Bolivian_Spy t1_iy2lx9b wrote on November 28, 2022 at 7:07 AM

Reply to comment by G65434-2_II in The just the right amount of smoothness and resistance by UnnecessaryMovements

This is not the issue actually. The issue is that the dac on the receiving end has a limited SNR budget for it's whole amplitude range, and windows can't tell it to switch gain modes or anything like that. So when you reduce the volume digitally, you are just sending the dac samples that are scaled to the lower register of voltages that it can put out. This hurts the SNR because you reduce the signal but not the baseline noise the dac makes. Using a pot on an amp completely sidesteps this issue by allowing the dac to work at its optimal output level while making the volume lower as desired.

blorg t1_iy2sbq3 wrote on November 28, 2022 at 8:37 AM

>when you reduce the volume digitally, you are just sending the dac samples that are scaled to the lower register of voltages

My understanding though, this isn't how it works with UAC2 in Windows, it sends a full scale signal along with a number for the volume, and it's up to the destination device to set the volume.

This is the behavior I see with for example the Qudelix 5K, if I drop the master volume in Windows to 50% volume does go down, but the input level displayed by the Qudelix stays exactly the same (very near 0dB for modern music, like it's at -0.08 to -0.09dB at the louder parts of a track, dropping in quieter parts).

Qudelix notes this is how it works for Windows and iOS (and Android over Bluetooth) but states that Android USB Audio does scale down the PCM samples:

>You can control volume in whatever comfortable way, either smartphone buttons or Qudelix-5K buttons, without any sound quality loss. It always keeps and guarantees the best sound quality over Bluetooth or USB. ...

>Smartphone, PC/Laptop volume control: Remotely adjusts the 5K built-in Volume Controller ...

>Unlike PC USB and iOS USB(over Camera Kit), Android USB Audio doesn't support the Absolute Volume Control. The Android Source Volume scales down the PCM sample as the volume gets lowered. For the best sound quality with Android USB Audio, you will need to keep the source volume at maximum.

https://www.qudelix.com/blogs/5k-dac-amp/volume-control

While if I take a track into Audacity and actually reduce the level of the samples, the number the Qudelix shows for input level goes down accordingly- by exactly what I drop it by in Audacity. But that's not what the straight Windows volume control does any more with UAC2, it actually sends a command to the volume control on the device saying "set to this volume" while sending a full scale digital signal. It should be no different than changing the volume directly on the device, if the device supports this.

DrStefanFrank t1_iy4m8bs wrote on November 28, 2022 at 6:40 PM

Thank you very much! That's really good to know about Android. I would've never known without you taking the time to write a thorough comment. Really appreciated. I guess it's the same deal with Ibasso dongles on Android and their UAC app for controlling volume and in general with dongles that allow seperate volume control somehow, right?

Now, if someone could tell me how it is with BT connections I'm all set. I usually enable "direct volume control/DVC" because the poweramp equalizer app suggested it somewhere for some reason I don't remember rn, then keep the android device on max volume and use the BT devices volume control separately.

I think it's right but I'm unsure. Should it be enabled or disabled for best SQ?

blorg t1_iy6m0z8 wrote on November 29, 2022 at 3:11 AM

I think that's exactly what the special app is doing, it would be sending the UAC command to change the volume on the dongle. The issue with low volume on Android with the Apple dongle is related, by default it is set to 50% and Android volume buttons only reduce the sample volume. Universal Audio Player Pro is another app people use to be able to control this hardware volume.

My understanding, with BT it is sending a full scale signal either way, some BT devices have the option of their own independent volume but I'm not sure whether you use the volume on the device matters.

With the Qudelix and Android it will show the input at -0dB all the way down to around 35% volume and then below that it does attenuate, but not very much until you get down to the very bottom. I don't think in practice there is any issue using the device volume, not for my devices anyway.

G65434-2_II t1_iy2ncxi wrote on November 28, 2022 at 7:27 AM

True that, good point! Though with modern DACs with their really low noise levels, I doubt turning down OS master volume a bit if needed (for instance to get more useable range on the amp's volume pot) would likely cause issues, but naturally, turning the OS volume waaaaay down should be avoided.