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Dorati NOS DAC kits

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J

jimk04

Member
Joined 2018
Paid Member
Got the first stage of my Dorati populated today. Well I got a bit carried away and started on all the small items until I looked again at the stuffing guide!
Performed the 1st test. Used a current limiting PSU to make sure I didn't mess up. All seems good at 14v. Drawing 0.06A.
My measurements seem OK to me but aren't quite within the tolerance so I share them here to get a confirmation that I'm good to proceed!

TP1 4.86v
TP2 2.49v
TP3 1.66v
TP8 5v.....good on this one!

IMG20220726183829.jpg
 
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J

jimk04

Member
Joined 2018
Paid Member
Dorati playing wonderfully. 14.5v from Salas Ubib set with 3v3 for 185mA.
I2s from Rpi/Fifo set at 44mhz. I forgot to do the last 2 measurements but seems I have no DC to worry about. Shall test them though at some point. Will let it play for a while. Great little DAC that saves a lot of space over the PhiDeca.
I put 220uf Pana FM on the outputs, bypassed with 0.68uf CDE acrylics, taking inspiration from Vunce.
It feeds a Salas DCG3 and Pass ACA at the moment. Really liking this small class A. Nearly finished Richard's amps though so will be trying those soon .
 
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bench2005

bench2005

Member
Joined 2005
abraxalito said:
Orders now are open on Dorati NOS DAC kits - PM me and be sure to include your payment method and location so I can quote you inclusive of fees and shipping. Dorati offers a sound quality upgrade over its predecessor 'Kubelik' but retains the same physical footprint of 81mm * 50mm, slightly smaller than a credit card; the maximum height is 24mm. The design is non-oversampling (i.e. there's no digital filter on-board) uses passive I/V and has a discrete output stage. What sets it apart from typical NOS DACs is the use of an LC filter prior to the active stages. 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 and headphones at 300ohm impedance and above can be directly driven. Power supply requirement is a single 12-15V rail at 150mA max. There's a digital invert function, selectable by a 0R resistor. Schematic may be found here : Dorati schematic updated 6.23

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 Dorati kit : 168RMB (~$25)

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 Dorati kit into a fully operational DAC?

First you'll need a well regulated low noise power supply of 12 - 15V rated at 150mA 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, many 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 Dorati'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 is useful to accept an I2S stream from a separate USB interface card to facilitate a USB input. A single pole switch acts as source selector, cycling through the four sources. An OLED screen is an option to indicate the selected input. If your DAC supply is 12V, you can directly power this card from the same supply as you use to feed the DAC. The simple coax/Toslink board needs a regulated 5V PSU which can be implemented via a regulator from the DAC supply.

Third you'll be wanting some output sockets, typically RCAs so you can connect your finished DAC to your amp or preamp. Or if you're feeding high impedance HPs, a 6.3mm (or 3.5mm) TRS socket. We can supply these. We also have a PCB for mounting a pair of RCAs which makes connection a little 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).

Whilst these links all worked when I posted, Ali links go stale very quickly so beware. CM6631A is rapidly becoming unobtainium, we couldn't find a single Taobao seller with stock :

USB CM6631A card examples : Aliexpress CM6631A USB-I2S
USB STM32 card example : Aliexpress STM32USB card
USB PCM270X card example : Aliexpress PCM2706 USB interface
Multi-input S/PDIF card : Aliexpress S/PDIF Toslink I2S switcher
Coax/Toslink S/PDIF card : Aliexpress DIR9001 S/PDIF receiver

Do I need special tools to build and test my Dorati 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 Dorati will be too challenging for a first project as there are around 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 (to be added) : 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 Dorati's design?

Commercial NOS DACs typically have minimal filtering after the DAC chip itself. Dorati 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 buffer 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. No opamps are used, the analog signal processing stages are all discrete transistors. Dorati'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.


View attachment 1062379

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Click to expand...
hi,

I live in Hong Kong, can you let me know how to go about ordering the kit?

Many thx.

Ben
 
bench2005

bench2005

Member
Joined 2005
Hi,

While I am waiting for the kit, just wonder has anyone have any experience with using the DAC on a Raspberry Pi or similar sbc? Just that most USB to I2S adapter cost almost as much as a SBC nowadays and apart from the mobile advantage ie. you can unplug the usb and move it somewhere else, it seem to me a simpler solution. Again YMMV.

Ben
 
bench2005

bench2005

Member
Joined 2005
jimk04 said:
Mine is from an Rpi but via a Fifo . You can take the i2s straight from the Pi but isn't the best option for sound quality due to the clock frequencies.... apparently .!
Click to expand...
Hi Jim,

'Good point about the clock frequencies. Linux or any non-realtime operating system isn't the best to generate a accurate, let alone stable clock. But then what I am looking for is somewhere to start, may be the PI is "good enough" to start off with. I am looking to start this "HiFi" journey again, now I have time. Last time I play around with "HiFi" is when you put needle to a spinning plastic disk :) .


Ben
 
G

Grarea

Member
Joined 2019
Yup, I reckon it is a great place to start.
I am not many steps ahead of you.
In fact you might already know more than me.
I kind of dived in and got a bit confused.
I wish I had done one step at a time.
My music in the garage is a pi zero, volumio and a dacamp hat.
(my lounge one is a bit more complicated, but Jimk understands mine better than me :) )

It is because of the clock frequencies is it?
I thought it was because the pi is noisy electronically?
Or is that a different thing?

@bench2005 while you are paying for postage, ask abraxalito about his other offerings.
 
J

jimk04

Member
Joined 2018
Paid Member
Apologies to Richard to thread OT but I'll just add this for bench2005.
I don't think the Pi clock is a game changer if this is just a start out piece of gear or maybe not for your main system. My first dabble with Rpi and a Hifibery DAC wasn't great. I added a seperate PSU and an isolator and things got a whole lot better. Even without the isolator the seperate PSU helped a lot. And this won't effect you as you won't be using Rpi gpio for power to the Dorati.
 
bench2005

bench2005

Member
Joined 2005
Grarea said:
Yup, I reckon it is a great place to start.
I am not many steps ahead of you.
In fact you might already know more than me.
I kind of dived in and got a bit confused.
I wish I had done one step at a time.
My music in the garage is a pi zero, volumio and a dacamp hat.
(my lounge one is a bit more complicated, but Jimk understands mine better than me :) )

It is because of the clock frequencies is it?
I thought it was because the pi is noisy electronically?
Or is that a different thing?

@bench2005 while you are paying for postage, ask abraxalito about his other offerings.
Click to expand...
Yes, a place to start, may be upgrade to something more later. As to why the RPI or other SBC might not be a good source, I think there are other thread to discuss this (try not to hijack this thread), but here are my take:

1) Linux is a Multitasking/Time Sharing OS, ie. it is doing many different things at any given time. Things will get done, but one have nearly no say in how long and when it will get done. This is bad news for generating things like clock signal, which you want things to happen on time and within a fix period. The end result is jitter, which is bad for all digital reproduction.
2) CPU clock don't usually divide well into Audio clock, ie. standard clock like 44.1K. So one can only get close to, but not exact clock from the CPU. This ends up in distortion.
3) SBC generate a lot of "noise", which without proper filter/isolation will end up in the analog output .

Again, a lot of people uses RPI as a source, so all the above may or may not matter, I better rest this subject in this thread.

Yes, I know Richard do a D-Amp kit (30W I think). Does this pair well with Dorati?

Ben
 
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