How to find a Bluetooth amp that doesn't suck29 Apr 2021
Living in a Scandinavian city has its perks. Like finding two perfectly fine speaker boxes on the street. Unfortunately, the amplifier was already gone. No problem, I’d just order a $10 bluetooth amp from aliexpress and have a nice stereo at home. I thought. Well, turns out there is a couple of ways they can suck.
The amplifier chip
Of course I watched a youtube video titled something like “The best china bluetooth amp” and adjusted my purchase to their trustworthy judgment. They recommended boards based on the TPA3118, a 2x30W amplifier chip by Texas Instruments. That’s what I bought. Turning it on for the first time, I was actually quite satisfied with the music quality. But listening to radio reports or audiobooks was a pain: I assume for power saving reasons, something inside the bluetooth stack turns itself off after a second of silence or so, and cuts a split second off the beginning of every sentence. Once you notice, you can’t not hear it.
The bluetooth chip
What I should have done is not only picking a proper amplifier chip, but also putting some weight on a good bluetooth module. The one I got was… not even listed on the offer page. So probably a shitty one.
If you want something more high-quality, you could check the spec sheets at Qualcomm. Chances are they also produced the bluetooth chip in your phone. I went with CSRA64215. In the spec it says
Bluetooth 4.2 and
aptX, aptX Low Latency, SBC and AAC decoder support. These codecs are important, they specify how your phone or laptop communicates to the amp, and this includes a potentially lossy audio compression. Likely, a broken codec implementation caused my problems. aptX (as much as I refuse to advertise for a proprietary codec) is a higher-quality one, aptX HD might have been even better. It’s also owned by Qualcomm, so I really hope they know how to properly implement it. Further reason to go for this chip was that there is bluetooth amps with it available. I went for this one that fraudulently claims bluetooth 5.0 support. Well, it will do the job, I guess. And I like that the bluetooth board is a bit separated, so I might desolder it if the amp breaks down. As a nice bonus, the board exposes serial pins that should allow me to mess with the firmware and change the bluetooth name. I’ll edit this post as soon as it arrives.