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Kubelik NOS DAC kits

Updated December 2023

Kubelik NOS DAC kits have now reached the end of their almost 2 1/2 year lifespan and are no longer available. If you'd like a more recent design, have a look at Dorati - https://www.diyaudio.com/community/threads/dorati-nos-dac-kits.387035/ and Abbado II - https://www.diyaudio.com/community/threads/abbado-ii-nos-dac-kits.400326/

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PM me and be sure to include your payment method and location so I can quote you inclusive of fees and shipping. Kubelik is an upgrade of 'PhiDAC' and keeps the same physical footprint of 81mm * 50mm, the maximum height is 19mm. The design is non-oversampling (i.e. no digital filter on-board) and the input format is I2S (three signal wire) at 44k1/16bits. BCK can be 1.4 or 2.8MHz, no MCK is required. Output is CD standard 2VRMS. There's a digital invert function which allows a balanced output DAC to be made from a pair of Kubeliks. Schematic may be found here : lingDAC - cost effective RBCD multibit DAC design

Preferred payment method is via Wise which typically adds a 2% fee. Our receiving currency is CNY, alternatively USD or Euro. PayPal may also be used, in USD but will attract higher fees, about 16%.

Price for a Kubelik kit : 128RMB (~$17.60)

Shipping is in addition and depends on your location and speed of service. Courier (FedEx, TNT, DHL) typically takes 8 - 10 days and e-packet four to eight weeks. Not all locations can be serviced by e-packet though.

FAQs

What else is needed to turn the built up kit into a fully operational DAC?

First you'll need a well regulated low noise power supply of 20V rated at 100mA or higher. An LM317-based board set to the correct voltage will suffice if you already have an unregulated supply (like a typical wall-wart). I don't recommend switching supplies due to issues with common-mode noise, its very hard to filter out. We can supply an LM317-based board with either DC (for unregulated DC) or AC (for a transformer) input option.

Second you may need a digital interface card. I say 'may' because some digital sources produce I2S directly (like Raspberry Pi, dedicated SDcard players) but most sources will either output USB (like a PC or laptop) or S/PDIF coax (a CD or DVD player) or Toslink. We can supply a card for interfacing one (or more) of those sources to Kubelik's I2S input. A CM6631A-based card for USB input is the premium choice as it operates under 'async USB' which is the lowest jitter. A mid-range alternative is an interface based on an STM32F4 microcontroller - while still low jitter, its output is not as clean on start/stopping as with CM6631A. In the bargain basement dept are the interfaces based on 'adaptive USB' such as CM108 and PCM270X. The S/PDIF board we recommend handles both coax (two inputs) and Toslink. Further, it has a switched I2S input - this can accept I2S from the USB source. A single pole switch acts as source selector, cycling through the inputs. An OLED screen is an option to indicate the selected input. The one drawback with this board is it needs a 5-12V supply, so a pre-regulator is necessary if fed from the DAC's supply. The simple coax/Toslink board needs a regulated 5V PSU.

Third you'll be wanting some output sockets, typically RCAs so you can connect your finished DAC to your amp or preamp. We can supply these and we're working on a PCB to mount them to make outputting Kubelik to your system easier.

Lastly, and this is obviously optional for a DIYer, is a case. We haven't supplied cases in the past because they're so heavy (i.e. expensive to ship).

USB CM6631A card examples : https://www.aliexpress.com/item/32874113831.htmlwww.aliexpress.com/item/1005004083748180.html
USB STM32 card example : https://www.aliexpress.com/item/1005003632369097.html
USB PCM270X card example : https://www.aliexpress.com/item/4000141799137.html
Multi-input S/PDIF card : https://www.aliexpress.com/item/1005002923079600.html
Coax/Toslink S/PDIF card : https://www.aliexpress.com/item/1005002772984954.html

Do I need special tools to build and test my Kubelik kit?

You'll need some fine diameter solder (0.3mm is recommended), a temperature controlled soldering iron with a fine bit and a pair of tweezers. A magnifier comes in very handy but that depends on your eyesight. Desoldering braid is helpful for correcting mistakes. If you've never soldered SMD before then maybe Kubelik will be too challenging for a first project as there are more than a hundred parts. However none of them are microscopic (the smallest is 0805) and none of the ICs has pins closer together than 1.27mm. For testing you'll need a DMM (digital multimeter).


What's supplied in the kit?

There's a picture directly below of the contents : the bare PCB plus all the components that mount on it (resistors, caps, inductors, LED, ICs etc.). Given that 0805 sized components are incredibly easy to lose, we include a spare or two for each value. Input, output and power are supplied via 4pin Molex-style headers, we supply the mating half with crimped wires to these too.


What, if anything, is unique about Kubelik's design?

Commercial NOS DACs typically have minimal filtering after the DAC chip itself. Kubelik has two kinds of filters resulting in a 5th order overall lowpass response - a 3rd order passive filter prior to I/V and a 2nd order active filter afterwards. The passive filter prior to any active stage improves subjective dynamics - it means the I/V opamp no longer 'sees' a step waveform out of the DAC chip, rather a continuous signal. The active filter provides 'NOS droop' compensation - meaning you get a flat frequency response to around 17kHz whereas a typical (not every) NOS DAC has roll-off approaching 3dB by 20kHz. It also has headroom to cope with 'intersample overs' which may occur on some heavily compressed recordings. Meaning it won't clip its output no matter what digital input you give it. Opamps are used but their outputs are buffered with discrete transistors as I've found this results in improved instrumental separation when the music gets very 'busy'. Kubelik's DAC chips are 'multibit' but they're not strictly speaking 'R2R' as internally they use no resistors. Instead capacitors are used as elements in the DAC which have their charge constantly refreshed (similar to the DRAM in your computer) to compensate for any drift.


Here's the build and test guide for Kubelik - lingDAC - cost effective RBCD multibit DAC design

Update : The two older versions of the stuffing guide had various errors, here is the up to date version : https://www.diyaudio.com/community/...-rbcd-multibit-dac-design.324933/post-6889095
 

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Yes all the parts are included, SMD and through hole.

LingDAC is going back three years or so - since then I've lowered the noise floor quite a bit. In practice this means a more holographic presentation, quite a bit more transparency meaning that when listening you'll hear much deeper into the recording. I've not done a direct comparison with lingDAC so this is from memory :)
 
Thanks to Abraxalito's patience and guidance, the test is successful right at the first time after completing the board. Instructions and guide is easy to understand and follow. Dac board is running off a crude lab supply now, with usb-i2s board powered by the computer supply. I am not going for a serious listening now. Waiting for my transformer and power supply board to reach me in a couple weeks' time.
 

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Thanks to Abraxalito's patience and guidance, the test is successful right at the first time after completing the board. Instructions and guide is easy to understand and follow. Dac board is running off a crude lab supply now, with usb-i2s board powered by the computer supply. I am not going for a serious listening now. Waiting for my transformer and power supply board to reach me in a couple weeks' time.
Nice one.
Any specific tips?
I have never even done any surface mount, so I am looking forward to this.
 
Grarea,

When you are soldering the Step 1, please solder the 4pin connector for the 20v supply last. There are a few components near the connector which will be impossible to solder if you solder the connector first.

A tweezer is very essential for this work and a good clean soldering iron tip will make things easier. I do not use any soldering flux or paste for this work. i put a drop of solder on one pad. Use the tweezer to place the component near to the pad which i had placed solder. Use the soldering iron tip to melt the solder on the pad, push one side of the component into the molten solder using the tweezer. if you need any adjustments, simply reheat the solder blob while using the tweezer to grab on the component and shift it into position. Then proceed to the other side of the component, which is much easier already.

The very important thing is to avoid mistakes. I will checked 3 times to ensure the correct components are in their correct locations before i solder. Takes time but also avoid any possible errors.

Believe me , this is the first time i solder a full surface mount board. I am sure you can do this too.
 
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Thanks for that.
It is much appreciated.
First job is working out how to see it without fear of burning my nose with the soldering tip :)


I am considering thinking long term (plus it looks fun) and bodging myself a pi zero soldering scope.
I think I have some threaded bar in the garage.



I am sorely tempted to make
 
@commstech : A good summary of how to solder SMD. Also I agree, I missed putting in the direction to leave the 4 way connector to last.

I'd add that I use tweezers which are angled and a component often needs a downward push to get it flush with the PCB and seated on its solder - slide it into position horizontally then hold it down while removing heat. For which tweezers which have serrations on the inside of their tips might be the best choice as that'll allow downward pressure whilst holding in place. Using thin solder is a big help in avoiding using too much - I use 0.3mm diameter. Its easy to add more solder, more fiddly to remove.
 
Kubelik power supply board

Out of sheer frustration in trying to coax Taobao-sourced LM317 boards into reliable action in the service of Kubelik, we decided to create our own LM317 PSU.

This is almost a text-book LM317 implementation just with a couple of differences. First there's a common-mode choke on the input to suppress mains-borne noise. Second its using zener diodes with a low value R in series to set the output voltage which defaults to 20V.

Price in ready-built up and tested form is 50RMB.
 

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Blimey, this looks like an awesome kit and project! Hope there will still be some kits available in a few months time, as I cannot commit now - busy finishing off some other stuff.

I have been lurking on the LingDAC thread and always wanted to try one of abraxalito's implementations. Although I am still extremely happy with my Matt Garman TDA1387 RPi HAT DAC - this looks like a smd solder slinger's dream. I've come to love smd soldering.

As a matter of interest - at what temperature do you set your soldering irons? I have a new one and still trying to find a sweet spot.
 
So many dacs such as Topping D90, Denafrips AresII, Musetec LKS MH-DA005, Schiit Bifrost 2, Mytek Brooklyn Bridge. Kubelik NOS DAC can compete?


Only one way to find out, right? 😁
As abrax says, none if those are kits, so don't have the fun factor. I am looking forward to having a hand in putting my DAC together.

It is also interesting being a tiny part of this project.


Also, it doesn't come in a box, so I have a choice of how I encase my system. Rather than just a pile of boxes.



Also, which of those is the cheapest?
Haven't you picked a range between about 900-3000 dollars?

It would be interesting to compare wouldn't it?
At 20 dollars, its got to be worth trying to see eh?
Do you have any of those to compare to?
It would be interesting to hear your thoughts.

I will be comparing to khadas tone board to see if I can tell the difference. but my Kubelik already has a place anyway.



You know abrax has a couple of other options available as well?
 
@audiostar - I haven't listened to any of those DACs you've listed so can't comment how Kubelik compares. Perhaps as more people who have those DACs build their own Kubelik we'll get some listening reports posted.

@Grarea - I think a Khadas Tone Board would be a useful comparison. I've only briefly listened to the Tone Board2 myself, and not side by side with any of my DACs. My wife's comment on the Tone Board2 was 'how is this better than my phone?'.
 
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My wife's comment on the Tone Board2 was 'how is this better than my phone?'.
:D
I am only near the beginning of my journey and the KTB was an eye opener for me. It encouraged me to start delving in more. It was definitely better than my pc and the DAC in my 20 year old receiver.
So, I am very much looking forward to comparing.
I need to improve my source another couple of steps as well to give a decent comparison.


@audiostar
I was also somewhat confused about where everything sits in the whole world of DACs. I asked a kind of vague bunch of questions to try and summarise it for myself after a bunch of reading:
https://www.diyaudio.com/forums/dig...rbcd-multibit-dac-design-127.html#post6765174


It might help.