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Review and Measurements of WesionTEK Khadas Tone Board DAC

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Nov 21, 2018
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Guess if you used that firmware upgrade shortcut in program group fram EVAL installation and process said okay you should be there.
Then there seems two ways to check your current firmware, one is if you have the shortcut at bottom right side for TUSBAudio control Panel then open that and go to its "Info" tab to see firmware version, example is the blue below which is how it looks on my Win7 for v6.F2 aka 1226, If one is on Win10 native UAC2 driver then there is no TUSBAudio control Panel then go to Win10 device manager and open XMOS device that have symbol as a USB terminal (forget the XMOS device that have speaker symbol) then on details tab shift proberties to same as below and version should be listed in lowest window there, one could imagine after upgrade a unplug replug of USB connector will refresh OS to probe for the new firmware version.

View attachment 23583

Yes you should uninstall EVAL version, but whether to use native Win10 UAC2 driver or the rather old v224 driver is up to you. Would imagine a native driver code written by same company that have written code for OS itself should be the preference but was it myself running Win10 i would do a physical analog loopback test to another input port using for example free REW to check everything looks right and if it doesn't then try v224 and make the same loopback test to get peace in mind, say this because first Win10 build that had build in native UAC2 driver worked not very good on a ASUS U7, sound was different than used to and after a loopback test one could see impulse response was scary weird and phase was nothing but grass, but maybe they fixed that since or that U7 hardware is not up to protocol other than use driver from ASUS.
Thank you. I uninstalled the eval version and then went back in and reinstalled v224. It has been working fine for me. Version via the info screen is 1.02.

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Joined
Nov 26, 2018
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Besides the need of a magnifying glass, sensible board layout and extremely steady hands:
Would it be possible to adress the "ESS-hump" by bypassing the I/V stage i.e. on a Khadas Tone board using a more "suitable" design?
(Somebody mentioned somewhere that the balanced I/V can be bettered)
BTW in the Khadas schematics I can not figure RT 6683 (last page second schematic from right)
 
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Feb 5, 2019
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Nothing wrong with the I/V stage, good engineering all around. About the schematics:

The schematic makes more sense when it's drawn out and not split to pieces. The official schematic is "a professional view" and one has to follow the singal markings.

Sorry for the crudeness, but here is my quick redraw of it with only the interesting components marked (and signal names to match the official schematic) but you can trace it out on the official schematic to see the resistor/capacitor values.

I can't make it more clear so I drew a new picture what RED markings mean on the schematic. They are "BUS" or "SIGNAL" markings and mean a single connections. Here is how it looks on the official schematic:


EDIT: I thought how to visualise it even another way. Here is how it looks on a more traditional schematic where connections are always split and marked, I left the left channel unmodified to show the difference even better:
 

BYRTT

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Not shure the implementations that live on a simple single +5 volt supply is going to have "ESS-hump" solved, its nothing but my own diy speculation so take it with a grant of salt but it looks solutions that have hump solved also have more advanced multiple higher voltage supply's involved, also will guess if Khadas guys have the clue and really can nail that hump ther's a chance we will see that improvement in the upcomming ballanced version announced down the road probably about Q2.
 
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I have a bunch of similarly tiered gear with different DAC's including ESS hunchbacks. In all honestly, I can't personally hear any hint of distortion or other "things" negatively affecting the audio. But, I am a casual but analytical listener and not an audio engineer who needs absolute precision.

Although impossible to do, an interesting graph would be all those DAC's on amirm's chart run through blind testing, rated, and then charted :)
 

Veri

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I have a bunch of similarly tiered gear with different DAC's including ESS hunchbacks. In all honestly, I can't personally hear any hint of distortion or other "things" negatively affecting the audio. But, I am a casual but analytical listener and not an audio engineer who needs absolute precision.

Although impossible to do, an interesting graph would be all those DAC's on amirm's chart run through blind testing, rated, and then charted :)
Sounds like a hella lot of work :p
 
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Dec 1, 2018
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I am monitoring this discussion for a while and can't understand why you guys are worry about voltage, output impedance, "ESS-hump" and other trivial things. I would like to add my 5 cents to it. My setup is as follows: Tone Board is connected to USB 3 in the back of the Asus motherboard, output from Tone Board is connected to the Mackie 1202VLZ4 mixer and mixer is feeding Mackie HR824 Studio Monitors. With that, Tone Board sound incredibly good. What I am trying to say is : you need to have very good equipment to fully enjoy that little thing.
 
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Feb 10, 2019
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I am monitoring this discussion for a while and can't understand why you guys are worry about voltage, output impedance, "ESS-hump" and other trivial things. I would like to add my 5 cents to it. My setup is as follows: Tone Board is connected to USB 3 in the back of the Asus motherboard, output from Tone Board is connected to the Mackie 1202VLZ4 mixer and mixer is feeding Mackie HR824 Studio Monitors. With that, Tone Board sound incredibly good. What I am trying to say is : you need to have very good equipment to fully enjoy that little thing.
In my case, with certain DIY amps without an input buffer having a high output impedance will affect the frequency response if the amplifier doesn't have a built-in input buffer. This will not be the case with any commercial amp because it will also have an input buffer that has the dual purpose of "tuning" a house sound. However,100 ohms is super lower for output impedance when for instance, and will play nice with any amp that has an input impedance of 1k or higher (the one that I will use has one of about 6.2kohms at 10khz and higher). So I worry about it because in my application it can cause measurable and audible effects to the frequency response of either the midrange or midwoofer in my active setup. We worry because our applications may not match yours so we may have different requirements.
 
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Dec 5, 2018
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So 100R will imply 100 ohms? for R406?
Correct, 100R is common notation for 100 Ohms. They're R50 and R43. The R0402 part is presumably the 0402 size smt resistor footprint. I'm not familiar with the opamp in the output buffer, but I'd be surprised if it had trouble driving 6.2k. It may be worth looking up just to be sure.
 
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Feb 22, 2019
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As far as I know, amirm used the PC USB power during the measurement.

He must have used some device in between to seperate data and power of usb maybe. Either way I measured it myself with rightmark and the difference is massive in my usecase. I believe ill get even better results with the DAC i ordered above from Amazon using it's coaxial digital out.
 
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