Portable Amplifier




Introduction: Portable Amplifier

So you're trudging through the woods, just you, your guitar, and your amplifier. Suddenly, a large bear approaches and you have no option but to shred him with your insane guitar skills! (running is not an option, as everybody knows that you never run from a bear, you fight him)

Unfortunately, there are no power outlets within sight! Steeling yourself for your grisly demise, you try to play a song acoustically.. but it's not loud enough. As the bear reaches over you with his jaws, you wake up. And are aware of the need for a portable amp. But, since you are a musician, you are obviously at poverty level and can't afford a small portable amp. So what do you do? You build one, for free of course, out of everyday parts.

Step 1: Collect Your Materials.

For this project, we will actually be using an Ibanez bass amp, and a bass guitar (my electric guitar isn't in yet, and the amp is obviously far too big to be portable, and this was just laying around).

Also, please keep in mind that this is a simple proof of concept project (proof for myself), and is in no way safe, complete, stable, smart, etc.

Basically, what we are going to do, is take this combo amp, and run it off some batteries, to make it portable. Why? Read the intro ;)

So what you need (and you should be able to find this anywhere in your house, friend's house, roommates gym bag, etc.)

2x9v batteries
2x9v battery clips
Wire (thicker is better, try 10awg)
Alligator clips (preferably 4)
Switch (SPDT)
Duct tape

Step 2: Wiring Things Up.

Once you've collected all your materials, go ahead and dismantle your entire amp. There are lots of screws, if you don't know which ones need to come out, take them all out. Just make sure you keep them separate, so you can put it back together later if you so choose.

Now, this amp in particular, takes a 120V current from the houseline, and steps it down to 13v for use with the amp. However, I am lazy, and don't really care what happens to this amp, so we're just going to completely bypass the stepdown converter, and hook up a sheer 18v directly to the mainboard. It's all solid state, so the worst that'll happen is a battery might explode, or you'll burn out the ICs. Hope you don't want this amp anymore.

So, basically, what we'll do, is wire the two batteries in a series, attach the negative to the mainboard, and the positive to a switch (because we're bypassing the built in switch). And that's pretty much it, as far as wiring goes. To wire two batteries in a series, attach one positive terminal to the other's negative, and then use the free positive and negative terminals to attach to your actual destination. I find that the little 9v battery clips are the easiest way to do them, although I could only find one of them when I did this project.

Step 3: Stick It All in There.

Now that you've hopefully gotten it all wired up, turn it on and give it a test run. Due to the increase in voltage, you'll have a nice little distortion effect. If you have everything working correctly (the little blue LED in the front turns on for me), then go ahead and stick it all in the case (or build your own!).

That paper towel is down there only to insulate the connections from touching the case and shorting out. Totally optional, if you're good at insulating your connections individually. Obviously secure everything with duct tape, and jam it all in there, making sure to reconnect the speaker.

Step 4: Go Shred!

Now that you have it all back together, attach a strap, or a belt clip, or a belt, and take it out and show your majesty over all things with ears!

Congratulations! Now, make it better. Because this is just a quick, 20 minute project that I threw together in my free time.

Some things to do better:

Either use exactly 13v in batteries, or get a stepdown converter.
Make it so that everything fits.
Use the built in switch.
Work on extending the battery life.

I have no idea how long the batteries last, but obviously don't expect to be playing any concerts or shows with this setup.



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    52 Discussions

    To be honest, I'm amazed two PP3 batteries would power this amp at all! The standard Alkaline model is specc'd with about 500mAh capacity and they're designed to discharge over 20 hours, giving you 25mA draw. At 18v that's almost 0.5 watts for the whole system. If you try and draw at 100mA then you'll get maybe 1 hour out of the batteries and they'll be burning hot. Even that will only get you 1.8W. I'd switch over to 3 4.5v 4Ah Alkaline lantern batteries. Drawing at their rated current of 200mA, you'll have almost 2.5W to play with and the power will last for over 10 hours. Also they're not too heavy and you're not messing around with Lead-Acid or Lithium.

    Also. Little deer feeder batteries are light.

    12v battery works better. Or maybe a voltage regulator.

    Hello again :) Something that has been confusing me: Would it simply not be easier to have, let's say a 12V Lead Acid battery (from a car, maybe) and simply strip a male computer cable (the end where it plugs into the power supply, which I believe in America is 2-prong 120V) and attach some alligator clips to it and plug the other end (when you want to plug your amp in) into the power feed of the amp?

    10 replies

    the problem there is weight. An amp can be very dense. (high weight to volume ratio) The same can be said for a car battery. So the weight of the car battery would easily double the weight and volume of the amp. That would not be conveniant.

    That is fair enough then. But would it still be possible? And how about using a really small car battery?

    It would work but I have never seen any small car batteries. I had a better idea though. I saw someone say somewhere that they had a circuit that would switch the power source to the next battery when the first one got too low. I thought it should be combined with a set of rechargable 12v camera batteries. Total price equal to a car battery but with longer battery life and no replacement costs within the near future.

    use a small sealed lead acid battery like what is used for backup power in an alarm system. I have some 12 volt 7AH batteries and they only weigh about 5 pounds.

    Thanks to you, i can impress chicks ANYWHERE now! nice instructable dude, and ill thank you ahead of time in case i ever get into an encounter with a bear!

    Legenary intro to the instuctable! I have to say that I am a musician along with several friends of mine and we are all at poverty.

    Dude, nice intro, that cheer'd me up! :D lol

    Maybe you could try using rechargeable batteries, and when the amp is plugged in, have the batteries charge. Perhaps you could also make a bypass switch, that, when plugged in, will let you switch between charge and battery bypass... hmmm. My old 15 watt amp is 500 miles away, when I get it back I'm definitely going to try that. Also, nice instructable, if I had a nickle for every time I've had to fight off a bear with my guitar...