[Teppka]

I have just switched from Android to iPhone and gave my new iPhone 11 Pro Max a try with Oppo HA-2 SE paired with PM-3. Connected using Oppo's supplied USB to lightening cable, everything works fine. But, the iPhone volume rocker change the volume. This is something I can't understand. Considering connection using lightening-USB is digital the signal is supposed to bypass iPhone's DAC and go straight forward to HA-2 SE for decoding and amplification. If so how can iPhone control change the volume? Or am I missing something here, is it just a headphones output where iPhones DAC and amplifier is used?

Used Spotify for playback.

https://www.whathifi.com/oppo/ha-2-se/review

 

[ClieOS]

I have just switched from Android to iPhone and gave my new iPhone 11 Pro Max a try with Oppo HA-2 SE paired with PM-3. Connected using Oppo's supplied USB to lightening cable, everything works fine. But, the iPhone volume rocker change the volume. This is something I can't understand. Considering connection using lightening-USB is digital the signal is supposed to bypass iPhone's DAC and go straight forward to HA-2 SE for decoding and amplification. If so how can iPhone control change the volume? Or am I missing something here, is it just a headphones output where iPhones DAC and amplifier is used?

Used Spotify for playback.

When you connect a DAC/amp via USB to a source (i.e. PC, smartphone, etc), there is a setting stored inside the DAC/amp's USB controller chip that tells the source device whether digital volume control on the source will affect the DAC/amp's internal digital volume control (which is a feature that just about every modern DAC chip has) or not - I assume there is no difference on how the same mechanism will work over Lightning connection as this is more or less the standard implementation for digital volume control on DAC chip. So to put it short - it is how it is designed. Sometime manufacturer will opt to disable this function to disable digital volume control all together, sometime manufacturer will want to enable this function and let the user to decide whether they want to use it or not. The volume knob on the other hand control the volume in the analog domain, after the DAC stage (as opposed to iPhone's volume control affecting the digital domain, in DAC stage).

 

[Teppka]

When you connect a DAC/amp via USB to a source (i.e. PC, smartphone, etc), there is a setting stored inside the DAC/amp's USB controller chip that tells the source device whether digital volume control on the source will affect the DAC/amp's internal digital volume control (which is a feature that just about every modern DAC chip has) or not - I assume there is no difference on how the same mechanism will work over Lightning connection as this is more or less the standard implementation for digital volume control on DAC chip. So to put it short - it is how it is designed. Sometime manufacturer will opt to disable this function to disable digital volume control all together, sometime manufacturer will want to enable this function and let the user to decide whether they want to use it or not. The volume knob on the other hand control the volume in the analog domain, after the DAC stage (as opposed to iPhone's volume control affecting the digital domain, in DAC stage).

Thanks indeed for detailed reply.
Should I then leave volume on max on iPhone and manage it through the knob on my portable DAC? I assume leaving volume on max on iPhone will sort of keep iPhone digital volume control off?

 

[ClieOS]

Thanks indeed for detailed reply.
Should I then leave volume on max on iPhone and manage it through the knob on my portable DAC? I assume leaving volume on max on iPhone will sort of keep iPhone digital volume control off?

Yes, you want to keep iPhone's volume to max.