TPA3116 Amplifier Boards
There are now many small low cost amplifiers based on the TI TPA3116 chip. When the chip first came out, it was touted as a step up from some of the low cost Tripath amplifiers on the market at that time. I had recommended one of those (the original Dayton DTA-100) to a friend who I built some speakers for. My speakers were nominally 4 ohms and not very efficient. The amplifier I recommended was not well suited to that application and didn't last long. At that time, the TPA3116 was relatively new, but there were several Asian suppliers that were selling amplifier boards. I decided to build a replacement amp using an amplifier board from Yuan Jing. There were two options, a red board and a blue board, so I bought some of both. Now, about 10 years later, I still have one of each, Yuan Jing is still in business, and it appears both boards are still available in at least a similar form. The red board costs about $20 and the blue board costs about $30.
For my friends amp, I decided to use the red board because it had a built in volume potentiometer and I was able to find a pre-made blank aluminum case that had rails that this could slide into. I threw in a 19V computer power supply and we were good to go. The amp has survived to this day, so the project was a success as far as we were concerned. First, let's see if 19V was a good choice. I tested at 3 voltages, 14.5 V, which the Dayton DTA3116HP used, 24V, which is near the maximum recommended voltage for the amp chip, and 19V, which allows use of readily available spare laptop power supplies.
At 14.5V, this is approximately a 10W amp into 8 ohms and 18W amp into 4 ohms at 1 kHz. In the 0.1W to 10W, distortion stays below 0.1%, which is decent, especially compared to some of the other small, cheap amps I have tested. At 24V, this amplifier board can deliver nearly 30W into 8 ohms and over 40W into 4 ohms. At 19V, about 18W into 8 ohms and nearly 30W into 4 ohms is available. It does look like 19V works well into both 8 and 4 ohms, while pushing the voltage up might we worth it if your speakers are an 8 ohm load.
I did a similar exercise for the blue board. The blue board is cleaner above 1W into 4 ohms, while 8 ohm performance is pretty similar, maybe a little cleaner above 1W. The blue board appears to do some limiting when running at 24V into 4 ohm loads. So, as in the case of the red board, 19V appears to be a sensible operating voltage for most situations. The remainder of the tests will be run that way.
The rest of the charts will be shown side-by-side with the red board on the left and blue board on the right for ease of comparison. Let's start with the dashboards. Gain is about the same with the red board pot set wide-open. Signal to noise ratio is close to the same, with the red board showing slightly less 60 Hz noise. The blue board has significantly less distortion at 5W into 4 ohms, which was also evident in the earlier distortion vs. power plots. A SINAD in the low to mid 70's is competitive with amplifiers like the Parasound Zamp and Dayton APA-150 as reported by Audio Science Review. The red board SINAD in the low-to-mid 60's still bests the Dayton DTA-120 (successor to the DTA-100) that I replaced with the red board-based amplifier. So, we have that going for us, which is nice.
Next up is the frequency response. Both boards have extended low frequency response, but the high frequency filtering approaches are different. The red board is well-behaved into 8 ohms, which lead to early roll off into 4 ohms (down about 4 dB by 20 kHz). The blue board high frequency response is down about 1 dB at 20 kHz into 4 ohms and up about 1 dB into 8 ohms, which is a more balanced approach and typical of many class D amplifiers.
Now, we'll do a side-by-side comparison of the distortion + noise vs. output power at 1 kHz. Looking this way, there isn't too much difference. There is more distortion above 1W with the red board into 4 ohm loads. The blue board makes a little more power, particularly into 8 ohms. When run with a 19V power supply, both will do about 30W into 4 ohms and 18-20W into 8 ohms.
A major difference between class D and more traditional class AB architectures is the high frequency filtering required for class D. This can show up in the frequency response, and can also show up when we look at distortion vs. frequency. Here one can see distortions approaching 1% above 5 kHz. This is still lower distortion than the Kinter or Lepai at any frequency... The blue board also loses it's performance advantage above 5 kHz. The red board has reduced output at 15 kHz, which is also seen on the 4 ohm frequency response curve.
The biggest issues with these TPA3116 amplifier boards are rising distortion and response issues at high frequencies. That said, compared to other low cost amps, usable power can be had with a 19V power supply that has long been a standard for laptop computers. I would want to make sure the impedance was 8-16 ohms at high frequencies for a speaker I was planning to use with the red board. My friend, for whom I built a red-board based amp, has a pair of my Lithium speakers which are between 11 and 15 ohms above 5 kHz. That combo has worked very well.