I use the opus format on all of my devices : android devices with foobar2000 for android, Rockbox driven DAP (such as Ipod and Sandisk Clipzip), and a linux PC. I settled for a bitrate of 76kbps, which is fine for my use, almost transparent. Listening my music on these devices with headphones give me nice results, no complaints.
However, I have 3 bluetooth receivers and problems with 2 of them :
- a LiNKFOR DAC 192kHz (the same as shown here https://www.youtube.com/watch?v=1RfTmxm3uXI&t=72s&pp=ugMICgJmchABGAE%3D compared with the logitech one) plugged on my stereo system.
- a JBL GO
- a Earfun Uboom L
Everything is fine with the LiNKFOR 192kHz but with the two others the sound can be awful in the high frequency range : very "washy washy" sound especially on the cymbals sound.
I made tests with 96kbps or 128kbps Opus file and even though I still have the impression that the quality is deteriorated it remains... fine. But with 76kbps or 64kbps sound files it's awful. Mind you, I am aware that 64kbps files can exhibit artifacts in the high range but I am talking about something even more degraded and really disturbing notably with long cymbal sounds.
Tests made with ~80kbps Ogg Vorbis files do not give the same issue, I notice no degradation.
Also, very important point : the awful sound is the same even when the speaker is connected via the AUX cord ! (for both speakers)
Does anyone have any explanation for that ? Could it be a sample rate issue between a 48kHz opus file and a maybe locked in 44,1kHz bluetooth device ? This is the only explanation that I have in mind.