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Review and Measurements of WesionTEK Khadas Tone Board DAC

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Given that other devices are affected and that not all installations of 1903 are affected I feel like the issue is probably on Microsoft's side. For what it's worth I appear to be running firmware version 4.11.0 and hardware version 1.04.

 

BYRTT

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Given that other devices are affected and that not all installations of 1903 are affected I feel like the issue is probably on Microsoft's side. For what it's worth I appear to be running firmware version 4.11.0 and hardware version 1.04...
Hi @dsissitka,

Now hope its alright correct your post a bit in below :)

What you see as "Revision" in "Device Info" sector is the firmware info, and it says "v1.04" which is the latest official Khadas version so you up to date there : )

What you see as "Version" in "Driver Info" sector is the Windows operating system driver version from Thesycon Systemsoftware, and if that package was downloaded from Khadas site its a evaluation package that is only meant for use to update firmware and should be uninstalled as soon one have updated the firmware. On Windows 10 for Khadas Toneboard one can either use operating systems native UAC2 driver which support MS DS and WASAPI or use officiel v2.24 driver made by Thesycon Systemsoftware which will support MS DS and WASAPI and also ASIO.
 

BYRTT

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Yes that's the driver. My DX3 Pro uses the EXACT same driver by default and it works without pops and crackles.

I think the Khadas needs a firmware update to be compatible with Windows 1903 and up again.
You could check if your firmware is the latest official version in go to device manager and find KTB device and after a double click go to "Details" tab and pick "Proberties" and schroll down to "Hardware-IDs" where it should tell a string saying "USB\VID_20B1&PID_00DA&REV_0104".

The last four numbers in above string is the code for latest firmware v1.04, if its tells something as "0102" or "06?2" firmware is not the latest one and needs a manual update procedure to get up to date of v1.04.
 

g29

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Here is the S/PDIF input performance. You activate it by just hooking up a USB power supply to USB port. I used the little switcher Wesion sent me.

View attachment 16368

With USB input, Channel 2 had some spikes around 10 kHz which are now gone, resulting in nearly 2 dB improvement.
@amirm ,

How did you get the S/PDIF input working? Does it require a special PS ?

I have read it automatically switches inputs when the USB input isn't playing/passing data. I have tried this method (USB plugged in to PC with no player active) and also using a USB charger wall wart (no data lines) to power it.

I have not been able to get the S/PDIF input working with either method.

TIA

Update: Found a post stating it needs a PS 500mA or greater. Mine are 1A and 2A.
 
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amirm

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How did you get the S/PDIF input working? Does it require a special PS ?
I just used a phone charger with USB cable. That way, there is no data and it will switch to S/PDIF.
 

g29

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I just used a phone charger with USB cable. That way, there is no data and it will switch to S/PDIF.
Thanks, got it working now.

Used another SPDIF output source. Was using an old DVD/SACD/DVD-A/CD multi-format player's SPDIF output. Works with the PC's USB power and the USB cell phone charger now. There must be a setting in the DVD player that I am missing.
 
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Got mine last week and stuck it in an Audiophonics case. Did I mention it's absolutely stupid good, but updating the firmware is a PIA, especially confusing was their instruction to take off the software I loaded in step one, and all the Khadas drivers--but I got it figured out.

Have a cute little set of 6 inch RCAs to connect it to the THX 789. Occupies a pride of place on my end table (from which hang my LCD Xs and HD 800s) right next to my grandpa chair. Now, just waiting on that Smyth A16 Realiser!
 
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Nothing wrong with the I/V stage, good engineering all around. About the schematics:
Has anyone tried removing the following series and grounding resistors after the output opamps: R50/R58 and R43/R47? The goal is to lower the output impedance, eliminate components in the signal path, and not have R58 and R57 interact with the headphones' impedance when driving headphones directly.

I am however not sure if the output state would be stable without the resistors. My speaker amp has 1k series and 22k grounding resistors at its input -- once connected things should be fine. Headphones range from 64ohm to 300ohm -- again things should be fine once connected. But if the output stage is not connected to anything (i.e., open), would the lack of grounding resistors cause any issues? I think not, but would like to confirm.
 

BYRTT

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Hi @338h10,

Know that we get some sound signal with head phones direct connected to KTB line outs, that said its not really designed as a head phone out put but a good quality normal voltage line output so we should use it as its intended is my opinion and connect it to preamps poweramps or head phone amps :)

A couple of reasons guessing why the 100 ohms R43/R50 sits there and never should be removed is it protects or isolate opamp against any weird or nasty cable reactive loads, also it protect opamp for a directly short should user by accident make a short to RCA terminal, any connected cable or head phones will work as antenna picking up unwanted RF noice bleeding into feedback loop of opamp where R43/50 up to a degree help isolate such problem.
 
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Hi @338h10,

Know that we get some sound signal with head phones direct connected to KTB line outs, that said its not really designed as a head phone out put but a good quality normal voltage line output so we should use it as its intended is my opinion and connect it to preamps poweramps or head phone amps :)

A couple of reasons guessing why the 100 ohms R43/R50 sits there and never should be removed is it protects or isolate opamp against any weird or nasty cable reactive loads, also it protect opamp for a directly short should user by accident make a short to RCA terminal, any connected cable or head phones will work as antenna picking up unwanted RF noice bleeding into feedback loop of opamp where R43/50 up to a degree help isolate such problem.
Make sense.

And I may very well give up the headphone idea -- I was looking for flexibility, but knowing myself I know that if I really want to drive headphones, I will build an amp for it.

But, I may still get rid of R50/R58 and R43/R47 as I intend to put the DAC in the same case as my speaker amp and solder the DAC outputs directly to the amp inputs -- as the amp already has 22k to the ground and 1k in series, there wouldn't be any short to the ground or float without the ground, and noise would not be a material issue as the case is made of metal. I will report back if it works. I see some are also housing the DAC with an amp, so being able to eliminate components in the signal path safely could be helpful.
 

BYRTT

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Makes sence you safer to mod or remove R50/58/43/57 when building KTB into same enclosure as the speaker amp, but then again will suggest why not just lower 1k/22k resistors a bit for power amp input section, it should relative give the same and then you shure KTB stay within specs and do not start any unknown for user out of band nasty hidden oscilation.
 
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Makes sence you safer to mod or remove R50/58/43/57 when building KTB into same enclosure as the speaker amp, but then again will suggest why not just lower 1k/22k resistors a bit for power amp input section, it should relative give the same and then you shure KTB stay within specs and do not start any unknown for user out of band nasty hidden oscilation.
Good question. I cannot raise the amp's input grounding resistor to 47K because doing so will cause DC offset issues at the amp. But I am certain the DAC's output stage can handle 22k (or lower) because in reality, the 47k will be paralleled with the amp's input grounding resistors in most cases, which will drag down the impedance anyways. Many amps have input impedance as low 10k or even 5k, so my 22k should be generous.

My amp might be stable with a series resistor lower than 1k. I will have to think about that. As a matter of principle I have always preferred no series resistors at all (not even 100ohm) in the signal path, but I remember I had a reason to put a 1k there -- it was more than a decade ago, and my memory has faded. The 1k resistors are metal foil resistors that cost $20 a piece, so I must had a real need to put something there at the time.
 

BYRTT

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Will guess or imagine when there is news for the next revision that @willow or @Ben1987 will post about it here and probably also send @amirm a unit to be tortured by panthers and AP sweeps :p that said have peice in mind here because current low cost version works and sounds excellent even its born with the famous unfortunate ESS hump and lack the good to have ballanced line output feature.
 
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to be honest i do not care about volume control balanced out etc. the current version would have been bought by me, but i do not understand if the ess hump is listenable or is more of a spec that noone really hears... but i think i heard that it can be noticed...
 

Veri

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to be honest i do not care about volume control balanced out etc. the current version would have been bought by me, but i do not understand if the ess hump is listenable or is more of a spec that noone really hears... but i think i heard that it can be noticed...
People here could not tell difference between D50 and D50s whatsoever. So I doubt sabre hump is a big deal, it's more for peace of mind :p
 

Herbert

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Same with me. Plug and Play via SPDIF + the knowledge that the hump
is cured and SINAD exceptionally well.
I hope that there is still a single ended
output. I have balanced output on my
DIY Twisted Pear Buffalo Dac (built it around 2012) and since then there was only once the occasion where we
contemplated to use balanced out for sample rate conversion via the analog path - but decided to do the conversion digitally. Bottom line. I never used balanced out in 7 years.
Volume control would be fine as long as it is done after conversion.
 
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