Chord Qutest

[beerandmusic]

^^^^  I just googled....and yes, on the Qutest advertising link, they specifically state:

 

Perfectly equipped to bring the benefits our digital technology to a wide range of connected devices, it features a galvanically isolated USB-B

 

I would trust that Chord is capable of providing a well designed isolated usb interface.

 

https://chordelectronics.co.uk/product/qutest/

 

[beerandmusic]

On 8/15/2018 at 11:39 AM, Miska said:

 

On 8/14/2018 at 3:12 PM, Em2016 said:

But if I understand both @JohnSwenson and Rob Watts (I could be wrong), the leakage currents are also responsible for RF pickup and radiation, potentially affecting the analogue stage and downstream analogue components?

 

Yes, but since that RF pickup and radiation is specifically isolated from the downstream analogue components by the isolation barrier, it cannot cross it, only data will.

 

So I ask in different way: how may times you need to isolate isolator with isolator for it to be effective? You believe putting 100 USB regens and isolators in row before a DAC that has isolation between USB and DAC sections and that will somehow provide ultimate quality?

 

 

 

This post has really impacted me, and has always been in the back of my mind.

Here you state that the RF (I am assuming you are talking about RFI/EMI) is "specifcally isolated"...where many suggest it can't be isolated, but i thought i read that it is part of FCC standard that it be isolated....is it isolated or not? 

If a name brand, such as Chord, states the qutest is galvanically isolated and it meets fcc standards, can cables and usb toys further minimize rfi/emi, or is that where the objective vs subjective comes in to play?

Right now, i am most interested in how it applies to so called JSSG360 double insulated cables that suggest it minimizes RFI.  I just read on another forum where Rob Watts (Chord Engineer) says these cables do nothing, yet we have others suggesting dramatic impact?  Perhaps dramatic impact with older dacs that do not have newer technology that has designed new methodology to limit noise??

I am curious as to what your take is?

 

[beerandmusic]

8 minutes ago, ElviaCaprice said:

Rob Watts, the designer, says that his own galvanic isolation does not protect the DAC from RFI.  Thus his recommendation for toslink.  The problem I am encountering with JSSG360 is that it kills the music from it's reflection (great transparency, awful listening fatigue), at least in my findings with PCIe ribbon.  Which I would assume also applies to USB cables.  NOTE:  I do not use a USB cable.  I opted for an adapter, the USPCB as the best option.

 

wow that is surprising that he would recommend toslink over usb...esp since you can't get highest resolutions from toslink....and to think the qutest would have been next dac (if any) i would consider.

 

you also have me confused inre your word "reflection"....i thought all the jssg360 did was stop rfi..and even if it didn't work as suggested, that it couldn't possibly hurt anything.

 

this industry is really starting to frustrate me...lol...so much for the cables i ordered that i was going to try to DIY...

 

i think i will just stick to enet still....

[beerandmusic]

Just now, ElviaCaprice said:

Rob doesn't recommend against using USB.  With the caveat to take care of RF contamination.  Measured against toslink they should be equal on his DAC's.  

so if Rob says the jssg360 doesn't do anything, what is his recommendation to deal with RFI?

[beerandmusic]

23 minutes ago, ElviaCaprice said:

Rob has never commented on this cable modification/design.

 

https://www.head-fi.org/threads/watts-up.800264/page-63

 

besides link above, even in threads on C.A. i just read others saying that Rob Watts doesn't agree with jssg360.

 

anyway, after spending about 24hrs reading stuff lately, i just have a headache and think i will stick with enet for now...going to lay down for a much needed nap.

[beerandmusic]

1 hour ago, ElviaCaprice said:

  The problem I am encountering with JSSG360 is that it kills the music from it's reflection (great transparency, awful listening fatigue), at least in my findings with PCIe ribbon.  Which I would assume also applies to USB cables.

you also have me confused inre your word "reflection"....i thought all the jssg360 did was stop rfi..and even if it didn't work as suggested, that it couldn't possibly hurt anything....what do you mean by "reflection".

[beerandmusic]

10 minutes ago, Miska said:

 

What I've tested, using bog standard USB HiSpeed certified cables with ferrites makes more difference than audiophile USB cables that usually don't make a difference or make things worse.

 

 

that seems to mirror what Rob Watts suggested...i have seen some cables with one ferrite and some with two.   Also, i have found some "standard" usb fcc compliant cables offer double shielding?  any comment about either 2 ferrites or 2 shields?

 

anyway, i have also purchased one of these besides 4 other usb cables...it has both 2 ferrites and double-shielded.

 

https://www.amazon.com/gp/product/B008VOPCGY/ref=oh_aui_detailpage_o00_s00?ie=UTF8&th=1

[beerandmusic]

3 minutes ago, ElviaCaprice said:

 

unfortunately clicking the link just takes you to page 1 and "reflection" is not searchable on that page?

[beerandmusic]

6 minutes ago, Miska said:

 

The stuff I have is with just one ferrite (these kind of things commonly also come with scanners, digital cameras, etc). I have also retrofitted ferrites on some of my cables, 2 cm from the B-connector. I don't think adding more shields or ferrites improves things anymore. USB uses differential signaling on twisted pair, so shielding as such is not so important from signal point of view. Power feeds of the USB are more problematic, especially the ground/shield link. Ferrites help killing some of the HF noise on these.

 

 

OK thanks....yes, i understand the the power on the usb is different and more problematic...Dac galvanic isolation for that...thanks again!

[beerandmusic]

20 hours ago, Miska said:

 

What I've tested, using bog standard USB HiSpeed certified cables with ferrites makes more difference than audiophile USB cables that usually don't make a difference or make things worse.

 

you mention that you think usb cables with ferrites seems to work best in your testing.  Do you think that  ferrites on "BOG" usb compliant cables are effective?  I read one mfr advertisement stated that Not all ferrites are tuned correctly (whatever that means?) to be used with  high frequency data transfer cable without changing the electrical properties of the cable to the point where the data transfer is corrupted and/or slowed down?

[beerandmusic]

since the qutest thread popped to the top, i thought i could ask the owners here does the qutest have the ability to either upsample everything that goes to it (e.g. NOT just from a music player) but everything on a windows pc...like if i am playing a youtube video will the audio automatically be upsampled?  And if so, does it also have the ability to play native dsd without modifying it?

 

I want a dac that has multiple modes, where in one mode i can have it upsample everything going out the windows pc, and then another mode where if i am using a player playing a native dsd file that it can play it without modifying it?

 

[beerandmusic]

8 hours ago, barrows said:

Yes, the Qutest over samples all incoming PCM to an extremely high rate in an FPGA using Rob Watts unique “long” oversampling/filtering algorithms.  No the Qutest does not convert DSD natively, it re-modulates DSD into a multi-bit format (a version of PCM) before conversion.

 

hmmm...your response seems to conflict with davides response above (although he said mojo but i asked about qutest), but this is closer to what i understood...but can you clarify a little please...

 

so whether my windows 10 pc is playing a 128k mp3 file from windows media player, or playing a youtube video from youtube.com, or a native dsd file from jriver, it will ALWAYS and with no other options, play everything at this "high rate fpga rate" you speak of?

 

do you know what this high rate is?  I couldn't seem to find it anywhere...

 

Also if that is the case does it work for both optical or usb the same way?

 

[beerandmusic]

31 minutes ago, ecwl said:

Yes. @barrows is 100% correct. Chord DACs always upsample. That's why you buy the DAC and it's also why most people enjoy the sound because the upsampling filter is generally superior to other products (although obviously some people would disagree). 

@davide256 just likes to upsample in software on his computer himself but that's his perogative.

Chord Qutest would upsample the same with optical & USB. Optical might sound better because there wouldn't be ground loop noise leaking from your PC to the Qutest via USB but Toslink is limited to 192kHz PCM and standard DSD over PCM if your PC supports it.

For most Windows PC, the bigger problem is making sure Windows is sending your music or YouTube sound natively to Qutest. JRiver would always send music natively to Qutest if configured properly (or by default). But Windows Media Player and YouTube would send sound based on your Windows settings so you should manually set Windows sound to 44.1kHz when using Windows Media Player and switch it to 48kHz when watching YouTube. What I actually do with my Hugo2/Mojo via Toslink from PC is that Windows is always set to 48kHz so that when I watch YouTube, it's playing natively. When I'm listening to music, I always use Tidal/JRiver/Roon so those apps would automatically switch to the correct sample rate to ensure the DAC gets native signal. Unfortunately, my PC doesn't support DSD over PCM or >96kHz PCM so I do have to downsample the Toslink to 88kHz/96kHz if it's playing at a higher sample rate.

thanks, i will read through closer and digest, but quick question...if the qutest "always" upsamples, then by davide upsampling to 705k First with software (seems like an odd number?), but then the qutest would upsample even more right?  Also what is the rate that the qutest upsamples to?

[beerandmusic]

7 hours ago, davide256 said:

 I find that upsampling a 44.1/48khz to max PCM rate 705/753

in the player application makes a large difference over USB audio using a Chord Mojo vs using PCM native rate. Its one of the reasons I plan to buy a Qutest.

To do this the application needs to allow you to enable rate conversion vs only set the max rate supported by the DAC

why would that be possible since the mojo or qutest will upsample it much higher?

so if you start with a 44.1k file and then upsample it to say 192k, it can't make new music that is not there, the software just guesses what "music would be there" right?  it can't make music that doesn't exist?  i would think the fpga algorithms would "guess" better which is what i thought we were buying when we buy an upsampling dac...one that sounds more natural.  Can you explain the "theory" where upsampling first to 192K then to mhz rate the mojo/qutest upsamples to vs just upsampling the 44k file to the mhz rate the mojo/qutest upsamples to?  it is just a subjective thought right, that the software does a better job of upsampling?  And if that is the case, why not just upsample to the same rate the dac can upsample to with software?  Not doubting, just questioning the theory?

[beerandmusic]

59 minutes ago, barrows said:

Here is some of the theory:

 

1.  The processor in a computer is many times more powerful than the one in a DAC. Therefore the software based oversampling algorithm can be mush more precise/sophisticated than the one in the DAC.

2.  The first oversampling step, is generally much more audible than subsequent ones, because any artifacts are at much lower frequencies-so the first oversampling step is the most important.

3.  Having the DAC do less "work" (processing) usually means the DAC will also produce less RF internally, and less internal RF often means better sound quality.

4.  No, of course you cannot get "more music" by oversampling, but what you can do is use a much simpler and more accurate conversion circuit for the final step of turning digital into analog when you have a much higher sample rate.  Many designers feel that the more simple conversion stage allows for better sound.

 

It should also be noted that even Chord themselves understands the above, and they make the mScaler external oversampling processor for precisely these reasons.

 

ok, thanks for the explanation...it seems to make sense to some degree, but if the computer software is more capable of upsampling, why not just use the computer to upsample to same rate as the chord does?

 

[beerandmusic]

7 minutes ago, barrows said:

I am not aware of any way to transport 104 MHz sample rate to a DAC from a computer: certainly I no of no DAC which can accept an input sample rate of 104 MHz.

104mhz? wow..had no idea....but still why not upsample to high rate dsd first and then to the dac...still higher than 705K?

I understand 705 is highest pcm, but chord accepts dsd input so why not go to dsd256+ before going to chord if computer software is better at upsampling...why stop at 705?

[beerandmusic]

and one more question for davide....

since you have mojo and plan to upgrade to qutest, can you tell me al the differences between the two?

[beerandmusic]

^^^thanks all..a lot to digest, but i have screen captured and will study closely.  At some point i want to buy a used qutest, so this is all good info...thanks!  Will likely try the gustard a18 first once it comes out mainly because it is more inline with my budget.