[Rob Watts]

So Chord DAC's are unlike some DAC's that only require 5V VBUS for initial handshake but will keep on working if 5V is turned off later?

Yes the USB VBUS powers the USB decoder and the source side of the galvanic isolator. The benefit of this approach is the USB device whilst decoding creates RF noise and correlated and distorted noise, so keeping that device away from the DACs ground plane is key here. As far as the FPGA is concerned it merely sees I2S type data, where the data clock comes from the FPGA, so the FPGA has the minimum amount of processing to do and being (almost completely) immune from source noise.

Hi Rob, in this example though, while you've removed one loop by removing the USB reclocker, let's say you are left with 3 x SMPS's and the USB source is earthed and integrated amplifier is earthed...

The USB galvanic isolation of Qutest can still be defeated here right, as the ground currents / leakage currents can see go through Qutest and amp?

Sometimes when I think about the different paths these currents can go I wonder how important galvanic isolation is in the big scheme? Sure you may block these currents on USB input but they still have a pathway via PSU's (including Qutest's?)?

Especially if the system has bad grounding overall, i.e. multiple earthed PSU's?

Galvanic isolation is absolutely crucial in the scheme of things; what we are talking here are second order or more accurately third order effects. My job is to make the quality of the source (with bit perfect data of course) become irrelevant to ensure maximum overall performance; and I am not quite there yet as sources still do make a difference. So given that source jitter certainly is irrelevant, then the only thing that can make a difference is RF and correlated noise being injected into the DACs ground plane. The only way this can happen with the galvanic isolation and the RF filtering built is is via external ground loops and currents being induced into the ground and mains. What I am trying to get over is adding extra complexity to the source will actually make matters worse, as you are creating ground loops that didn't exist; the resultant performance may be easily mistaken for an improvement - increased perceived width because the depth has collapsed, a brighter more analytical SQ due to more noise floor modulation - but of course degraded timbre variation, more listening fatigue and things being perceived to be louder.

 

[flyte3333]

What I am trying to get over is adding extra complexity to the source will actually make matters worse, as you are creating ground loops that didn't exist

I absolutely agree with this.

I guess my only point (and it's not even your problem of course) is if someone (for example only) connects Qutest to an earthed USB source and earthed preamp then the USB galvanic isolation of Qutest will essentially be defeated as both sides of USB interface are connected to earth, no?

But as mentioned, this is not your problem to worry about. You are dead right (of course!) when you say "My job is to make the quality of the source (with bit perfect data of course) become irrelevant".

How we integrate your gear is out of your control.

 

[Ragnar-BY]

What I am trying to get over is adding extra complexity to the source will actually make matters worse, as you are creating ground loops that didn't exist; the resultant performance may be easily mistaken for an improvement - increased perceived width because the depth has collapsed, a brighter more analytical SQ due to more noise floor modulation - but of course degraded timbre variation, more listening fatigue and things being perceived to be louder.

You’ve did a great job, Rob. I have used various decrapifiers with my other DACs and it gave some improvements, but Qutest is best on it’s own. It was hard to believe at first and I spent a lot of time testing it, but after all my ears confirmed that you are absolutely right about “false improvements” from RF noise.

 

[Rob Watts]

I absolutely agree with this.

I guess my only point (and it's not even your problem of course) is if someone (for example only) connects Qutest to an earthed USB source and earthed preamp then the USB galvanic isolation of Qutest will essentially be defeated as both sides of USB interface are connected to earth, no?

But as mentioned, this is not your problem to worry about. You are dead right (of course!) when you say "My job is to make the quality of the source (with bit perfect data of course) become irrelevant".

How we integrate your gear is out of your control.

Actually you are OK in the instance of one earthed/mains powered component on source side and one on the Qutest output side; you may think you are shorting out the galvanic isolation (and indeed you are) but there will be no current flow through the isolation and into Qutest ground plane - hence everything will be OK. You have a piece of wire that's not connected, so no current can flow through the isolation loop. We need a current flow to happen for problems to occur, and this won't happen in this instance. You will only get current to flow if there is a mains/earth loop through Qutest and it's output, and this loop being intersected with another source loop; if the source is not looped (that is a single source with one sole connection to ground/mains then no current will flow in the Qutest output loop, and hence Qutest can't see any noise as there is no current flow to create voltages within Qutest's ground plane.

I know it's not easy to understand this, it took me some time to figure it out!

 

[Ivodam]

Hi everybody,

I am new to this forum and this thread. I decided to join, since I have owned for some months now the Chord Qutest dac.
I am very happy with its performance, but I have some questions as well.
I have read a bit through this thread now and saw that some of my questions and findings have already been discussed here.
My "workflow" is the following (I listen to floorstanders): laptop running Win 10, Foobar software player - Qutest over USB - directly into power amp Moon W 3.5 RS.
Volume control is done within the Foobar. All cables - USB, RCA and speaker cables are from the Chord Company (this is another British company).
I have tried different combinations - through preamp to power amp , connected to integrated amp, volume control through a passive attenuator.
The best solution is direct connection to the power amp - beautiful transparent sound.
About the power supply - I use a simple battery power bank, to my subjective perception it sounds a bit better.

I listen to highly detailed and multilayered music: symphonies and German opera. I find the Qutest just marvelous for my musical taste.

Only problem I have at the moment is the direct - so-called native reproduction of DSD files with the Foobar. I have downloaded Chord's official ASIO driver
from Chord's Website and have installed the relevant ASIO plugins in the Foobar, still when choosing DSD output I get distorted sound.
Some friends of mine tried to help, but there seems to be the problem that Chord's ASIO driver does not have any control panel, or I have not been able
to find it and to make the proper adjustments.
Anyone with Qutest and Foobar experience here?

P.S.: Of course, I have not been able to read the whole thread - if this subject about native DSD and ASIO drivers has been discussed already, please just let me know -
I will find it.

 

[nick77]

I read a post earlier in the thread about isolation and Herbies Tenderfeet. Isolation products can get crazy pricey but wanting to give it a shot I contacted Herbie and he recommended the Baby Booties. I was a bit skeptical but the price was right so I purchased 4 pieces. I am pleasantly surprised by a real nice bump in focus, and improved imaging. They fit nicely and well worth the price of entry.

 

[flyte3333]

Actually you are OK in the instance of one earthed/mains powered component on source side and one on the Qutest output side; you may think you are shorting out the galvanic isolation (and indeed you are) but there will be no current flow through the isolation and into Qutest ground plane - hence everything will be OK. You have a piece of wire that's not connected, so no current can flow through the isolation loop. We need a current flow to happen for problems to occur, and this won't happen in this instance. You will only get current to flow if there is a mains/earth loop through Qutest and it's output, and this loop being intersected with another source loop; if the source is not looped (that is a single source with one sole connection to ground/mains then no current will flow in the Qutest output loop, and hence Qutest can't see any noise as there is no current flow to create voltages within Qutest's ground plane.

I know it's not easy to understand this, it took me some time to figure it out!

Thanks Rob.

Next question is genuinely for my learning purposes (not for being a pain in the a$$) but aren’t things further complicated because these leakage currents can also travel through the AC neutral wire, like Qutest’s SMPS?

From what I read by John Swenson, they don’t necessarily have to travel through an earth wire of a PSU...

So Qutest’s SMPS can still form part of a loop, and ground currents can still get into Qutest’s ground plane, for the example where USB source and amp are earthed? Or maybe they don’t even need to be earthed.

John S has said we would be surprised to know the different paths these leakage currents can take to get through our DAC and other AC powered analogue electronics.

Of course with a Hugo TT2 directly driving headphones or passive speakers, then the built-in USB galvanic isolation does indeed block this single loop. So no worries.

But Qutest obviously is not designed to directly drive cans or passive speakers, so naturally needs to be connected to more mains connected stuff, which naturally complicates things.

Again, it’s not your problem to have to worry about everyone’s potential system issues but I do like trying to learn about this stuff , which can get complicated as you said.

Cheers again!

 

[Tobes]

I'm a new Qutest owner only had it 4 days and still experimenting.

My setup is in the signature below and I've done some comparisons with the Benchmark DAC3 using various setups with either Roon or Audirvana players on my Mac Mini.
Since I already owned an iFi 5V iPower plug pack, I started listening to the Qutest via that.
Most of my initial findings were via my speaker setup, but listening via the HPA4/Utopias confirmed differences were consistent in the HP setup.

Initially I compared both dacs in Roon - feeding both native (predominately 44.1) rates. All DSP/filters in Roon disabled. USB connection from the Mac to both dacs via the iFi usb3 decrapifier.
I briefly played with the Qutest filters and quickly established the Incisive/Neutral filter sounded best to me.
In this scenario I preferred the Qutest. Among other things the DAC3 had some hardness on vocal peaks that was absent from the Qutest.

Next, I configured the Benchmark in Hqplayer upsampling to 176/192 using one the closed form filters, still using Roon as the player. The Qutest was still getting native rates from Roon.
This swung the comparison back towards the DAC3, which lost the hardness above and sounded better organised/defined and a touch more clarity than the Qutest.
I tried the Qutest with Hqplayer but, at least with the filters I tried, this made the Qutest sound worse.

Then I configured the Qutest in Audirvana (no upsampling) comparing to DAC3 with Roon/HQplayer (with upsampling above).
Now this was harder to choose - both excellent.

Just for fun I thought I would try powering the Qutest form the second output of my Uptone JS2 LPS (outputs individually adjustable to 5, 7, 9, 12V - Mac Mini already powered from one dc output). I wasn't expecting much from this as iFi seem to think LPS is much noisier than their SMPS.
Wow. This takes the Qutest to another level. Greater clarity and size to the sound field and greater solidity/physicality to instruments/voices. Not subtle at all.
For now, the Qutest is my clear preference over the DAC3.
https://www.dropbox.com/s/upuvj6vjpq3eutv/20190317_132158.jpg?dl=0

EDIT: So I went back to confirm my observations of last night - using Qutest in Audirvana (no upsampling) comparing to DAC3 with Roon/HQplayer (with upsampling above). With this setup I can switch with a single button on the HPA4. After flicking back and forth I had to trim the Qutest level back by 1dB.
Not sure if I messed up a setting with Hqplayer, but now the DAC3 has a hair more transparency, letting through a shade more textural detail. Perhaps because of this the Qutest can sound a tad smoother/sweeter. Also the Qutest can come through with more percussive 'thwack' on some music.

One other thing worth mentioning - interconnects. I'm using the Wireworld Eclipse 7 with the Qutest and pretty low cost pro Mogami Gold Studio XLR with the DAC3. Perhaps a different i/c with the Qutest could get better results(?).

FWIW I ended up returning my Qutest as, in the final wash-up, the DAC3 was consistently more transparent in my system.

 

[azabu]

If you like the Qutest with the JS-2, try it with the LPS 1.2.

It's a match made in heaven

 

[Jon L]

I contacted Herbie and he recommended the Baby Booties. I was a bit skeptical but the price was right so I purchased 4 pieces. I am pleasantly surprised by a real nice bump in focus, and improved imaging. They fit nicely and well worth the price of entry.

I just remembered I have both Herbie Tenderfeet and Baby Booties somewhere in my house and will try to find them. However, IME, vast majority of isolation devices tend to improve some aspects while other aspects well...change. Whenever certain footers improve focus and imaging IME, they tend to decrease density and warmth. How do Baby Booties do in this aspect?
P.S. I am talking about my speaker system mainly...

 

[Qute Beats]

What RCA interconnects are you people using from your Qutest to your amplifier? I have the same cables that I bought 20 plus years ago and I m ready for something new.I m sure cable technology can't have moved on all that much since then but with how my rig is shaping up I will need an extra pair of analogue cables anyway I have the Chord Shawline in mind and I m thinking about something that wouldn't be over £200, any suggestions will be appreciated.

If still looking, I use Chord Shawline after moving up from C-line and very pleased with improvements, especially in the bass. Bought mine 2nd hand for £100 rather than the £200 list price.

 

[dj1978]

Wow. This takes the Qutest to another level. Greater clarity and size to the sound field and greater solidity/physicality to instruments/voices. Not subtle at all.
For now, the Qutest is my clear preference over the DAC3.
https://www.dropbox.com/s/upuvj6vjpq3eutv/20190317_132158.jpg?dl=0

I agree with this opinion. I use a line power supply and the M2Tech Hiface Evo Two USB converter. This brings Qutest at least two levels higher. The sound is amazing.

 

[HumanMedia]

If you like the Qutest with the JS-2, try it with the LPS 1.2.
It's a match made in heaven

What was improved over the JS-2 powering the Qutest?
And enough to warrant the upgrade?
(Another JS-2 owner here)

 

[Tobes]

If you like the Qutest with the JS-2, try it with the LPS 1.2.

It's a match made in heaven

My concern with LPS 1.2 would be current output.
Uptone states the LPS has "Maximum guaranteed output current" of 1.1A.
Although you report good results, the plug pack supplied with the Qutest is 5V/2.1A.
However I don't know what the actual power requirement is for the Qutest (not specified) - and not knowing I wouldn't choose a PS offering less current than the one Chord provides.

I have another option. The iFi usb3 hub/decrapifier can supply a super regulated 2.5A@5V - so I could run the Qutest off one of the 'power only' usb-A sockets.

 

[claud W]

If still looking, I use Chord Shawline after moving up from C-line and very pleased with improvements, especially in the bass. Bought mine 2nd hand for £100 rather than the £200 list price.

WyWires Silver interconnects and their Platinum USB cord. Sounds great with my Liquid Carbon amp.