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

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rickmcinnis

Member
Joined 2006
The easiest way to allow us to use other regs ...

would be to offer the boards without as a choice.

One part of me is interested in trying shunt regulators and the other is a bit skeptical of the "goodness" of these mini shunt regs not having ever used them.

Will the existing power supply be able to supply the extra current needed with multiple boards? A proper shunt regulator has to throw away a fair amount of energy and heat to perform well. Plus all of that circuitry flapping in the wind ... Makes one wonder if it is more "different" than "better"?
 
A

AudioDAC

Member
Joined 2010
DDDAC with DAVE SLAGLE Autoformer Modules

dddac said:
It has been a Long time after the DDDAC1543 saw the light and the world moved on, especially if we look at available sound track material. So much great soundtracks with high Resolution. Red book is not dead of course, but if I spend money on sound tracks, I look for 96/24 or even better 192/24, or the SACD equivalents 88.2 and 176.4...

In the past year I have been working on my new project: designing a DAC which will play up to 192kHz / 24bit material from a PC (or Mac...) There are many DACs who can do this, but I wanted to design a NOS version, as so far, every listening test I did, this led to a more open, natural and detailed sound.

I found this to be possible by using the well-known PCM1794 and avoiding the digital filtering built into the chip. This proved to be quite tricky, but I managed to find the key to do it. It has been a great adventure with much to learn and a fantastic result at the end....

To feed the DAC, I kind of integrated the WaveIO USB Receiver from Lucian. Great design and better sounding than all others I tried (see my website for this as well); I give a very detailed report on www.dddac.com

You can download the circuits here: dddac1794_nos_ver30.pdf



The Images below show:
The Mainboard with I/O and I2S to right justified conversion
The actual dual mono DAC Module (can be stacked parallel)
Built up with 4 modules and two power supplies (5 and 12 Volt)
Wired up in Chassis (Mundorf Gold silver oil output and optional Sowter 1:2
The DAC in my Audio rack
Another view inside
Block diagram


I opened this thread to share my design and experience and give a platform for questions, feedback, remarks and/or discussion...
Click to expand...

Hellow Doede.
I plan to build your DDDAC with Sowter output trafo but I would like to know if it will suit well with my passive preamp and amp.
Preamp is based on DAVE SLAGLE Autoformer Modules and the amp is made with NC400 | NCore®Amplifier Modules.
I am not afraid about signal level as the 4.7 V form DDAC is enough. But more about impedance matching, transformer ringing or quantization noise.
The autoformer is stackt to have 30 H inductance.
According to Dave sugestions the reflective load for DDDAC for 20Hz will be [FONT=Arial, Helvetica, sans-serif][SIZE=-1] (Z=2piFL) about 3800 ohms.

It looks ok. as it is more then 10x the output impedance of four bourd DDDAC with Sowters (270ohms). But what about sowter ringing and any noise?

I would be very gratefull for your deep analize of this configuration as I do not want to [/SIZE]
[/FONT] change the preamp as it is really very good one.
regards
 
I

IanS1

Member
Joined 2012
Supersurfer said:
Hi guys,

Nice review.
Sorry I could not be there with my shunt regulated dac, but my sons birthday last saturday was also very nice ;)
But we will make an appointment to compaire the shunt dac to the standard one in the near future, if we can match our agendas.

Regards,
Click to expand...

That would have been a real good comparison Stefan, it's a shame you couldn't be there, would be great to know how your DAC sounds against the very special DAC's on show here.
 
dddac

dddac

Member
Joined 2003
blog.dddac.com
Paid Member
Chanh said:
I can confirm that bigger transformer did too improve SQ from my experiment. In my case I was using 120VA may considering 250VA for the DAC. Wondering if my unused 25VA 2x15V from DAC PS could be replacing stock 2x9V USB PS? :confused::confused::confused:
Click to expand...

I did some testing as well now with bigger transformers and can also agree it is a nice tweak. I am always a bit concervative as it Comes to "dramatic" and totally played against the wall ;) so nothing like that...

but It does seems to give more headroom tot the whole Sound stage. Tighter bass, somewhat better texture on instrumensta nd voices.

For the Price and how easy it is to implement, it is a stayer and a recommended tweak if you like to DIY anyway :D
 
dddac

dddac

Member
Joined 2003
blog.dddac.com
Paid Member
Chanh said:
Looking for another 8 more DAC boards if you have successfully revised this incorporation? :p:p:p
Click to expand...

actually my next thinking is to use one complete 8-stack for the LEFT channel and another for the Right channel. for true DIY easy to omplement of course as you lead the data Signal to the other side of the stack and the Audio current Output Need to be lead to one (half value) Rload.
Spdif Input and USB Input can be looped through. between Mainboards. and of course two poer supplies. than it become true double mono stereo
 
dddac

dddac

Member
Joined 2003
blog.dddac.com
Paid Member
rickmcinnis said:
would be to offer the boards without as a choice.

One part of me is interested in trying shunt regulators and the other is a bit skeptical of the "goodness" of these mini shunt regs not having ever used them.

Will the existing power supply be able to supply the extra current needed with multiple boards? A proper shunt regulator has to throw away a fair amount of energy and heat to perform well. Plus all of that circuitry flapping in the wind ... Makes one wonder if it is more "different" than "better"?
Click to expand...

up to 4 stacks this should be no issue ate all
 
dddac

dddac

Member
Joined 2003
blog.dddac.com
Paid Member
AudioDAC said:
It looks ok. as it is more then 10x the output impedance of four bourd DDDAC with Sowters (270ohms). But what about sowter ringing and any noise?

I would be very gratefull for your deep analize of this configuration as I do not want to [/COLOR][/SIZE][/FONT]
[/FONT][/COLOR] change the preamp as it is really very good one.
regards
Click to expand...

I see no issues at all on ringing etc. the sowtre Show not be very critical on load according to my measurements. Most important is that they are driven from low impedance, hence the 4 stacks.

noise from the quantization noise side Need to be given attentention when directly connected to an end amplifier without volume controll. too much gain makes nosie audible than. when using volume control after the dac, no Problem ...
 
G

G600

Member
Joined 2014
Doede, what do you think for the power supply upgrade : replace the 2 blue trafos with one big toroidal maybe 250VA with two secondaries : 15V and 8V (1A on each ?), and wire them to 2 of your power suply boards ?
Or maybe it's a better idea to buy a big one just for 12V, no improvement for 5V ?

One thing I don't understand with regulator upgrades : we just have to replace the existing ones and voilà, or is there a voltage increase to do for the "voltage drop" ?
 
I

ijscobar

Banned
Joined 2012
Let's D-D-Do it! Today two dac boards, two power supplies and a WaveIO arrived. Spdif board will come soon also! :D
 

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C

Chanh

Member
Joined 2013
dddac said:
actually my next thinking is to use one complete 8-stack for the LEFT channel and another for the Right channel. for true DIY easy to omplement of course as you lead the data Signal to the other side of the stack and the Audio current Output Need to be lead to one (half value) Rload.
Spdif Input and USB Input can be looped through. between Mainboards. and of course two poer supplies. than it become true double mono stereo
Click to expand...
Sound exciting! Kinda lost here, did you mean one main-board with 8-decks and with its own ps for each channel? What's about discrete regulators for the DAC board?
Cheers
 
Supersurfer

Supersurfer

Member
Joined 2013
dddac said:
actually my next thinking is to use one complete 8-stack for the LEFT channel and another for the Right channel. for true DIY easy to omplement of course as you lead the data Signal to the other side of the stack and the Audio current Output Need to be lead to one (half value) Rload.
Spdif Input and USB Input can be looped through. between Mainboards. and of course two poer supplies. than it become true double mono stereo
Click to expand...

Hi Doede,

Nice thinking! Some more food for thought:

What about a separate bigger mother board that can accomodate two stacks of dacs. One for right channel, one for left.
Routing of data and power can be nicely implemented on this board.
That way you can easily make two stacks of the height of your choice, start with 4 boards each and go up to 8 or more?

You can also make a provision to feed with two separate power supplies, and a jumper for the ones who want to start with one power supply.

It also will be easier to place such a stack in one standard casing.
 
dddac

dddac

Member
Joined 2003
blog.dddac.com
Paid Member
Supersurfer said:
Hi Doede,

Nice thinking! Some more food for thought:

What about a separate bigger mother board that can accomodate two stacks of dacs. One for right channel, one for left.
Routing of data and power can be nicely implemented on this board.
That way you can easily make two stacks of the height of your choice, start with 4 boards each and go up to 8 or more?

You can also make a provision to feed with two separate power supplies, and a jumper for the ones who want to start with one power supply.

It also will be easier to place such a stack in one standard casing.
Click to expand...

:p :p haha any idea of the cost involved to set up a series of Motherboards? :(

that's why I come up with "creative" Solutions and use what is available ;)
 
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