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Solved: Khadas Tone Board - Tune Sound quality
#1
Hello everybody,
a few days ago I installed this beautiful application on a RPI 3 B + connected to a Dac Khadas Tone Board.
Before discovering Moode, I used Foobar installed on a Windows 7 PC and connected via USB to the Dac KTB.
The sound quality of Moode is excellent but I can't get the same sound quality as Foobar in Windows which is better.
To configure the KTB Dac in Moode I simply indicate in the specification MPD - "USB Device".
I therefore believe it is a KTB driver problem that I installed in Windows while in Moode I don't know how to make a more specific configuration.
Can you give me some advice to improve sound quality?
Thanks.
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#2
(11-25-2019, 12:44 PM)happymax Wrote: Hello everybody,
a few days ago I installed this beautiful application on a RPI 3 B + connected to a Dac Khadas Tone Board.
Before discovering Moode, I used Foobar installed on a Windows 7 PC and connected via USB to the Dac KTB.
The sound quality of Moode is excellent but I can't get the same sound quality as Foobar in Windows which is better.
To configure the KTB Dac in Moode I simply indicate in the specification MPD - "USB Device".
I therefore believe it is a KTB driver problem that I installed in Windows while in Moode I don't know how to make a more specific configuration.
Can you give me some advice to improve sound quality?
Thanks.

You haven't given us any clues about the 'better' audio quality you get with Foobar/Windows.

In any case, there isn't a more specific configuration for this USB audio device in moOde/Linux (or any audio player on MacOS either). If you are suffering glitches you might try turning on the "USB (UAC2) fix" setting in the moOde System Config panel.

I've owned a KTB since last June. I'm satisfied with its performance (especially for its price) and use it regularly with one of my moOde players but for one specific reason I won't buy another.

Khadas has not implemented hardware volume control in the onboard XMOS firmware even though this function is supported in the ESS DAC chip. (The XMOS chip and firmware provides the interface between the USB port and the DAC chip).

This has been an ongoing issue on the Khadas forum. The response from Khadas has been "Use XMOS I2C can adjust volume but you need to update XMOS software,if you familiar with XMOS I think can have a try." 

Apart from the poor grammar, this response illustrates what I perceive as the basic problem with Khadas. They appear to be hardware guys who depend on third parties and third-party tools for firmware/software. Good luck getting useful documentation or support. I've read every post on the forum and given up. I had to do my own detective work to find the bug in their USB descriptor which was preventing moOde from recognizing it (and which Tim immediately patched around).

A minor issue with the KTB is the noticeable but mild audio "pop" I get if my amplifier is on when I power-cycle my moOde player. That's fixable; I've just been too lazy busy to do it.

Regards,
Kent
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#3
Thank you Kent for the answer. 

For better sound quality I mean that with Foobar the sound is clearer, fuller and realistic and this is not only my impression but also of other people who have heard the same song in the two environments.

I have also checked the "USB (UAC2) fix" without any benefit.

Massimo
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#4
You are comparing apples to oranges from a hardware source perspective and so the assertion that perceived differences in the characteristics of the sound are due to software is simply not valid.

At a minimum you would need to run foobar on the same Raspberry Pi as moOde to factor out any hardware differences hardware that may be causing changes in sound characteristics.

If you want the best possible Pi platform for audio then go for the Allo USBridge Signature. It's an ultra low noise, clean power CM3+ based Audiophile platform. Feed it with a high quality LPS and enjoy the music :-)
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#5
Thank you Tim for your message and many compliments for your enormous work; I'm also a programmer (absolutely ignorant in digital sound management) and I can understand the effort to develop an operating system like MoOde.

I stupidly believed that the Windows infrastructure could penalize the audio quality reproduced via USB while a totally dedicated hardware could improve it.

However I wanted to clarify that MoOde is able to pilot my system very well and the quality is excellent and the differences with Foobar are few.

As a neophyte and programmer accustomed to changing the settings of the systems, I just wanted to understand if it was possible to drive the KTB better because I believe that the difference is made by the driver that in Windows is dedicated to KTB.

Thanks again.
Massimo
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#6
Hi Massimo,

There are two schools of thought on software and SQ. Some believe that tweaking the OS and audio player software produces audible improvements in SQ and some feel that it does not. I really don't know for sure but the real challenge is that even if tweaks and modifications somehow change the characteristics of the sound i don't know of any empirical way to measure the quality of the sound to determine whether it's undergone some sort of improvement.

That leaves the ultimate determination up to each individual listeners own ears and mind. Some audiophiles prefer sound that has some amount of distortion present in the signal and others prefer sound thats as distortion free as possible.

As far as driver settings go, the Linux kernel USB audio driver has some but they are not well documented. They pop up occasionally in some of the posts in the Linux kernel repos.  I don't have a list and so cannot be any help.

The Linux OS itself has a zillion settings and there are all sorts "audio tweaks" posted by users in various Forums. The tweaks fall into two general categories: (1) Reduce resource utilization and give higher scheduler priority to audio tasks, and (2) Reduce frequency and voltage of CPU and RAM, turn the LEDS off, etc to try and lower electrical noise and EMI.

I don't know of these approaches work but some users feel that that they do.

YMMV
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#7
Hi, Massimo.

What Tim said Smile

As a footnote, it seems you were misled by the fact that Khadas provides a driver for Windows. It's easy to imagine using this custom driver will necessarily result in enhanced audio quality. 

Actually, this driver is necessary because the generic Windows USB 2.0 Audio Driver doesn't support all the functions implemented in the KTB. For example, the generic driver doesn't support a complete set of audio formats nor does it support clock selection. The KTB driver is based on the Thesyscon USB Audio 2.0 Class Driver which does. In particular, it supports direct DSD through ASIO.

Thesyscon represents that "the audio class driver is optimized for low latency and low CPU load." Just remember they are making an implicit comparison to the generic Windows driver. We have no idea how it compares to the Raspbian/Linux audio subsystem. Which brings us back to Tim's remarks about tweaks.

Regards,
Kent
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#8
I did some tests ages ago of a Topping D10 USB DAC on Windows and Moode:

Windows 7 - Foobar2000 with Asio Driver on a Fujitsu laptop
vs
moOde 4.1 on a Raspberry Pi 3B

I played back some sweeps, pink noise and music and recorded the output with an RME Fireface UFX at 96 kHz.

I couldn't easily blind-test the setups, but I didn't notice any audible SQ differences between Windows and Moode. However, looking at the recorded files in audio software I did notice that the RPi setup had slightly higher mains interference (but still very low) and quite a lot of ultrasonic "chatter" above 30 kHz (in this case interference from the nearby laptop). It seems the RPi is more prone to EMI but it should be inaudible.

In short, the only differences I could find were hardware-related.
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#9
I apologize in advance for my imprecise and non-competent considerations and in any way I don't wish to diminish MoOde vs Foobar; simply as you explained to me they are two different environments.

Unfortunately it is objective for me that in my system Foobar with Windows  reproduces the flac with more detail.

So my goal is if possible to get the same sound output that I had in the past because I absolutely want to use MoOde as an audiophile player.

Considering that the KTB Dac I use is correctly configured in MoOde, do you think it is possible to act on the hardware to improve quality using, for example, RPI 4 or by installing a HIFIBERRY DIGI + PRO card on the RPI 3 or other solutions ?

Thanks.
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#10
Solution A: (costs zero time and zero money) Keep using the KTB/Foobar/Windows solution.

Solution B: (costs time and zero money) Use the KTB/moOde/RPi solution and try all the software tweaks which have been mentioned elsewhere in this forum and DiyAudio.com, to name two. I haven't tried any and can't make any recommendations.

Solution C: (costs time and money) Use the KTB/moOde/RPi solution and start exploring alternative power supplies, for example a linear power supply for the KTB/RPi combo or a linear power supply just for the KTB.

Solution D: (costs even more money) Start swapping in DACs---spoiler alert, each will likely sound different to you. Start swapping in different computing platforms, for example try the Allo USBridge Signature. There are as many options as you have money to spend.

Stop when you achieve the sound quality you like.

Regards,
Kent

[added in post edit] Rereading this I realize I've made the assumption you are already using a competently built, switching power supply for your RPi with an adequate current rating for the KTB/RPi combo. Phone chargers and no-name wallwarts can be a constant source of problems.
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