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MonoBox Powered Speaker

Build a small powered speaker to amplify your iPod or other headphone music player.

MonoBox Powered Speaker

MonoBox is a small, inexpensive powered speaker that amplifies the output of your headphone music player. It’s little but it’s loud! All the circuit parts are available from RadioShack. The speaker and cabinet are left to your preference.

You’ll learn how to assemble and solder an audio power amplifier using an integrated circuit (IC) chip, and how to choose a speaker and install it in a cabinet with the amplifier.

The core of MonoBox is a compact and efficient audio amplifier based on the LM386 power amp chip. It will run on 200mA of current using power supplies from 6V–15V DC. This gives you the flexibility to power it from a wall adapter, a 9V battery, or a car accessory outlet.

You’re probably thinking, “Sure, but it’s so small. Does it rock?” Fair question. The prototype has been exhaustively tested and it does indeed rock. Maximum volume output is 90dB, and with the added bass boost your socks will be rocked clean off!

 

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Steps

Step #1: Select your cabinet.

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  • There are many options for housing your MonoBox. I've used nice old wooden cigar boxes; you could also use a lunch box or small toolbox. Choose something between 1/8 and 1/4 cubic foot (equal to 6"×6"×6" and 6"×6"×12", respectively). Make sure it's deep enough for your desired speaker, and has one surface suitable to mount your speaker on.
  • NOTE: A box that can be tightly sealed against air leaks will provide the best bass sound.
  • Wood and plastic are good cabinet materials, as they're easy to work. Metal is more challenging. Almost anything relatively rigid can be used. Construct a box from cardboard in any shape you like, and cover it with colored duct tape!
  • RadioShack sells two project boxes that are about the right size. They're made of black ABS plastic that's very easy to work. They measure 7"×5"×3" for model 270-1807 (shown here), or 8"×6"×3" for model 270-1809.

Step #2: Choose your speaker.

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  • The driver (speaker) will determine the sound quality to a great extent. Good-quality drivers are available cheap as manufacturing surplus. Look for a driver at least 3" in size that's described as "full range." This type will reproduce the entire frequency range of sound from one driver.
  • Good online sources of drivers include Parts Express, Madisound, and any websites that sell overstock or surplus parts. Look in the Specials, Closeouts, or Bargains sections for great deals. The driver I used in my prototype cost $0.98 from Parts Express and sounds great.
  • If specifications for the driver are stated, the impedance should be between 6 and 12 ohms (6Ω–12Ω). Resonance frequency should be below 150Hz for good bass. High frequency range should extend to at least 8,000Hz (8kHz). And sensitivity of 90dB or higher will provide better volume output.
  • Drivers repurposed from table radios, computer speakers, etc. are often perfectly acceptable for DIY projects.
  • TIP: You can test a candidate speaker's bass by temporarily mounting it in a cardboard box or in the middle of a panel of cardboard at least 20" square. Connect it to any stereo and play music. The panel, or "test baffle," will separate the front and rear bass waves, allowing you to hear what it will sound like in a finished cabinet.

Step #3: Mark the circuit board.

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  • Now you'll build the guts of the MonoBox: the amplifier circuit board. The board has 20 copper traces, each with 5 holes connected together. Eight of these traces will be used for the chip socket. Others will be used for component interconnections and off-board wires.
  • Mark the hole designations on your board before installing components, because it can be difficult to tell the holes apart once some are obstructed. On the soldering side of the board (with the copper traces), use a fine-tipped marker to label the traces, from 1 at the upper right clockwise to 20 at the upper left.
  • Flip the board over to the component side (without the copper), and label the traces from 1 through 20 on this side too. Note that the left/right handedness reverses when you flip the board over.
  • Now label the 5 holes of each trace A through E, with A at the center of the board and E at the outer edge. Thus the inner hole on the trace at the upper left is 1A and the outer hole of the trace at the upper right is 20E.

Step #4: Solder the socket and the caps.

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  • Insert the DIP-8 socket for the amp chip into holes 2A–5A and 19A–16A, orienting the notch in the socket body toward 2A and 19A (up). Flip the board over and solder the socket leads to the traces.
  • NOTE: The electrolytic capacitors are polarized and must be installed in the proper orientation. The negative (–) lead is identified by a vertical band on the housing as shown in the second photo.
  • Insert capacitor C3's (470µF) negative lead into hole 11A and bend its positive lead over to hole 16B. Insert capacitor C4's (100µF) negative lead into hole 20C and bend its positive lead over to hole 17C. Solder and clip the leads.
  • Insert capacitor C2 (0.047µF) into hole 13D and bend other lead to hole 15D. (The ceramic caps aren't polarized, so it doesn't matter which lead is which.) Solder and clip the leads.
  • Capacitor C1 (0.033µF) consists of 0.010µF and 0.022µF capacitors in parallel. Install them together by inserting one lead of each into holes 16C and 14C. Solder and clip the leads.
  • NOTE: If you have a film capacitor with a value of 0.030µF to 0.035µF, you can use that in place of the two in parallel.

Step #5: Add resistors and jumpers.

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  • Insert resistor R3 (10Ω) into holes 15E and 16E. Insert resistor R2 (10K) into holes 1D and 2B. Insert resistor R1 (100Ω) into holes 4B and 5B. Solder and clip leads.
  • TIP: Where a resistor body is longer than the distance between its insertion holes, stand the resistor vertically on one hole and bend the other lead down toward the second hole.
  • Insert a short jumper wire, such as a cut-off lead, from hole 3C to 5C. For all other wires, solid-core insulated wire is recommended for ease of working. 24-gauge telecommunications wire, as from telephone or CAT5 cable, is ideal.
  • Cut a 5cm jumper wire (shown grey), strip 3mm of the ends, and run it from hole 1E to 14E, passing around 19 and 20 as shown.
  • Cut a 5cm jumper wire (shown brown), strip 3mm of the ends, and run it from hole 13E to 5C, passing around 8 and 9 as shown.
  • Cut a 4cm jumper wire (shown orange), strip 3mm of the ends, and run it from hole 20D to 5D, passing around 1 and 2 as shown.

Step #6: Connect the off-board wires.

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MonoBox Powered Speaker
  • Wires to reach the power input socket, shown red and black, are soldered to holes 20E (black, –) and 17E (red, +).
  • Wires to reach the signal input socket, shown yellow and green, are soldered to holes 4E (yellow, signal) and 5E (green, ground).
  • Wires for the speaker, shown blue and purple, are soldered to holes 11E (blue, +) and 20A (purple, –).

Step #7: Check your work.

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  • Carefully examine both sides of the board. On the components side, check the connection holes against the assembly instructions.
  • On the solder side, use a magnifier to look for missed solder joints, cold joints, or accidental solder shorts between traces. This is a tiny board and problems are easily overlooked by the naked eye.
  • If you think you see a solder bridge between traces, run a knife point between the traces to scrape it away.

Step #8: Add the amp chip.

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  • Finally, carefully plug the LM386 amp chip into the socket. Orientation is as follows: with the board held with the socket in the upper part as shown, the 'dot' on top of the chip will be at the upper left.
  • That's it! You've just built an amplifier.

Step #9: Cut and drill the cabinet.

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  • Trace the shape of the speaker on paper using a pen or crayon. Cut out your tracing and use it as a template to mark the box surface for cutting.
  • Place the speaker on the box and mark its mounting holes with a Sharpie.
  • How you cut the box will depend on the material. For my wooden cabinet, I roughed out the speaker hole with a 50mm × 1mm cutoff disk on a Dremel, then finished it to size with a 2" sanding drum followed by 100-grit sandpaper.
  • In a rear corner, locate and cut a 10mm hole for the power socket and a 6mm hole for the audio signal input jack. My box was so thick I needed to cut a little relief inside so the power jack would reach through.
  • TIP: Place the jacks in a corner so the cords will be low if the box is placed either vertically or horizontally.
  • Near the jacks, place the circuit board on the cabinet surface and mark through 2 of its corner holes to place mounting holes. For #6 screws, drill the holes with a 1/8" bit for a snug fit.

Step #10: Install the amp and jacks.

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  • Solder the audio ground wire (green) to the outer tab of the audio input socket. Solder the audio signal wire (yellow) to both the left and right signal tabs of the jack.
  • The power jack mounts from the outside. Thread the black/red power wires through the power jack's nut and washer, then pass the wires out through the power jack hole from inside the cabinet. Solder the black wire to the outer power jack tab and the red wire to the inner tab.
  • The circuit board requires standoffs to give it about 1" of clearance from the cabinet. I used sections of ¼" plastic water tubing. Pass two #6-32 × 1½" screws through from the outside, and slip the standoffs onto them inside. Slide the circuit board onto the screws and install the nuts.
  • Put the audio jack through the 6mm hole and nut it on the outside. Pull the power jack through its hole and nut it on the inside.

Step #11: Make the speaker grille.

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  • The speaker needs an acoustically transparent fabric grille to protect it. You can use a variety of materials including speaker grille cloth, cane material, metal screen, or anything else that will pass sound through.
  • My speaker needed a gasket to keep the cone from hitting the grille. I recommend sheet cork. Use the speaker frame as a template for the outside of the gasket, and the cabinet speaker hole as a template for the gasket inside. Drill screw holes in the gasket also.
  • For a gasket, you can also use pasteboard, foamcore, thin wood, plastic, or other stiff foams. Soft foams and corrugated cardboard won't work.

Step #12: Install the speaker.

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  • I used #6-32 flat-head brass screws in finishing washers from the hardware store because that looks fancy with my wood box. Again, use a 1/8" drill bit for #6-32 screws.
  • Solder the blue (+) speaker wire to the + terminal of the speaker and the purple (–) wire to the - terminal.
  • For the best bass performance, seal any gaps or air leaks in the box with hot glue or caulk then fill the box with a moderate density of Dacron pillow stuffing. Fiberglass insulation works well too, but it's an irritant and should be handled carefully.
  • If you've chosen a box that opens and you don't want to permanently seal it, you can apply felt or adhesive foam to the edge of the lid rim to stop air leakage.
  • Done! Cool! Now we just have to talk about power and input signal and you're ready to play your MonoBox.

Step #13: Power up your MonoBox.

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  • Your power source needs at least 300mA of current capacity. Voltage as low as 6V works for driving 4Ω speakers, but 12V is best for 16Ω speakers, so 9V is a good compromise. RadioShack's Enercell 9V/300mA AC adapter is ideal. Install the type N power plug with the center (tip) positive. Now you can plug your MonoBox into wall power.
  • To build a battery adapter, solder the red (+) lead of a 9V battery snap connector to the center contact of a size N coaxial DC power plug. Solder the black (–) lead to the outer contact. Attach the battery to the back of the cabinet with the 9V battery holder.
  • TIP: After screwing the power plug's body together, you can fill it with hot glue to secure the wires in place.
  • To use a car or boat's 12V power system, make an adapter for the accessory "cigarette lighter" socket. Again, use a size N coax power plug and solder the negative lead to the outer contact, positive lead to inner contact.
  • Other DC power supplies can be used the same way, but make sure the voltage does not exceed 15V DC.
  • The MonoBox has no power switch. To turn it off, unplug the power from the back. Leaving a battery plugged in will drain it overnight even if no music is playing.

Step #14: Hook up the music.

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  • Audio signal input will depend on your music player. Purchase or make a signal cable suitable for your player with a 1/8" stereo plug on one end to plug into MonoBox. Most smartphones and MP3 players accept a 1/8" plug in their headphone jack.
  • Plug in the power source and the audio signal cable. Set your music player's volume to minimum, start the player, and increase the volume until you hear sound from MonoBox.
  • MonoBox has no volume control, so use your music player's volume control. Also use any tone controls or equalization on the music player to adjust the tone of the sound to your liking.

Step #15: How your amplifier works.

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  • The amplifier circuit is designed to be fed by a headphone output, so the input impedance set by R1 is a relatively low 100Ω. This helps load down the source and eliminate noise. Use a 10KΩ resistor for R1 if you'll drive your MonoBox from a line-level source like a home stereo CD player.
  • Most small speakers need bass boost. Components R2 and C1 provide a high-pass feedback loop to boost bass by reducing frequencies above 200Hz. If the sound is too bassy with your speaker, R2/C1 can be eliminated or disconnected.
  • For the best bass in a 4Ω speaker, C3 can be increased to 1,000µF. In a 16Ω speaker, C3 can be 470µF or reduced to 250µF without losing bass performance.
  • R1 provides a load for the signal source and ground reference for the chip input. C4 decouples and filters the power supply. R3/C2 is a Zobel network to ensure a low impedance load at high frequencies and to damp oscillations.
  • Pin 5 is the audio output of the IC chip. This pin has a DC voltage of 4.5V added to the audio signal. Capacitor C3 blocks the DC voltage from reaching the speaker and passes only the audio signal.

Conclusion

Going Further

What if you really want stereo? Make 2 MonoBoxes! In each, connect only one channel (left or right) of the input jack directly to the amplifier circuit board, and use a SPST switch to connect or disconnect the other channel, so each box has its own mono (or 1-channel) selector switch.

Set both boxes to 1-channel, then use a stereo headphone splitter to connect both MonoBoxes to your music player.


Comments

  1. Peter123 says:

    To power the speaker you could also have a solar panel on top so during the day you can switch from battery power to solar power by just adding a switch.

  2. fontmark says:

    Found the diagram in the PDF.

    1. gbelectronics says:

      this wouldn’t work in britain would it. any suggestions on how to make it work. also dont know where id get the components

      1. ALRUI says:

        No reason it wouldnt except youd need an adapter for the power brick (one of those travel adapters). Should be an electronics shoppe or order off the web.

  3. Nick Normal says:

    hi saulx350z, the diagram is one Page 2 of the project: http://makeprojects.com/Project/MonoBox+Powered+Speaker/2396/2 – it’s Step 15, or, if you can’t see that for some reason, here is the image: http://guide-images.makeprojects.org/igi/X3WB2Tny1O2xSlQb.large – hope this is what you were looking for.

  4. Ross Hershberger says:

    Volume: I measured peaks 90dbs at 1 meter distance before distortion set in. This was with an 8 Ohm speaker of mid/high efficiency. Not enough to throw a disco party but way above a typical computer speaker. I recommend a wall-wart power supply rather than a 9V battery for extended high volumes. Uses a lot of current.

  5. Ross Hershberger says:

    It depends on the speaker. A larger speaker may have reduced high frequency response unless it’s designed as a full-range driver. If you’re unsure I’d say build the amp circuit alone and try it with that speaker mounted on cardboard as described in the article. if you don’t like it you can change to a different speaker for the final assembly.

  6. Ross Hershberger says:

    I wish I could give a full answer. Do you mean it plays at low levels but stops completely when the volume is turned up?

  7. Ross Hershberger says:

    Note that a number of the Radio Shack parts like the circuit board and some of the resistors come 2 or more to a pack so you won’t have to duplicate the whole list when making 2 amps.

  8. ambrosehone says:

    Also, I guess I would also need to adapt the power for Australian sockets.

  9. ambrosehone says:

    *Complete Battery Overkill*
    Also, I guess I would also need to adapt the power for Australian sockets. Hmm…..

  10. Ross Hershberger says:

    Stereo is covered at the end of the article. The LM386 amp chip has only one channel of amplification. The easiest way to go stereo is to build two of them. You have to make a small modification to the circuit at the input jack because the stock mono circuit connects right and left together. You would want one built with only the right channel connected and the other built with the left connected. Option: install a switch at the jack so you could switch to mono operation by connecting in the other unused channel.

  11. tripsofjacks says:

    I went into radio shack today and they had no problem helping me find all the items on the list. I’m going to build this over the next couple days. I found this on flipboard and thought it sounded too awesome not to try… I have never done a project like this, but your instructions appear well done. I will post on the outcome when I am done. Thanks for sharing this project.

  12. tripsofjacks says:

    My project is a sucsess, my amp is working well, and is really cool!!! Much thanks to the author for sharing these awesome and easy to follow plans!!!

  13. Ross Hershberger says:

    Note from the author here. I’m abruptly out of the country for work and have unreliable internet. Apologies for the lack of replies. I will read all responses and answer as soon as I’ve sorted out certain industrial laser issues and made my back north of the border. Thanks. Ross Hershberger

    1. rkan665 says:

      so, when i plug in my amp via 9V battery or the enercell adapter 9V(dc) it makes a popping noise.. can anyone explaing that? regards, ryan

      1. Suicidewafle says:

        That is simply a small burst of electricity moving through the speaker, and causing it to ‘work’. Like when you play music, but instead of a controlled signal it is just an uncontrolled current.

  14. Michael Lewis says:

    Looks like I’m going to answer my own posting: The author clearly intended to indicate by use of a triangular symbol that the LM 386 is the IC in the circuit. However, by adding the + and – signs to the input leads, he created the symbol of an op amp. This is a mistake that only a person with limited electronic knowledge would notice, since the square wave output of an op amp makes it clearly unusable as an audio amplifier.

    1. hollyjester says:

      I think you are incorrect, in that there should be + and – terminals on the schematic symbol

  15. Scott W Vincent says:

    Hauke, you need a log (audio) pot for audio signals. I don’t what exactly would be best for this circuit, but it seems that values between 10k and 50k are most common these days, though I’ve seen some amps that use 100k pots.

  16. Scott W Vincent says:

    That is very nice! I like how the lion artwork surrounds the speaker, looks great!

  17. Fergal says:

    Tim – Vocals are normally in the centre of a stereo recording. This means that they are present in exact same amounts on the left and right channels. Instruments tend to be placed more on one side than the other.

    When making a mono speaker like this, the left and right signals get summed together. However, if at some stage during the construction, the polarity of either the left or the right channels is inverted, then anything in the centre, like the vocals, will get lost. This is because the vocals are now present as exact opposite signals on the left and right, and perfectly cancel out when summed.

    This phenomenon doesn’t affect the instrumentation as they tend to be in different amounts on the left and right, and so do not cancel out when one side is subtracted from the other.

    I can’t help you with regards the specifics of the circuit (I haven’t looked in detail at it yet), but a good place to start would be to look at the wiring of sockets and jacks – have you swapped a shield and a tip, for example?

  18. Arnoldas Gribas says:

    setup would be the same
    yes it would be capable powering a bit more powerful driver, but don’t expect much because its only 1W

  19. Arnoldas Gribas says:

    very nicely done :)
    distortion is boosted by increasing gain?

  20. Hauke says:

    i made a stereo version because i had enough parts left: https://www.dropbox.com/s/fqv7p5zpogspep2/lm386-stereo.jpg

    1. Pete says:

      Is there a schematic for the stero circui? I built the mono curcuit and am building a second but I dont know how to connect the two for stereo.

      1. Zorro says:

        build two circuits. stereo line in has ground, right and left channel. use ground for both and left for one circuit and right for the other. the original version has left and right together in one circuit.

        1. Pete says:

          Awesome. Worked great. My only issue is that the volume is half as loud in one speaker. I swapped speakers ad determined it is the circuit. Any immediate ideas. I’m assuming it is my craftsmanship to blame. I’ll probably have to make a new circuit.

      2. Havok says:

        Really want to build a stereo Do this :
        Make 2 monoboxes In each, connect only one channel (left or right) of the input jack directly to the amplifier circuit board, and use a SPST switch to connect or disconnect the other channel, so each box has its own mono (or 1-channel) selector switch.

        Set both boxes to 1-channel, then use a stereo headphone splitter to connect both MonoBoxes to your music player.
        (I got this from the down of the article!)

        1. jacob says:

          i was wondering if you could get a picture of this im starting out in electronics and such and i was wondering if you could upload a diagram on how to make the mono amp into a stero amp.

  21. Scott W Vincent says:

    Very nice! The pot is a great addition. I’m thinking of doing another some day with an option for line in level sources with a volume control.

  22. Scott W Vincent says:

    That’s interesting – thanks for sharing. I might try the 1 watt chip on my next build.

  23. Ross Hershberger says:

    Check your email inbox.

  24. Jakub Czarnecki says:

    I would say check that there is no short and make sure the chip is not in upside down

  25. Ross Hershberger says:

    I’ve checked with Parts Express and they have the $0.98 oval speaker tha twe used in some of the prototypes still in stock.

  26. Ross Hershberger says:

    Capacitor voltages are not critical, as long as they are at least 50% higher than the power supply that you’re using.

  27. Ross Hershberger says:

    The bass boost in the circuit can exceed the voltage swing capability of the amplifier. If you get distortion on bassy music consider using the EQ on your music player to turn the bass down. Or refer to the article and disable/remove the bass boost parts.

  28. Ross Hershberger says:

    We found in testing that some portable headphone players delivered a lot of noise when loaded with a high impedance. They need a lot of current drawn to shunt out and damp the high frequency hash in particular. That’s why the 100 Ohm input resistor. Terminating the headphone output with a higher resistance will result in higher noise on some source devices.

  29. Ross Hershberger says:

    Builder’s issues solved via email. He built it right, but had the worng IC chip. See his further comments below.

    1. rkan665 says:

      can you help me?

  30. Alec Spicer says:

    I soldered, drilled the box, and the whole nine yards. I finally hooked up the power to see if it works but there is no audio. All I’m getting is a little bit of noise when I hook the power chord into the power jack. Ask me questions about the problem so I could give more detail and so I can get this awesome project to work.

    1. Jake T says:

      I’m having the same problem. I’ve double checked all my work but everything looks like it’s in place. The IC chip I bought the LM386N from radio shack. I don’t know if that might be a problem.

      1. Havok says:

        Your IC might be upside down. (I think.)

  31. praveen says:

    I think its very helpful for me .

  32. jerry says:

    I want to have the option of my box being powered by a battery(in the box) and a wall plug. I know i’ve seen the instructuions here somewhere. can someone point me in the right direction?

    1. I actually did this with mine. I just with a simple solution of soldering a 9V adapter to the same positive and negative power leads on the power jack. This resulted in being able to use the power supply not only for a source of power but also for a charger for my rechargeable 9V battery. If you want to do this I would also recommend adding a power switch to the system so that it will charge better, instead of the amp chip using current sitting idle. You end up with a nice rechargeable amp that you can take anywhere. this is the link for the rechargeable battery I have: http://www.ebay.com/itm/New-9V-280mAh-Ni-MH-PP3-Rechargeable-Battery-/310406636702?pt=US_Rechargeable_Batteries&hash=item4845ad649e

  33. Phil O says:

    Awesome guide! I’m using a Nightfire Electronics LM386 kit I bought for $10 from Amazon. Saved me a little trouble assembling all the components. One comment on the circuit: looks like you bridged the input signals without resistors. I’ve read that this causes distortion and can even damage the source, because the two signals are essentially fighting to set “their” voltage on the same wire. It’s a good idea to run each signal through a 10k resistor before connecting them. But it seems that lots of people are following these instructions with no complaints, so maybe it’s not that important?

  34. Pete says:

    i did it. Awesome. powerful

  35. gary green says:

    Where Can I add a pot so I can have volume control?

    1. jeromymurphy says:

      Can you just use the volume control on your mp3 player?

    2. Zorro says:

      Ad pot at audio line in.

  36. jeromymurphy says:

    I had a great time building this. Great project for an amateur. My radio shack was sold out of the 8 pin connector so I used a 14 pin instead. Same cost, I just had to be careful what I plugged into and soldered. I used a speaker driver scavenged from an old Samsung surround sound. The speaker was flush with the face of the box so I used the metal lid from a canning jar with fabric glued in to finish it out.

  37. Havok says:

    Is it necessary to use an ic pc board? Reply!

  38. bonsai171 says:

    Can this be modified to make a preamp and drive an amp instead? How hard would that be?

  39. Havok says:

    Hi in the schematic there are two triangles pointing down so, i am a newbie to this and schematics. so can you help me?

    1. bonsai171 says:

      Those two arrows are ground connections.

      1. Havok says:

        Thanks bonsai171, But there is only one positive connection.

        1. bonsai171 says:

          Ground is negative

          1. Havok says:

            But there are 2 ground connections and 1 positive connections.Right?

  40. Havok says:

    Thanks bonsai171, But there is only one positive connection.

  41. Havok says:

    Hey, Ross there are 5 caps in the photos but in schematic there are 4 caps. But how?

    1. Pete says:

      Two of the caps “stack” together to get a higher value.

  42. Havok says:

    Thanks, Pete that helped a lot.

  43. SkipF says:

    I found an electronic crossover PCB via ebay in china…And I’m using a pair
    of aluminum 2 way speakers; each speaker has it’s own amp. Power is a bit
    funky. 2 18650 lithium batteries for the power, plus 2 14500 LBatteries for the
    negative supply of the Xover.

  44. Havok says:

    Is it necessary to use an ic pc board?

  45. SkipF says:

    No… but it’s a whole lot easier. I used to build prototype cameras @Polaroid. Once we
    got BOARDS, they worked a lot better than the WWrap or P2Point vector boards we originally
    modeled the circuits with. 2 boards for $13.00…

  46. Tommy says:

    This is a cool project. I actually used a circuit similar to this to build a guitar amplifier into a cigar box (same workhorse LM386 and all). Only difference is that you would use a pot to control the gain. For any guitar players out there, you can very easily modify this exact same build (just sub out a couple of parts) to get a sweet-looking portable guitar amp. The following link shows the schematic (though it’s not my site or my work).

    https://lh3.googleusercontent.com/-X8sUApMtOhM/UNEB4o8zwOI/AAAAAAAAArY/oQHvUsvDA2U/w500/amp-diagram.png

    1. Acacia460 says:

      What speaker do you use? In terms of specs what works best for guitar?

    2. bjarnen96 says:

      Is there any more information on this, or just the picture? I wasn’t sure about a few of the connections as well- specifically, if the wires were crossing over each other or actually connected in and around the chip socket. Thanks.

      1. Tommy says:

        There is an instructable for the Little Gem at http://www.instructables.com/id/The-Little-Gem-Mini-Amplifier-Guitar-Amp-/. Between their schematic, and the image I posted above, things should come together nicely.

        The main difference between this schematic, and the one listed in this article, is that you have an extra potentiometer to control the gain (a must have with a guitar amp). I generally build my cigar box amps with a 1/4″ jack for a guitar input, and a 3.5mm jack for an iPod input. It’s nice to have something that you can play anything on. I’ve built about a dozen of these things, and I can’t say enough about them. This entire project can be assembled from RadioShack components for around $30-$35. I’ve also used allelectronics.com in the past in order to source cheaper parts (including a speaker).

        For my speaker, I went a little overkill and used a ~40-50 watt rated mid-range woofer. I was able to find one of these for about $5 (though allelectronics is listing something similar at $9 http://www.allelectronics.com/make-a-store/item/GW-2048/4-40W-SHIELDED-WOOFER-8-OHM/1.html). This is a much better speaker than you need in order to build out the project, but I liked my speaker so much that I ended up putting the same speaker into all of my designs.

        Please let me know if you have any questions!

        -T

  47. Doug says:

    I used a pvc pipe to house everything! its great

  48. Havok says:

    Can i use a 4 0hm 100watt speaker driver? Will it run on a 9 volt battery ?

  49. My speaker is making a cracking/buzzing noise when played at all loud.

  50. Organell says:

    Is it really a good idea to short the left and right channels at the input jack? I don’t know about the output impedance of a typical phone/computer/mp3player but very few sources are really happy about outputs being shorted

    1. Phil Oertel says:

      I agree, it’s not a good idea to short them. Pass each through a 10k resistor before shorting.

      1. Dave Jones says:

        Did you try this yet? I’m getting a lot of buzzing from my speaker even with no input (just power). I’m wondering if the resistors here will fix that…

  51. maker mike says:

    I think I noticed a typo in the magzine article… it says to run the off-board wwire from 4E to the outer tab of the audio input jack and from 5E to theleft and right tabs. This online article has the wires switched. I don’t want to short anything. Do any of the success stories have advice? Thanks in advance!

  52. aktive0 says:

    i’m experiencing clipping/buzzing at 50% volume while sourcing from phone or laptop. is there anything that can be done? is this why people are recommending to add resistors before shorting? how exactly would i do that?

    1. Novaorbitdragon says:

      Did you use a 10kohm resistor

  53. Jacob Stork says:

    How can I fix this so that at high volumes the sound does not begin to distort and get fuzzy? I’m using 6×9 car speakers and I created two circuits and connected them together to make true stereo sound. Any thoughts or ideas on how I can fix this?

    1. Novaorbitdragon says:

      I’m getting the same sound

  54. lasko says:

    Will it work with a 3 Ohm speaker?

  55. Acacia460 says:

    I’m building this today, but I wanted to make a modification or two. The problem is I’m an electronics noob. Someone mentioned that a way to add a volume pot would be to put it at the audio input, but there are two audio inputs, so how would that work? Would it make sense to add the volume pot after pin 5?

    Also, someone mentioned current is an issue with low current if running from a battery. Could that be fixed by having several batteries in parallel?

  56. Mike says:

    I would like to try and add a rechargable battery and integrated charger into this circuit. Has anyone tried this?

  57. Travis says:

    How do you make a monobox for a subwoofer

  58. jpeck says:

    i built the box and it works. but i tried to substitute the stereo 1/8 jack with a mono 1/4 jack to play guitar through it and get nothing. anybody know what i’d need to do to get a guitar working with this design?

  59. Rex says:

    Can 1/4 watt resistors be substituted for the ones that are supposed to be 1/8 watt?

  60. Jen says:

    Cool. But what I want to do is take my dad’s old wood bookshelf speaker and power it with a micro usb rechargable power supply. Do I have to add an amplifier? I could leave it plugged in at home or charge it for on the go. Then I want to add an a2dp bluetooth ( via a a2dp headset?it has a 3.5 jack) and have my own little version of a portable sonos streaming device on my departed Dads old bookshelf speakers. This http://www.youtube.com/watch?v=XQ-vaNTqIPM and and your homemade portable speakers got me thinking. I have 2 of them and they’re great speakers. Since I have 2 stereo would be nice. Any ideas on how I would go about this? Thanks, any ideas I could get, I’d love to make this.

  61. Jen says:

    Found this,http://www.youtube.com/watch?v=tFGhPUzCirM but not a micro usb or rechargeable power supply.

  62. aktive0 says:

    Upcycle your old food tubs to make awesome sounding speaker cabinets!: http://www.youtube.com/watch?v=ZfIhq6xhRJE

  63. Marco says:

    Hi all,
    I live outside the USA, and I’m a beginner, how can I replace this PCB with something else that I can easily find?
    Thanks!

  64. Nemanja says:

    hi, can you give schematic with tweeter aded?

  65. Vishal says:

    I had follow exactly the same circuit and with almost same parts….i am getting a good amplified sound…but the problem is that when the 3.5jack is fully inside the phone (audio source) bass comes but the sound is very low, and when i plug out half of the 3.5jack in the phone a high sound comes but no bass also it is a little bit disturbing in high volume….

    So what to do?? How to make clear loud sound with bass, as we listen in speakers that we bought from market….

    plzz mail : tyrus429@gmail.com

  66. Charlie says:

    I just built this amp but I have the PCB hard-wired to the audio cable wires. It only works when the audio plug is pushed into my source half way. Push it all the way into the jack and no sound. Is this because the shield in the audio cable is really the ground, and both wires in the audio cable carry signal?

  67. Charlie says:

    My mono-box works great with my ipod, but I get no audio from my computer or radio. I’m happy that it is working great with the ipod. I tried 10k resistors on the source leads as suggested in a few of these posts and then I got no audio from my ipod too. I am back listening to my ipod with NO resistors on the leads. Go figure.

  68. kc2dqp says:

    Ross- love the build. HAD a lot of fun with it.

    2 questions though-

    1. do you have the part number for the PE speaker you used for this build?
    and
    2. How would one go about setting up a solar panel power back up in this build? I got a 9v panel on clearance when I was getting the parts..

    1. Hyrum says:

      I know the answer to your 2nd question. As he said in the description on step 13 “Your power source needs at least 300mA of current capacity. Voltage as low as 6V works for driving 4Ω speakers, but 12V is best for 16Ω speakers, so 9V is a good compromise.” So as long as the panel is at least 300mA it should work fine.

  69. Charlie says:

    Here is a short non-professional video of my MonoBox with a Maker Shed Color Organ Triple Deluxe II kit installed on top. The effect is cool.

  70. Travis says:

    What wattage can this unit produce at 8 ohms? Also how many volts will work above 9? I was told this can handle 12?

  71. Jae says:

    Hello. Just finished building the circuit. Checked everything and seems fine. Only thing is at around 70% volume on the ipod it distorts a lot (seems like the bass and even higher frequencies) I read the message that had similar issues but there was no reply.
    I used a 1000uf cap that was recommended since my driver is 4 ohm. The frequency range (of the driver) is from way below 150Hz (50Hz) and goes to 22K. Another thing is the volume isn’t as loud as I had imagined. I would guess that 90db is pretty loud but to me the circuit seems too low in output. Used the LM386 chip. Any ways to trouble shoot this?

  72. Hyrum says:

    You said that it could be used with 16 ohm drivers. I have two 8 ohm 5″ drivers that are exactly the same. Could I use them in series?

    1. Travis says:

      Absolutely. Series will raise the ohms and parallel will lower it.

  73. Niggamp says:

    Hey! I’am a beginner to electronics. And i really want to try this out. So can you hook me up a easier schematic. I’am only 11 years old

  74. Niggamp says:

    Forgot to mention, if possible, Can you guys make a animation. (Anything is fine!). i’am not that beginner i made lots of complicated projects.

  75. ALRUI says:

    Heres a link to the schematic (its in the “project steps” #15 above)

    http://makezine.com/projects/make-34/monobox-powered-speaker-2/

    Keep at it, refreshing to see young people experimenting & using their hands to make things!

    1. Niggamp says:

      I asked for a Easier schematic or animation.. Well i already saw that! BTW Thanks!

      1. ALRUI says:

        Thats what a schematic is & to my knowledge there isnt an “easier” way to show the circuit. What part about it are you having trouble with?

        1. Niggamp says:

          It is very confusing to me. Especially when building in a perf board. And those power supply thing. LOL.

          1. ALRUI says:

            Just think of it as a roadmap and follow the lines (wires).

  76. Niggamp says:

    Hey! ALRUI could you make a easier schematic for me? may be something like this:amazonaws.com/files.digication.com/M1fe471f05d04ba6c141449d65990ade3.jpg.

    Thanks in advance!

    1. ALRUI says:

      The link is bad

        1. ALRUI says:

          Its the same concept just not in color and not with pictures of the components:-) The R’s are resistors, the C’s are capacitors, U1 is the amp chip, etc.

  77. ALRUI says:

    Any speaker experts out there? I have a nice 4″ Pioneer but its 4 Ohm. Not sure how it will work with the circuit seeing the specs state 6-12 ohm yet mentions changing C3 if using 4 ohm.

  78. Luckymat says:

    How many W has this speaker? And hot to increase power?

  79. Harnon says:

    Hello,
    I have 2 speakers, 8 W – 6 Ohms each written on.
    1) Does they match for this project ? Any mods to do for it ?
    2) For doing the stereo , should it be necessary 2 separate power sources or is it possible to use one and share it ? If yes, how ?
    Thanks for advice !

    1. ALRUI says:

      You would be fine with that since the LM386-4 is 1 watt output, also the one power source would be sufficent for powering 2 of these circuits.

      1. Harnon says:

        Thanks for quick and kind reply.
        Soldering iron will be warming this WE…

  80. Is it possible to add something like this:
    http://www.ebay.co.uk/itm/Rechargeable-Battery-For-CE-RoHS-Apple-MA005LL-A-400mAh-Li-pl-/300903003229?pt=UK_MP3_Player_Accessories_Batteries&hash=item460f37745d

    How could you add this to make the speaker rechargeable?

    Also where can you add a switch in the wiring to turn off completely even if a battery is still connected to stop killing the battery?

    1. ALRUI says:

      As for the battery rechargeable would be great but the problem is you would need a charging circuit or a quality external LiPo charger as LiPo batteries are extremely dangerous (explosion/fire hazard) when not properly charged! As for the switch just put a toggle switch in the – (black) line to break the circuit between the battery and ground.

  81. Novaorbitdragon says:

    Could I use a 4kohm resistor instead of a 10kohm for a 4ohm speaker

  82. Great project, I had a lot of fun making this. I have one problem though. If I wanted to use 5 smaller speakers instead of one big one, should I wire them in parallel or series? They are 4 ohm and 25 watt.

  83. gbelectronics says:

    This wouldn’t work in britain would it

  84. Hot website uncovers the critical info on the gucci and also the reasons you have to take action straight away. soldes longchamps http://www.rep-search.com/

  85. googolplex says:

    If I wanted to make a stereo box, would I need twice the voltage to power the two drivers and the two LM386 chips?

    1. ALRUI says:

      The voltage will remain the same, when you add more complexity to the circuit the only issue would be current draw but in this case youll be fine.

      1. googolplex says:

        Thanks a lot!

  86. Alasdair says:

    Hi I was wondering what the output wattage of the MonoBox is? I am interested in building it but not sure if it will be loud enough. Thanks.

    1. ALRUI says:

      It depends on which version of the LM386 chip you get is. According to the National Semiconductor data sheet for said chip the wattage is as follows:

      LM386N-1 0.325 watts, LM386N-3 0.7 watts, LM386N-4 1.0 watts

      I got the -4, with a small speaker in a small enclosed box it will be fairly loud given its size.

  87. Lah says:

    what about 12V amplifier? would it be the same?

  88. If I want two speakers in my box, do I have to make two circuit boards?

  89. […] built a simple amplifier using the following instructions off make.com (the instructions are for building an amplifier and speaker enclosure, I simply used the amplifier […]

  90. Havok says:

    Guys!, I thought i’d build this as it was useful for me. After looking at the schematic i found it confusing. So, Can any of you give me a ‘ready to transfer’ PCB layout. Any help would be appreciated. Thanks!

  91. Havok says:

    Could you guys give me a ready to transfer pcb layout.Thanks!

  92. Havok says:

    Could you guys give me a ready to transfer pcb layout.Thanks! Please, need it urgent. Need it by 1 week.

  93. Garnet says:

    Just finished my first mono box. I am getting sound that is very distorted and not loud. Does anyone have a suggestion to what is causing the distortion?

  94. Steve says:

    I am having the same problem as others – that after 50% volume I start to get distortion. I have played with capacitor values and that has helped some but no way do I get full volume without some distortion. Is there a fix or modification?

    1. ALRUI says:

      How many are having this issue, Im curious before I start my build.

    2. ALRUI says:

      Curious as to what vendors LM386 you guys are using as well as the dash # which designates power output of the devise.

    3. Charlie says:

      It might, just guessing here, have to do with the source. I noticed my iPod shuffle can play very loud and sound great, while my Android phone has distortion at higher volumes. I am going to try a headphone amplifier to see if it clears up the distortion from other devices.

  95. glory0712 says:

    Can somebody help me get the amplifier circuit board? i don’t know where i can get the right one…they don’t have it at radio shark…if anyone knows a website where i can get the right,

    1. alrui@earthlink.net says:

      Radio shack has them back in stock as of today (at least online) also mcr has them.

      1. alrui@earthlink.net says:

        Sorry typo MCM Electronics

  96. Eleeg says:

    On the schematic, pins 7 and 8 aren’t connected to anything. does this just mean they’re not being used?

  97. Joey says:

    The “parts” description tells about 3 or 4 different capacitor and resistor but in the video they use just a couple… how’s that??

    1. ALRUI says:

      In the text is a description of the options for a couple of the caps/resistors, likely the video shows the defaults only.

    2. ALRUI says:

      Anyone finished one of these up and posted results on YouTube?

  98. Joey says:

    Radioshack doesn’t ship to Europe… right? How can I do??

  99. Charlie says:

    My mono powered speaker box works beautifully, if I plug in an iPhone or iPod. Any other source, i.e. computer, non-iPhone, radio, record player (with headphone jack) does not play any music. No sound at all. Why would this work with Apple headphone jacks and not work with non-Apple headphone jacks? This is confusing and a little bit annoying. Any ideas out there? Thanks.

    1. ALRUI says:

      Hmm Im curious about this as well as Id like to plug in iPhone & guitar (through separate jacks). Anyone have an answer to this one?

    2. Charlie says:

      Not sure yet what happened, but I built two new amplifiers and they both work with all music sources, but, as in Animal Farm, not all sources are created equal. The iPod and iPhone have the strongest and almost distortion free signal that amplifies quite loudly. I’m really pleased. The other sources (portable radio, PC, and Android phone) all amplify but the signals are not as clear or strong (and give distortion at loud volumes). I am going to try a headphone amplifier to see if I can reach a state of happiness with every source signal. My original problem may have had multiple causes i.e. dirty jacks, not having volumes turned up enough, or a fluke in my construction (I’ll have to check this out when I get the boxes back from their recipients). I’ll post again if I come up with a definite cause.

      1. ALRUI says:

        Did you give some as gifts? Cool idea!

        1. Charlie says:

          I gave one to each grandson. I added the Maker Shed color organ kit (see my post earlier with the short youtube video).

  100. Landon says:

    Could this be made into a WIFI system by plugging the headphone jack into a WIFI enabled raspberry pi? Im curious about the power supply. Would this system work if the rasp was powered by a 5V micro usb?
    Great DIY by the way, very clear and understandable.

  101. Vesko says:

    I made it but if the bass is too much it starts to crackle please help

    1. ALRUI says:

      What speaker did you use as it probably cant handle to low freq’s well without distortion. Also try to adjust the bass/treble on your input device (iPhone, etc.).

  102. […] be a pretty good ‘intro to electronics’ project for me. Inspired by these projects: MonoBox, this one from Instructables, and this Australian […]

  103. ALRUI says:

    The Amazon link is for an amplifier that is already assembled using the LM386 chip. If you but that and add a speaker/enclosure, power & a signal you have basically the same thing as the instructions here make except you dont get the fun & learning of building it yourself:-) The project steps are at the top of the page. Hope this helps you.

  104. Daniel says:

    Thanks ALRUI… I plan on using both the pre assembled as well as building my own..

    I had asked about a pdf version of this build because I didn’t want to have to print it out to get over to RS..

    Thanks again!!

  105. ALRUI says:

    Yeah the way they have the “shopping list” set-up leaves a lot to be desired! There should be not only the links to RS but also a list one could print (or create a PDF of, etc.) that has all of the specs. & part numbers. I ended up buying my parts from Newark as several of the RS parts were out of stock online & the nearest RS to me is a 45 miles round trip since the one in town went belly up a few years back.