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

Jump to Latest
Supersurfer

Supersurfer

Member
Joined 2013
Bummer :(

I think I will modify the spdif input :D

I can put a switch on the i2s output of the wolfson and put in an extra i2s channel to the 74vhct244. It's easy to just solder out the three resisitors.

Maybe I will make a small pcb with a 74vhtc244, just copy your design and place it after the wolfson.

Or ditch the spdif entirely. I2s is much better anyway.


Is it also rainy and cold in Germany? Today is perfect weather to stay indoors and do some music listening or soldering :rolleyes:
 
dddac

dddac

Member
Joined 2003
blog.dddac.com
Paid Member
Supersurfer said:
I think I will modify the spdif input :D

I can put a switch on the i2s output of the wolfson and put in an extra i2s channel to the 74vhct244. It's easy to just solder out the three resisitors.

Maybe I will make a small pcb with a 74vhtc244, just copy your design and place it after the wolfson.

Or ditch the spdif entirely. I2s is much better anyway.


Is it also rainy and cold in Germany? Today is perfect weather to stay indoors and do some music listening or soldering :rolleyes:
Click to expand...

I agree on all points! good solution to use the inputs after the wolfson ;-) here you can always solder a small signal relais to get spdif if you still need it sometime...

YES, the whole week summerly warm and then when free time weekend starts, cold and badass weather & wind :mad: I wan't o be like this :cool: :p

but you are right, time for hobby. I am packing a lot of shipments right now. will make some people happy :D
 
palmito

palmito

Member
Joined 2010
Supersurfer said:
Would it be possible to connect two i2s inputs parallel on the dac?
F.i. Wave io and raspberry pi.
Click to expand...
Twisted Pear Audio has a board called the Otto that is designed for switching between two i2s inputs. It's not real cheap, but people use it and it works.

Doede, if you are redesigning the motherboard for two i2s inputs, could you add u.fl connectors along with the waveio header? Better than plain short cables is short u.fl cables for connecting the reclocked/isolated i2s signal. The two standalone reclocker/isolators I use have u.fl output. They are not cheap, not very reusable and if you reuse (just a few times is all you can reuse them) you need to get the little remover tool, but they seem to be the best signal carrier. You could do as other kit providers do and not solder the u.fl but sell them as an option for anybody who needs it, if you don't need them you leave the pads unpopulated.
 
P

PET240

Member
Joined 2010
Supersurfer,

Have a look at brand "Pickering", trying to think who carries them(pommyland), they are a reed relay and as far as I know the contacts are in a vacuum.
From all accounts they are the best relay for I2S we have used and we have tried signal relays from alot of peoples! If you have a reclocker, do the switching beforehand.....

Chuz,

Drew.
 
C

concept

Member
Joined 2014
Stacking dac chips just like your nos dddac 1543 .

Hi deode just an idea....would it be possible to just stack the pcm1794 dac chips onto each other using an ssop to dip adapter with long pin female headers and using one 3.3v psu for the digital sections and one 8v psu for the analog section.The first dac chip would of course be tied up to all the resistors, caps and what not for signals and all.
If it is possible than I might give it a go as this would lead to less component count and space saving. Not sure if the values of the decoupling caps, resistors and what not needs changing though.
Hope to have some input regarding this from you or anyone else. Thanks.
 
G

gentlevoice

Member
Joined 2007
Paid Member
2 reasons,
1. I wanted to make sure I did not increase unnecesarily the disipation in the not used Output (as Delta V would be 8 Volts instead of 5.3 Volt)
2. On top you will have working extra Output or can go into balanced without any Change

why you ask?
Click to expand...

Hi Doede - thanks for replying - first: What you are doing is very interesting and inspiring to me so thanks for making it available ;-)

My reason for asking is that I'm doing a PCB layout based on your design, however, omitting extra resistors for the outputs not used (I'll go single-ended) allows for more space and closer-to-the-PCM1794 placement of some of the other components.

Also I was thinking that maybe you had a technical insight/reason that was related to how the PCM1794 interiors are designed for loading both branches of the DAC evenly ...

Yet, I just found this thread:

http://www.diyaudio.com/forums/digital-source/221743-testing-pcm1794-2.html

... and can see that the question just above is answered here.

Cheers ;-)

Jesper
 
I

ijscobar

Banned
Joined 2012
leifchristensen said:
hello folks
have spent the last couple of weeks A/B testing my all out choke input Buffalo III/Legato dac against my new 4 boards std psu DDDAC1974, which by the way needed a couple of weeks power-on to loosen up
The BIII has exaU21 usb to I2s converter with separate 5v psu besides also getting 3,3vdc from BIII board
both dc voltages to Legato and the dac board are fed from separate 250va transformers through MUR860 rectifiers , choke fed Placid HD shunt regs...the regs reg from 13,5 to 5,8 and 23 to 14,6 respectivelys(regs sounds better when plenty to regulate on)
have the two very different dac´s connected to two separate inputs and just change between exa and wave Io driver in foobar
very easy to compare
first verdict
BIII smoother and more dynamic and powerful
BUT the NOS has something going on that I like (which I also experienced with other dac builds) despite that it at first sounded pretty anemic and cold with less harmonics
my first thought was to increase transformer va and I took what I had at hand
250va for the dac psu and 80 va for the usb psu and the dynamics and basscontrol improved slightly, but less than expected
obviously something acted as a dynamic brake in the psu(I thought)
I then bypassed R1, R2 and the fuse and the impact was dramatic and suddenly the dac was up in league with my BIII in terms of basscontrol and dynamics
however I still perceived it a little harsh and cold in the top end which didn´t figure
(I use SE out and NO CAPS to S&B TVC)
I then tried replacing C7 and C8 with one Panasonic FC 1.000µF/35 and most of the "harshness" was gone....hmmmmmm tried removing the C9 and suddenly the whole dac sounded dull....back in with it and that´s the present status

best
Leif
Click to expand...

I have the same experience. At this moment I like my Buffalo better than my 2 decks DDDAC. I will try your tweaks and see what happens...
 
L

leif christensen

Member
Joined 2005
does that mean you tried the psu trick and it worked as described?
I use AN 2watt tantalum reistors for Rload and they´re very transparent and musical
a veil disappears
just now I also connected the output for balanced operation without any caps or 100K to gnd
got the doubled 2,4vout and more relaxed and detailed sound
silky hights and very "balanced" harmonics
thxs DD
now just waiting for new MB and an extra experimenting dac board
best
Leif
 
I

ijscobar

Banned
Joined 2012
leifchristensen said:
does that mean you tried the psu trick and it worked as described?
I use AN 2watt tantalum reistors for Rload and they´re very transparent and musical
a veil disappears
just now I also connected the output for balanced operation without any caps or 100K to gnd
got the doubled 2,4vout and more relaxed and detailed sound
silky hights and very "balanced" harmonics
thxs DD
now just waiting for new MB and an extra experimenting dac board
best
Leif
Click to expand...

Yes, I shorted the fuse and the two 5W resistors. And I ordered the Panasonic caps. Lot more dynamics now. I caught myself this afternoon actually listening to music instead of listening to a dac.
I'm already running the DDDAC balanced with a pair of CineMag transformers...
 
You must log in or register to reply here.
Top Bottom