Hello All. I just thought I'd introduce myself a bit here. My name is Dan and I've been repairing and building instruments for a few years now. Mostly repairing, and I've built just a couple of instruments. A year ago, I helped with a music camp where we build instruments out of household stuff. The main instrument was the canjo, using a food can, a 1" X 1", eye bolt tuner and staples for frets. Before that though, I built a few other instruments such as an acoustic guitar out of two cookie tins and a broken guitar's neck, a 5-string banjo using a Ford hubcap and food tray for the rim and resonator, and a Kalimba with a coffee can.
Since then I wanted to get into building cigar box guitars and ukes. I finally decided to do this last week, and successfully finished one using an Arturo Fuente box and an oak neck, guitar frets, tuning machines, and a Radio Shack buzzer for a pickup. What a fun guitar it is. I also made the slide out of a wine bottle and I also made a cigar box amplifier. The amp does work, but is a bit quiet. I think it's more the speaker than anything though, but I'm still tinkering.
So, here's what I came up with
Dan
Replies
Looking great! Also thanks Robert JOnes, I did not know that 386 chips had differing output. My new thing learned for the day. One of the many reasons I love this site!
First check the number on the LM386.
Chances are if it's from Radio Shack it is the LM386-1 which has a max working output of 250mW.
That's a 1/4 watt maxed out so it's going to be quiet.
A LM386-4 will give 1Watt but those are better powered off 12v.
The LM386-3 rates approx 3/4 Watt and works well with a 9v supply.
Personally I've had better results with the NJM/JRC386D chips.
The 386 chips also have a default gain of 20. Adding a 10 micro farad cap and variable resistor between pins 1 and 8 allows you to run the gain from 20 - 200.
I can't tell from the photo if you already did this so it's okay to point and say, " Did that already". :-)
Don't worry about the speaker frame touching the back of the box. You are not pushing enough power through the speaker to make enclosure movement an issue.
I used the instructions from this link along with the parts list, though I wired in the power switch and LED. I took an electronics class in high school, but that was 20-years ago, and I've probably forgotten more than I remember from that class.
I do have the LM386-1 chip that you speak of. Since the box is so small and I can't fit a large battery in the box, I think I will 386-3 chip. It's got to be an improvement. I assume I wire it the same way, correct? I may just start a new biscuit board on the next one. Now I just need to figure out where to get that chip since it seems Radio Shack is pretty limited as that's the only 386 chip they sell.
Dan
Check out this page at BevisAudio for 386 pinout diagram and some different ideas for 386 based amps.
The LittleGem does have a gain pot but leaves out the cap as does the Noisy Cricket but I've had better results by including the 10 micro farad cap in the gain circuit.
I would suggest buying one and trying with and without the cap.
Wiring for the 386-3 chip is exactly the same. Something you might want to do if you plan on experimenting is to get chip sockets. This prevents damage to the IC's from soldering and desoldering cycles.
Order the chips on-line, type in "lm386n-3 for sale" and pick your poison. The 386 amp chips have been around a looooong time so are easy to find and cheap.
http://www.alibaba.com/countrysearch/CN/ic-lm386--3.html
Excellent!!
Here's the amp and slide