Review and Measurements of WesionTEK Khadas Tone Board DAC

[somebodyelse]

No, you can't use Tone Board as I2S DAC for RPi.
It works like that only for their VIM SBCs.

Even the VIM uses USB via GPIO pins 3 & 4. The I2S pins on the header are a passthrough to the 'I2S Ext' FPS connector. The only accessible I2S is on the '8 Channels Ext' FPC, and those are connected to the XMOS so you'd need custom firmware to do anything with them.

 

[MalinYamato]

Even the VIM uses USB via GPIO pins 3 & 4. The I2S pins on the header are a passthrough to the 'I2S Ext' FPS connector. The only accessible I2S is on the '8 Channels Ext' FPC, and those are connected to the XMOS so you'd need custom firmware to do anything with them.

thanks for detail explanation. I am totally new to Khada stuff and is only guessing: Thus, as far I understand you, only the VIM version may use the I²S bus and does it through the headers corresponding GPIO pins. I still dont quite understand the need for two separate versions of the board? My wild guess, is it because the I²S bus may only have one master either the XMOS or the VIM SOC? Having the VIM version of the sound card and the VIM SOC assembled together, is it still possible or advisable to direct audio from Windows/Linux to the sound card through its USB C port?

 

[Veri]

I still dont quite understand the need for two separate versions of the board?

There is the generic version for general purpose, and the other version is to mate it with one of their other products:
https://www.khadas.com/vim

 

[somebodyelse]

thanks for detail explanation. I am totally new to Khada stuff and is only guessing: Thus, as far I understand you, only the VIM version may use the I²S bus and does it through the headers corresponding GPIO pins. I still dont quite understand the need for two separate versions of the board? My wild guess, is it because the I²S bus may only have one master either the XMOS or the VIM SOC? Having the VIM version of the sound card and the VIM SOC assembled together, is it still possible or advisable to direct audio from Windows/Linux to the sound card through its USB C port?

The only difference between the versions is whether or not some of the headers are soldered on. Leaving the headers off for the general purpose version means it'll fit in a smaller case for standalone use, but I think the headers are still supplied if you want to solder them yourself.
I think there was a plan for connecting multiple boards via the FPC connectors and a separate interconnect board, but that never appeared. This would have made things like 7.1 surround or active crossovers possible.
I'm basing the stuff about I2S and USB on the published schematic rather than having tried everything myself. I _think_ it's correct but I'm not certain.
The USB connection is switched between the GPIO pin USB and the back panel USB-C by the 5V supply in the USB-C, so if the cable is plugged in it overrides the GPIO VIM connection. The VIM has 2 pins to switch how the SPDIF RCA is used too.
It's a little tricky talking about 'the i2s bus' as there are 3 of them:

1. Fron the VIM via the GPIO connector to the 'I2s Ext' FPC connector - these are just wire connections that don't go to any of the chips on the TB.
2. From the XMOS to the '8 Channels Ext' FPC connector, unused so far as we know in the current firmware, but could be used for up to s channels in or out by a custom firmware of connected to suitable I2S devices
3. Between the XMOS and the ESS DAC chip - the only one that's actually in use.

This is contrary to some of the statements from khadas representatives on their forum - in one case I've asked for clarification as I don't think what they've said is possible. It could be me reading the schematic wrong, or an error in the schematic though.

 

[wiz2596]

> I assume that most of you have problems in getting clean DC current from the PC without ground loops through the USB C power linens.

I can assure you that most of us are just happily listening with this DAC without any kind of problems with "clean DC current" or "ground loops through the USB C power lines".

I've just moved from PC to Raspberry Pi and there as absolutely no ground loops in any of them. It sounds identical to me.

I'm using a desktop PC and have never had issues with ground loops or something, it sounds perfect

 

[phoenixdogfan]

No audioable problems so far powered from notebook or desktop PC, it can be there technical is a ground loop but as told its not audioable and i have it hard hear a audioable diffence into head phones unplug power brick of notebook PC.



Jep a fine enough practical case, not luxury.

View attachment 63051

I have the same case. Think it looks great. Only problem I have is with the shipping cost. TB + Audiophonics case pushes total price north of $140.

 

[musiclover]

Hello! I’m new to this forum and this is my first post. First of all, I want to thank all of you and especially Amir for providing these measurements.

Now, I have a question regarding this Khadas Tone Board.

Is it possible to connect my headphones directly to this Board without an amp in between?

Obviously, it will work with an RCA to headphone jack interconnect cable, at least theoretically. But my question is: is it intended to be used this way or will it degrade sound quality?

I am new to audio stuff so I don’t know a lot yet, but I know that there is such a thing called output impedance. On this forum, output impedance is measured on amps and they are rated based upon the output impedance (while a low output impedance is considered to be good, and a higher impedance (e.g. significantly higher than 1 Ohm) is considered to be bad).

Now I know that the KTB is not an amp, but don’t do the same rules regarding output impedance apply when connecting an output device (whether it may be a DAC or a dedicated amp) to a headphone? As I have read in this topic, the output impedance of the Khadas Board is 100 Ohm (correct me if I’m wrong). This is rather high from what I would tell. Will this effect sound quality as in altering the frequency response e.g. towards a bloaty bass?

Thank you.

 

[somebodyelse]

You are correct that the KTB has 100 Ohm output impedance. It's designed to drive line level inputs not headphones. It will 'work' in that you'll get sound from headphones, but it won't be ideal. Output power will be limited, and distortion will be increased. The effect on frequency response will depend on how the headphones' impedance varies with frequency. Increased bass is certainly possible for some headphones. Whether this is subjectively better or worse is another question entirely.

If you want similar DAC performance but with a case and a headphone amp for not too much more you could check out the Loxjie D10 review

 

[musiclover]

Thank you very much for your reply. So it is designed to drive line level inputs, that was the info I was looking for I guess.

I already own a dedicated headphone amp though, which I use with the Khadas Tone Board and I am very satisfied with by the way. My question was out of sheer curiosity.

 

[Milesian]

I am using KTB powered from RPi 3A+ without issues. So, the RPi4 USB 3.0 is more than enough to power KTB.

I might recommend going for a higher current 5vdc power source for the Pi 4B/KTB combo, something 3amps and above, especially if you are using a Pi case with a fan. The 4B has a higher draw than the 3 and also runs hotter, so you might consider, as I did, a passive full size heatsink for cooling the Pi. Also pretty easy to solder a couple of pins on the KTB and run off it’s own 5vdc power supply. Apparently this option disables the USB C power.

 

[Milesian]

KTB works well only powered with Pi4. I am using picoreplayer. With deactivated hdmi and wlan the sound is better.

I did one "extreme" KTB setup and the sound is phantatstic.

I am using for the Tone Board linear ps with this ps

https://www.ldovr.com/product-p/tps7a4700-spsu.htm

PI4 is powered with mezzanine prepowered with 6,2V LT1083CP

https://www.ldovr.com/product-p/mpower.htm

View attachment 62745

now somebody will write, that it was measured, that ps should not have any influence on the KTB perfomance, but IMHO with a good ps KTB sounds just better. Just try.

Pretty brave of you to post a pic here with a Jitterbug in the Pi. LOL!

 

[wjszbd14895]

Hello everyone:
I am using khadas tone V13, I would like to ask a question, in the process of listening to the music, why do I have a beep noise, and it is once a minute, I don't know why?There was no noise like this before. Have you ever seen this before?
Thank you very much!

 

[Veri]

Hello everyone:
I am using khadas tone V13, I would like to ask a question, in the process of listening to the music, why do I have a beep noise, and it is once a minute, I don't know why?There was no noise like this before. Have you ever seen this before?

You are using a special XMOS driver to update firmware, you cannot use this driver continuously.
You should uninstall the audio driver and install another one, like this latest version:
http://www.soncoz.com/uploads/1/2/7/2/127246176/soncoz_thesycon_usbaudio_driver_v4.82.exe

 

[wjszbd14895]

You are using a special XMOS driver to update firmware, you cannot use this driver continuously.
You should uninstall the audio driver and install another one, like this latest version:
http://www.soncoz.com/uploads/1/2/7/2/127246176/soncoz_thesycon_usbaudio_driver_v4.82.exe

Thanks.i will have a try.

 

[sinski]

Which type of digital filter is set in KTB ? Will there be one KTB version without ESS hump ?

 

[Labjr]

Which type of digital filter is set in KTB ? Will there be one KTB version without ESS hump ?

Yep, well sort of, it's made by @Ben1987 who used to work for Khadas.

https://www.audiosciencereview.com/forum/index.php?threads/soncoz-la-qxd1-balanced-dac-review.13459/

 

[BYRTT]

Which type of digital filter is set in KTB ?.....

KTB use default filter as seen below, datasheet for ES9038Q2M chip is available at Khadas site where one can see the other six filters, some users here in thread have upgraded their KTB with IAN's ESS controller that can give access to change filter and have a visual display that show status of audio stream data.

 

[Milesian]

Which type of digital filter is set in KTB ? Will there be one KTB version without ESS hump ?

What is it about the ESS hump that bothers you? Just curious.

 

[wiz2596]

What is it about the ESS hump that bothers you? Just curious.

to me the hump is not audible at all

 

[Labjr]

Sometimes I think I can hear a camel.