Topping BC3 optical output

[speewo]

Hi,
Hope I am posting at the right place.
I listen to music from my phone onto my Hi-Fi amplifier via the BC3 bluetooth receiver.
On my old amp I used to connect the BC3 to the RCA connectors.
Now my new amp (marantz pm6007) comes with a DAC and so a toslink input.
However, when I connect the BC3 on the amp toslink I get no sound. The fibre is well lit. It works when I plug the receiver on another DAC.
The optical source light on the amp flashes, seems like the amp can't manage the signal format it receives.
It does work on the same input with the TV or the Internet router.
I guess there is probably nothing I can do, but if someone has ideas on what is going on, I will be glad to have an explaination.
Thank you.

 

[Hatto]

Check if BC3 allows you to set a contant bitrate (and downsampling). If so, roll it down to output 16-bit 44.1kHz (downsampling as needed) and try again with the Marantz.

 

[speewo]

Thanks for the answer. I think there is no way to manage bitrate on this device. Shame...

 

[speewo]

Thanks to your advice, I did solved my issue by changing the bluetooth settings on my phone. In the Android dev options, the default bitrate settings for LDAC codecs are 32 bits / 96 kHz. Changing them to 32 bits / 88,2 kHz made it work.
Thanks

 

[Hatto]

Glad to be of help.

I don't know where it shows you 32-bit 88.2kHz, but it is certainly deceptive as LDAC is limited to compressing 24-bit 96kHz stereo (4608kbps) into 990kbps.

Another thing with bluetooth audio transmission that most people aren't aware of:
Even Bluetooth 5.0 has a theoretical bandwidth of 2000kbps, however accounting for package headers, error correction, re-sending of dropped packages etc, the actual throughput lives around 1000kbps (or 1Mbps) at the shortest distance without any physical barriers of EMI presence. Even under the best of circumstances (minimum distance, no barriers, no EMI, DLE enabled), it doesn't go over 1315kbps*. The more any codec tries to squeeze through that opening, the more aggressive compression and more frequent dropped packages it would encounter. Any dropped packages or aggressive compression would lower the throughput even more (because the same data needs to be transmitted over and over or it takes more time to decompress packages) as would any distance or barriers between devices.

With those considerations, the resolution of the digital audio transmission will always be limited with the actual throughput. The bitrate of 16-bit 44.1kHz stereo audio (1411kbps) is already above the maximum real-world throughput of latest bluetooth (1315kbps) technology. Therefore it would be wise to lower the bitrate settings of any codec down to at least 16-bit 44.1kHz. Increasing the bitrate to anything more than redbook CD format would not only be ineffective but actually detrimental to sound quality due to increased throughput requirements as explained above.

I can't go without saying that anything over 44.1kHz sampling rate has absolutely no effect on sound quality and the difference between 24-bit and 16-bit is NOT recognizeable by most people, so by lowering the bitrate you're not loosing anything, but actually gaining SQ through less compression artefacts, decreased lag and increased throughput (which woud alow for better range or signal resilience through barriers).

TL;DR:
Always lower your bitrate down to 16-bit 44.1kHz for increased SQ over bluetooth.

* Source: https://www.engeniustech.com/technical-papers/bluetooth-low-energy.pdf