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DIY cigar box amp help

Discussion in 'Amps and Cabs [BG]' started by Milothicus, Feb 23, 2004.


  1. I found this online just now and want to build it:

    http://www.harpamps.com/micKdiy/Cigar-Box-Amp.html

    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. ostrzoskrzydly

    ostrzoskrzydly

    Jul 1, 2003
    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
    
     
  3. Ok, another question. i've bought the components and a board to put them on, but i'm wondering where the negative battery terminal should be connected. does it get connected to ground? that doesn't make any sense to me.......
     
  4. ostrzoskrzydly

    ostrzoskrzydly

    Jul 1, 2003
    yup, to the ground. it makes perfect sense but i really have to go now, maybe someone else will explain
     
  5. 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.
     
  6. So who's the local electronics wiz that's gonna change this up for bass and start adding tone controls?

    :)
     
  7. not me. i'm trying to solder these little things and it's tough. i think it's going ok, just really really slowly.

    maybe after i've screwed up about 10 of these.

    on a related note, does the signal go to the tip or the sleeve connector on the jack?
     
  8. seanm

    seanm I'd kill for a Nobel Peace Prize! Supporting Member

    Feb 19, 2004
    Ottawa, Canada
    The sleeve goes to ground, signal goes to tip.
     
  9. 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....
     
  10. pretty much, yeah. only it cost me about a quarter of what the smokey amp costs......of course, i don't have the speaker cab output..........
     
  11. Shouldn't be fuzzy, if it's the amp I'm thinking.

    Something's driving the IC into clipping.
     
  12. 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.
     
  13. Cool, this sounds fun. I might make oone to learn guitar on. I'd really like to try making a bass headphone amp though.

    You could start an online project for this, similar to that diy tube amp site. Care to write out a breif explanation of what each part does, and maybe draw up a better diagram in paint?
     
  14. 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: http://www.national.com/ds/LM/LM386.pdf

    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.
     
  15. 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.
     
  16. 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.........