A NOS 192/24 DAC with the PCM1794 (and WaveIO USB input)

Thanks for keeping me busy last year; reading this Doedes site and the forum with more than 6000+ posts in 7 years takes some time ;-)

All due the journey isn't over yet, I'm finally reaching the level that my build is livingroom approved.
And offcourse very satisfied with the sound.

I am already looking forward to the next improvement.

Best
Marcel



The build contains two momentary buttons for power on/off (Tiny85 controlled) and source select (Pi controlled).
An amoled display shows the selected source of stats from a MPD server (like Rune and Volumeio).
SPDIF out is used to compare the sound results with my reference.
 

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Ok Doede, I am a relative newbe, so please forgive me if I not completely understand.
When you say play a silent track I’m not shure what you mean. I can hear the noise when my Aurender is shut off. Waveio has dedicated choke-psu design. My friend told me that the nois was gone when he switch over to s/pdif on the mainboard. Can you explain why ?

Anyway my setup have never performed better, just curious.

I use SPEC PRA 7EX as pre-amp. It’s a very special design and I am not sure what kind of volume control it has.

as soon as the waveio is powered on there is a clock signal, as it generates it's own - regardless if music is played. It is unimportant if the pc/player is switched on
 
Thanks for keeping me busy last year; reading this Doedes site and the forum with more than 6000+ posts in 7 years takes some time ;-)

All due the journey isn't over yet, I'm finally reaching the level that my build is livingroom approved.
And offcourse very satisfied with the sound.

I am already looking forward to the next improvement.

Best
Marcel



The build contains two momentary buttons for power on/off (Tiny85 controlled) and source select (Pi controlled).
An amoled display shows the selected source of stats from a MPD server (like Rune and Volumeio).
SPDIF out is used to compare the sound results with my reference.

Thanks for sharing a very nice Build Marcel. For sure this kept you busy ;)

and what are the comparison results versus the reference?
 
Thanks for sharing a very nice Build Marcel. For sure this kept you busy ;)

and what are the comparison results versus the reference?

I use it in combination with a pair of HD800s cans and a Lake People RS8.
Before I sometimes switched sound source for specific songs, just some equipment did more justice to a song then others.
That need is completely gone. It makes listing easy and I don't mean that as relax and smooth, because the clarity, details, darkness and soundstage are great.
For me it is more like looking at fresh painting. This is perhaps what the others mean with the natural analog sound.
 
OK , let me give some background - probably interesting for the other readers as well -
The version 1 of the dac, as described on my website, has the 6k resistor. The CCS has been introduced in version 2. Many listening test showed improved sound quality. Similar improvements as in power supply improvements.

In terms of noise in the audioband, the S/N ratio from the current source noise ending up in the reference current is -107dB. The thermal noise of the 6k resistor delivers -110dB (at 1MHz for example it is -90dB versus -93dB)

I believe more important is the ~ -40dB damping the current source is giving on any power supply noise coming from pin 20 versus using a 6k resistor for the bias current. As the FET has less gain in higher frequencies, The point where the damping is equal to a ideal resistor is 22MHz. But truly, I do not thing a resistor has no inductance at that point playing an important role, so all in all, the CCS has clearly better performance in noise and power supply noise suppression in the bias current.

And most important, listening test unanimously shows that as well :)

I have read further in this other 1794 thread and Joel (jdlvfr) covers a really excellent explanation here.

http://www.diyaudio.com/forums/digi...e-board-pcm1794-nos-dddac-69.html#post4697234

Of note is the 60nV/rtHz at iref pin. I think his solution is very good using a negative supply to reduce CCS current noise. There are other ways to do this - supply based CCS but they all end up with the same result.

T
 
Hello,
Regarding the direct output connection:
I connect the pos to RCA hot pin and neg to RCA ground and my solid state amp is working fine, but the amp RCA ground inputs are common so if I connect the other channel of the DAC the neg from left side will be common with neg from right side of the DAC. This will be a problem regarding SQ?
 
Hello,
Regarding the direct output connection:
I connect the pos to RCA hot pin and neg to RCA ground and my solid state amp is working fine, but the amp RCA ground inputs are common so if I connect the other channel of the DAC the neg from left side will be common with neg from right side of the DAC. This will be a problem regarding SQ?

Sounds like asking for trouble. Why not use a transformer at the DDDAC output for proper isolation?
 
Because my amp has allready an input cap so I can connect with no problem the DAC pos to hot pin RCA and common to RCA ground on both channel. I just wondering how could I use the balanced mode - well I guess only with a transformer :)
Thank you !

Or you could use some active electronics to go from unbalanced to balanced. There are a number of such circuits using opamps, discrete semiconductors or tubes. But some would think that adding active electronics is not in line with the DDDAC spirit ;-)
 
But some would think that adding active electronics is not in line with the DDDAC spirit ;-)
Yes I know :)
I have build a Broskie Unbalancer with russian tubes but at first impression the sound seemsa little distorted although the bass improves. For now I will skip the tube output until I finish all the test with the DAC and I will give it another chance.
 
Hi all,

I bought a DDDAC from a hifi and electronics enthusiast a few years ago.
The DAC board is the SPDIF one and today the input is configured with SPDIF input.
I also use a singxer SU-1 USB/SPDIF converter before the DAC. This interface has an I2S output over HDMI.
My question: would I have better result using theI2S input of the DAC rather than the SPDIF?
In that case, how should I link the HDMI cable to the I2S input of the DAC?
Thanks!
 
Hi all,

I bought a DDDAC from a hifi and electronics enthusiast a few years ago.
The DAC board is the SPDIF one and today the input is configured with SPDIF input.
I also use a singxer SU-1 USB/SPDIF converter before the DAC. This interface has an I2S output over HDMI.
My question: would I have better result using theI2S input of the DAC rather than the SPDIF?
In that case, how should I link the HDMI cable to the I2S input of the DAC?
Thanks!

Without the double conversion from I2S to spdif and back again, it is likely you will gain by using direct I2S connection. I can make. A sketch for you how to connect, but for that I need you to post what the pin layout of the HDMI connector is they are using. Can you do that ?
 
Hi Volant,

In the past I have used a modified version of the Singxer f1 and used I2S output. It is much better compared to the SPDIF!

Now I am using a Micromedia Dante Device with I2S output... again better. Unbelievable 3D Stage!

Greetings

Christian

Which device exactly?? I can't see any board on their website that explicitly states it has I2S out...

Micromedia Products | Audinate
 
hi,

At the moment I didn't find any information on how the HDMI output of the SU-1 is wired. Still trying to find...
I took a picture of the inside but I doubt it will be helpful..
An externally hosted image should be here but it was not working when we last tested it.


I have a second question. I have added 2 Dac boards to my DAC (this makes a 4 decks dac now). I read that the rload should use 34 ohm resistors. What kind of resistor is it better to use ?

thanks
 
Sorry, it's me again, I just found the description of the HDMI connection:
I2S port use HDMI socket output:
1.Electrical level is 3.3V LVDS differential signa.
2.DSD ON singnal,5Vpower supply,CPLD has processed the MUTE signal,so do not need to process it again.
3.DSD ON signal can be user-defined,DSD ON signal can be connected to PIN 13,14,15,16 on the socket.
4.You can adjust the phase of PIN 1-3 and PIN 7-9 with a switch.
Flexible HDMI-I2S output configuration:
Switch 1-4 is for PIN13-16 on the HDMI socket.
When you turn it into "ON",it means that HDMI PIN has DSD_ON function.
Switch 5 is clock output mode,"OFF" is MCLK,"ON" is WCK.
Switch 6 is for HDMI PIN1-3 and PIN 7-9 phase,ON is positive phase,OFF is negative phase.(ON is for Gustard DAC,OFF is for PS audio)
If it is Gustard DAC,please turn Switch 3 and 6 into "ON",others are "OFF.
Switch 7 and 8 are standby.
The case of formal version(we will write it when formal version finished,now it is not formal version),we will design a hole in the back of the case,so if you want to change configuration,you do not need to open the case.


An externally hosted image should be here but it was not working when we last tested it.
 
Sorry, it's me again, I just found the description of the HDMI connection:
I2S port use HDMI socket output:
1.Electrical level is 3.3V LVDS differential signa.
2.DSD ON singnal,5Vpower supply,CPLD has processed the MUTE signal,so do not need to process it again.
3.DSD ON signal can be user-defined,DSD ON signal can be connected to PIN 13,14,15,16 on the socket.
4.You can adjust the phase of PIN 1-3 and PIN 7-9 with a switch.
Flexible HDMI-I2S output configuration:
Switch 1-4 is for PIN13-16 on the HDMI socket.
When you turn it into "ON",it means that HDMI PIN has DSD_ON function.
Switch 5 is clock output mode,"OFF" is MCLK,"ON" is WCK.
Switch 6 is for HDMI PIN1-3 and PIN 7-9 phase,ON is positive phase,OFF is negative phase.(ON is for Gustard DAC,OFF is for PS audio)
If it is Gustard DAC,please turn Switch 3 and 6 into "ON",others are "OFF.
Switch 7 and 8 are standby.
The case of formal version(we will write it when formal version finished,now it is not formal version),we will design a hole in the back of the case,so if you want to change configuration,you do not need to open the case.


An externally hosted image should be here but it was not working when we last tested it.

mmmhh... it gets more tricky than expected... The signals are no problem, Data, BCLK and LRCLK are the ones you need to attach to the DDDAC mainboard to the corresponding I2S pins (plus connect the GNDs which are in between the P and N signals of course)

This might work already if you use the "P" only, but I am not sure. you can try - Otherwise you will have to build a receiver which makes single ended output from the differential inputs
 
hi,

At the moment I didn't find any information on how the HDMI output of the SU-1 is wired. Still trying to find...
I took a picture of the inside but I doubt it will be helpful..
An externally hosted image should be here but it was not working when we last tested it.


I have a second question. I have added 2 Dac boards to my DAC (this makes a 4 decks dac now). I read that the rload should use 34 ohm resistors. What kind of resistor is it better to use ?

thanks

The Dales/Vishays are absolutely ok. Some (including myself use the audio note resistors. Make sure to use minimum 0,5 Watt (better 1Watt)