My latest endeavor has been to create my own stereo amplifier for use with speakers I already own. This has been something I’ve wanted to do since taking the Microelectronics course at school.
Before actually creating one, I considered which topology/class I might have wanted to use for the amplifier: A, AB, D, etc. That ultimately didn’t matter much in the end since there are a number of ICs out there that implement most of the topology for you, only requiring that you supply the right filter caps, input impedance, input bias, etc. With this in mind, and after reading some great online reviews, I ended up purchasing TDA 2030′s as the amplifier IC for the project.
The basis I used for the circuit was the “Single supply amplifier” in the datasheet. This circuit is fairly impressive as is, using reasonably common components and outputting a good amount of power. The only lacking thing I would note of the circuit is an absence of volume control. Volume control would hopefully be easily implemented with a potentiometer, I thought, so I went to work.
All the components for this particular project are through-hole components, so I prototyped the circuit with a breadboard. I tried the prototype out with a couple different power supplies, one 13 volts and one 19 volts. The datasheet only graphs response of this amplifier for 24 volts and up, but I was quite pleased with the volume this put out with even the 13 volt source. The breadboard version of the circuit can be seen below.
The breadboard version was mostly a success, although the volume control did not work out quite the way I wanted it to. I could use the potentiometer to vary the volume, but it also varied the frequency response of the amplifier. Because of the caps in use, and the input being biased (the bias is required due to this being a single supply amp), the potentiometer would lower the volume by changing the RC time constant of the input effectively lowering the overall gain and increasing the lower frequency cut-off. Only high frequencies could be heard at lower volume (intuitively this would make sense, as the higher frequencies carry higher energy, but it felt very audible that less low frequencies were allowed to pass altogether).
After the breadboard version turned out a success, I set out to create a PCB version with two channels. The datasheet contains a PCB layout for the “Single-supply high-power amplifier” circuit, which is fairly similar to the “Single supply amplifier” I had already prototyped. With this in mind, I placed all my components down in Eagle, connected the appropriate signals, and used the autorouter to produce the traces. (Tip: To do a single sided PCB with the autorouter, set either the top or bottom trace to “N/A”.) After getting traces oriented, I widened them where applicable to ensure adequate power could reach the necessary components. The ending PCB layout is below.
After completing the PCB, it was time to print and etch the traces. I used toner transfer here, and decided to try a somewhat new method for transfer. I first heated the copper clad board with a heatgun to ensure the surface was warm and would hold the paper containing the traces. I then placed the paper with the traces on top of the board, and proceeded to heat the paper with the heat gun. Next, I used a makeshift rolling pin to apply pressure and press the toner onto the copper (think laminator, I tried to imitate that same effect). This method actually produced a very good transfer; only one of the outer traces had any issue fully transferring (which I “repaired” using bits of wire soldered between the gaps of the offending traces).
After the board was etched, I realized I did not connect the signal ground input pin to the reference ground of the rest of the circuit. I ultimately remedied this by adding some jumper wires to the overall wires needed to connect power, speaker terminals, and input terminals. The extra wires made it seem a bit more disorganized, but I’m happy with the result. The board and power/input/output panel can be seen below:
At this point, I decided to test the board to see if everything was working. It didn’t unfortunately I was getting sound output at the time, but it was maybe 10% of the output I’d gotten out of the breadboard prototype. I looked over the breadboard and the PCB multiple times trying to look for issues. I found another broken trace, and also a few resistors that didn’t look quite right. It turns out I had placed some 100 Ohm resistors where I needed 100 kOhm resistors. (I took a quick sanity check at that time and looked through my parts. Whoever sent me these resistors marked 100 kOhm on the package, but the color code clearly indicated 100 Ohm.)
I ended up replacing the resistors with the correct values, and repairing the last broken trace. With everything complete, I tested the setup and it worked perfectly. My final steps were to cut out a hole in one of the speakers and mount the board as well as input/output panel. I measured, then fired up the jigsaw and cut out the hole in the speaker as seen below:
With the box prepped for the speaker. I soldered in the channel for the speaker that houses the amp. I also mounted the PCB inside the box, which presented a slight challenge; there was no easy way to maneuver inside the box. To get some sort of mounting in place, and prevent too much unwanted movement of the PCB, I ended up drilling a hole in the bottom of the box and PCB which I used with a bolt and nut to hold the PCB in place while it is in the box. The input/output panel was easy enough to mount, and was put into place with 4 small wood screws. The panel and board mounted are shown in the photos below:
Everything was finally put together, so I could finally do a quick demo and record the final product. Have a listen, it’s not bad for a ~$8 amplifier!
You can download the PCB layout here: TDA2030 SSA
Note: The final PCB included above has the ground traces connected for the input signal. This change was too late for etching, but I did make it on the PCB layout.
- (2) TDA 2030 ICs (my particular part no is now “obsolete”, but a newer TDA 2030 chip should substitute just fine)
- (2) 2200 uF capacitors
- (2) 470 uF capacitors
- (8) 100 kOhm resistors
- (2) 1 Ohm resistors
- (2) 4.7 kOhm resistors
- (2) 2.2 uF capacitors
- (4) 0.1 uF capacitors
- (4) 1N4001 diodes
Optional parts (used for input/output panel):
- (1) Size N coaxial power jack
- (2) Phono jacks (could substitute for 3.5mm stereo jack)
- (2) Banana style jacks
- (1) Power switch