Review and Measurements of WesionTEK Khadas Tone Board DAC

[gvl]

Is there any info what filter the ESS chip is set to?

 

[zephyros]

It's mind boggling how such stellar performance can be reached in this tiny board and at this kind of price. Definitely worth a celebration. The only downside I can see is that it would looks pretty, insubstantial, pairing with a big headphone amp
Now to find a case for it.......

 

[Veri]

Is there any info what filter the ESS chip is set to?

I had asked them this question this was their answer:

you can use the XMOS to DIY the structure and adjust by the PINs on board.
XMOS source code we can't open.
more you can check on khadas forum for more technical details:

 

[TimW]

Really starting to feel the impulse buy itch now. Trying to wait until Amir reviews the SBC Khadas sent him to see how it can be used with this DAC.

 

[Red_Red]

Wow, wow, wow ! Thank you very much amirm ! The SPDIF input is excellent !

 

[gvl]

I had asked them this question this was their answer:

you can use the XMOS to DIY the structure and adjust by the PINs on board.
XMOS source code we can't open.
more you can check on khadas forum for more technical details:
View attachment 16373

Hmm, is this really the answer to the question as to what filter type is set by default? One would hope it is linear phase.

 

[gvl]

A few posts earlier, I asked Amir if he could generally measure impulse and/or step response to identify the filter type. I'm hopeful.

IR of Linear Phase, apodizing fast roll-offs and brick-wall in the ESS datasheet all look the same to me. The apodizing fast roll-off is the DAC default, if Khadas doesn't set another that's what it is.

 

[rajapruk]

Maybe this chip could be made as a mono-balanced dac maybe? If input is 2 of the same channel, with polarity flip on one.
I.e 2 of these pcb could make a balanced stereo dac with 4 volt output?

Then maybe the common-mode intermodulation distortion hump is canceled out as well?! (this concept maybe @amirm can test)

(I am way out of my league here, just speculating)

 

[gvl]

I looked at the schematic, I'm not 100% positive as it is fragmented and there appear to be some discrepancies but it seems the I/V conversion is done on both legs of the differential signal and further fed into the output op-amp buffer, so the common mode noise should already be cancelled on the RCA outputs.

 

[gvl]

Anyway, the default filter is linear phase with almost no aliasing and (to me) the second best. I could live with it very well.
Nice information from ESS, by the way.

I'm looking at a bootleg ES9038Q2M datasheet and the default is the apodizing fast roll-off filter not the linear phase one, are we looking at the same document? Or are you saying that the apodizing filter is also linear phase?

 

[Ron Texas]

Here is another highly pertinent report. The unit tested kicks ass on the bench, is inexpensive and available. This thing might become a legend.

 

[TheObjectivist]

If I used a metal enclosure would I have to ground the board? And if I used a plastic one would it be affected by external electrical interference?

 

[helloworld]

LOL.

But seriously though, how do they recoup the money for R&D (assuming that they own the APx555 unit) and still provide the schematics while selling well-engineered products for very little money in this niche market?

They are mainly selling the vims not this dac. So they are not like the small dac company and definitely can afford an apx instrument

 

[Eric Auer]

Biggest draw back here is no optical option which leaves out the Chromecast Audio as a source.

Eric

 

[lastexile]

Since there are two version at the same price which should I buy?

 

[gvl]

Since there are two version at the same price which should I buy?

It seems they are the same board, the generic version doesn't have the VIM headers soldered on but they can be added later if needed. If you plan to run it standalone just get the generic version.

 

[miero]

In a schematics[1] of this DAC there are opamps marked RT6862D and RT6863. And also a dual voltage regulator R1286K010F. Are this from ESS? Is there any public info about them?

EDIT: Nice! The R1286K010F is a 2ch. PWM Step-up / Inverting DC/DC Converter with Synchronous Rectifier for AMOLED / LCD from RICOH[2].

[1] https://dl.khadas.com/Hardware/ToneBoard/Schematic/Tone_V13 SCH.pdf
[2] https://www.e-devices.ricoh.co.jp/en/products/power/dcdc/r1286/

 

[gvl]

In a schematics[1] of this DAC there are opamps marked RT6862D and RT6863. And also a dual voltage regulator R1286K010F. Are this from ESS? Is there any public info about them?

[1] https://dl.khadas.com/Hardware/ToneBoard/Schematic/Tone_V13 SCH.pdf

These could be just internal reference numbers, the actual parts may vary depending on what they have.

 

[miero]

Or some custom ICs from Richtek guessing by a prefix RT.

 

[gvl]

Or some custom ICs from Richtek guessing by a prefix RT.

Custom ICs for a $99 boutique board sold in limited quantities? Maybe but seems unlikely.