When using an iPod Touch or iPad as a Roon Endpoint, with an Apple Lightning to USB 3 Camera Adapter to enable output of audio data over USB to a Chord Qutest DAC (with or without a Topping D10 in-between as a USB to Toslink converter), I’ve found that the iPod/iPad volume buttons can change the volume coming from the integrated amplifier that the Qutest is providing its RCA outputs to. The iPod or iPad are always set to Fixed Volume in the Roon Device Setup and DSP is turned off, so I don’t understand this behaviour.
I think that the ability to change the volume using the volume buttons implies that either Roon or IOS is processing the PCM data output, but I would prefer that the iPod/iPad not process the data sent to the DAC over USB, i.e., I cannot be sure that that PCM data is not being processed even if I have the iPod/iPad set to maximum volume.
I am aware that IOS has a Guided Access feature that can be used to lock out the Volume Buttons, but use of this feature does not imply to me that Roon or IOS software will no longer be processing the PCM data to control volume.
Have I got it wrong here? Is there something I’m missing?