A couple weeks ago, I mentioned that I was learning how to build audio amps and I tried building one using Sparkfun’s STA540 audio amp kit. Well, I tried to design the PCB for my modified version of Sparkfun’s audio amp kit, but I ran into a very….large problem. In order for me to make sure the STA540 properly drives two speakers at 25 Watts, I needed a multiwatt heatsink. However, the heatsink takes up 1/3 of the PCB! Not to mention it will be a pain fitting it inside a box since the heatsink is also very tall! In otherwords, I needed to find something else.
Then I heard about the TPA3122, a 15 watt stereo audio amp. Although it can only drive 10 watts less than the STA540, the space it saves more than makes up for it. After building the circuit, I ran into latching issues, or when the ic stops working due to voltage spikes on the dc bus. At first, I thought adding more bulk capacitance would help, but it had no effect. After asking around, one person suggested to rewire the circuit to be much more orgainized. Not only did I rebuild my circuit on the breadboard, but I place .1uF decoupling capacitors as close to the IC as possible. Afterwards, the amplifier worked marvelously! I even recorded a video of the amplifier in action.
Suffice to say, I will consider using the TPA3122 for my next audio project. Well, that’s all from me today! If you have any suggestions, comments, or concerns, please feel free to use the comments below. See you guys again next week!
Despite the fact I’m learning more about power electronic circuits, I’m also trying to branch out my analog circuit knowledge. I figured a good place to start is by building an audio amplifier. But, I did not want to start with a simple 1 watt audio amp. I wanted to go up to 25 Watts. Since I had no prior knowledge of audio amps before this post, I figured I started with something that exists. So I brought Sparkfun’s Audio amp kit as a starting point.
To make sure I’m getting the most out of my amp, I drove down to Do It Yourself Electronics in Needham,MA and brought a pair of 25 watt speakers. These speakers were ironically $25 dollars and it wasn’t until later I found out that Sparkfun were selling 25 Watt speakers as well. Could of saved me the trip!
To power my speakers, I used my trusty 150W DC power supply. The audio was provided by my usually Jpop music video. When I powered the amp and played the video, I was surprised by how loud the amp was! However, I noticed occasionally 5Hz thumping that the speakers were producing.
So I carefully attached one of my oscilloscope probes to the DC power of the audio amp. I noticed that when the 5hz thumping occurred, the DC bus dropped close to 0V. I suspected that there was not enough capacitance on the audio amp’s power supply rail. So I added 2000uF to the audio power supply rail, and it was not enough.
It wasn’t until a week later that I realized the cause of the thumping. The first thing I realized was that I failed to add DC blocking caps to the speakers since they are AC only components. Another issue that I failed to realize was that the thumping occurred when the volume of my computer was set to max. Therefore, there was a chance that the pre-amp section of the amplifier was getting saturated.
Thus far, I modified Sparkfun’s audio amp circuit with more bulk capacitance on the power supply rail as well as DC blocking capacitors on the outputs of the audio amp. Of course, I’m still trying to figure out how to solve the clipping issue, but for now, I will not set my input volume to its max.
Thank you guys for reading today’s post and if you have any suggestions on how I can make this audio amp better, then please leave a comment below!