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Introduction and first build

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

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Permalink Reply by Daniel Hoenisch on September 13, 2014 at 3:23pm

Here's the amp and slide

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Permalink Reply by Dan Sleep on September 13, 2014 at 4:22pm

Excellent!!

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Permalink Reply by Daniel Hoenisch on September 14, 2014 at 3:29pm

Thanks, Wayfinder. Your suggestions do help. Number two is what I suspected as well. I had a broken set of PC speakers at work, and before I tossed them, I snagged the speakers from them. They are a pair of Harmon Kardon speakers that sounded great as computer speakers, so I figured I didn't have enough to power them, so I was actually going to pick up some lighter speakers. I can't find them at a Radio Shack anymore, but I believe I can get them at a Microcenter. That should give me more sound. However, my amp does sound pretty good, just quiet.

As for suggestion 1, I tried the amp out before mounting any of it into the box, so I knew it was pretty quiet before I mounted it. You may be right on the grill and I need to open it up more, but I'll try the new speaker unmounted first. If I can get more volume out of it, I will mount it as is and see if it kills any volume. If so, I will open up the grill more.

Thanks,
Dan

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Permalink Reply by Ron "Oily" Sprague on September 14, 2014 at 3:55pm

Dan,

Nother thought along the lines of what Wayfinder was thinking. That magnet is big, true. So big, I wonder if it is actually touching the bottom of the box, and thus maybe just maybe locking up the speaker? Maybe you need to have some free space for the speaker to actually move.

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Permalink Reply by robert jones on September 14, 2014 at 7:45pm

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.

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Permalink Reply by Daniel Hoenisch on September 15, 2014 at 1:40am

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

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Permalink Reply by Ron "Oily" Sprague on September 15, 2014 at 3:09am

You could always order them direct from China:

http://www.alibaba.com/countrysearch/CN/ic-lm386--3.html

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Permalink Reply by robert jones on September 15, 2014 at 10:04am

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.

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Permalink Reply by Bluesheart on October 10, 2014 at 4:29am

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!