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Upsampling Background
#1
I posted this in the DIYAudio Moode thread in 2015, but I think it is worth putting here in the more focused thread.

John Swenson discusses his experience with upsampling in the following slimdevices forum post:

https://forums.slimdevices.com/showthrea...mpressions

This started me on my experiments using SoX inside and outside Moode looking for the best match for my system. I think one group of SoX settings my be optimum for one DAC/Pi combination but not for others. As I've mentioned, I like SoX medium quality upsampling to 384/32 for my Allo Boss 1.0 on both my Pi2 under 3.8.4 and my Pi3Bplus with 4.1.

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#2
Very interested in this topic and the different matches.

My first line of thought was: who would I trust with upsampling? my $40 RPi running off the shelf software or my $1500 DAC? So I left the audio bit-perfect from the RPi (the very reason I bought the Pi and why I did everything I did!), and left my DAC to do the audio processing.

I may have under estimated the scenario, I am looking forward to some experimentation.

I'll report my findings wit external USB DACs which is all that I have.

Best regards,
Rafa.
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#3
Interesting topic.

I read the John Swenson thread and then tried to replicate his settings on my RPi3/Allo Boss (older version)/moOde 3.84 setup.

The Allo Boss DAC is based on TI PCM5122. I'm still running the DAC powered from the Pi, but am using a power bank to supply the 5V DC instead of straight from an SMPS.

I'd been listening quite happily with SoX disabled and the DAC set to perform the upsampling to 24bit/192kHz. I'd tried higher bit depths/sample rates, but they didn't seem to make a noticeable difference. Then I saw this thread and its link to John Swensen's posts, so I thought I'd experiment a little.

In the moOde Audio Configuration settings, you can turn off the internal digital filters of the DAC, so I did. (Nice feature!)

To compensate, I enabled SoX upsampling, setting it to 32bit/384kHz. (Too bad it can't automatically upsample to 352.8kHz for 44.1kHz/88.2kHz source files and 384kHz for 48kHz/96kHz source files.)

I'm pretty sure I hear a difference between the two choices of setting the DAC to upsample with Medium Quality interpolation and 24bit/192kHz as opposed to DAC internal filters off and SoX doing the upsampling to 32bit/384kHz. The differences are more about how I 'feel' while listening to music at these settings, about the 'texture' of instruments and voices presented. All very subjective, so apply your skepticism here. I don't hear one option as obviously 'better' than the other. But differences there are.

What I (think I) hear is with the DAC doing the upsampling and SoX disabled, the sound is somehow brighter (not in a frequency response way, though), or maybe a bit more aggressive somehow. Things sound a bit sharper than...

When I disable the DAC's internal filters and use SoX instead. Now the sound is most definitely 'softer,' although high frequency sounds are just as loud (orchestral triangles, the high harmonics of cymbals, raspy/buzzy 'bite' of trombones and trumpets, bowing of stringed instruments, attack of piano notes, etc.). It's the 'texture' that's different. I like this, it feels more 'relaxed' to me, but I wonder which is the more 'correct' presentation of the original audio. I don't know.

I listened to a modern digital recording of jazz group with both acoustic and electric instruments (Ahmad Jamal "Digital Works") and a couple of orchestral recordings, one an analog master (1970s Deutsche Grammophon), the other a 2000s DSD master to CD (Telarc). The differences held through for all recordings.

I'm thinking this might be a taste thing more than an objectively provable 'this is better than that' sort of thing. Has anybody else tried this with their setups?
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#4
(08-04-2018, 01:41 PM)rongon Wrote: Interesting topic.

...details omitted...

I like this, it feels more 'relaxed' to me, but I wonder which is the more 'correct' presentation of the original audio. I don't know.

...

I'm thinking this might be a taste thing more than an objectively provable 'this is better than that' sort of thing. Has anybody else tried this with their setups?
--

@rongon

And an interesting description of your experience. You've induced me to try this for myself.

I don't see a point in trying to prove objectively that 'this is better than that.' We're dealing with a psycho-acoustical experience. To quote my graduate-school officemate, "there's no accounting for taste."

Fortunately I live close to two urban areas (Baltimore MD and Washington DC) with access to plenty of live performances across the full musical spectrum set in many different venues from intimate rooms to orchestra halls and outdoor stages. In the last month, I've heard a soloist pianist, a jazz trio and a jazz quintet, a tribute rock band, and a Scottish pipe and drum band. Orchestra season starts in the fall. I find that the more live performances I attend, the more tolerant I am of my system at home. You'd think it would be the other way around. Maybe that's just me or maybe it's a memory effect. 

Regards,
Kent
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