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Review and Measurements of WesionTEK Khadas Tone Board DAC

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amirm

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.
 
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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.
 

phoenixdogfan

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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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338h10

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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.
 

338h10

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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.
 

338h10

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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.
 

porotikos

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Hi guys. any news on the new revision of the dac? they said october it should vbe available. shouldnt we have more info?
 

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.
 

porotikos

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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...
 

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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.
 

Presently42

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Twisted Pear Buffalo Dac (built it around 2012)

Assuming you have both the Buffalo and the ToneBoard, have you noticed any difference between the two? I also have the Buffalo II, with Twisted Pear's 16 bit USB converter and am strongly considering getting the ToneBoard, if only to get a better USB converter.
 

matgir99

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This is a review and detailed measurements of Khadas Tone Board DAC from WesionTEK. It is on kind loan from the company. The retail price on Amazon is USD $99 including free shipping.

As the name indicates, this is a bare board DAC:


Don't confuse this with Raspberry Pi boards though. This is a complete DAC and doesn't need a host to operate. It is just like any other desktop DAC except that it doesn't come with a case.

The Khadas Tone Board is powered and accessed through the USB port and S/PDIF. For my review, I only tested the USB input.

Output as you see is through a pair of RCA jacks that have a great high-quality look and feel (as does the S/PDIF one). It would be at home in DACs at much higher prices.

WesionTEK sells two versions of this board, one of which mates with their host processor to make a complete networked DAC and player. They were kind enough to send me the host which I will review later.

Let's get into measurements and see how well it does.

Measurements
As usual, we start with our dashboard view:
View attachment 16340

I must say, I was not prepared for such excellent performance from such an unassuming board! Essentially 110 dB SINAD (signal above noise and distortion) in a $99 DAC? That is most excellent:
View attachment 16341

I should have of course paid attention to the web page for this product: http://szwesion.com/khadas-tone-board/

Right there is the same dashboard measurement with the same Audio Precision APx555 analyzer I have with identical response!

Khadas-Tone-Data1.jpg


Their THD+N is 0.000337% and mine is 0.000331%. Wow, what consistency!!!

This is a company that does things right, measuring and verifying designs.

Continuing on with jitter and noise we get:

View attachment 16342

There a lot of little spikes visible but that is partly due to very low noise floor which reveals more of these. Worst case spike is below -130 dBFS which is well below any threshold of audibility.

Here is intermodulation distortion versus level:
View attachment 16343

Here, we have typical response similar to what we get from other desktop DACs using ESS' later DAC chips.

Dynamic Range comes next:
View attachment 16344

This is very good but a bit shy of their numbers. This measurement though is very sensitive to such things as ground loop so in other situations it may be possible to get close to the 120 dB number they post.

I have been asked for crosstalk measurements so here it is:

View attachment 16345

The spec better than 127 dB and it definitely seems to be there at almost all frequencies.

Crosstalk usually increases with frequency as we see in Schiit Modi 3 graph but here, the Khadas Tone Board maintains the same level throughout audio band which is excellent.

Lastly, we have linearity test:

View attachment 16347

I like to see less than 0.5 dB of deviation at -120 and Khadas Tone Board easily sails through that criteria.

Conclusions
WesionTEK contacted me and joined the forum immediately after someone mentioned this board as something to test. They quickly sent me the samples but due to my busy schedule, I was remiss in not testing it until now. I regret that delay seeing how well their product did in my testing.

The Khadas Tone Board is a high performance DAC and a bargain price. It is exceptionally well engineered and easily earns my highest recommendation!

Get your own case for it and tell your friends you designed it. :)

That WesionTEK is active on forums and ready to support their owners is a fantastic bonus.
Am I the only one using the khadas tone board also as amplifier directly for my IEMs?
 

Veri

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Am I the only one using the khadas tone board also as amplifier directly for my IEMs?
Considering it is not built for this, the impedance output of the DAC will have unexpected effects on the frequency response.
It's not really recommended. I'm sure noise-wise it will be not a problem, but FR-wise... not the best idea!
 

g29

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Considering it is not built for this, the impedance output of the DAC will have unexpected effects on the frequency response.
It's not really recommended. I'm sure noise-wise it will be not a problem, but FR-wise... not the best idea!

FWIW: Khadas sells this optional adapter cable for an additional cost.

Connect your Tone Board's RCA stereo output to a 3.5mm compatible set of speakers or headphones.

Compatibility:
  • Khadas Tone Board
  • Audio Equipment w/ RCA Output
  • Headphones or Speakers with 3.5mm Male Audio-Jack
RCA to 3.5mm cable


04a2a6_37f2f53c73314521b8da9bbff758e120~mv2_d_2500_2500_s_4_2.jpg
 

zermak

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@g29
If I recall looking at the Kahdas TB schematics the impedenceof the RCA outputs is 100 Ohm very high impoedence to get a flat FR with IEMs and their low impedence. I suggest you to use a amp with low output impedence to enjoy the music with your IEMs.
 

g29

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@g29
If I recall looking at the Kahdas TB schematics the impedenceof the RCA outputs is 100 Ohm very high impoedence to get a flat FR with IEMs and their low impedence. I suggest you to use a amp with low output impedence to enjoy the music with your IEMs.

Mine goes straight into an electronic XO. No earbuds or headphones.
 
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