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Topping DX7s Balanced DAC/Amp

Audiophile

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Topping DX7s Balanced DAC/Amp

PKeith

Feb 9, 2018

Does anyone know if you can connect to the DX7s DAC via usb on a Linux based host (like from Volumio)? Thanks..

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JCruk

108

Feb 9, 2018

PKeithBased on the updated XMOS chip and comments below, it looks like it'll work with recent linux kernels. I sure hope it does!

slugman

Feb 9, 2018

PKeithper JCruk's reply, it uses the XMOS chip. I've had no problems using Slackware 14.2 x86_64 in recognizing my Sabaj Da2 (XMOS), or my Topping NX4DSD (also utilizes XMOS).
The biggest thing you need to worry about is if you are using ALSA or PulseAudio. You want to use ALSA, because ALSA will play the stream directly on the hardware. Unfortunately Pulseaudio literally remixes everything into 48Khz--regardless of the sample rate of the input file. I confirmed this by playing a 32/384 file and realized that pulseaudio downgraded it to 32/48. I was soooo pissed.
Most modern distributions use pulseaudio. It is possible to downgrade to ALSA, but the procedure is different for every distro.
You can easily check if your dac is downmixing, first grab a 32/384 file from the following testbench site: http://www.2l.no/hires/index.html
Figure out which card your dac is: aplay -l
Then run the following command (make sure you use the correct card# from the command above): cat /proc/asound/card0/pcm0p/sub0/hw_params

earlgrey77

Feb 17, 2018

slugman"Pulseaudio literally remixes everything into 48Khz" This is not quite correct. But it is the default behavior. I am on Ubuntu 16.04, and I have configured Pulseaudio to output 176.4/192 KHz to my XMOS device. For playback of 48k files, it would choose 192k, and for 44.1 files (or streams) it would output at 176.4. You can also tell it to use a better upsampling algorithm.

slugman

Feb 17, 2018

earlgrey77That is true, however i would rather have alsa stream it directly to the hardware though. Although, i should probably adjust the default sampling rate. Reverting to alsa is a pain in the ass and i honestly dont have it working quite correcly. I had to remove the pulse audio libraries and recompile deadbeef, so at least thats able to use alsa with my dac . I was able to turn on pulseaudio for a seperate sound card though for the rest of my applications. For this reason i mostly use my dac with my android phone, and im saving up for a decent dap.

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earlgrey77

Feb 18, 2018

slugmanInterestingly, I have found to achieve better results (i.e. improved treble resolution, cleaner sound and reduced stress / fatigue) with upsampling at the source. For a long time I had favored bit perfect playback, but with the rise of 352k+ devices like XMOS I found that this is no longer desirable. On Android I use UAPP with the setting "Resample to highest sampling rate of the DAC", which produces 352k. And on Ubuntu we are limited to 192k, since Pulseaudio does not support 352k or higher rates. Both setups are satisfying to me, particularly for less-than-perfectly produced files and streams, which I find less bearable with bit-perfect playback at 44.1/48k. I believe that this is the reason why so many people prefer upsampling and / or DSD conversion at the source and before the audio leaves the player (even if the audio material has not been produced that way).

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slugman

Feb 18, 2018

earlgrey77alright so I just made the changes. I set my primary sample rate to 176.4k and the alternative to 192k. I have to say I'm actually impressed. I was skeptical because I played with upsampling plugin in deadbeef . I honestly wasn't very fond of it because it would generate artifacts randomly (pops and clicks). I was skeptical that my experience would be the same in pulse audio. I would prefer to have my dac perform the upsampling (bit-perfect playback)--my dac is already upsampling to 32 bit audio (ess9038). So far, its been a positive listening experience.

earlgrey77

Feb 19, 2018

slugmanLet's document this, other readers might be interested as well:
cat /etc/pulse/daemon.conf ...
; resample-method = speex-float-10 resample-method = src-sinc-best-quality
default-sample-rate = 176400 alternate-sample-rate = 192000
...
And to restart: pulseaudio -k

slugman

Feb 19, 2018

earlgrey77Good idea. Also, good call on the resample method, I will add that now.

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scoopbb

184

Mar 26, 2018

earlgrey77thanks, this was very useful. why set the defalt to 176.4 out of curiousity.
does either default or alternate hold priority if the files are actually that sample rate and the other is just fallback if they dont?

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slugman

Mar 26, 2018

scoopbbFrom my understanding, the default holds priority. The alternate is used when you have things that are not 44.1 multiples (i.e. dvd audio at 192 or other hi res stuff).
I set the default to 176.4 because thats 44.1 * 4 (so 4 times upsampling). Really it depends on what your dac can handle, but the value you settle on is personal choice really. My ess9038 pro (same dac thats in DX7s), can handle up to 512 pcm, so I could bump it up more. I'll mess around with it when I get home and let you know.
The unfortunate thing is, this is all pulse audio resampling. I chose 192 as the alternate because thats the highest sample rate flac files that I have. (Although, I suppose those 192 files can easily be upsamples to 384.)