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CHORD ELECTRONICS DAVE
May 13, 2016 at 11:59 AM Post #2,941 of 25,842
I have to admit I am a little confused regarding several of these issues that we've been discussing. 
 
On the issue of the importance of impedance and power supplies, Rob says "forget it" as it is irrelevant to RF generation. Paul Hynes (as reported by Roy), who is an expert power supply designer, says it is critical and the lower impedance, the greater rejection of RF from the source. Both can't be right, can they? Or is there a way to reconcile these statements?
 
On the question of whether sonic quality varies with the quality of the power cable, Rob says that he has found essentially no variance with DAVE on his world travels. But Roy reports hearing differences with different power cables, most especially with the High Fidelity Cables power cable, and more so when paired with an HFC power conditioner. Of course it is doubtful that Rob has heard that particular power cable and power conditioner. 
 
On the question of sources, Rob basically says, don't worry about it too much with DAVE, use what is convenient. Roy and others report hearing significant differences from one source to another, to the extent of being able to consistently discriminate among sources in blind testing. Maybe this is just a question of degree or it can be chalked up to different listeners, but still . . .
 
Finally, the question of switching power supplies vs. linear power supplies raises a question in my mind about the benefits of using a linear power supply with something like the microRendu (or any other component in an audio system). If it is difficult to shield other components in the system from RF generated by linear supplies, are the potential benefits of using a linear supply with something like the microRendu outweighed by the potential RF and/or magnetic pollution caused by such supplies? Does it just come down to how well the designer of the linear supply has shielded the supply from this type of pollution?
 
I don't claim any expertise (far from it!) on any of these issues, so I won't be offering any opinions of my own. Are other folks reading the various statements and findings discussed in this thread at least a little confused as well?
 
May 13, 2016 at 12:07 PM Post #2,942 of 25,842
I find them very contradicting. No idea who is right or wrong. But eventually the only thing that matters is what you hear yourself. On the other hand, It's rather expensive to verify everything on your own :wink:
 
May 13, 2016 at 12:10 PM Post #2,943 of 25,842
nepherte said:
I find them very contradicting. No idea who is right or wrong. But eventually the only thing that matters is what you hear yourself. On the other hand, It's rather expensive to verify everything on your own
wink.gif
Click to expand...


Very true. I rely on forums like this, however, to try to minimize the expense of the audition process and learn as much as I can. It's an imperfect process, but I guess it mirrors life in that sense. 
 
May 13, 2016 at 12:28 PM Post #2,944 of 25,842
shuttlepod said:
  I have to admit I am a little confused regarding several of these issues that we've been discussing. 
 
On the issue of the importance of impedance and power supplies, Rob says "forget it" as it is irrelevant to RF generation. Paul Hynes (as reported by Roy), who is an expert power supply designer, says it is critical and the lower impedance, the greater rejection of RF from the source. Both can't be right, can they? Or is there a way to reconcile these statements?
 
On the question of whether sonic quality varies with the quality of the power cable, Rob says that he has found essentially no variance with DAVE on his world travels. But Roy reports hearing differences with different power cables, most especially with the High Fidelity Cables power cable, and more so when paired with an HFC power conditioner. Of course it is doubtful that Rob has heard that particular power cable and power conditioner. 
 
On the question of sources, Rob basically says, don't worry about it too much with DAVE, use what is convenient. Roy and others report hearing significant differences from one source to another, to the extent of being able to consistently discriminate among sources in blind testing. Maybe this is just a question of degree or it can be chalked up to different listeners, but still . . .
 
Finally, the question of switching power supplies vs. linear power supplies raises a question in my mind about the benefits of using a linear power supply with something like the microRendu (or any other component in an audio system). If it is difficult to shield other components in the system from RF generated by linear supplies, are the potential benefits of using a linear supply with something like the microRendu outweighed by the potential RF and/or magnetic pollution caused by such supplies? Does it just come down to how well the designer of the linear supply has shielded the supply from this type of pollution?
 
I don't claim any expertise (far from it!) on any of these issues, so I won't be offering any opinions of my own. Are other folks reading the various statements and findings discussed in this thread at least a little confused as well?
Click to expand...

 

Good questions. Maybe one person’s non sensitive to power cable etc etc. is another person’s immune to power cable etc. etc.

 
May 13, 2016 at 12:31 PM Post #2,945 of 25,842
rob watts said:
  When you were doing your listening, was this with Dave on its own via headphones?
 
Click to expand...

Yes, Rob, during my blind listening, headphones were connected direct to DAVE and I could hear a difference that was more subtle but on 3/3 occasions, I correctly picked out one source over the other.  As I was confident I could hear an even more prominent difference on speakers, I blind tested here also and on 2/2 occasions, I was able to correctly pick out one source over the other.  To be honest, there's no need to blind test because the improvement with the microRendu is quite evident.  While more subtle, I can hear differences among different USB cables also although this evaluation was not blinded.
 
As I stated, the beguiling thing about the DAVE is that nothing sounds bad and so when not comparing one source against another, all my brain and my heart tell me is that I am hearing something wonderful and like you, I hear no variance whether I'm listening at 12 noon or at 12 midnight.  In direct comparison, however, there is no doubt in my mind that certain bit-perfect sources sound different (better) than others.
 
May 13, 2016 at 2:26 PM Post #2,946 of 25,842
shuttlepod said:
  I have to admit I am a little confused regarding several of these issues that we've been discussing. 
 
On the issue of the importance of impedance and power supplies, Rob says "forget it" as it is irrelevant to RF generation. Paul Hynes (as reported by Roy), who is an expert power supply designer, says it is critical and the lower impedance, the greater rejection of RF from the source. Both can't be right, can they? Or is there a way to reconcile these statements?
 
On the question of whether sonic quality varies with the quality of the power cable, Rob says that he has found essentially no variance with DAVE on his world travels. But Roy reports hearing differences with different power cables, most especially with the High Fidelity Cables power cable, and more so when paired with an HFC power conditioner. Of course it is doubtful that Rob has heard that particular power cable and power conditioner. 
 
On the question of sources, Rob basically says, don't worry about it too much with DAVE, use what is convenient. Roy and others report hearing significant differences from one source to another, to the extent of being able to consistently discriminate among sources in blind testing. Maybe this is just a question of degree or it can be chalked up to different listeners, but still . . .
 
Finally, the question of switching power supplies vs. linear power supplies raises a question in my mind about the benefits of using a linear power supply with something like the microRendu (or any other component in an audio system). If it is difficult to shield other components in the system from RF generated by linear supplies, are the potential benefits of using a linear supply with something like the microRendu outweighed by the potential RF and/or magnetic pollution caused by such supplies? Does it just come down to how well the designer of the linear supply has shielded the supply from this type of pollution?
 
I don't claim any expertise (far from it!) on any of these issues, so I won't be offering any opinions of my own. Are other folks reading the various statements and findings discussed in this thread at least a little confused as well?
Click to expand...

To be upfront, I haven't received my Paul Hynes supply yet and what sounds good in theory and what may be a prominent chasm with another DAC may be only a minor improvement with the DAVE, I'm not sure.  I will find out in about 6 weeks.  As I stated, the difference I am hearing between an inexpensive HD Plex linear PSU and the iFi supply that came with my microRendu is very small with a slight preference for the iFi.
 
I also don't want anyone to have the impression that Paul Hynes is saying one thing and Rob Watts is saying something contradictory because if you read my post carefully, you will see that I made the speculation that low output impedance and RF are directly related.  Specifically, here is what Paul Hynes has to say about output impedance:
 
"To ensure no interaction with the powered circuit, an ideal power supply, should have no output voltage fluctuations under any load conditions, which means that the output impedance should be zero at all frequencies of operation. You can't generate a voltage across zero impedance. Also, it should not allow interference to break through from other sources like the supply line, such as rectifier diode switching, digital clocking and radio frequency interference (RFI) etc via the mains supply. This implies that the power supply should have infinite PSRR of its own power source.
 
Unfortunately, due to the limits of the various power supply design options available, power supply interaction will occur. The level of interaction is governed by the ability of the power supply to approach the ideal performance of zero output impedance, and infinite supply rejection of it's power source, at all frequencies of operation. It is logical to conclude that the better the power supply performance in these areas, the better the audio performance. Practical application proves this to be true.

Any regulator design worthy of consideration in high performance audio systems must offer a low output impedance over a very wide bandwidth (much wider than the audio bandwidth to deal with digital and RF interference). It should also have a high slew rate, fast rise-time and fast settling time to control the regulator output voltage during fast varying load current transients. It should be noticeably faster than the circuit to be powered to avoid load induced output fluctuations. It should also be quiet enough not to compromise the noise performance of the audio circuits it powers."
 
Here are Paul's measurements on his power supplies:
 
Here are the NF at 10Hz to 100 KHz:
PR3 series reg – 44nV/sqrt. Hz
ALW series reg – 70nV/sqrt. Hz
(40 nV/rtHz  = 5 uVrms).
Measured from DC to 100 KHz the output impedance remains below 3 
milliohms and the supply line rejection exceeds 80 dB. Regulation 
operating bandwidth is from DC to approx 300 MHz allowing for device 
tolerances. Transient response for a 5A load current change is typically 
<100nanoseconds and the settling time is also <100nanoseconds. Transient 
current delivery for PR3HD modules >30A.
 
As you can see, his supplies have a noise floor in the 5 uV range and have an output impedance of <3 milliohms across a very broad frequency spectrum and according to John Swenson, this is "superb" as far as the microRendu is concerned.  If the output impedance used in the switching power supply of the DAVE is <0.5 milliohms, obviously that is even more stellar.  As far as linear vs switching, it is clear to me that both can be very very good.  There is the assumption that switching power supplies are horrible because they backwash noise into the circuit which can negatively impact your other sources.  According to Alex Crespi and John Swenson, so can most linear power supplies.
 
I want to re-iterate that all my sources sound excellent with the DAVE.  Unfortunately, I am stricken with the disease of not wanting to leave well enough alone.  If I had to live with a basic Mac and $10 USB cable, I could and be very happy.  I certainly wouldn't spend a lot of money on a source but for the asking price of the microRendu, I am finding it to be unquestionably worthwhile.  
 
As for High Fidelity cables, this is a different story.  This one is proving to be a game changer.  Yes, their CT-1 power chord and MC-6 Hemisphere line conditioner make a very worthwhile difference in my system but it is their analog cables that are making the largest difference and this applies to both their interconnects and to the prototype headphone device I am testing.  
 
May 13, 2016 at 2:58 PM Post #2,948 of 25,842
sonic77 said:
  I'm getting a power source for the micro Rendu, and If I hear a difference, then there is a difference, somewhere somehow, I'll let my ears be the judge, if you disagree fine, go jump in a lake.
Click to expand...

I am very much looking forward to what you have to say about the Sonore Signature PSU.
 
May 13, 2016 at 4:05 PM Post #2,949 of 25,842
Shuttlepod just made me aware of another review of the microRendu by Hanz Beekhuyzen.  The specific relevance of this review is that he is using the microRendu on a Hugo (and also on a TT) and in his opinion, the microRendu was superior to his other sources.  The Hugo is supposed to sound best using the SPDIF connection and in his opinion, with the microRendu on USB, it is still sounding superior to his other sources even when those sources are connected to the preferred SPDIF input.  If I have interpreted him correctly, he also indicated that on the TT, even though there is galvanic isolation on the USB port, the microRendu is distancing itself from his other servers.  It is clear his experience is mirroring mine and Sonic77s experience with the DAVE and that an exceptionally designed source can sound superior.  Here is the link to that review (thanks, Jon!).  If you want to skip straight to his listening impressions, they begin at 7:08:
 
https://www.youtube.com/watch?v=2XRi9utNBl4
 
May 13, 2016 at 9:30 PM Post #2,950 of 25,842
Few days ago,HeadphoneClub website(A Chinese audiophiles website) hold a "Blind Listening Test",Name: Delta-Sigma Vs. R2R.
 
http://www.headphoneclub.com/thread-418239-1-1.html
 
Eight DACs take part in this test and divided them into two groups .
 
R2R:
1. TOTALDAC D1-DUAL
2. Lavry DA2002
3. SCHIIT YGGDRASIL
4. AQUA La Scala

Delta-Sigma:
1. Chord DAVE
2. Lavry Quintessence DA-N5
3. Merging NADAC
4. dCS Vivaldi DAC
 
Click to expand...

 
I wasn't aware that Mr Watts' DAC designs are Delta-Sigma. Isn't the DSP section of the DAVE, Hugo, etc 48-bit?
 
May 13, 2016 at 10:24 PM Post #2,951 of 25,842
I wasn't aware that Mr Watts' DAC designs are Delta-Sigma. Isn't the DSP section of the DAVE, Hugo, etc 48-bit?
Click to expand...

 
It is Delta Sigma, but Chord uses custom delta sigma implementation so they don't use off the shelf DACs. I'll reference you to this post for more info: http://www.head-fi.org/t/702787/chord-hugo/4305#post_10621034
 
PS. Someone knowledgeable should correct me if necessary: that post doesn't mention that some R2R DAC designs like those from Schiit also employ proprietary signal filtering (functionally similar to WTA filter?) which is also represented by "tap counts". Schiit posted that the Bifrost R2R gets 9000 taps while Gungnir R2R and Yggradsil have 18000 taps. This just shows that with custom chip implementation, one can achieve greater filter tap length.
 
May 13, 2016 at 10:49 PM Post #2,952 of 25,842
tkteo said:
I wasn't aware that Mr Watts' DAC designs are Delta-Sigma. Isn't the DSP section of the DAVE, Hugo, etc 48-bit?
Click to expand...


AFAIK his designs aren't really traditional DS at all - or at least if they were to be classified they are DS on mega steroids. They use his WTA filter in the ridiculously powerful FPGA (166 DSP cores in the DAVE) to handle the math and that sends the filtered signal to the Pulse Array DACs (which I believe he invented), which are inherently much less noisy, to output the analogue signal. DS typically does this all in one noisy chip (the biggest advantage here is cost, not fidelity) with much more limited processing power. In simplistic terms, many DS designs are built up around the shortcomings of the all in one chip format vs dealing with audio fidelity from the beginning, which is what the WTA filter and Pulse Array DACs do in Rob's designs. Of course Rob would be better able to explain it than I can. The take away I get is you really can't classify his DAC designs as DS and certainly not R2R.
 
May 14, 2016 at 12:17 AM Post #2,953 of 25,842
romaz said:
  Yes, Rob, during my blind listening, headphones were connected direct to DAVE and I could hear a difference that was more subtle but on 3/3 occasions, I correctly picked out one source over the other.  As I was confident I could hear an even more prominent difference on speakers, I blind tested here also and on 2/2 occasions, I was able to correctly pick out one source over the other.  To be honest, there's no need to blind test because the improvement with the microRendu is quite evident.  While more subtle, I can hear differences among different USB cables also although this evaluation was not blinded.
 
As I stated, the beguiling thing about the DAVE is that nothing sounds bad and so when not comparing one source against another, all my brain and my heart tell me is that I am hearing something wonderful and like you, I hear no variance whether I'm listening at 12 noon or at 12 midnight.  In direct comparison, however, there is no doubt in my mind that certain bit-perfect sources sound different (better) than others.
Click to expand...

Cool.
 
Something I meant to do a few weeks ago was to listen via my lap-top with battery on or off. My design lap-top is a serious windows 10 machine - a 17 inch Intel I7 with 16 GB SRAM, and does not last very long on batteries.
 
So I listened on HP via Dave with the lap-top being powered by the mains or battery. This will test to see how sensitive Dave is to RF noise on the mains from the lap-top.
 
Yes I could indeed hear a difference - battery operation on the lap-top was smoother (less grain on female vocals), bit softer on the bass, and more natural. It was a worthwhile improvement, but not a change that is large. I would not be able to accurately hear the difference blind, just to get a feel for the scale of the change. But this change in SQ is completely consistent with lower RF noise levels.
 
I have recently bought a Windows 10 two in one (tablet and lap-top - its HP pavilion) that has fully featured USB ports, so I can plug in 4TB portable hard drives, but it is power efficient (6 hours on battery). I will be using this on battery in future for serious listening - I have also got a battery pack for it which I use on flights.
 
Something else for me to ponder - perhaps I should resurrect my mains RF filters from the past... 
 
Rob
 
May 14, 2016 at 12:20 AM Post #2,954 of 25,842
tkteo said:
I wasn't aware that Mr Watts' DAC designs are Delta-Sigma. Isn't the DSP section of the DAVE, Hugo, etc 48-bit?
Click to expand...

I just don't know what the headphoneclub game want to achieve! You listen to your own system to decide which DAC used for the recorded files is a really laughable idea. How could your system could repeat what the original DAC's sound characteristics； may be only if you have a perfect system to play the records.
 
May 14, 2016 at 12:29 AM Post #2,955 of 25,842
romaz said:
  To be upfront, I haven't received my Paul Hynes supply yet and what sounds good in theory and what may be a prominent chasm with another DAC may be only a minor improvement with the DAVE, I'm not sure.  I will find out in about 6 weeks.  As I stated, the difference I am hearing between an inexpensive HD Plex linear PSU and the iFi supply that came with my microRendu is very small with a slight preference for the iFi.
 
I also don't want anyone to have the impression that Paul Hynes is saying one thing and Rob Watts is saying something contradictory because if you read my post carefully, you will see that I made the speculation that low output impedance and RF are directly related.  Specifically, here is what Paul Hynes has to say about output impedance:
 
"To ensure no interaction with the powered circuit, an ideal power supply, should have no output voltage fluctuations under any load conditions, which means that the output impedance should be zero at all frequencies of operation. You can't generate a voltage across zero impedance. Also, it should not allow interference to break through from other sources like the supply line, such as rectifier diode switching, digital clocking and radio frequency interference (RFI) etc via the mains supply. This implies that the power supply should have infinite PSRR of its own power source.
 
Unfortunately, due to the limits of the various power supply design options available, power supply interaction will occur. The level of interaction is governed by the ability of the power supply to approach the ideal performance of zero output impedance, and infinite supply rejection of it's power source, at all frequencies of operation. It is logical to conclude that the better the power supply performance in these areas, the better the audio performance. Practical application proves this to be true.

Any regulator design worthy of consideration in high performance audio systems must offer a low output impedance over a very wide bandwidth (much wider than the audio bandwidth to deal with digital and RF interference). It should also have a high slew rate, fast rise-time and fast settling time to control the regulator output voltage during fast varying load current transients. It should be noticeably faster than the circuit to be powered to avoid load induced output fluctuations. It should also be quiet enough not to compromise the noise performance of the audio circuits it powers."
 
Here are Paul's measurements on his power supplies:
 
Here are the NF at 10Hz to 100 KHz:
PR3 series reg – 44nV/sqrt. Hz
ALW series reg – 70nV/sqrt. Hz
(40 nV/rtHz  = 5 uVrms).
Measured from DC to 100 KHz the output impedance remains below 3 
milliohms and the supply line rejection exceeds 80 dB. Regulation 
operating bandwidth is from DC to approx 300 MHz allowing for device 
tolerances. Transient response for a 5A load current change is typically 
<100nanoseconds and the settling time is also <100nanoseconds. Transient 
current delivery for PR3HD modules >30A.
 
As you can see, his supplies have a noise floor in the 5 uV range and have an output impedance of <3 milliohms across a very broad frequency spectrum and according to John Swenson, this is "superb" as far as the microRendu is concerned.  If the output impedance used in the switching power supply of the DAVE is <0.5 milliohms, obviously that is even more stellar.  As far as linear vs switching, it is clear to me that both can be very very good.  There is the assumption that switching power supplies are horrible because they backwash noise into the circuit which can negatively impact your other sources.  According to Alex Crespi and John Swenson, so can most linear power supplies.
 
I want to re-iterate that all my sources sound excellent with the DAVE.  Unfortunately, I am stricken with the disease of not wanting to leave well enough alone.  If I had to live with a basic Mac and $10 USB cable, I could and be very happy.  I certainly wouldn't spend a lot of money on a source but for the asking price of the microRendu, I am finding it to be unquestionably worthwhile.  
 
As for High Fidelity cables, this is a different story.  This one is proving to be a game changer.  Yes, their CT-1 power chord and MC-6 Hemisphere line conditioner make a very worthwhile difference in my system but it is their analog cables that are making the largest difference and this applies to both their interconnects and to the prototype headphone device I am testing.  
Click to expand...

OK, just to clarify - its not the switcher power supply that is <0.5 milliohm, but a linear discrete circuit for the reference supply. It is also only 0.22 uV of noise 20-20kHz. I have to have such low levels of noise to ensure no measurable noise floor modulation from Dave.
 
Rob
 
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