I dont see the point in debugging such a simple circuit. I would just start again from scratch. The only times I try to save a build is when it's a relatively huge circuit like the Blue Box or something with rare ICs in it. This circuit is all from radioshack. Nothing worth saving, and I doubt it's a problem with the soldering. If hes double checked all components and connections, than its time to rebuild.

If you've put together a bunch of tube amps, why did you use the radioshack IC PCB for such a simple circuit? You could do a better job with pad-per-hole. It'd prolly be smaller. I also think it'd be much simpler. I think the problem is the IC and/or the PCB. Just rebuild. It'll take what...30 minutes?

[anchovie]

In his first post he says that it's already been built on perf after it didn't work with the Radio Shack board.

[markrocknroll]

This started out as a project to keep me busy over Christmas.  I wanted to build a cigar box amp.  It has stretched out to more than that.

More debugging tonight:
1) I will swap out the 386.
2) Measure voltages per the debugging tread.
3) Put a 220uf cap across pins 3 & 6 (if I have one).
Will post results as soon as I'm done.

[markrocknroll]

I was wondering, if you haven't figured out the problem, could you humor me and connect a 220uf cap across pins 3 and 6 and see if that clears up the problem. As I said, I know it sounds strange and shouldn't do anything but I'm curious as to why mine worked.

I assume you mean an electrolytic cap.  So, which pin do I connect to +?

[compuwade]

Positive to pin 6

[dano12]

I know this is going to sound very very strange. However, the Noisy cricket was my very first project and I had the exact same problems with it that you are having using the radio shack board. I tried many different IC's, different caps, resistors and even rebuilt it on a new RS board. All resulting with the same issues. When troubleshooting it for some reason I decided to connect the 220uf cap across pins 3 and 6 of the IC and this fixed the problem. I even emailed Dano from Beavis Audio and he said that it should do absolutly nothing. But it did fix the circuit. I was wondering, if you haven't figured out the problem, could you humor me and connect a 220uf cap across pins 3 and 6 and see if that clears up the problem. As I said, I know it sounds strange and shouldn't do anything but I'm curious as to why mine worked.
Thanks,
Wade

I remember your email!

What you suggested, in bridging pins 3 and 6, was effectively connecting connecting another 220uf cap from V+ to ground.

Looking at the schematic, I was pretty sure that would not fix anything:



But since this worked for you it means that you have added an additional 220uf cap to ground for power supply filtering.

This is a particularly vexing issue as I've not seen LM386 circuits ever calling for more than 100uf between V+ and ground. If I recall correctly, both the little gem and ruby from runoffgroove call for 100uf caps.

If you don't mind, a few questions: Did you build yours on a radioshack board as per my project pdf? Also, did you use a wall wart or battery?

Thanks for any help you can provide.

[markrocknroll]

OK did some debuggin'. First I swapped the LM386 from RS back to the NJM386 I got from Mouser.  There was no change to the way it worked.  Everything as I decribed before.  I have operated with with a wallwart and gotten same results.  Next I took some voltage measurements per the sticky thread:

Battery - 8.3
AC Adapter - 7.9
Input to board - 7.6
IC pin 1 - 0.9 Grit Switch On
IC pin 8 - 0.9 Grit Switch ON
IC pin 1 - 1.2 Grit Switch OFF
IC pin 8 - 1.2 Grit Switch OFF
IC pin 2 - 0.0
IC pin 3 - 0.0
IC pin 4 - 0.0
IC pin 5 - 0.9
IC pin 6 - 7.6
IC pin 7 - 3.7
JFET D - 7.9
JFET S - 3.6
JFET G - 0.0
C1 + leg - 7.7
C1 - leg - 0.0
C8 + leg - 0.9
C8 - leg - 0.0

Finally didn't have a cap close to 220 uF so couldn't jumper pins 3 & 6.  Will do tomorrow.

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