When I first came across the tiny 2.5 cm x 3 cm "PAM8610 stereo mini class D digital power amplifier board 2 x15W" - around USD 5.00 on Ebay, I just had to have it.
It turns out that the 2 x15W is only possible using 4 Ohm speakers and a small heatsink on the IC. I don't have 4 Ohm speakers so I settled for 2 x 10W with my 6 Ohm speakers.
The Class D amplifier has received a lot of negative press from "serious" listeners, but to my low-spec ears it sounds great (and loud!) especially with good sized bookshelf speakers and an MP3 player with a built-in graphic equalizer and various environment settings.
Using an MP3 player also means that you don't need to have bass, treble and balance controls on your amplifier - just a volume control.
Since the wiring-up is so simple, I thought it would be a great medium level project for beginners.
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Step 1: Getting the Parts Together
The parts required are as follows:
- 1 pc Plastic Box. Mine is approx 8cm x 5cm x 2.2cm (31/8" x 17/8" x 7/8")
- 1 pc PAM8610 Digital Power Amplifier Board 2 x15w
- 1 pc 50K + 50K Dual Potentiometer
- 1 pc Knob for the above potentiometer - colour to suit your theme.
- 1 pc SPDT (Single Pole - Double Throw) Switch
- 1 pc 3.5mm Panel Mounting Stereo Audio Jack Socket
- 1 pc Panel Mounting DC Jack Socket
- 2 pcs 10uF 25V electrolytic capacitors - the smaller the better
- 2 pcs 2-terminal or 1 pc 4-terminal Interlocking Screw Terminals
- 1 pc 3mm Blue LED (or other colour depending on your design theme)
- 1 pc 4.7K 1/8W resistor (current limiting for the LED - more details in the attachment)
- 1 pc 12V 2A AC Adaptor or wall wart - more details in the attachment.
- 1 pc diode 1N5401 or 1N5822 (optional)
Besides these you will also need multistrand (7-strand) hook-up wire (various colours) for the interconnection of the components.
Attached is a PDF with very detailed explanation of each of the parts in the parts list. I wrote this mainly for beginners, so if all you need is the parts list, you can skip most of it and just read the part on the AC Adaptor - very important.
Step 2: The Tools
In this project there is a minimum amount of mechanical work. Only three basic tools are needed for making holes and one tool for soldering:
- A hand drill for drilling the pilot holes
- A larger size drill (3mm) for enlarging the holes
- A Reamer
- 18W - 25W Soldering Iron
THE HAND DRILL: With a 1mm drill-bit.
THE MINI-DRILL (or a Power Drill): With a 3mm drill-bit to match the tip of the reamer.
It is easy to make your own Mini-Drill:
- The motor is from an old printer.
- The drill chuck with interchangeable collets is available from Ebay - very cheap. Check the mounting hole diameter with the seller before buying. It should match the shaft diameter of your motor.
THE REAMER: This is my favouite tool for making holes in plastic and metal; one I recommend that you have in your toolbox.
You start off with a 3mm hole at the centre of the position that you want to mount the component, insert the reamer and push forward gently while rotating clockwise. After every few turns, check if the component fits snugly in the hole. With practice you will be able to make holes quickly and accurately.
THE SOLDERING IRON: Not much more can be said on this topic that has not already been covered in detail in any number of Instructables. All I can say is practice makes perfect. This is a surface mounted PCB, so be very careful. Avoid splashing solder. One solder splash can short a number of components together - almost impossible to recover from.
Step 3: Preparing the Box
It is now time to get your box ready for mounting the components.
Stick blank white stickers on the surfaces on which you are going to mount your connectors and controls. In my case I decided to have a front and rear - like a full sized amplifier. I marked out where each control would be (see the pictures).
The sticker provides a clean white surface for making clear markings and also protects the surfaces from scratches while drilling, etc.
Next, using the hand-drill, drill the pilot holes with a 1mm drill in the places where each control comes through.
Follow up with the 3mm drill on all the holes except ones for the speaker connector.
Finally enlarge the holes with the Reamer following the guidelines in the previous section. The hole for the 3mm LED is not enlarged unless you are using a bigger size LED.
The results are shown in the pictures above - absolutely neat holes with no further cleaning up to be done.
As you can see from the picture with the components mounted, all the components are screwed in except the speaker terminals which are super-glued to the box after passing the leads through the 1mm holes. Make sure that the terminal holes in which the speaker wires are inserted point upwards for easy connection. The LED is push-fit or held in place with contact adhesive.
Step 4: Connecting Up the Components
THE WIRING: The wiring is pretty straightforward.
For easy future fault-finding I recommend some kind of colour coding e.g. Red for all the Positive wiring, Black for all the negative or ground wiring, Orange for all the Right channel wiring and Blue for all the Left channel wiring. For the speaker wiring I have used Orange for R+, White for R-, Blue for L+ and Brown for L-. You can use your own colour combination but try to stick to the same identifying colour for Left and Right throughout.
There are just a few things related to polarities that you need to take care of. Please see the attached PDF file for all the details.
Also please note, in my case, I am mounting everything inside the box and using it as the top of my amplifier. The lid is the bottom. This means I am working on a kind of mirror image to the Wiring Diagram. In use, all the components that are mounted on the left side will be on the right side and vice versa. Be careful when wiring the speaker connections, if your layout is the same as mine, on the side shown in the picture, the Left speaker connections are wired on the right side and the Right speaker connections on the left, so when you flip the box over they will be in their correct places.
You can see how simple the wiring is in the "Wiring Completed" picture above.
Step 5: Troubleshooting and Precautions After Assembly
INITIAL TESTING: Now that you have completed the wiring, before powering up or connecting anything to your amplifier, it is best to do some preliminary tests:
Have another look at the Wiring diagram along with a friend, if possible, and check that everything matches with your wiring. Fresh eyes usually notice things you wouldn't see after working hours on the project.
With your multimeter in low Ohms range, check for short circuits at points 1, 3, 4, 5 & 6:
- If there is a short at point 1, you may blow your AC Adaptor as soon as you plug it in.
- If there is a short between the speaker pins or between any of the pins at points 3 or 4 and ground , you may blow your Amplifier Module. R- and L- are not common points so don't, under any circumstances, short them together or connect them to ground.
- If there is a short between L & G or R & G at point 5, one of the channels may not work when you power up.
- If there is a short at point 6, you may blow your AC Adaptor after you turn the power switch on.
At the Power Switch (point 2) if you are expecting down to be On and up to be Off, set the switch in the Down position and and with your multimeter in the Ohms range, measure the resistance between its two solder points. If you get anything besides zero Ohms, the switch may be upside down. Loosen the mounting screw and rotate the switch till the lever is now up. Put it in the down position and check the resistance again. If it is still not zero Ohms, you may have a defective switch.
ADDITIONAL PROTECTION: As mentioned previously, you can damage the Amplifier Module if you use a different polarity AC Adaptor than the one your Amplifier is wired for. You can prevent this from happening by adding a single diode in series with the positive connection to the PCB. The wiring modification is shown in the attached diagram.
In this case when you connect the wrong polarity Adaptor and turn the switch on, the diode is reverse biased and will not allow the voltage to reach the Amplifier Module. Also the LED will not light up because it is reverse biased. It therefore acts an indicator that the AC Adaptor may be of the wrong polarity or defective.
The only problem with this protection is that there will be some voltage drop across the diode, which is important if your adaptor supplies exactly 12V.
The diodes recommended can both handle 3 Amps. The difference is in the forward voltage drop. If you use the standard rectifier 1N5401 the voltage drop is around 0.7V so the available voltage will be 11.3V or less. With the Schottky Barrier Rectifier 1N5822, the drop is only 0.4V at 2 Amps so you have available at least 11.7V (closer to 12V). Please select one of these diodes depending on your requirement e.g. if your AC Adaptor measured output is 13V (which is quite possible), a 0.7V drop shouldn't matter, so you can use the 1N5401.
MAXIMUM VOLTAGE CAUTION: The maximum voltage that the Amplifier Module can handle is 16V. To avoid damage, please check the actual output voltage of your AC Adaptor with your multimeter, and confirm that it is well below 16V before connecting up.
Step 6: Powering Up
Once you have confirmed that all your wiring checks out and there are no shorts, AND if you have connected the series protection diode recommended. You can happily connect your AC Adaptor, your speakers (push each wire all the way into the connector till it reaches the start of the insulation - to prevent short circuit) and your MP3 player (via the earphone jack), turn up the volume slightly and power on. Enjoy the sound.
If you didn't use the protection diode, one further precaution you can take before powering up is, keep the Red +12V connection to the Amplifier Module disconnected, plug in the AC Adaptor, power on, and using your multimeter in the DC range, Red lead to the disconnected Red wire and Black lead to any Black (ground) connection, check that the voltage reading is positive (around) 12V.
Once you are confirmed that the voltage and polarity are correct, power off, disconnect the AC Adaptor, solder the Red +12 wire to the Amplifier Module and follow the previous instructions for powering on. You're on you way to beautiful sound!
Step 7: Conclusion
When I started this Instructable, I wanted it to be a short quick instruction for beginners, to show how simple it is to make a reasonably powered small size stereo amplifier.
As I kept writing I found that there was more and more that I needed to explain to make the project a success for beginners. Rather than include it all in the main text, I have made a couple of PDF attachments.
I hope I haven't crossed the boundary from informative to plain boring.
If you are a newcomer to electronics and you are intending to do this project, I am assuming that you at least have the basic tools i.e. a soldering iron, solder, a multimeter, a screwdriver set (interchangeable tips) and a pair of long-nose pliers and wire cutters. Also, read all the PDF attachments before starting off.
Much of the information is based on my many years experience in the consumer electronic service business, repairing and training technicians to repair. I found it very difficult to not mention all of it especially the fault finding part which most writers don't go into. To me this is the difference between the success or failure of a project.
I hope you like it.
I have made another of these amplifiers, involving an additional PCB in a smaller box 5cm x 3.5cm x 2cm, which I will publish soon.