A NOS 192/24 DAC with the PCM1794 (and WaveIO USB input) - Page 138 - diyAudio
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Old 23rd March 2014, 07:10 PM   #1371
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Join Date: Dec 2005
Location: Norway
you dont need a board...just a relay and a toggle...
best
Leif
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Old 23rd March 2014, 08:39 PM   #1372
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What about these relays: http://pewa.panasonic.com/assets/pcs...tq-catalog.pdf

Using two pieces dpdt with 12v coil would do I guess.
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Old 23rd March 2014, 11:04 PM   #1373
PET-240 is offline PET-240  Australia
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Join Date: Feb 2010
Location: Brisbane Northside
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.
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Old 24th March 2014, 01:15 AM   #1374
concept is offline concept  Singapore
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Join Date: Jan 2014
Smile 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.
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Old 24th March 2014, 09:03 AM   #1375
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Location: Aarhus, Denmark
Quote:
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?
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:

Testing the pcm1794

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

Cheers ;-)

Jesper
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Old 25th March 2014, 09:07 AM   #1376
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Quote:
Originally Posted by leifchristensen View Post
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
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...
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Old 25th March 2014, 09:19 AM   #1377
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By the way, is there any reason not to replace C7 and C8 with 2 1000uF Panasonic FC's? They have the same size.

I also read about replacing the Rload resistors with tantalum resistors. What does this do with the sound?
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Old 25th March 2014, 03:10 PM   #1378
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Quote:
Originally Posted by leifchristensen View Post
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

best
Leif
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Old 25th March 2014, 06:16 PM   #1379
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Join Date: Dec 2005
Location: Norway
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
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Old 25th March 2014, 06:46 PM   #1380
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Join Date: Sep 2012
Quote:
Originally Posted by leifchristensen View Post
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
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...
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