LDAC, aptX and AAC: what the player controls over Bluetooth

Who chooses the codec

When headphones connect, the phone and the headphones agree on a codec both support. On iPhone that is AAC (or SBC). On Android it can be SBC, AAC, aptX variants or LDAC, depending on both devices, and on some phones you can pick in Developer options. The music player does not take part in that negotiation.

The codecs

All of them are lossy. Bluetooth audio re-encodes whatever the player sends, which is why “bit-perfect over Bluetooth” does not exist.

What the player does control

• What goes into the encoder. A clean signal without hidden limiting, needless resampling or truncation gives the codec the best material. MP95’s path is 32-bit float with nothing in it unless you add it.
• Loudness headroom. A signal that clips before the encoder cannot be fixed after. MP95 only limits when something adds level, and ReplayGain never raises a track past its peak.
• Tone. Headphone EQ and crossfeed work over Bluetooth like anywhere else.

Getting the best from Bluetooth

1. On Android, check which codec is in use in Developer options, and prefer LDAC at 990 kbps or aptX HD if both ends support them.
2. Keep the phone close; LDAC drops its bitrate when the link is weak.
3. For critical listening, use a cable and a DAC. USB DAC setup.