loading

You love to play guitar and you love your amplifier collection.

But, what if I told you that you could make the most unique guitar amplifier known to modern man. From the hills of North Georgia comes the Jelly Amp. Sure there may be some commercial examples of this available but by following this Instructable, you can easily make your own. Not from a kit, but from scratch. Just like MeeMaw makes her prize pies: not from a Betty Crocker kit from the Piggly Wiggly like those city folk, but from the sweat of her dag-nammed blessed little wrinkled brow.

This project has a very simple design. The amplifier is a version of a "Little Gem" amplifier from the brilliant Runoffgrove's runoffgrove.com site. It is based on a 1/2W LM386 audio amplifier with a fixed gain and full output volume. There are no on board controls. The volume and overdrive are controlled by your guitar's volume and tone controls. There is no on/off switch neither. The amplifier turns on when you plug your guitar cord into the input jack. It's powered by a 9V alkaline battery that sits inside the jar.

The sound comes out of a mylar speaker in the lid. Also there is an output jack that will allow you to connect your Jelly Amp into your favorite "big boy" speaker cabinet. It will drive anything from 4 ohms to 16 ohms. Will it blow out the stadium? No ya big dummy its only half a watt. Is it great to practice with? You're darned right it is. At full volume it has just the right amount of distortion. It's a great little practice amp and a great conversation starter.

So lets get ready to build one.......

Step 1: Safety and Parts List

First a word about safety. Don't be an idiot. This project involves drilling holes in a glass jelly jar. You can get hurt. You can put your eye out. If you're an idiot, don't attempt this. I can't be responsible if you get hurt. Wear safety goggles. When you're working in the shop leave PeePaw's other mason jars alone. This ain't the time to be fooling with his "medicine".

So here is the parts list:

1 8oz (half pint) regular mouth mason jar, or jelly jar. You can get these from Walmart or any other place that sells canning supplies. You want to get a plain jar. No fancy quilting or writing on the glass. Take MeeMaw with ya. She'll know what you need.

1 3/8" diamond hole bit

1 9V alkaline battery

1 9v battery snap connector cable

1 mono 1/4 inch jack with nc (shunted) switch ( I like the Switchcraft 12A)

1 stereo 1/4 inch jack ( Switchcraft 12b)

1 LM386 amplifier. Any version is fine, I like the LM386N-4, but I'm kinda funny that way.

1 66mm Mylar Cone Speaker (MCM #SR00187)

1 Red LED

Resistors:

1 470 Ohm

1 1K Ohm

1 10 Ohm

Capacitors:

1 100nF

1 47nF

2 220uF

Protoboard. I use a Radio Shack DIP protoboard (276-159B). It keeps things neat. But any type of protoboard is fine as long as it fits in the jelly jar.

Soldering iron and solder

Double sided tape

Epoxy

Step 2: Schematic and Amp Board Fabrication

Assemble the amp board according to the above schematic. I have attached a photo of my protoboard build so that you have an example of a component layout that works. Any protoboard will work. If you want to get fancy, you can design a fancy board on the computer and send it to a foreign land to be magically fabricated.

Lets explore the pinout of the LM386 a bit more shall we?.....

Pin 2. Inverting input. The signal from the guitar is fed into pin 2 through a 100nF cap that eliminates any DC signal. You can play around with the capacitor value. 100nF works well for an electric guitar. The original Runoffgrove schematic used a 10nF cap. I like the sound of the 100nF better. But play around and see what you like. Some of the later mods used a 47nF cap just to confuse the issue more. But dammit I like the 100nF.

Pin 3: Non inverting pickup. This pin is grounded

Pin 4: Ground. This pin is grounded

Pin 6: V+. We are using 9V for this project. In order to reduce oscillation in the amplifier, a 100uF or 220uF capacitor is placed across the negative and positive supply voltage. Ideally this should be as close to pin 6 as possible.

Pin 7: This pin is used to reduce power supply noise. I like to live on the edge. Do you? Go ahead. Leave this pin unconnected. I did, but thats just how I roll. If you want to be a baby about things, put a 100nF cap from pin 7 to ground. Wimp.

Pin 5: Output. The output of the amplifier goes though a Zobel RC network for stabilization. Don't mess with it. Greater minds than ours have worked this out.

Pin 1 and 8: Gain. Leave these pins disconnected for minimum gain. Connect a 10uF cap between the pins for max gain. Mid level gains can be had by placing various resistor values between the pins. The art in choosing the right resistor values is to have enough gain to produce a pleasant overdrive but not make this amp into a screeching harpy. I like using a 1K resistor. When the guitar's volume control is turned down, a fairly clean sound will be produced. With the volume all the way up, the amplifier breaks up nicely. Experiment to find out what you like.

Step 3: Marking and Drilling the Jar

Now is the time to drill the holes for the input jack and output jack.

Let's measure and mark the places where you will drill the holes. My jar had a circumference of 25cm. That means the holes should be 12.5cm apart. Also they worked best about 3.5 cm from the bottom. I wrapped the jar in masking tape and marked the drill sites.

I used a 3/8 (10mm) diamond glass hole bit to drill the holes. Don't scrimp on this. Get a good one. You can use it in the future to drill holes in Bud bottles to make you some Christmas lights for PeePaw's porch. He'll love them. Believe me.

When you drill into glass you have to keep the bit cool by submersing it in water. I use plumber's putty to make a well around drill bit. Go slowly. Use light pressure and clear the glass dust frequently. A drill press is best for doing this.

When you are done you will have a nice clean hole as shown above.

Step 4: Connecting the Input and Output Jacks

The input and output jacks are wired as shown above

Step 5: Assembly and Finishing.

Once you have everything assembled, use double sided tape to mount the amp board to the bottom of the jar.

Feed the input and output jacks into their holes. You can use some epoxy to help secure them and ensure that the nuts don't loosen with use.

Snap the 9V battery into its strap and place it beside the board in the jar. The battery will wedge in the jar and won't flop around. If it flops in your jar, you can use a little double sided tape to secure it to the jar wall.

Solder the speaker to the output jack and put it on top of the jar. Use the jars retaining ring to screw the speaker in place. You won't need the jar's metal lid. Give it to MeeMaw. She'll thank you.

If you want to mark the input jack, borrow MeeMaw's red nail polish. You know the one that PeePaw says makes her look like a Paris Street Walker (the kind he likes). Put a red dot just below the jack.

If you've done everything right when you plug a guitar into the input jack the red LED will light up and sweet sweet music will come out of the speaker. If you haven't done everything right then it'll be time for some troubleshooting. Read this Instructable over and over again until you find the errors of your ways and you're set back on the path of righteousness.

When you plug a speaker cabinet into the output jack, the built in speaker will turn off and sound will now be coming out of the external speakers.

Have fun building this one guys!

And now for your enjoyment, above is a link to a short video of a guy playing this very Jelly Amp to the admiration of all those around him.

Step 6:

****** UPDATE ********

For this of you with build questions, I have made a new Instructable showing how to build this circuit on a protoboard. The link is here:
https://www.instructables.com/id/From-Schematic-to-...

There is a companion Youtube video showing the entire build. The link is above.

Good Luck and get building!!!

<p>I made 2 already and they're awesome!! </p><p>Random question, anybody knows how would it sound for a bass guitar? I don't have one to try and a friend wants one for it. Thank you!</p>
<p>The input cap is should be fine for a bass. You might want to play with the gain resistor in order to keep the bass &quot;clean&quot;</p>
Maybe I can substitute the output jack for a potentiometer? Which maximum resistance value would you put? I don't have components around to try.<br>Thank you in advance.
<p>Thats a great idea. You could use either a 1K or 5K pot. Id try the 5K and if there isn't enough variability then go down to the 1K</p>
<p>Cool, I'll do that! I might just put a pcb pot inside and adjust it until the sound is clear at full volume with the bass. Thank you!! </p>
<p>Thanks for making this. I just saw www.thejamjaramps.com and knew it had to be super easy to make, just wasn't sure what ic they were using. Totally want to build one of these now.</p>
Yeah. Like MeeMaw always said. Don't buy the biscuits when you can make the biscuits But when you aren't expecting company it's nice to know that can of biscuits is there.
I FINALLY FINISHED IT! <br><br>Thanks for posting this original Instructable and especially for the follow-up instructions and video. I was able to complete it with the 2nd instructable alone but the video was really helpful to verify that I was doing it correctly. <br><br>I sure hope my son loves it as much as I do!<br><br>Thank you NizzyAmps and have a Merry Christmas!!!
Excellent work! Looks great!
This project just one a first prize on Instructables!!! Thank you guys! I appreciate the support from all of you in the Instructable community.
Congratulations! You definitely deserve it!
<p>I have made a new Instructable showing how to build this circuit on a protoboard. The link is here:</p><p><a href="https://www.instructables.com/id/From-Schematic-to-Protoboard-Building-a-Simple-LM3">https://www.instructables.com/id/From-Schematic-to-Protoboard-Building-a-Simple-LM3</a></p><p>There is a companion Youtube video showing the entire build. Its kinda long but if you need a step by step this is the place to go:</p><p>https://youtu.be/7qR-CQzQiWo</p>
Ok, I will check it out! THANK YOU!!!
<p>Speaking of 'woefully ignorant&quot;... </p><p>I have all my parts but I just have absolutely NO CLUE where to start. I have been watching videos and reading articles to learn how to read an electronic schematic but I am completely lost. I have also been staring at the photos of your board and the others posted here but still just clueless and have no idea where they connect on the backside of the board. </p><p>Can anyone suggest a good starting point for me to learn the basics on how to read the schematic or where to start on building this board? I REALLY want to build this for my son but the only thing I have a shred of confidence about is drilling the hole and screwing on the lid ring - beyond that.... deer in the headlights....standing on the yellow divider in the middle of a rainstorm....</p>
Where are you located. The reason I'm asking is that there is a British company that makes a kit version of this type of amp. They have commented on this Instructable. That may be your best bet and it will help you learn about schematics and guaranty you success. Also if you would like I could make a step by step Instructable on how to wire the amp on a protoboard.
Hi, I am located in the Seattle area. Yes, I saw their post with the weblink and I am not opposed to ordering from overseas but it just kind of felt like I was cheating or something? More like I was just assembling something vs actually building it - does that make sense? Kinda silly since I am basically just assembling anyway by following your instructions... I dont know. <br><br>That would be great if you were willing to provide another step by step but I dont want to create more work for you - you have been really great responding to questions from everyone here. I dont mind doing the 'legwork' and research to learn on my own I just feel like I dont know where to start and letting it intimidate me. I did order a little 'DIY circuit kit' on Amazon hoping that would give me a little experience to get going, hopefully it will be here in a day or two. Plus I watched a couple videos tonight after I commented so with those and your advice to go one step at a time and test along the way I am feeling a bit better. <br><br>So I will keep hammering away to learn and then if anything just experiment since I did buy spare parts. And any extra info you are willing to provide is MORE than welcome! Thank you!!!
Ok in the next couple of days I'll do a general Instructable on going from schematic to protoboard. I'll use this amp as the example circuit. What board did you use? The RadioShack DIP protoboard or just a plain protoboard. I'll do one of each but will do the board you are using first
That would be great! Im in the same boat, got everything ready and was going to figure out how to make the board this weekend but if you make this instructable it will save me hours of frustration for sure. By the way I live in New Zealand and got all the parts from mouser.com and it was a cool experience, recommended for anyone who want to get everything from one place, the only issue was deciding about the resistors as I had no idea about the wattage so I got 1 and 2 watt resistors but they look quite big
<p>I have made a new Instructable showing how to build this circuit on a protoboard. The link is here:</p><p><a href="https://www.instructables.com/id/From-Schematic-to-Protoboard-Building-a-Simple-LM3">https://www.instructables.com/id/From-Schematic-to-Protoboard-Building-a-Simple-LM3</a></p><p>There is a companion Youtube video showing the entire build. Its kinda long but if you need a step by step this is the place to go:</p><p>https://youtu.be/7qR-CQzQiWo</p>
<p>put me on the list for the step by step deal. I put mine all together and the only sound that came out was the thud-thud-thud of my hitting my head on the wall in frustration.</p><p>I am no dumb bunny, but I don't have as much experiential knowledge as I think I need for this really great and, if I may say, adorable project. </p>
Ok I have a step by step video I shot this am. I am making another Instructable on step by step how to go from schematic to a radio shack dip board build of this. Same way applies to regular protoboard but I'll prob do one with plain protoboard. Hopefully I'll have it up tomorrow. I'll post here and give links
<p>yay! Looking forward to it. </p><p>Will Mee-maw and Pee-paw be making an appearance!??</p>
<p>I have made a new Instructable showing how to build this circuit on a protoboard. The link is here:</p><p><a href="https://www.instructables.com/id/From-Schematic-to-Protoboard-Building-a-Simple-LM3">https://www.instructables.com/id/From-Schematic-to-Protoboard-Building-a-Simple-LM3</a></p><p>There is a companion Youtube video showing the entire build. Its kinda long but if you need a step by step this is the place to go:</p><p>https://youtu.be/7qR-CQzQiWo</p>
<p>Cool! You are SO AWESOME! Thank you NizzyAmps! YOU ROCK!! </p>
It also goes step by step how to troubleshoot each step of the build
<p>I have made a new Instructable showing how to build this circuit on a protoboard. The link is here:</p><p><a href="https://www.instructables.com/id/From-Schematic-to-Protoboard-Building-a-Simple-LM3">https://www.instructables.com/id/From-Schematic-to-Protoboard-Building-a-Simple-LM3</a></p><p>There is a companion Youtube video showing the entire build. Its kinda long but if you need a step by step this is the place to go:</p><p>https://youtu.be/7qR-CQzQiWo</p>
Thanks For your help! I bought the Radio Shack board that you listed. I bought everything exactly as listed.
<p>I have made a new Instructable showing how to build this circuit on a protoboard. The link is here:</p><p><a href="https://www.instructables.com/id/From-Schematic-to-Protoboard-Building-a-Simple-LM3">https://www.instructables.com/id/From-Schematic-to-Protoboard-Building-a-Simple-LM3</a></p><p>There is a companion Youtube video showing the entire build. Its kinda long but if you need a step by step this is the place to go:</p><p>https://youtu.be/7qR-CQzQiWo</p>
<p>I am part way through the project. Going well, but, for the woefully ignorant, where do the ground wires go? It's been a long time since grade 9 electricity class. And then we were doing basic household stuff like lamps and wall switches. Way back when, the ground went to, well, the ground. </p><p>Where do I put those little wires with the arrow on the end in the schematic.</p><p>'Scuze me while I adjust my dunce cap...</p>
<p>All the grounds can go to a common point and then to the black (-ve) lead of the battery </p>
<p>thanks!!!! </p>
<p>www.thejamjaramps.com</p>
<p>Hi! This is awesome. I've sourced all the materials but I can't find a jar like yours here in the UK. Could have a look at this for me, please? </p><p><a href="http://www.lakeland.co.uk/70511/6-Ball%C2%AE-Mason-Quilted-Crystal-Small-Glass-Jam-Jars-%26-Lids-240ml" rel="nofollow">http://www.lakeland.co.uk/70511/6-Ball%C2%AE-Mason...</a></p><p>I have found similar jars to yours but I'm afraid the speaker won't fit properly.</p><p>Thanks in advance. </p>
<p>I am going to pick up a couple jars tomorrow so I can start my build as soon as the amp module arrives - if you are interested I can pick up one or two extra for you and ship them to you if you want to pay for the cost. Actual cost, no added fees. Just let me know.</p>
I'm interested. The minimum I can buy here is 6. I'm up to buy 2 off you if the price postage is not ridiculous. I bought the speaker already so I can go around London checking the price.
Okay I picked up a couple half pint jars with no writing or quilting on the side. They were only 1.49 each but they had the wrong kind of lids so I'll have to swap them out with some I have here at home. But if you want to send me your address I will see how much it is to ship them off to you. I'll probably just cover it for you as long as it's not too crazy
<p> okay I will let you know once I get back from the store later today and then figure out a way to exchange info with you so I can get a quote on shipping.</p>
The 66mm speaker will fit a standard Mason (or Ball) jar mouth. In order to drill the holes you need a jar that has smooth sides. So the one you linked won't work because of the quilted sides. You can go with a bigger jar if you can't find the half pint size - no big whoop. I'd think that with the bigger size the sound prob would be even better. You can build it in a bigger jar then transfer it to a smaller when you find one.
Thank you for your reply and sorry for my delay. I didn't want to make it bigger but I will if I have to. I might buy the next size speaker and check other jars.
<p>Guys. I made an error in the parts list. The output jack is a 1/4&quot; mono switched jack. I mistakenly gave the wrong Switchcraft number. It should be a 12A switch. </p><p>I have corrected the parts list and have come to terms with my short fallings as human being.</p>
<p>Dang it - just got most of parts delivered today and now see I ordered the wrong switch! Great, there's $1.49 down the tube!! HAHAHA KIDDING! Thanks for updating with the correct info - I am still waiting for the LM386 since the place I ordered from was out of stock so I have time to get the correct switch. Thanks again and I will share it here once I am done. </p>
Yeah, I had a brain fart. Let me know how it turns out. Post some pics!
<p>I haven't built anything since 1998 when I was an electronics student. This really got me excited. LM386 was such a common IC back then. Still is as far as I can I see. It'll sound amazing with my Stratocaster.</p>
<p>So I tried to build it today and Im not sure if it is just that Im too much of an amature to tackle a project such as this or what. I actually bought the pcb but was a little confused about how to arrange it so I tried to put it together on a breadboard first. something is wrong and Im not sure what :( I didn't buy the speaker yet but most of the other things I had already from my arduino projects. I can hear the speaker come on when I turn it on and the red LED turns on :/ the blueprints were a little bit of a struggle for me but I thought I had it all figured out till I plugged it in and didn't hear any of the sound from the guitar coming from the speaker itself.</p>
<p>I forgot to say that i do have a speaker just not the one you use, this was just something out of the scrap pile this is an 8ohm 1 watt speaker</p>
The speaker specs are fine. If you can do arduino, you can do this one. When I look at your breadboard photos everything looks organized well. I think you just have some things hooked up wrong.
Ok. So. Two things I see wrong off the start. You have both ends of the input cap and the input plugged into pin2. You have to chain it across a couple of rows. Input to cap, cap to pin 2. <br>Your output is wrong. I don't think you have the 10ohm resistor plugged into pin 5, I think you're a row off (unless there's jumpers I'm not seeing). Anyways start minimally , test, and then build up from there. Start with power to pin6, 3 and 4 to ground speaker directly to pin 5 and ground. Add 9v, the speaker should pop. Then touch a metal screwdriver to pin 2, it should buzz. If not your chip is shot or in upside down. Then add the guitar input. If that works add the caps and resistors to pin 5 and add speaker. If that works, add gain resistor to pin1 and 8. If that works add the output jack and power filter cap. You should be good to go. Let me know!!
<p>that hole in the glass is what made me open this instructable. That is just cool, very very cool</p>
Thanks!
<p>The Jelly rocks</p>

About This Instructable

31,526views

299favorites

License:

More by NizzyAmps:Azurophone - A marvelous Steampunk Bluetooth Speaker From Schematic to Protoboard - Building a simple LM386 Guitar Amp on a DIP Protoboard DIY Jelly Jar Guitar Amplifier : The North Georgia Jelly Amp 
Add instructable to: