I'm making my 2nd CBG and decided a matching amp would be nice. I've made other amps (noisy cricket) so I followed that again but omitted the tone knob. I had it working on the bench but now that I have it all installed in the box I have really low volume and lots of noise/static. The weird thing is if I open the amp and touch one of the speaker chassis the noise is cut down and the volume comes up. If I touch the speaker and the shaft of the cable jack pin it's perfectly quiet and has nice clear volume.
I'm a relative noob to electronics so the only test equipment I have is a multimeter.
Any help or ideas would be much appreciated.
Replies
Not sure if it's grounding but a wire from the speaker to the tube of the jack has made it work. As I worked with the touch method I noticed I could one handed touch a speaker mounting screw and the jack mount nut to get the fix. So I wrapped a length of wire around a mount screw, tightened it down, and started probing with the other end.
After trying the speaker ground at the speaker, the ground at the board, and the ground tab at the jack - nothing
Touch the mount nut or the tube(shield tube?) - bingo!
Once I had it figured out that I needed a connection from the speaker chassis to the center of the jack I routed the wire, pulled the jack and wrapped the other end around the tube. Retighten jack nut done.
Now the bad, I'm not happy with it I get a sweet clean sound out of the treble strings/notes but the bass is muddy. Not too mention the volume is low. I think asking the NC to drive the two speakers is asking too much. So all this tinkering and I may pull the PCB out and try a little gem2.
That is unless someone has some other ideas as to what else I may have messed up.
I have't had time to get back to it yet but I'm working off of this schematic from Beavisaudio.
My changes were to omit the circled tone part in the circuit, use the two speakers previously linked, powering it with a six AA battery pack, and add a hot wire from the power to the grit to include an LED (uses same switch but separate contacts) to show when the grit is on.
Thanks for the replies guys
RTZ - I ask as I haven't noticed any ground side caps in schematics, where do you put the cap on the ground side?
Jim - I find it interesting that you have trouble with the ceramic ones as that's all I've used (size and application) and have had no problems.
Well I haven't had much time to fiddle with it but here's where I'm at.
I'm starting to think my problem lies in the fact that I'm trying to use two 2.25x4 speakers. As I messed with my test amp and breadboard I did accidently stumble across the fact that putting an extra cap (47 or 100 tried both) in before the vol pot helped but didn't solve the problem.
I may tinker with it some more but after looking at runoff (Thanks for pointing me there Oily) I'm starting to think about starting over and going w/ a litle gem2. When I had this one working it has a nice clean sound that I was using the 2 speakers to achieve but I think they are a bit much for the cricket. <-- Possibly part of my overall problem?
The circle is the cap to ground the line going up is a way I have done them for some reason but don't take my word cause I just wire them tell they sound good. I think this is the Ti. schematics thats the site to go to. I only wire volume and gain and don't do anything that cut volume. Watch the polarity of the caps.
Thanks RTZ, that's way different than what I had pictured when I read above. I think that would would act like a treble bleed for tone but it gives me something else to try.
Ross,
That circled cap is listed as a .047uf in the little cricket. It needs to be there to make mine work - I messed with one for way too long trying to toubleshoot before I realized a 10 M ohm resistor is definitley different than a 10 ohm ( the one in series with the circled Cap)
A cap ( .022u , .047u or .1u ) in series with the input going to the Vol pot does help considerably.
The Little Cricket has a .1u cap from 7 to ground that helps a lot if you are getting imperfect voltage input. I noticed a huge difference whan using a 9v adapter.
I assume you are looking a a schematic like:
lil cricket.jpg
didn't see that i dont use .05uf I use the 47nf like the cricket
I use the LM386 - Noisy Cricket plan for my amps. I have to jump a ground to the speaker chassis from the negative lead of the speaker.
I also could not get mine to work with ceramic caps for the small ones (100nf, 22nf, 47nf, etc). The worked when I used mylar (gumdrops) not sure why?
At the very least you need the speaker output to go through a cap and then another cap to ground. This will get a lm386 working and at the right temp. Listen to Oily it sound like a lose ground somewhere best to ground eveything you can. It takes a few chips and boards to get what you want cause we ain't electrical engineers. I don't use the tone on my amps mostly not enough room or i'm lazy if I want to shape the sound i use my pedals. GOOD LUCK
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