Recent News and Articles

« Back

Audio quality of Bluetooth music receiver TS-BTAD01

Audio quality of Bluetooth music receiver TS-BTAD01

Initially this device was planned to be used for aptX testing/research. Two guys responded to the call for donations in the article Audio quality of bluetooth aptX and after some time Bluetooth Music Receiver TS-BTAD01 was delivered from DealeXtreme.


Bluetooth Music Receiver TS-BTAD01 package.
   Figure 1. Bluetooth Music Receiver package contents.


The plan was to use digital out of the receiver to record bit-perfect output of aptX decoder. Such recordings could be used for analysis/comparison of aptX and SBC codecs.

Unfortunately the quality of output interfaces of the device both digital and analog is so extremely low that the mission is impossible. The main problem with its S/PDIF out is low quality resampling to 48 kHz using very unstable clock. Even more, according to the measurements below the signal is converted twice. First, decoded aptX/SBC stream is converted to analog and then converted to digital again @48kHz using low-cost IC solution. Needless to say that such processing distorts the signal much more than the codecs alone, making this device unusable for aptX research.

Nevertheless, I performed standard SE objective measurements of the device using real-life music material and comparing input and output waveforms. Results are below.

Df measurements of Bluetooth music receiver TS-BTAD01
   Figure 2. Df measurements of TS-BTAD01 with real music material.

As you can see the difference between aptX and SBC codecs (and three quality modes for the latter) is almost completely eliminated by the awkward design of output circuitry. Resulting sound is harsh and leads to listening fatigue in minutes. Exactly such Bluetooth devices make bad reputation for Bluetooth audio as a technology.

Manufacturing of this audio crap is possible not least because usual THD+N measurements look good even for such devices. The enclosed leaflet for TS-BTAD01 proudly specifies THD = 0.05% (-66 dB). Indeed, if we look at Df measurements with pure Sine signal instead of real music signal we can see that the above THD value is quite correct. Even the difference between codecs and digital out is not so dramatic.

Table 1. Df measurements of TS-BTAD01 with Sine signal
(1kHz, -10dBFS, 30s, L=R). Df (dB) ≈ THD - 3 (dB)
  Codec alone Digital out Analog out
aptX@352 kbit/s   Df measurements of TS-BTAD01-d-aptX@352kbit/s with sine signal 1kHz Df measurements of TS-BTAD01-a-aptX@352kbit/s with sine signal 1kHz
SBC@328 kbit/s Df measurements of SBC@328kbit/s with sine signal 1kHz Df measurements of TS-BTAD01-d-SBC@328kbit/s with sine signal 1kHz Df measurements of TS-BTAD01-a-SBC@328kbit/s with sine signal 1kHz
SBC@229 kbit/s Df measurements of SBC@229kbit/s with sine signal 1kHz Df measurements of TS-BTAD01-d-SBC@229kbit/s with sine signal 1kHz Df measurements of TS-BTAD01-a-SBC@229kbit/s with sine signal 1kHz
SBC@201 kbit/s Df measurements of SBC@201kbit/s with sine signal 1kHz Df measurements of TS-BTAD01-d-SBC@201kbit/s with sine signal 1kHz Df measurements of TS-BTAD01-a-SBC@201kbit/s with sine signal 1kHz

The problem with THD measurements is that degradation of pure Sine wave is always substantially less than of real music signal. In other words, an awfully sounding device can still have decent THD measurements.

Anyway, Bluetooth Music Receiver TS-BTAD01

  • has nice plastic case with blue LED and various outputs,
  • easily pairs with any SBC/aptX Bluetooth devices,
  • is worldwide available on-line for $30 (under various names and brands) and
  • is suitable for playing quiet background music in your garden.

There is no way to use it for attentive/critical listening.

Thank you, Pierre and Alexey for your donations and sorry for not completing the mission – to compare SBC and aptX codecs. I will do this in some other way.


Trackback URL :

No comments yet. Be the first.

What is SoundExpert

SoundExpert - How it works SoundExpert (SE) is a crowdtesting service that provides audio quality ratings of sound equipment and technologies such as mp3, aac, wma ... encoders, portable players, sound cards, amplifiers ...

The ratings are based solely on results of blind listening tests when listeners don't know the particular device they test. So the values are completely unbiased and free from any marketing and advertising noise.

SoundExpert provides ratings thanks to visitors who take part in testing. The more number of participants - the more devices and technologies could be tested. The ratings are computed in real time while new grades are returned by visitors. The testing procedure is simple and short enough that anyone, including you, can participate. Just download a test file (<3Mb), listen it (<15s) and send back your judgment. Details are in test file. The more accurate grades - the more reliable ratings.

SoundExpert is independent non-commercial research project. It's in beta state because it uses new audio metrics and corresponding listening test design which are not widely adopted by audio engineers. The key feature of this new method is possibility to hear sound artifacts which are normally beyond threshold of human perception. So, please, use these ratings with caution. Detailed but still easy to understand explanation of SE internal mechanics is in the article "SoundExpert - How it works".

The main idea behind this service is consumer control over sound quality measurements of various audio equipment on the market. SE, being a distributed human project, combines tiny efforts of audio enthusiasts for carrying out this task.