(10-24-2020, 04:04 AM)KC9UDX Wrote: I have the need to record audio from my 1970s HiFi.  The most convenient way to do that at the moment is to use my Pinebook Pro.  I run NetBSD.

I bought two devices from Newegg, hoping that one of them would work.  This turned out to be very fortuitous.  The first is a StarTech ICUSBAUDIO7D.  The second is a Toshiba PA3390U-1MPM.

First off, connecting or disconnecting either of these whilst the system is booted risks locking up the PBP. I am using Audacity to record, which also occasionally locks the machine. Since I am running NetBSD-current, this is not totally unexpected.

First the StarTech:
I was able to record audio via /dev/audio1, but this does not source the audio from Line In.  It sources it from the microphone jacks, which there are two and they are mono.  The audio level is about 10db too low.  There is a periodic tschk-stck noise in the recorded audio which I cannot figure out how to avoid.  I can play back audio, also via /dev/audio1.  This routes audio to the front speaker jacks.  The output audio seems to be an adequate level, and seems to be clear and acceptable.  Despite that these are labeled as speaker jacks, they seem to be line level.

Next the Toshiba:
I was able to record audio via /dev/audio1, and this sources audio from Line In.  The audio level again is about 10db too low.  The record audio seems to be clear and sufficient, albeit a low level.  I cannot get audio to play back from the device.  There is a mute button with indicator light on the front of the device, and this indicator is always on.  I assume that I would need the Windows software that comes with the device to turn the mute function off.

So, you can see I have one device that records well and one that plays back well.  I was able to daisy-chain them; the Toshiba device has an inbuilt USB hub.  In this case, the StarTech device becomes /dev/audio2.

The low record audio may have something to do with "line level" standards changing over the years.  The only other computer I've used with this stereo system is an Amiga with a Delfina audio card, and I don't recall ever having issues with low level audio on that.  (In fact, I'm pretty certain that there was plenty of headroom in the audio level; I did a lot of recording with that).  But that was over twenty years ago.  Things may have changed in the industry since; I have no idea.

This was my first experience ever using a "USB sound card".  So perhaps there are other things I could have done better and I am not aware.  But at least this is a workable solution, and I was able to record the audio that I needed.