A few days later ....
Still noticing that digital bleep very occasionally, maybe once or twice per LP and then only one one stereo channel. A very distinctive electronic noise that lasts a fraction of a second. Hunting around on the web, I found a reference to an identical problem but then with someone using a different USB interface and different recording software - but it was on a Windows PC.
The advice he was given is that somewhere in Windows there must be an active program that is trying to send a notification or asking for attention. Looking at my own Netbook, my precautions are to disconnect the network link whilst recording, use no other applications, set the notification sounds to 'silent' and have speeded up the CPU, so what else could it be?
The security system, perhaps. I have the very excellent ESET security installed on this PC, only because it is a backup device that can be called on should one of my business-use computers fail. Despite the makers claiming that it doesn't put too much of a load on the system, I think the Intel Atom chip struggles with it. Checking ESET, I saw that it has a 'Gamer mode' which temporarily suspends high CPU usage and stops things like updates and scans. Switching this on it was like the netbook had a supercharger activated and ran much faster.
Will try it with this for a few ripping sessions and, if it helps, I might consider removing ESET completely as it does have a major impact on performance on this computer.
... and now, 'Adventures in Modern Recording' :
The difference between hi-res vinyl rips and ripped-CD playback is astounding me, and I'm finding it hard to enjoy listening to 441KHz 16bit at the moment, when I can have luscious, vinyl-sourced playback that gets my foot tapping and me singing along. Then my mind went down a dark, mental side-alley and I thought 'What if I record directly from the DAC's analogue output? Then I can get a hi-res 96KHz recording from a CD.'.
No time like the present, so I gave it a try. Having just made a copy of Heart's totally wonderful 'Dreamboat Annie' LP, I then switched the NVA preamp over to the output from an Allo DigiOne streamer running into the Metrum Musette DAC. Playing the opening track 'Magic Man' as a WAV file from a Japanese SHM CD version and then recording that, real-time, in Audacity at 96/24.
Very interesting. Comparing the Audacity hi-res copy of the CD against the original 44.1/16 file, there is much more depth and detail, wider soundstage, fuller, more 'presence'. But then playing the vinyl rip, the sensual richness shows up a major difference in the character of the sources. You can feel the warm, weighty and slightly woolly sound of the vintage A&R P77Mg cartridge against the somewhat dry and clinical output from the Musette, which somehow misses 'soul'. This was why I prefer the Teradak Chameleon and Ares II over it - both of those DAC's have a far more emotionally-charged perfomance.
So the next experiment on these lines might be to put the Chameleon in place and see how that fares against vinyl. The major drawback is then that ripping a CD via EAC takes about 10 minutes (and I can do 2 discs simultaneously). Making copies in real-time means just that - about an hour per album. Worth it for LP's but then doing my entire CD-collection as well? No way.
Got Klaus Schulze '... live ...' from 1980 spinning on the TT now - did you know that side 2 'Sense' has a playing time of over 31 minutes! Could be the longest LP side ever pressed.