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Review and Measurements of WesionTEK Khadas Tone Board DAC

sojer2005

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Hi,
I have recently installed Khadas Tone Board in my main system and I really like it’s sound quality. IMHO sounds better than my Node 2 streamer.
Currently, I am using: Raspberry Pi3 (ropieee Roon endpoint) -> USB KTB -> Marantz integrated amp. I am using Roon software and I really like hardware volume control, everything works fine.

I am thinking about using something better as transport than plain Raspberry Pi3. Mayble Allo DigiOne? But my main concern is hardware volume control. Is it possible over spdif interface? In this case it wolud be: AlloDigiOne with ropieee -> spdif KTB -> Marantz integrated. Will I losse hardware volume control with this config?

Thanks.
 

Veri

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March Audio

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So looking at the headphone 'conv', this thing can properly direct drive headphones :) ? If so, a cool feature.
It can but due to the 100 ohm resistors in the output it will have limited volume capability dependant on headphone impedance. Also due to this its probably only really suitable for headphones that have a constant impedance V frequency, i.e. magnetic planer types.
 

Veri

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It can but due to the 100 ohm resistors in the output it will have limited volume capability dependant on headphone impedance. Also due to this its probably only really suitable for headphones that have a constant impedance V frequency, i.e. magnetic planer types.
Ahh, yes. Makes sense. I asked because the PecanPi has <1ohm output impedance over RCA and can drive headphones with such a converter/adapter. I was thinking maybe the Khadas could, too :) but alas, won't work well with most headphones!
 

solderdude

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In a schematics[1] of this DAC there are opamps marked RT6862D and RT6863.
RT6863 is the output opamp. As March Audio correctly explained the output R is a bit high (100 Ohm) for all headphones and output voltage a bit low to properly drive high impedance headphones.

As it is a DIY board one can lower R43 and R50 to say around 5 Ohm by paralleling a 5.6 Ohm resistor to R43 and R50 and have a lower output R but the max output voltage will remain the same. The RT6863 is spec'd to deliver 100mA so a 32 Ohm load can be used without issues it seems.
The question is whether or not the DCDC converter can supply 200mA and what the power supply voltage is.
Maybe the output voltage can be increased a bit and it could drive higher impedance headphones better directly.
 
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When we have a new version of audio board, we would love to ship to Amirm for testing, it will be our great honor. Thanks to the review of Khadas Tone Board on Audiosciencereview.com, people began to know it and have to accpet it as a single board without casing. That is really appreciated. As in the past 3 months we dont have any good selling score until the review comes out. @amirm Appreciated.
Cool beans. Any ETA's and information on the new Balanced Version ?

Balanced Version
 
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It can but due to the 100 ohm resistors in the output it will have limited volume capability dependant on headphone impedance. Also due to this its probably only really suitable for headphones that have a constant impedance V frequency, i.e. magnetic planer types.
this is the type of things i am mad i don't know about.
i have jds labs atom and i have in mind getting HD650 which has 300 ohm's
i also planned on getting khadas tone board. but i thought i was being smart for waiting since everyone saying khadas will release in Q2 some updated version (have no clue about that and will it affect my listening experience).
now i don't even know if i should get khadas tone board whatsoever.

@March Audio please explain your quote to me. halp me o_O
 
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@bornstron, he's talking about trying to listen to headphones through the Khadas Tone Pro's RCA output jacks instead of the headphone jack of a power amp (like the Atom) that it's connected to. For whatever reason, Khadas includes a cable that allows you to connect headphones to the DAC's output jacks.
 

March Audio

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this is the type of things i am mad i don't know about.
i have jds labs atom and i have in mind getting HD650 which has 300 ohm's
i also planned on getting khadas tone board. but i thought i was being smart for waiting since everyone saying khadas will release in Q2 some updated version (have no clue about that and will it affect my listening experience).
now i don't even know if i should get khadas tone board whatsoever.

@March Audio please explain your quote to me. halp me o_O
Bottom line is that the board has high output impedance which is fine for driving amplifiers but not the best situation for driving headphones directly.

Really you need an external amp to use with it, which you do, so all is good :)
 
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