Remove these ads by
Step 1: Parts and schematic
Parts list:
B1 - 9 volt battery clip and battery
C1 - 4.7μF 16v capacitor
C2 - 100μF 16v capacitor
C3 - 470μF 16v capacitor
C4 - 10μF 16v capacitor
D1 - green diffused LED (just about any color/type will work)
J1 - ¼" (6.5mm) mono jack (guitar input)
J2 - 1⁄8" (3.5mm) stereo headphone jack (headphone output)
R1 - 1kΩ ¼-watt resistor
R2 -10kΩ ½ watt potentiometer
SP1 - 8Ω ½ watt speaker (2¼" diameter, from an old PC)
SW1 - DPDT "on-off-on" mini toggle switch
U1 - LM386N-1 low voltage audio power amplifier IC
Misc. - breadboard and breadboarding jumper wires (for optional Step 3), hookup wire (small-gauge stranded), small perfboard, solder, knob for R2
Sources:
The only really critical parts here are SP1 for it's diameter and SW1 because of it's special "on-off-on" function.
For SP1, you just need a simple 8Ω speaker - around ½ watt, and exactly 2¼" (60mm) in diameter. I found several of these in my parts box that were pulled from old PC's so it seemed to be a standard size for that application. If you don't have one handy, here are a few places to find them:
- Jameco #135765 (currently $1.59)
- Jameco #10840 (currently $1.95)
- All Electronics #SK-285 (currently $1.25)
For SW1, this type of switch can be easily found. You want to find a mini or sub-mini sized switch with solder lug (not PC-mount) terminals. Here are a few places I found a suitable model where I typically look for parts:
- Radio Shack #275-664 (currently $4.99 each)
- Jameco #21952 (currently $1.55 each)
- All Electronics #MTS-120PC (currently $1.50 each)
- Futurlec #DPDT101 (currently $0.90 each)
The rest of the components should be pretty easy to find wherever you usually buy parts, but here are some links to Futurlec:
B1 - (battery clip) #9VBATTCLIP (currently $0.10 each)
C1 - #C0047U50E (currently $0.05 each)
C2 - #C100U16E (currently $0.10 each)
C3 - #C470U16E (currently $0.12 each)
C4 - #C010U16E (currently $0.05 each)
D1 - #LED5R (currently $0.08 each)
J1 - #P065SCK02 (currently $0.75 each)
J2 - #P035SCK02 (currently $0.50 each)
R1 - #R001K14W (currently $0.10 each)
R2 - #POT10K (currently $0.55 each)
U1 - #LM386N-1 (currently $0.75 each)
My personal recommendation would be to bundle all the parts you can from Futurlec. It takes a few extra days to ship (from Thailand) but the prices are unbeatable. Their electrolytic capacitor pack (#ELEPACK) includes 100 pieces for $3.95. I can't say for sure what values are included in every pack, but the four values needed for this circuit were included when I bought one. They also have a 300 piece resistor pack too (#RES14WPACK) for $2.95, which makes them less than a penny each. Probably don't need that for this project, but it's a good way to re-stock your parts bins.
The schematic:
At the heart of course is the LM386 amplifier, which delivers decent sound with just a few external components. I used the "N-1" version of the chip. This amp delivers 250-325mW of output power, which is plenty for this application. (You could drop in an N-3 or N-4 version pin-for-pin to get either 700mW or a full watt of output power, but you'll need a speaker rated for the additional power - and I would not recommend using the amp for headphone output).
The circuit is designed to deliver the input signal from the guitar via J1 through capacitor C1 into the LM386's non-inverting input at pin 3. The inverting input at pin 2 is connected to ground along with the chip's ground pin 4. The audio output is delivered through capacitor C3 into DPDT switch SW1 which simply directs the amplified audio signal to either speaker SP1 or the headphones connected to J2. The other pole of SW1 acts as a power switch to the circuit, connecting the positive lead from 9V battery B1 to the chip's voltage source pin 6 as well as to the LED power indicator D1 through current-limiting resistor R1. Filtering capacitor C2 sits across the power supply rails. Finally, the RC series circuit of capacitor C4 and potentiometer R2 provides variable gain control for the amp. I found that with these values, I could get an output range from a really clean output into the headphones all the way up to a nice distorted overdrive into the speaker. If you need to experiment with any component values with your particular instruments, those will be the ones. I found with the guitars I worked with that it took a combination of guitar volume knobs and the amplifier's gain knob (R2) to get the right sound level, especially for comfortable headphone listening.
B1 - 9 volt battery clip and battery
C1 - 4.7μF 16v capacitor
C2 - 100μF 16v capacitor
C3 - 470μF 16v capacitor
C4 - 10μF 16v capacitor
D1 - green diffused LED (just about any color/type will work)
J1 - ¼" (6.5mm) mono jack (guitar input)
J2 - 1⁄8" (3.5mm) stereo headphone jack (headphone output)
R1 - 1kΩ ¼-watt resistor
R2 -10kΩ ½ watt potentiometer
SP1 - 8Ω ½ watt speaker (2¼" diameter, from an old PC)
SW1 - DPDT "on-off-on" mini toggle switch
U1 - LM386N-1 low voltage audio power amplifier IC
Misc. - breadboard and breadboarding jumper wires (for optional Step 3), hookup wire (small-gauge stranded), small perfboard, solder, knob for R2
Sources:
The only really critical parts here are SP1 for it's diameter and SW1 because of it's special "on-off-on" function.
For SP1, you just need a simple 8Ω speaker - around ½ watt, and exactly 2¼" (60mm) in diameter. I found several of these in my parts box that were pulled from old PC's so it seemed to be a standard size for that application. If you don't have one handy, here are a few places to find them:
- Jameco #135765 (currently $1.59)
- Jameco #10840 (currently $1.95)
- All Electronics #SK-285 (currently $1.25)
For SW1, this type of switch can be easily found. You want to find a mini or sub-mini sized switch with solder lug (not PC-mount) terminals. Here are a few places I found a suitable model where I typically look for parts:
- Radio Shack #275-664 (currently $4.99 each)
- Jameco #21952 (currently $1.55 each)
- All Electronics #MTS-120PC (currently $1.50 each)
- Futurlec #DPDT101 (currently $0.90 each)
The rest of the components should be pretty easy to find wherever you usually buy parts, but here are some links to Futurlec:
B1 - (battery clip) #9VBATTCLIP (currently $0.10 each)
C1 - #C0047U50E (currently $0.05 each)
C2 - #C100U16E (currently $0.10 each)
C3 - #C470U16E (currently $0.12 each)
C4 - #C010U16E (currently $0.05 each)
D1 - #LED5R (currently $0.08 each)
J1 - #P065SCK02 (currently $0.75 each)
J2 - #P035SCK02 (currently $0.50 each)
R1 - #R001K14W (currently $0.10 each)
R2 - #POT10K (currently $0.55 each)
U1 - #LM386N-1 (currently $0.75 each)
My personal recommendation would be to bundle all the parts you can from Futurlec. It takes a few extra days to ship (from Thailand) but the prices are unbeatable. Their electrolytic capacitor pack (#ELEPACK) includes 100 pieces for $3.95. I can't say for sure what values are included in every pack, but the four values needed for this circuit were included when I bought one. They also have a 300 piece resistor pack too (#RES14WPACK) for $2.95, which makes them less than a penny each. Probably don't need that for this project, but it's a good way to re-stock your parts bins.
The schematic:
At the heart of course is the LM386 amplifier, which delivers decent sound with just a few external components. I used the "N-1" version of the chip. This amp delivers 250-325mW of output power, which is plenty for this application. (You could drop in an N-3 or N-4 version pin-for-pin to get either 700mW or a full watt of output power, but you'll need a speaker rated for the additional power - and I would not recommend using the amp for headphone output).
The circuit is designed to deliver the input signal from the guitar via J1 through capacitor C1 into the LM386's non-inverting input at pin 3. The inverting input at pin 2 is connected to ground along with the chip's ground pin 4. The audio output is delivered through capacitor C3 into DPDT switch SW1 which simply directs the amplified audio signal to either speaker SP1 or the headphones connected to J2. The other pole of SW1 acts as a power switch to the circuit, connecting the positive lead from 9V battery B1 to the chip's voltage source pin 6 as well as to the LED power indicator D1 through current-limiting resistor R1. Filtering capacitor C2 sits across the power supply rails. Finally, the RC series circuit of capacitor C4 and potentiometer R2 provides variable gain control for the amp. I found that with these values, I could get an output range from a really clean output into the headphones all the way up to a nice distorted overdrive into the speaker. If you need to experiment with any component values with your particular instruments, those will be the ones. I found with the guitars I worked with that it took a combination of guitar volume knobs and the amplifier's gain knob (R2) to get the right sound level, especially for comfortable headphone listening.
Visit Our Store »
Go Pro Today »
If you haven't solved this on your own already, I would start by double-checking for good connections throughout the circuit, whether you have breadboarded or soldered it. If you have extra parts, try replacing C1 or C3 to see if that helps.
"Finally, the RC series circuit of capacitor C4 and potentiometer R2 provides variable gain control for the amp. I found that with these values, I could get an output range from a really clean output into the headphones all the way up to a nice distorted overdrive into the speaker. If you need to experiment with any component values with your particular instruments, those will be the ones. I found with the guitars I worked with that it took a combination of guitar volume knobs and the amplifier's gain knob (R2) to get the right sound level, especially for comfortable headphone listening."
Note that the circuit is designed to give a little overdrive (distortion) at the upper range of the gain pot, but it should cut the signal off completely at the lower end of its range. This amp will behave differently with different instruments at its input.
Try adjusting the volume knob of the guitar, and also different values for C4 and R2. You could swap in another 16v capacitor value anywhere from 1μF to 100μF for C4, and try a different pot for R2 anywhere from 5K to 50K.
http://www.instructables.com/id/LED-VU-meter-that-dances-to-computer-music/
http://www.instructables.com/id/LM3915LM3916-VU-Meter/
I've made meters like these before, but I haven't done so recently so I haven't actually connected one to one of these amps.
Then, here's it:
Putz! I haven't realized the LED, I messed up something so easy! xD
Thanks!
I think now it's right, I'm just waiting for the pieces, to start assemble it! ^^
Thank you again!
sorry for the bother. ^^
I'm preparing the materials to start doing this, but I would like to make an amp more simple based on yours, with just an ON/OFF button and without the headphone output, like the step 6, but with the speaker instead the headphone.
please, can you take a look on my schematics, and see if they're correct?
thank you!
The input side of your amp circuit should work fine, but the lower-right area of the schematic needs a couple adjustments. I think you may have been confused by the wiring of the DPDT switch SW1 in the original schematic.
Here's what you need to do:
1. Connect the cathode of your LED connected to ground instead of to the amplifier output.
2. Pin 6 of the IC and the (+) terminal of C2 need to be connected to positive side of the power supply. A connection between S1 and R1 would allow S1 to turn your amp on and off.
I think your best bet would be to first connect SW1 and SP1 only, and make sure you get audio at the speaker when SW1 is switched to that side (and no audio when it's flipped the other way).
Once that's working, solder your leads to J2 and test the headphone output by temporarily connecting those leads to the circuit (touching the wires to the correct points in the circuit by hand). The 5-pin jacks can be tricky, so this "trial and error" before you make the final soldered connections should help.
I need a little more help....
The 1/4 mono plug I am using has 3 pins. I am using trial and error to connect 2 pins together. Is this correct or should I find a plug with only 2 pins?
I also have a 1/8 stereo input which has 5 pins I have pictures of both. Do I just need to figure out how to short some pins together or am I way far off and do I need to purchase a different part?
The 1 k resistor I am using is a 1/2 watt. Your list calls for a 1/4 watt...Is mine okay?
I am breadboarding this project but am having difficulty. My led wont light up and it almost did for a second but went dim very quickly. Could this be from my 1/2 watt resistor?
I am not asking for detailed list of further instructions but would appreciate a little insight when you have the time.
Thanks
Tip: Lable one of the pins with a sharpie - a dot will do.
Ive actually figured some things out with a little help.
For the 1/4 mono jack in the right hand pick, I will use the two right pins only and not short any pins. The pin on the far right is connected to the insert hole which I learned is the ground and the middle pin is connected to the prong. The pin on the left is connected to a tab which is connected to the prong until a "male" plug is inserted. I will leave the left hand pin alone.
As for the 1/8 stereo plug in the left hand picture, I was told to connect the 4 left most pins together and together as a whole use this for positive and to use the far right pin as the negative. I will attempt to do this and hope it is correct.
I still have a major issue going on and can use some direction for help.
For now I have everything wired to spec except for the 1/8 plug. I have the negative from speaker going directly to breadboard instead of through 1/8 jack first. One lead from my switch is also not connected to the 1/8 plug. I assume this should be fine to test the 1/4 plug for sound.
Here is the problem
My led wont light up right away and only really does when I play the guitar. Every time I pluck some strings it lights up a little but then dims down when I stop strumming.
The other problem is that I have a lot of feedback all the time. Just turning the system on gives noise out of the speaker. I turn the pot down and it does go quieter but not really. This all happens with and with out a guitar hooked up. When a guitar is hooked up, the sound of playing is heard through the speaker but barely and is accompanied by the same unwanted noise as when no guitar is hooked up.
Any ideas?
also just to be clear the only differences in parts is:
1k 1/2 watt instead of 1/4 watt
all caps are 16 v except the 10 microFarad is 50v and the 4.7 microFarad is 25v. Could any of these parts be of fault?
I have success. I came to the conclusion that the breadboard itself was presenting me with problems. There are many ways for wires to be loose and I believe a lot of my feedback was caused some how as well.
I assembled everything on a circuit board and have no problems at all. My led works all the time. There must have been loose connections on the breadboard.
I get no feedback anymore either. I know a breadboard can cause unwanted capacitance so maybe this was to blame.
Anyhow this was a great instuctable. I learned a lot on this build. Thanks you very much for your time.
I hope I am not breaking any rules by leaving such long posts and hope someone else can learn from them.
Must have done something wrong
Is there some components such as capacitors or resistors that I could change out for different valued ones to raise the threshold at which the distortion comes in at?
And is there a way of 'softening' the distortion a bit, maybe smoothing it out a little?
Side note: I get a radio hum/ crackle when running it off a AC/DC wall wart that I do not get from the battery, Is this because the power supply isn't shielded or something? I've read that there are special audio grade DC transformers?
You might want to try Rev 2.0 if you're looking for a smoother sound - the overall gain is a lot lower, so you could send a larger signal from your guitar and it should distort less. You could also try substituting C1 and C4 with different capacitor values (a little larger for C1, a little smaller on C4). Try them one at a time to see if you're going in the right direction. Hope that helps.
Also i was wondering why the schematic calls for a linear pot, almost all audio electronics i've seen are log because the human hearing is nearly logarithmic.
Cheers
Looking at this thing, Im thinking that what would be really helpful is a step-by-step instruction guide for this thing, or at least some instructions on what goes where, and to what pin on the IC, etc. I only say this because i would like to try to use this with a Scout troop to teach Electricity merit badge.
Sounds like a really cool thing though dude! Keep it up!
Here's an example that's under $10 and includes what looks like a good quality PCB - http://www.vakits.com/product_info.php?cPath=43&products_id=1481
i just tried building off your schematic and am having the same problem as a lot of the guys in the thread who you haven't responded to.
I quadruple checked my work and still can't get the pot to effect the volume.
Thanks for the awesome project! I'm breadboarding it right now, but am having some trouble...
My 1/8" jack has three lugs: two are on one side, and one is on the opposite side.
http://imgur.com/6UHGL
^^^ This is how I wired (sorry, bad picture). I have the black wire from the speaker wired to the solitaire lug on one side, and then I wired the blue wire from the switch (I used the same colored wires as you) to BOTH the lugs on the other side. When I plug the headphones in I only get mono.
Also, I'm getting severe distortion regardless of the volume of the input. Also, my LED only lights up when I have the potentiometer wide open, or if I touch the 1/4" input.
I'll keep messing around, but I figured I'd ask to get some ideas.
Thanks!
It is hard to see the headphone jack clearly, but for most of these 1/8" jacks there should be a way to get both channels going. It may be useful to plug your headphones into it and then use some trial-and-error (apart from the amp circuit). Use a known audio source as an input - this could be two wires coming from a plug that's plugged into a headphone output, or even speaker wires from one channel of a stereo receiver (keep the volume really low if you use speaker wires!). Try different combinations of the two wires briefly connected to the three terminals until you have audio coming to both sides of the headphones.This way you can make sure the headphone jack is good (or not) before you put it back into the amp circuit.
As far as the distortion - that could be a lot of things but I would start by double-checking all the wiring, especially to make sure that all the ground points are connected to ground.
Good luck!
I'll keep tinkering around.
Thanks!
I have a question about the potentiometer. In your diagram, your potentiometer has three terminals. Mine has five. What should I do if I don't want to purchase another potentiometer?
See if this helps. You'll need to use an ohmmeter and some trial-and-error to identify the correct two terminals. Connect the ohmmeter across any two terminals and see if you get a resistance reading between 0 and 10,000 ohms. If you do, rotate the knob to see if the resistance changes. When you find two terminals that work this way you're all set.
Note that two different sets of terminals may work, and the resistance may increase and decrease by turning the knob in opposite directions. You'll want to use the terminals that decrease the resistance (and thus increase the gain) when you turn the pot clockwise.