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DIY cigar box amp help

M

Milothicus

Nov 23, 2001
676
4
Greensville, Ontario, Canada
#1
I found this online just now and want to build it:

[This invalid link has been removed]

but.....the diagram is made with ascii characters and doesn't seem to line up properly. I don't have a lot of experience with reading schematics, and so i don't know where to start trying to realign or guess at how to wire this thing. If anyone has experience with this, could you help me out with how i'm supposed to read this diagram? or show me another schematic for a cigar box-type amp?
 
#2
That's how it should look like
Code: 
                    +9Vdc
                     |
                 |\  | 10uF
               3 |  \| | |
 Signal in-------|+  6\| |  
                 |     1\|             +|| 220uF
                 |       8\_____________||___________
                 |        /    |        ||           |
               2 |      /      |        ||           |
       ----------|-   /      ------                  |
       |         |  /|4      ------0.1uF        Low Impedence Speaker
       |         |/  |         |_______/\/\/\____    |(8 ohm Walkman Style)
       |             |                 10 ohm    |   |
       |             |                           |   |
       |_____________|___________________________|___|
                     |
                   GND
 
#6
yeah, it's for guitar. i have a guitar i can use it with too. also, if i do use it for bass, it's just so i can hear it. i don't need much volume. if the small speaker can't handle the bass, then maybe i'll install a headphone jack. right now it's just for fun.

as for explaining it for dummies......
the big triangle is an integrated circuit you buy that has 8 pins on it numbered 1-8.

according to the diagram, from pin 1 to pin 8, you connect a 10 microfarad (spellcheck: should there be an h in there somewhere?) capacitor. the 10 ohm thing is a resistor. connect as shown, and then it's plug and pray.
 
#10
Well, this thing is great. everything that comes out of this thing is distorted, but it's a great-sounding distortion for guitar, and bass plays fine, but it's fuzzy too. Also, the IC that's used (LM386) has a pdf file online that shows a few variations on the circuit..... total cost: $11.00 canadian, plus one fossil wallet case. My roommate made one too, and fit it all into an altoids can. It's a lot louder than i thought it would be, and not too hard to make.

Just thought i'd let everyone know how it worked out....
 
#13
well, i looked at the manual for the LM 386 IC and the values of capacitors and other parts that they recommend are not exactly what the above picture shows. the capacitor from 1 to 8 increases the gain from 20 (with the circuit open) to 200. That may be the source of some of the overdrive. If my guitar volume is set really low, it doesn't distort until i really dig in, but as soon as i increase the volume, it's a pretty nice fuzz. also, the speaker i used is a $3, 2" speaker from the electronic supply store. nothing special, so it's easy to get some serious farting from it.

I plan to try some other variations on the circuit, but for a first try, i'm really happy.
 
#15
I'm not experienced in this at all, but i'll tell you what i understand. maybe it'll help.

well, it's all based around the IC. it does all the work. here's the manual for the IC: Link Removed

The IC has 8 pins, each with a purpose. if you look at page 1 in that manual, you'll see what the 8 pins are used for. the pair at the top (#1 and #8) are used for gain. the default gain (if nothing's connected) is 20. adding the 10 uf capacitor increases the gain to 200. there are input and output pins, a ground pin, a voltage supply pin, and a bypass (not used here).

you can use this IC in a lot of different circuits. page 5 has a few examples. unfortunately, i can't tell you what each component does within the circuit. i know how each component works individually, but i have no idea how they work with each other to create an amp.

i decided yesterday morning that i wanted to make a pocket-sized amp. last night at about 2 am i had it done. a headphone amp wouldn't be much more difficult, i don't think.

as usual, there's an endless amount of info on the web.
 
#16
I'm also quite interested in a pocket sized amp. I took a quick look at the manual and they mention something about a bass boost with a series RC between 1 and 5. That might be able to be used for tone shaping. Also, the diagrams in the manual for their amps show a pot on the input that wasn't shown in the diagram that you found. It will be interesting to see what someone comes up with for a decent pocket bass amp.
 
#17
boosting the bass in this thing would only make the speaker flap more, i'd think. it's really hard to get any bass sound out of a 2" speaker without the speaker really farting.

as for volume, having never soldered on a perf board, i decided to find the simplest possible schematic for a pocket amp. this one had nothing extra, so i went with it.

the smallest amp i've seen that can be used with bass is the pignose. has anyone else seen smaller?

i suppose you could make the basic wiring from the manual, and put in a headphone jack instead of the speaker, and that might work.........
 

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