Does lossless audio actually survive on LDAC Bluetooth earphones?
Is music still lossless once it reaches Bluetooth earphones? Rather than stop at codec names, I wanted to trace the file’s path from storage to sound. I’ve left aside some of the detail around receiver chips, mixers, and DSP to keep that overall journey easy to follow.
Bluetooth behavior depends on both the standard and each device’s implementation. If I’ve misunderstood something, or your equipment behaves differently, I’d welcome corrections. Those practical observations make an explanation like this more useful.
“Lossless Audio Over Bluetooth Is Pointless, Right?”
I put a lot of work into this PowerPoint…
It’s a fact we often accept at face value, but this time I decided to follow the audio file’s entire journey to the earphones. While sound seems to play instantly the moment you hit play, it actually takes about 0.2 seconds. In that brief window, the music transforms from stored digits into compressed numbers, radio waves, electrical voltage, and finally, air vibrations. Our baseline here is Bluetooth Classic (BR/EDR) 5.x operating with LDAC.
The Starting Point: Numbers Stored in the File
A locally saved FLAC file and a newly fetched Tidal stream begin as the same kind of thing: a sequence of numbers.
📖 Related: Understanding DAC Specs in 1 Minute
How sampling rates, bit depths, and SNR intertwine was covered in my previous post, so feel free to check that out. The key takeaway is that an uncompressed 44.1kHz / 16-bit CD-quality track demands 1,411 kbps.
A FLAC file itself is usually compressed and stored at around 700–900 kbps. However, it only shrinks for storage; the moment you hit play, it expands back to its original 1,411 kbps. MP3 and AAC permanently discard audio components masked by louder sounds. That’s precisely why we bother using FLAC—because once thrown away, those details cannot be revived.
The Bottleneck: 1,411 kbps vs. 1,000 kbps
YouTube: Buying Bluetooth without knowing version 4 or 5 is a loss! The ultimate guide to wireless gear so you never buy twice.
If you are streaming, data arrives via Wi-Fi or LTE. Handling hundreds of Mbps means speed is never an issue here. Your phone buffers these incoming chunks, and the decoder unpacks them—a software process that restores the compressed data back into its original numerical values. At this exact moment, your phone holds the exact same values as the original file.
The real problem lies in the final 1 meter of air. The theoretical maximum throughput of Bluetooth Classic is around 1.5 Mbps, assuming transmission slots are completely packed with the largest possible packets. Once you subtract protocol overhead, retransmissions, and wireless interference, the actual bandwidth available for music is barely over 1,000 kbps. This is precisely why 990 kbps is the upper limit for LDAC. A sprawling 1,411 kbps stream simply has no room to fit.
This raises a question: Since FLAC files are 700–900 kbps, can’t we just send them as-is? The issue is that FLAC is not listed among the codecs defined by Bluetooth audio specifications (profiles). Your phone must decompress the file and re-compress it using a mutually agreed-upon codec before transmitting. Therefore, the “lossless” span of a lossless track lasts only briefly inside your phone.
Profiles: Dividing Connection Purposes
SONY WF-1000XM6 Spec. Sheet
To see where the codec operates, it helps to separate the purposes of the connection first. A Bluetooth profile is the set of rules for a particular task, rather than another name for the radio link itself. I find it easier to picture several lanes sharing the same connection, each responsible for a different job. The devices exchange their supported profiles during pairing, and more than one can operate over the link afterward. Music, button commands, and a microphone therefore don’t all have to be treated as the same kind of traffic. That distinction explains why a change of task can alter the audio behavior even though the earphones remain connected.
A2DP (Advanced Audio Distribution Profile)
Transmits stereo audio in one direction. This is the actual highway where music travels, and where codecs do their work.
AVRCP (Audio/Video Remote Control Profile)
Handles playback controls like play, pause, track skipping, volume adjustment, and metadata display. Because it uses a separate channel from the audio stream, pressing a button won’t interrupt your music transmission.
HFP / HSP (Hands-Free / Headset Profile)
Designed for phone calls. Since it requires a microphone, communication is bidirectional, which severely limits available bandwidth. HSP is an outdated standard rarely used today.
This explains why sound quality changes when you join a video conference using your earphones. Once HFP claims wireless bandwidth, A2DP gets pushed aside. That is why audio quality plummets the moment a call starts, and since LDAC operates exclusively within A2DP, it sits out entirely during voice calls.
Codecs: Re-compression Inside A2DP
SONY, LDAC Features
Once an A2DP connection is established, both devices exchange supported codec lists and select the best option available. If they share no common high-tier codecs, they fall back to SBC, which is mandatory for all devices. This is often why newly bought earphones might initially sound flat. SBC maxes out around 328 kbps, AAC around 256 kbps, aptX HD at 576 kbps, and LDAC at up to 990 kbps. Even LDAC falls short of the 1,411 kbps CD benchmark.
Developer Options, Bluetooth Audio LDAC Codec: Playback Quality
LDAC dynamically scales its speed based on wireless signal conditions. However, the maximum bitrate is determined by the sample rate: 48 kHz supports 990 / 660 / 330 kbps, while 44.1 kHz supports 909 / 606 / 303 kbps. Since Tidal CD-quality audio is typically 44.1 kHz, its effective ceiling is 909 kbps. In Best effort (adaptive) mode, Android does not judge signal strength or packet loss directly. LDAC playback quality follows how many packets pile up in the phone’s Bluetooth transmit queue: when the signal gets worse, retransmissions increase and the queue backs up, so the bitrate drops, then it climbs back once the queue clears. In effect it responds to the wireless environment, but the mechanism is a little different.
SoundGuys, Bluetooth Codec Connection Quality
On this chart, the signal gets weaker toward the right, and dropout time per minute grows toward the top. For example, with the phone in a back pocket and the signal falling to about -63 dBm (the red dotted line), LDAC 990 drops out for about 5 seconds per minute and LDAC 660 for about 2 seconds, while SBC and AAC do not drop out at all. Because 990 kbps pushes right up against the physical limits of the wireless medium, it leaves zero safety margin. This is why locking your connection to “Prioritize Sound Quality” causes frequent dropouts in crowded areas.
Android Authority. Bluetooth audio codec specifications
Dropping down to lower bitrates isn’t a silver bullet either. Settings like 330 and 303 kbps offer roughly the same bandwidth as standard SBC (328 kbps). However, measurements by SoundGuys show that at these lower tiers, high frequencies roll off around 18 kHz—falling short of true CD quality—while noise floors tested worse than both aptX and SBC across all frequencies. Because LDAC is engineered specifically for high bitrates, its efficiency degrades significantly at lower settings.
Earphones: From Numbers to Physical Vibration
Once the receiver chip organizes incoming data packets sequentially, the earphone’s onboard decoder reverses the LDAC compression process—performing the exact opposite task of your phone.
This is where a common misconception arises. In the case of LDAC, the decoding output is strictly PCM. If the transmission link was negotiated at 24-bit, the resulting PCM stream can scale up to 2,117 kbps. That number is even larger than the original 1,411 kbps source! Does that mean the original master quality has returned? Not quite. The actual information payload remains capped at 990 kbps; the PCM bitrate is merely a formatting standard and does not reflect actual information density. If 990 kbps could fully reconstruct 1,411 kbps, it would be a lossless compression algorithm, yet even FLAC struggles to squeeze files below 700–900 kbps.
📖 Related: What is a DAC? The First Gear to Buy
The DAC converts these numbers back into electrical voltage. How this conversion works was covered in a separate post, so feel free to check that out. Low-pass filters smooth out stepped digital values into continuous analog waveforms. When the amplifier boosts this voltage, electrical current flows through the dynamic driver’s voice coil, turning it into an electromagnet that pushes and pulls against a permanent magnet. This causes a thin diaphragm to oscillate at micrometer scales. These microscopic movements displace air molecules to generate sound waves—and at last, the journey ends.
Returning to Our Initial Question
The moment music streams over Bluetooth, lossless audio ceases to be truly lossless. Any marketing claims suggesting otherwise should be met with skepticism.
Codecs are only one part of what determines the sound. Drivers, amplification, ear tips, and surrounding noise all play a role, and the weakest part limits the chain as a whole. Sending a high-rate LDAC signal doesn’t give an inexpensive driver capabilities it lacks. Equally, a well-made earphone in a quiet place can make differences between SBC and LDAC more apparent. Keeping the full path in view is more useful than expecting the codec name alone to guarantee the final listening experience.
Qudelix-5K DAC AMP – SONY LDAC
You don’t have to keep searching endlessly for the perfect codec. (I’m happy to do some of that worrying for you.) Understanding the choice between maximum quality and adaptive stability is more useful. The whole sequence unfolds within about 0.2 seconds after pressing play. Knowing the path doesn’t change the sound by itself, but it helps explain what to choose or upgrade next.
