Chord Qutest

[ecwl]

2 minutes ago, Gavin1977 said:

I used to have an EtherRegen - good device.  It's effect/purpose is somewhat different to the IsoRegen though.  I'm mainly interested in the performance disparity between optical and usb at the moment.

Right. But the USB performance is interlinked to both EtherRegen and maybe less so IsoRegen. For IsoRegen, I believe you're just doing routine filtering the USB noise on the data and power line. But it would not block the ground loop leakage current introduced from the USB source power supply and all the other power supplies that is connected to your USB source via Ethernet cable, e.g. cable modem, router, NAS, main music server PC, maybe even the monitor connected to your server) into the Chord DACs. The hope is that EtherRegen can block these types of noise so the only ground loop leakage current noise you'll get would just be from your USB source power supply but not everything else that is connected to your USB source via Ethernet cables.

 

After exploring all of this and grounding everything I can think of, I just threw up my hands and switched to optical because it's a little challenging for me to address every conceivable source of ground loop leakage current noise. That's why I ended up switching to optical.

[Miska]

5 hours ago, ecwl said:

Right. But the USB performance is interlinked to both EtherRegen and maybe less so IsoRegen. For IsoRegen, I believe you're just doing routine filtering the USB noise on the data and power line. But it would not block the ground loop leakage current introduced from the USB source power supply and all the other power supplies that is connected to your USB source via Ethernet cable, e.g. cable modem, router, NAS, main music server PC, maybe even the monitor connected to your server) into the Chord DACs. The hope is that EtherRegen can block these types of noise so the only ground loop leakage current noise you'll get would just be from your USB source power supply but not everything else that is connected to your USB source via Ethernet cables.

 

Unless you are using wrong type of Ethernet cable, it doesn't have any ground connection. Only transformer isolated differential signals.

 

So always make sure you use only UTP cables... (plastic connector body)

 

[Superdad]

16 hours ago, Miska said:

Unless you are using wrong type of Ethernet cable, it doesn't have any ground connection. Only transformer isolated differential signals.

 @ecwl was incorrect to refer to “ground loop leakage.”  The leakage currents blocked by the EtherREGEN are common-mode differential AC, which sail right through the port transformers.

[Miska]

3 minutes ago, Superdad said:

 @ecwl was incorrect to refer to “ground loop leakage.”  The leakage currents blocked by the EtherREGEN are common-mode differential AC, which sail right through the port transformers.

 

They don't, and even if they would, they wouldn't end up anywhere because only the differential signal coming out of the transformer is used by the PHY and signals don't have ground connections they could leak through.

 

Let's see spectrum analysis results from Qutest analog outputs when used with/without EtherREGEN and UTP cables? Thanks!

 

P.S. AFAIK, EtherREGEN is limited to 100 Mbps which is absolute no-go for me.

 

[matthias]

34 minutes ago, Miska said:

AFAIK, EtherREGEN is limited to 100 Mbps which is absolute no-go for me.

 

+1

It is limited when crossing the moat from A to B.

The better the equipment the better it sounds staying on the A-side only which has 1Gbps specs.

 

Matt

[Gavin1977]

BNC vs Toslink.  Anyone compared on the qutest?

[jos]

Yes, I did this with a few young people and they all choose Toslink, using a 192khz Qed toslink cable, see: https://www.hansaudio.nl/product/qed-reference-optical-quartz/

 

In addition: At first I was using the ultraRendu with USB out, but then I decided to buy a Yamaha streamer with optical and coaxial out for internet radio, without using the DAC in the steamer, directly to the Qutest. So I did make a comparison with a very good Qed BNC cable. After that, I did sell my UltraRendu.

[jos]

1 hour ago, jos said:

Yes, I did this with a few young people and they all choose Toslink, using a 192khz Qed toslink cable, see: https://www.hansaudio.nl/product/qed-reference-optical-quartz/

 

In addition: At first I was using the ultraRendu with USB out, but then I decided to buy a Yamaha streamer with optical and coaxial out for internet radio, without using the DAC in the steamer, directly to the Qutest. So I did make a comparison with a very good Qed BNC cable. After that, I did sell my UltraRendu.

In addition: I have the EtherREGEN feeding the Yamaha streamer.

[CheapSplurge]

Is usb from laptop or optic better to dac? 

As far as sound quality? Or coax? What are their limitations? 

[asdf1000]

27 minutes ago, CheapSplurge said:

Is usb from laptop or optic better to dac? 

As far as sound quality? Or coax? What are their limitations? 

 

Rob Watts uses laptop (and phone) USB output but laptop running off battery (AC charger disconnected).

 

But according to him, optical is just as good and maybe even technically better since it is 100% free of RF.

 

These are the 2 'best' according to Rob.

 

[Middy]

Just try the phone and see same adapter for adding external memory on a samsung. USB audioplayer pro is about the best for android and uses its own driver. I am not agreeing with Rob on SQ but a really noisy source always benefits from decoupling that noise. Whether you like it is a different matter..

No one mentions the quality of the transmitter or the receiver (TOSLINK), are they clean.. really clean.. Toslink jitter signal attenuation, glass plastic Tos. 

The information is really poor on the net and audiophile community. Well.. within my googling skills...

 

 

 

 

[Gavin1977]

Hi Middy - completely agree.  My experience with glass optical and a matrix audio x-spdif 2 have been really good.  There's a dearth of information out there.  But here is what I have found:

 

Regular PCM - use toslink.  Performance will not be matched for regular PCM.  Clocking and glass cables work well to retain detail (chord DACs cannot recover lost information, same as other DAC's to be fair, they only remove jitter).

Rates over 24/96 - a very good usb converter/DDC with a good linear power supply.  Otherwise noise gets injected into the USB receiver.  Unfortunately you can't use an unpowered usb cable with the Chord.  Potentially even better is some form of optical isolation Monoprice slimrun, audiowise.  Coax or dual data coax will likely perform slightly better, this is mainly because RF/EMI from the USB received is not present when using coax - coax signals are decoded on the FPGA.  This is why the m-scaler uses coax IMO (also a reason why Naim used spdif as well, and tend not to have USB on their DACs).

 

Took me a while to find this out, Dan at Audiowise was very helpful.

 

Chord have said they will update they're marketing, it presently states 24/192 over toslink, that incorrect.  The qutest can only do 24/96.

[asdf1000]

18 minutes ago, Middy said:

No one mentions the quality of the transmitter or the receiver (TOSLINK), are they clean.. really clean.. Toslink jitter signal attenuation, glass plastic Tos. 

The information is really poor on the net and audiophile community.

 

The designer of the DAC of this thread doesn't believe in this difference between TOSlink sources - as long as full chain is bit perfect...

 

[Middy]

Another small piece of information to add to the list. I had some unused ifi i silencers and tryed them on my unused USB in on the Qutest. No discernible effect. I hoped using them as a mini plug in power conditioner would work. I dont know about the ground plane but i am sure that parts of the circuit are cut off no 5v.. Software or Microswitch isolated.. somone might know..

They worked lovely on the fanless NUC on unused ports as a 5v  filter.

They did nothing for me inline on the data signal but alone tempered the noise on the USB bus.

Ive got a cheap NORD easy-stream pro 3 streamer with an LPS1 powering it. I though why not and tried 3 on there as its COAXIAL out.

Lovely result it had a usb memory reader free and i am on wifi so got a usb to Rj45 converter and tryed that for fun... a more refined sound cleaner details abit more sound stage. 

My wife ran in screaming what did you just do... ( that wasnt sound related)...☹

If noise is on the whole circuit use these in a source and see it they help..

 

Still better power and signal in as the only Qutest hack.. i am out of ideas..

 

Cheers all

Dave

 

[Middy]

Thanks both, i thought i was going mad about 24/96... didnt know that.

 

One lesson learned is that even though we get a foothold on the Chord ladder... there is no free lunch as an audiophile. Just look at the Dave Jacobs MOD yes theres some gains and imagine lovely beyond my wildest dreams but that cost... Ive got cables adapters boxes computers clogging up cupboards and i was warned....

On here years ago... still chasing the dream..

 

Cheers @asdf1000 and @Gavin1977

 

Hope you are both well and happy in these times..

Good luck

David 😊

 

[barrows]

5 hours ago, Gavin1977 said:

this is mainly because RF/EMI from the USB received is not present

The above is only true if the USB receiver implementation in the DAC is inadequate.  Also note the amount of RF energy which could possibly be produced by, for example, an XMOS USB receiver, is much less than that produced by a Chord DAC's FPGA processor.

It is also relevant to always remember that when using SPDIF optical toslink, or electrical BNC, RCA, or AES), the DAC is at the mercy of the quality of the clock in the source, whereas with USB, the DAC clock is the master, and the source clock is irrelevant to jitter performance of the DAC.  Things are not so simple as they may seem at first, and claiming that there are "problems" with USB as an interface is not accurate.  All interfaces have their challenges, and there performance will be determined by how well the DAC (and source maters as well) implement the interface.  Given equal interface implementations, USB does have the clear advantage of being fully asynchronous, and not reliant on transporting (an often not so good) clock from the source.

One additional note on USB receivers: using the 5 VDC power to power the USB receiver is not a compromise, this is actually a very good way to make sure the USB receiver can be fully isolated from the DAC.  Now, if a USB interface does use USB power, it will matter how good that power feed is, and how good the USB cable is.  So in this case, the source will matter a lot.  A well designed USB source component will have a dedicated, ultra low noise and impedance regulator with proper filtering of its output, to provide the 5 VDC USB power.

As far as I can tell from Rob Watts' remarks about preferring toslink connections, is that he prefers toslink to a USB feed directly from a regular computer (laptop)-this is certainly not surprising as a regular computer has a fairly poor and noisy USB feed.  There is a huge difference from the quality of the USB feed from a well designed high end source component and a regular commercial computer.

[asdf1000]

22 minutes ago, barrows said:

The above is only true if the USB receiver implementation in the DAC is inadequate.  Also note the amount of RF energy which could possibly be produced by, for example, an XMOS USB receiver, is much less than that produced by a Chord DAC's FPGA processor.

The FPGA generated RF is in complete control of the designer (Rob Watts).

 

The nasty RF Rob always talks about is mains borne RF making its way into the DAC.

 

He describes RF as a fungus... affecting IM distortion.

 

TOSlink is 100% immune of upstream RF. 

 

For USB input to be immune of mains RF , there is only one way - battery powered USB source. Eg. mobile phone, laptop with charger disconnected.

 

opticalRendu is great but tricky to make it's PSU 100% isolated from mains RF. Powering with a battery is one way.

 

 

[asdf1000]

27 minutes ago, barrows said:

As far as I can tell from Rob Watts' remarks about preferring toslink connections, is that he prefers toslink to a USB feed directly from a regular computer (laptop)-this is certainly not surprising as a regular computer has a fairly poor and noisy USB feed.  

 

Rob mostly uses a laptop USB source to listen to music... he doesn't say he prefers TOSlink to a battery powered laptop, this isn't correct.

[ray-dude]

@barrows is spot on.  It is all about balancing tradeoffs, since there isn't an ideal (yet).  

 

The insidious thing is that a recipe/scheme that works astonishingly well for one person, may have marginal impact for another person.  The trends and tendencies and levers are pretty clear, but getting to the right balance is very much dependent on your system, your home, your environment, and your ear/brain.  

 

For example, Rob has shared that when he got a new laptop, the balance and impact of toslink and USB changed for him.  Not a surprise, but very easy to forget when we're all scrambling to fit all these pieces together into something that works for us.

 

I've learned (alas, and relearned again and again and again) to keep an open mind, be systematic, and after you make a major change, go back and revisit all the things that were obvious before.  Any (new) thumb on the scales shifts the balance of the entire system.  There was a time where TOSLINK was the end all for me (until I did upsampling differently), optical BNC (until I did upsampling differently), USB with regenerators (until I did my source differently), vibration absorption (until I did power differently), etc. etc.  

 

All of those were local optimum points (the top of the hill).  However, there is always a new and different hill that may be higher still.  Best you can do is climb the hill with your own system, and look to ideas and experiences from others for new hills to explore (if you're so motivated...there is something to be said for parking a comfy chair on the hill you're on, and enjoying they view)

[barrows]

16 minutes ago, asdf1000 said:

For USB input to be immune of mains RF , there is only one way - battery powered USB source. Eg. mobile phone, laptop with charger disconnected.

The above is untrue.  Good engineering of power supply design solves these kinds of issues.  the same applies every audio component which is powered form he AC mains.  I have experimented a lot with battery power to avoid mains borne noise, and have concluded that there is no advantage to using battery power for anything, versus properly designed and implemented mains powered components.  There is nothing about a USB interface which makes it anymore susceptible to mains borne power supply noise than any other audio component.

[barrows]

17 minutes ago, asdf1000 said:

 

Rob mostly uses a laptop USB source to listen to music... he doesn't say he prefers TOSlink to a battery powered laptop, this isn't correct.

I did not mention anything about battery power?  I was referring to rob Watts' comments where he has advised users to use the toslink input on his DACs.  Such as his many comments at the headphone forums.

[asdf1000]

7 minutes ago, barrows said:

I have experimented a lot with battery power to avoid mains borne noise, and have concluded that there is no advantage to using battery power for anything, versus properly designed and implemented mains powered components.  There is nothing about a USB interface which makes it anymore susceptible to mains borne power supply noise than any other audio component.

 

But do you have access to the kind of measurement equipment Rob has, in your experiments?

 

I don't know what he has access to but when he makes these comments about mains RF, he has measured increases in IM distortion at the analogue output of DACs...

 

I do know he owns his own APx555 (purchased himself, doesn't belong to Chord).

[asdf1000]

8 minutes ago, barrows said:

I did not mention anything about battery power?  I was referring to rob Watts' comments where he has advised users to use the toslink input on his DACs.  Such as his many comments at the headphone forums.

 

You said: "he prefers toslink to a USB feed directly from a regular computer (laptop)"

 

This isn't correct - he uses a laptop to listen to music... 

 

[The Computer Audiophile]

40 minutes ago, asdf1000 said:

The FPGA generated RF is in complete control of the designer (Rob Watts).

 

The nasty RF Rob always talks about is mains borne RF making its way into the DAC.

 

He describes RF as a fungus... affecting IM distortion.

 

TOSlink is 100% immune of upstream RF. 

 

For USB input to be immune of mains RF , there is only one way - battery powered USB source. Eg. mobile phone, laptop with charger disconnected.

 

opticalRendu is great but tricky to make it's PSU 100% isolated from mains RF. Powering with a battery is one way.

 

 

Ayre uses optical isolation inside the QB-9

[barrows]

2 minutes ago, asdf1000 said:

 

But do you have access to the kind of measurement equipment Rob has, in your experiments?

 

I don't know what he has access to but when he makes these comments about mains RF, he has measured increases in IM distortion at the analogue output of DACs...

 

I do know he owns his own APx555 (purchased himself, doesn't belong to Chord).

Yes, I have (distant) access to an AP which is capable of measuring DAC output down to below audible levels.  Not here right at hand, but all of my work is verified via an AP.

I think you may have mis-interpreted Rob Watts' statements though, although I have certainly not read every single forum post he has made.  He has mentioned that the RF produced by the high power FPGA in the mScaler is severe enough that it needs to be in a  separate chassis from the DAC, for example.

My point being, that given good power supply design in our audio components (and perhaps the addition of very good power conditioners in some situations) AC line noise is the least of one's worries.  Reducing the amount of noise which is actually produced by the audio components themselves (especially digital components, but not limited to those) is a major challenge.  Also, proper PCB board layout techniques are critical for producing components which reject the pickup of this noise into their circuitry-this is where a really, really good engineer at PCB board layout can be a big advantage.

As to AC line noise, this is the responsibility of the power supply design to eliminate, and perhaps in situations where the line noise is very, very, bad, the addition of a suitable AC line conditioner is warranted (AC line noise varies widely from location to location).