ALL volume fixed with USB-Out ? Why ?




  • Official comment
    Tony W.
    Product Support Manager

    Hi Richard

    Thanks for your feedback. You can easily toggle in the BluOS App, under Settings, Audio if you wish to switch output sources on the fly. As for the very best audio quality, it is best to remove as many devices from the Audio Chain as possible using the onboard Texas Instruments PCM 5242 Burr-Brown DAC, which has been implemented with a differential output design in an endeavour to cancel out as much unwanted noise as possible while carefully engineered specifically to provide a neutral response thus replicating the recording as faithfully as possible. If however, you do prefer adding or adjusting the tone control using a third-party DAC, COAX is still your best option for audio quality.

  • William Heck

    Hi Tony

    First, thanks to the entire Bluesound crew for enabling USB output. Yes, it took longer than expected -- but there was a pandemic going on, among other issues!

    So just to clarify regarding USB output:

    1. Given that there is a volume control, some digital processing of the original signal is occurring, right?

    2. Is there any way to change that to a straight pass-through? For the other digital outputs, one needs to set the output as "Fixed"; that option does not appear to be present for USB. Is that correct? Or am I just missing it?

    3. If there currently is no way to simply pass through the original digital signal (which is the most appropriate for a situation in which a high-quality DAC/preamp is in use), is a bypass or Fixed switch/control under consideration? Or can you make that a feature request for the future?

    Of course, as you point out one could use the COAX (or optical) out. But for some of us, USB would work out better if available. 

    Thanks in advance for your help!

  • Tony W.
    Product Support Manager

    Thanks William - will pass your feedback on to the entire team (contrary to popular belief I am not a developer myself...)

    That being said it's all actually the opposite of what you said. USB Audio Output is always fixed - there is no volume control when USB is selected while the default sources do have that ability. The reason is that, at least to my understanding from the development team, is it IS all pass-through and why other sources are disabled. The only exception is MQA has to be rendered first by the NODE.

  • William Heck

    Hi Tony

    I'm a bit confused, but I think I see where the problem arises:

    Start by using the Coax output (USB disconnected) running to an external DAC. In the Settings/Audio controls, i can toggle Fixed Output ON (the volume control is locked) or OFF (volume control works).

    Now in the BluOS controller,do NOT leave the Settings/Audio page. Disconnect the Coax output and connect the USB output. The Fixed Output control is still there,and it works.If you set Fixed Output to OFF, the volume control still works, even though you are using the USB output.

    If you then leave the Settings/Audio control screen, then go back to it, the Fixed Output control no longer shows up. The volume control (circle with a speaker icon) in the player control area at the bottom of the screen) still works. If you mess around a bit (can't remember the exact sequence), that volume control becomes locked.

    So here is the *real* question: for any of the digital outputs (coax, optical,USB), if Fixed Output is engaged (and the volume control is indeed locked), is the digital stream being passed through without processing? By that I mean is the digital stream exactly what is being received from the streaming service, no digital volume control, no DAC/ADC reconversion, etc? Or maybe that's true of USB but not Coax/Optical?

    I'll leave it to the development team to decide whether that backdoor way to have a volume control on the USB output is a feature or a bug. :^)

    BTW, happy new year!



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