USB-C Hub and channel volume issue

[Chris115v]

Hi all, i had an odd problem and was wondering if anyone else had ever seen it. I'm using a Music Hall pa2.2 ADC to record onto a Macbook Air under latest Ventura os. I had been using a Rega Phono Mini and all was fine, but I wanted higher resolution so i upgraded to the Music Hall. I record at 96khz/24bit now. The issue is that the pa2.2 is going through an Anker USB-C hub since the pa2.2 has USB-A output but Macbook Air only has USB-C input. What happens is that the right channel records much lower than the left.

I sent the pa2.2 back and they were not able to find anything wrong with it, but sent me a different new unit back just in case. Same issue. On a whim i bought an Amazon Basics USB-C to USB-A converter cable, and now the recording levels from the pa2.2 are matched fine across the channels, no problem. So it seems like some kind of odd interaction between the pa2.2 and the Anker hub?

[Paul Sanders (AlpineSoft)]

Hmmm, strange.

At a guess, the Anker has some kind of bug when passing on an audio stream.  You'd probably get the same behaviour with any USB ADC, although the sample rate and / or bit depth might also be a factor.

Do Anker have any way to issue firmware updates?  Might be worth checking.

[Chris115v]

Definitely something odd going on. I ended up with the same channel imbalance issue with the Amazon Basics adapter, but found out that sometimes it works and sometimes not. If I restart and use the Amazon adapter with VinylStudio immediately, channels are balanced. If I then unplug and re-plug the adapter, mostly i have the imbalance. But sometimes I don't and it works fine. Usually the right channel is lower, but not always.

I was able to get the Anker adapter/hub to work this way also. Using it immediately after a restart seems to be the most reliable way, but sometimes it works if I un/re-plug it. Or if I leave the hub plugged in but un/re-plug the USB-A pa2.2 from the hub.

Since it happens with both hubs maybe it is an issue with the Macbook Air?

[Paul Sanders (AlpineSoft)]

Interesting.  For me, that makes it more likely that the Music Hall is the guilty party.  Do you have another computer (PC or Mac) that you can test it with?  It sounds like an irritating fault to have to live with.

[Chris115v]

I've now tried it with an older Mac Mini with USB-A and a 24" iMac M1 with USB-C. The issue happens with the iMac and the USB-C adapter but not nearly as much as with the MacBook Air. It has not happened at all with the Mac Mini, so it seems to be some interaction with the USB-C adapter. Fortunately with the iMac it happens a minority of the time so I can live with it.

One other note is that sometimes the channel volume is ok initially, but when I adjust the input volume slider it can cause the issue to happen. I've found that with any of the Macs, when you plug into different USB ports the system (and Vinylstudio) don't carry over the input slider setting. That is, if you use one USB port on the machine and set the input slider in VS, then plug into a different USB port, the input slider setting doesn't carry over even if it identifies the ADC as the same thing.

[Paul Sanders (AlpineSoft)]

OK, thanks.

Regarding your second comment, the reason for that is that the Mac sees each USB port as a different device (albeit the same type of ADC), and each device has its own recording level setting.