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

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ed linssen

Member
Joined 2004
Saying that, it might also help to use shorter cables too but I wouldn't have thought 150mm was excessively long.

Hi Ian,
150mm seems on the long side indeed.
If possible, using shielded connections of equal lenght (<100mm) preferably with Ufl connectors on both sides could better it.
 
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S

Sovereign1

Member
Joined 2014
dwjames said:
The DAC wants a neatly regulated power supply, but it has local regulators to take care of that. If you're using a shunt regs or similar here, what they thrive on best is a good, low impedance power supply. This is why people are hearing improvements from removing the resistors and using a bigger transformer in the standard power supplies. The shunt regs handle the accurate regulation of voltage, so as long as the power supply feeding them has filtered out any large spikes, it's more important that it offers a nice, free, low impedance supply than it is that it's exactly bang on a perfect regulated 12v at all times. An unregulated supply using just rectifiers, capacitors and chokes provides a real low impedance supply which makes the shunts happy, so they sing with sweeter voices :)
At least, that's what listening tests have shown.
16280103162398e0bfaf79dbd0f7eef8.jpg
Click to expand...
Thanks James

Where can I get the psu you show in the picture?
 
I

IanS1

Member
Joined 2012
ed linssen said:
Saying that, it might also help to use shorter cables too but I wouldn't have thought 150mm was excessively long.

Hi Ian,
150mm seems on the long side indeed.
If possible, using shielded connections of equal lenght (<100mm) preferably with Ufl connectors on both sides could better it.
Click to expand...


dwjames said:
Yeah, that is long for i2s. Try and keep it as short as physically possible.
Also, can help to add an Isolator between pi and dddac. Diyinhk do a free board for that. I have a spare one if you want to try it while you get your s03 done
Click to expand...

Actually, you are both probably right. I did try an old Pi B a few weeks back with a shorter ribbon cable and that didn't sound as bad. I'll give it a go later.

I can't try the ufl connectors just now but I should be receiving a Ufl adapter board for the DDDAC from ACKO in the next week or so. No Ufl board for the Pi B+ though!! Will have to see if I can make something.

Thanks for the offer on the DIYINHK isolator board James, would love to try it. I'll PM you later.
 
dwjames

dwjames

Member
Joined 2012
Sovereign1 said:
The PSU that is next to the torodial transformer, I presume thats the unregulated supply you mentioned?
Thanks :)
Click to expand...
That's an R core transformer. It's this one
230V 80W 12V X2 OUTPUT R CORE TRANSFORMER With SHIELDING FOR AUDIO | eBay
But the output is a bit low when the load is applied, so if I did this again, I'd get a 15v version rather than the 12v one I have. The seller of that one will get you other ratings if you ask.

To the right of that are 2 Lundahl LL1694 chokes, some Panasonic caps (after the first choke and after the second choke) and on the front of the case, a 56R bleeder resistor to provide a constant load through the power supply and keep the chokes in their optimum loading.

Sorry that's a bit vague, I don't have the exact specs and layout to hand, but it's very simple.

A couple of guys here have this type of setup, mine's really messy at the mo, but someone like Stijn has done a nice neat job of putting it all into a case
http://www.diyaudio.com/forums/digi...pcm1794-waveio-usb-input-238.html#post4011980
 
D

dusty128

Member
Joined 2014
IanS1 said:
Not just me then Si. To be honest, in my system it sounds terrible. I have been using the HiFiBerry Digi + with the Pi into the SPDIF on the new 1794s mainboard for the last few days and it's been really quite impressive for such a cheap streamer.

Connected up the I2S tonight and it just doesn't sound right at all. I know the clocks on the Pi aren't up to much but the timing is completely off, sounds quite flat and recessed too. I've got one of ACKO's S03 re-clockers waiting to for parts to be built, I'm hoping that will at least bring it up to the level of the SPDIF input. Saying that, it might also help to use shorter cables too but I wouldn't have thought 150mm was excessively long.
Click to expand...

Very interesting - I personally like the sound, however, I have no comparison as I only have the Raspberry as a source to the DDDAC.

I have the following findings:


  • The Raspberry has a jitter of 2ns due to the clock generation logic
  • It can only do 16bit
  • The S03 reclocker can currently only be used in synchronous mode, which actually adds another 10ns of jitter (for a 100MHz clock)
  • An I2S isolator does improve sound quality (e.g. the isolator of the S03 or of the DIYINKH)
  • I suspect that the I2S playback of the RPi is not bit-perfect. I'm currently doing some tests by watching the I2S Data signal with a DSO while playing either a Zero signal or a 0dB DC signal. In both cases, the I2S data is not stable - which I think should be. So I suspect that there may be some driver issue as well, but I have to investigate this further
I wonder if not the BBB with mieros driver and synchronous reclocking is not a much better solution.



Best Regards,
Hermann
 
S

Sovereign1

Member
Joined 2014
dwjames said:
That's an R core transformer. It's this one
230V 80W 12V X2 OUTPUT R CORE TRANSFORMER With SHIELDING FOR AUDIO | eBay
But the output is a bit low when the load is applied, so if I did this again, I'd get a 15v version rather than the 12v one I have. The seller of that one will get you other ratings if you ask.

To the right of that are 2 Lundahl LL1694 chokes, some Panasonic caps (after the first choke and after the second choke) and on the front of the case, a 56R bleeder resistor to provide a constant load through the power supply and keep the chokes in their optimum loading.

Sorry that's a bit vague, I don't have the exact specs and layout to hand, but it's very simple.

A couple of guys here have this type of setup, mine's really messy at the mo, but someone like Stijn has done a nice neat job of putting it all into a case
http://www.diyaudio.com/forums/digi...pcm1794-waveio-usb-input-238.html#post4011980
Click to expand...

Massive thanks James

I have the Rcore Trannies on way from China as we speak.
I'll have a look at the link when I have a bit of head space to give it
Thanks Again
 
dwjames

dwjames

Member
Joined 2012
Sovereign1 said:
Hi James, so is this the PS you now use for the DAC in place of the DDDAC one?
Free Amanero Isolator bare PCB Twin pack - DIYINHK
Thanks
Click to expand...
wrong link?
I use this power supply for feeding 5v to my rPi and s03 reclocker
4.17uV Ultralow noise DAC power supply regulator 3.3V/5V 1Ax2 - DIYINHK

For the raw power supply for my DDDAC, I use an unregulated power supply which consists of only a transformer, a couple of rectifier diodes, 2 chokes, some caps and a bleeder resistor. This forms an LCLC (choke, capacitor, choke, capacitor) or 'Choke input' power supply. These tend to be found in valve amps usually, but makes an excellent low impedance raw supply for the shunt regs.
 
G

G600

Member
Joined 2014
For example two 2200 µF after each choke (not before).
Make sure they are rated above spec, like 35 or 50V.
You can bypass them or change values at your taste.
James posted scope captures a while ago with the effect of tweaking capacitance, etc...
Personnally I use 2*2200 after the first choke and 3*2200 after the second, with 50V Panasonic FC.
 
dwjames

dwjames

Member
Joined 2012
Yeah, as Jean-Denis says, I've used 2 x 2,200uf after the first choke and 2 x 2,200uf after the second choke for now, but you can tweak the figures about a bit and see what you like. I'm rebuilding my power supply soon into a new case so might change stuff about a bit then. I used Panasonic FC.

The chokes are Lundahl LL1694, I got them from Charlie at bigbearaudio.com. Something like £100+ vat for the 2
 
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