DDDAC 1794 NOS DAC - Non Oversampling DAC with PCM1794 - no = digital filter - modular design DIY DAC for high resolution audio 192/24 = 192kHz 24bit

From: "Saved by Internet Explorer 11" Subject: DDDAC 1794 NOS DAC - Non Oversampling DAC with PCM1794 - no digital filter - modular design DIY DAC for high resolution audio 192/24 192kHz 24bit Date: Thu, 2 Jul 2015 15:27:42 -0700 MIME-Version: 1.0 Content-Type: multipart/related; type="text/html"; boundary="----=_NextPart_000_0013_01D0B4DB.A3415630" X-MimeOLE: Produced By Microsoft MimeOLE V6.1.7601.17609 This is a multi-part message in MIME format. ------=_NextPart_000_0013_01D0B4DB.A3415630 Content-Type: text/html; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable Content-Location: http://www.dddac.com/dddac1794_spdif.html DDDAC 1794 NOS DAC - Non Oversampling DAC with PCM1794 - no = digital filter - modular design DIY DAC for high resolution audio 192/24 = 192kHz 24bit

DDDAC1794=20 NOS

Vintage=20 dddac.de

Other=20 Projects

Download=20 / Links

Sales /=20 = Webshop

DDDAC1794 = NOS
High Resolution Audio =

Introduction

Initial=20 Tests

Design=20 Phase

Circuit:=20 step-by-step

Construction

Sound=20 Check 1

Sound=20 Check 2

USB=20 asynchronous Input

S/PDIF=20 Input

Foobar/Wasapi/USB=20 Drivers

Power=20 Supplies

Analog=20 Output Options

Testimonies<= /TD>

Test=20 Results and Specs

"Others"

A S/PDIF solution for the = DDDAC1794

There was still a lot of request for good old = S/PDIF, so I=20 designed a "S" version...

I assumed high res audio was only about PC and Mac, = so I=20 never bothered to implement S/PDIF right in the = beginning. But=20 I learned that there are still quite some CD Players = in use or=20 other media players (or PCs which use S/PDIF output). = As=20 S/PDIF is not that difficult to implement, I took this = up and=20 started designing again. As you know the KIT is = already=20 available for some time. I just had no time to update = the Web=20 Site ;-)

These were the design requirements I wanted to = implement in=20 the new mainboard:

It needed to be fully compatible with the "USB = only=20 mainboard" and the DAC Modules, electrically and=20 mechanically=20
The S/PDIF functionality=20
- Use best available technology (is a bit = arbitrary of=20 course ;-)=20
- Sampling rates Up to 192kHz (Optical 96kHz)=20
- Option for a 12MHz XO Clock (like the ones = from Guido=20 Tent)=20
- Easy to switch between USB and S/PDIF source =
Improve a few things on top:=20
- LED signal part can be broken off for use at = the front=20 panel of the chassis=20
- Improve buffering of signals to be able to = drive more=20 boards (so far 11 is done)=20
- Improve timing of I2S signals with flip flop = in stead=20 of the 1k resistor solution for data-delay=20
- Make logic voltage 5 Volt for higher = compatibility=20 inside the design

The only important selection was the receiver = itself....=20 There are a few choices, like DIR9000 CS8416 and the = Wolfson=20 WM8804. I have been listening around and for arbitrary = reasons, I thought the Wolfson WM8804 would be the = best choice=20 for me. I bought a few chips, made some breadboard = tests and=20 voila it woked within a few weeks. Let me explain a = few things=20 I did in the new mainboard...

You can = download the=20 full schematics (S/PDIF and USB mainboard version) = from the=20 download section or push the button below:
3D"click

Theory of operation of the S/PDIF mainboard

First part was the implementation of the WM8804. It = is done=20 of course in hardware mode. In the schematic below you = recognize the option for the XO clock. Further more = there is a=20 set of resistors, which are used to configure the = WM8804 at=20 start up. Of course I need to Wolfson chip to output = I2S=20 signals based on S/PDIF input signal. All easy, after = studying=20 the somewhat complex data sheet..... In the circuit = clip below=20 you see I have chosen to separate the power supplies = for the=20 chip to maximize performance. In case of a Tent Clock=20 installed, the two ceramic Cs and Crystal should be = removed=20 (or not installed). The 75 Ohm resistor (R1) is not on = the=20 mainboard. It is meant to close the impedance of the = coax=20 cable, so best position is directly at the RCA=20 connector...

<= /A>=20

I had two problems which needed to be solved: = First.... The=20 WM8804 is outputting 3,3 Volt logic and I wanted to = control=20 the DAC boards (and WaveIO) with 5 Volt logic. = Secondly I=20 wanted to be able to switch between USB (WaveIO I2S = signal)=20 and the S/PDIF I2S signal.

After some reading and checking I came up with the=20 following solution. The 74VCHT244 is a bus buffer = which=20 converts 3-5 Volt logic to 5 Volt logic. As it can go = in=20 tri-state (high impedance on the bus) I saw a kind of = two way=20 switch in front of me :-) Have a look at the circuit = clip=20 below and you will understand the beauty of this = solution.....=20

- The inputs are switched without use of = mechanical=20 switches
- The strong output buffers can have the = clock=20 signal drive more DAC boards (the USB only board can = do max 4=20 DAC modules)
- All is 5 Volt logic now at the = output=20

=20

The final difference with the USB only mainboard is = the=20 improved data delay. Remember? The Data needed to be = delayed=20 half a clock cycle. I did that with a 1k Ohm resistor = at the=20 data input. I was not sure how well this worked at = multiple=20 boards (now 11 have been tried ;-) so as I was = designing, I=20 simply implemented a standard flip flop to delay the = data=20 signal with an extra half cycle. This means, that when = data is=20 being clocked into the DAC, the state is rock solid at = clock=20 transition...

=20

The=20 DDDAC1794S
Next to S/PDIF functionality, = several=20 practical improvements=20

<= /TD>

The Board itself

Compared to = the "red=20 USB only board, you can easily recognize the = section,=20 where the WM8804 chip is and the extra power = supplies=20 (3,3 volt)=20

At the Left is now the connection for the LED = indicators. It can be easily broken off for = front panel=20 use, or just let it stick of course

This example shows a 4 deck version. Several = 8 Decks=20 have been implemented without any drive issues. = I know=20 of two cases where 11 boards were stacked with = great=20 success !

As mentioned, the board is fully compatible = with the=20 old DAC boards, as well the somewhat revised = second=20 version of the DAC module, which is now being = delivered.=20 You can freely use them through each other. So = easy of=20 DIY is guaranteed :-)

Keep reading ...... the story continuous with = installing=20 all software ( Programs=20 and Drivers )

Information

mail@dddac.com=20 ● Impressum

Happy Building and = Listening!

dddac1543mk2=20 ● Tube = Projects=20 ● Speaker = Projects=20 ● Audio = Tweaks