Chord Qutest

[ecwl]

2 hours ago, jos said:

The purpose of these settings are also to make a match with other source components. I don’t have any, so the lowest was the best choice in my case.

 

Actually, the main purpose of the settings is not to match other source components but to accomodate for preamps that would clip the signal if you feed the preamp 3V (or in some cases even 2V). I made the mistake of recommending a friend 2Qute which is fixed at 3V to be paired with his Krell preamplifier. He later switched to a Marantz processor and when I dropped by next time, it was clear that in all loud passages, the Marantz processor was clipping the 3V signal. The problem was fixed with 6dB attenuators. Chord recognizes the problem which is why Qutest has the option to output 1V, 2V or 3V to match the preamplifier to avoid clipping.

In theory, because of the Chord DAC design, the highest voltage that your preamplifier can handle would offer the best signal to noise ratio. So 3V should in theory be better than 2V which should be better than 1V in theory (but not by much). In practice, even if your preamplifier does not clip the 3V signal, because you need more attenuation, it is possible that at the lower volume setting, your preamplifier would be less linear and have worse SNR so listening at the same volume, you may still find that 1V sounds better than 3V without clipping. Most preamplifiers/volume knobs sound best when they are at the 12 o’clock position. Ultimately, the “best” Qutest voltage setting would be one where your preamplifier doesn’t clip the signal AND what sounds best to you. If you’re not sure whether your preamplifier/volume control is clipping, it is best to listen to 1V first so that you get used to what non-clipping sounds like and then crank up to 2V or 3V to see if you can hear the clipping in any loud notes.

[ecwl]

10 hours ago, iansen said:

Hi Jos,

 

Just wondering:

(a) which output voltage have you chosen for your Qutest?

and

(b) did you try the different voltage output settings and did they affect sound quality?

 

 

For example, with your Linn Akurate Kontrol, based on the specifications, it almost definitely will not clip at 2V (middle setting) and it probably (though I’m not sure) will not clip at 3V (highest setting). So I would try setting it at 2V first, listen to lots of music, get used to the sound, and then listen to 3V at the same volume and see if you hear any clipping. 

[ecwl]

3 hours ago, jos said:

At first i used the middle one, but that was to loud in combination with my Amplifier, the Yamaha A-S2100, so I took the lowest setting.

 

I just found the Yamaha A-S2100 specifications. It can handle up to 2.8V input so lowest or middle one should work fine either way from a clipping standpoint. If 1V at the lowest setting sounds best to you, that’s the setting to use.

[ecwl]

23 minutes ago, iansen said:

Certainly when feeding a Chord 2Qute into my previous pre-amp - the Linn Kairn - something was not right with the sound, and that may well have been clipping. Interestingly, when this was raised with Chord via my dealer, Chord offered to mod my 2Qute to ensure compatibility - which impressed me no end.

 

Yes, looking at the specs, Linn Lairn would probably clip at 2V and 3V. Chord probably attenuated the 2Qute output for you to 1V. Very cool.

I’ve listened to 2Qute and Hugo 2 and Hugo 2 is a big leap forward. You’ll enjoy Qutest tremendously. 

[ecwl]

Chord Hugo 2, Hugo TT 2, Qutest, Blu2 decimating DSD to 705.6kHz 24-bit is definitely not a rumor.

Rob Watts the designer has confirmed this on multiple threads in Head-Fi.

He just recently commented on this again in this post:

https://www.head-fi.org/threads/watts-up.800264/page-61#post-14332413

 

Chord Mojo and Hugo also decimates DSD to 705.6kHz? 24-bit but it doesn't sound good enough so for Chord DAVE, he used a non-decimating filter so I think DSD+ mode turns DSD to 2.822MHz 24-bit but then he developed a better decimating filter for Blu2 DSD goes to 705.6kHz 24-bit and it sounds better than DAVE's DSD+ mode.

 

Keep in mind too that most DACs don't actually play DSD as DSD anyway. Nor do they play PCM as PCM. e.g. PS Audio plays DSD as 2xDSD so there is conversion. And one can argue if a DSD DAC plays at 2xDSD by repeating the signal whether that is conversion or not but in my mind, you're not getting "true DSD" since you're still getting 2xDSD. (and yes, I know I'm simplifying). I think dCS now plays at 5.6MHz with 5 elements. Sabre DAC chips are 64 elements at 3MHz? (not sure). Qutest plays at 104MHz with 10 elements.

[ecwl]

1 hour ago, beerandmusic said:

I was kind of curious myself when i read that chord can play native dsd and they convert to pcm?

How can it play native dsd512, when pcm can't even go that high?  Doesn't sound very native to me??

There are two concepts of "native DSD". One is that your DAC actually plays back the DSD signal as recorded. That's what most audiophiles think about and so manufacturers always like to claim that's what's happening whenever possible (although Chord never did). The other has to do with how to get the DSD signal digitally via USB to a USB DAC. There are two ways to do that: "native DSD" which truly send the original DSD signals directly to the DAC (but a lot of computer/DAC USB interfaces can't handle) or "DSD over PCM" which repackages the DSD signals without decimation into a PCM format that the DAC can convert back to straight DSD. Why even make the distinction if either way, the DAC is getting the original DSD signals? Because to convert the native DSD signal into a re-packaged DSD over PCM signal, it actually requires a decent amount of CPU power so if your streamer can't catch up, you may hear drops while playing DSD signals. Newer Chord DACs support native DSD and DSD over PCM playback.

 

As for DAC design philosophies, I would say there are two "extremes"? One is that whatever the original recorded signal was, that should be the playback. So if you recorded in PCM, you need an NOS R2R DAC to play it back and if you recorded in DSD,  you need a DSD DAC to play it back. The other philosophy would be Chord/Rob Watts where the recorded signal is just a sampling of the original analog wave form. The only way to reconstruct the original analog wave form digitally is to take the sampled digital signals, do a lot of math on it (large tap lengths) and then reproduce the analog waveform via a very high frequency (104MHz) modulation with multiple elements. This theoretically would get the most accurate reproduction of the analog wave form in the time domain and the frequency domain. We can go very deep into this discussion and reading what Rob Watts said scattered throughout the many forums at Head-Fi.

 

I think instead of insisting one philosophy is better in a simple sentence (like any DAC that can't playback the original DSD signal exactly as digitally recorded is inferior for DSD playback), my take is that people pay for their DACs with their own money so if they like the sound of their DAC, then that's the right DAC for them.

 

And in defense of some on the forum, having read every single thread Rob Watts has written in the past 3 years, I acknowledge it is difficult to expect others to read everything he wrote as it would probably take weeks to do and it'll take months to mentally process what he said. People come to forums hopefully for quick answers, not to take a university level course and do homework. I think having cordial discourses is what should be expected as I'm sure we all get enough crap from colleagues at work that we can at least be polite to each other on the forum for our favorite hobby.

[ecwl]

2 hours ago, beerandmusic said:

 

do you use one of those DIY cables for the power of the rendu that everyone is talking about here lately?

I use LPS-1 that’s powered by HDPlex 100W power supply. No special cables. But I do use grounding cables for my router and cable modem. 

 

2 hours ago, beerandmusic said:

 

Also curious why you went with bookshelves and subs rather than a full range tower with your high budget?

I live in an apartment. I didn’t want to turn my living room into a hi-fi shop. 

[ecwl]

3 hours ago, kbkaran said:

I am really surprised (and disappointed) that the USB input is not cutting it. USB sounds little harsh and soundstage clarity is not there (compared to Mutec). 

Does anybody have any experience like this ? Or am I preferring a harsher sound from the Mutec.

I don’t have Qutest but have owned Chord DAVE since it came out. Qutest USB galvanically isolation is identical to DAVE. When DAVE was released, the designer Rob Watts originally thought that the USB galvanic isolation was outstanding and eliminates any noise issues. However, he uses a modern laptop playing off battery. Once the product is in the field, what he found was that 1) there are many worse USB sources out there with so much noise that the USB galvanic isolation cannot filter and 2) many people don’t run their USB off batteries so there is always some ground loop leakage current noise and varying degrees can get through. My experience is that while Jitterbug can reduce these effects, depending on your source, it may not completely eliminate the noise. Fortunately, @JohnSwenson has extensively posted here on various CA forums the best way to optimize USB sources and how to eliminate ground loop leakage current noise.

That said, having tried many USB DACs, I still find DAVE’s USB galvanic isolation to be amongst the best. But ultimately, if you want to get the very best USB performance out of Qutest, you still need to optimize your USB source.

If you want to hear what Rob Watts intended the Qutest sound to be like, you can actually use the Mutec to connect to Qutest using Toslink (and unplug the USB+coax from Qutest just in case some noise leaks in). Chord DACs jitter rejection are outstanding so Toslink jitter would not influence the sound of the DAC.

[ecwl]

16 minutes ago, Frojo said:

troubleshooting -  I have just found my Qutest with all of its lights flashing- i am powering it with an LPS1.2 at 5V.

Any suggestions gratefully received....

Hmmm... If you go back to the original power supply, does it still do that?

If not, at least you know Qutest is fine. If you still get all the flashing lights, maybe you accidentally fried the Qutest when you accidentally put LPS1.2 into a higher voltage?

What are you powering the LPS1.2 with? Is it possible that for some reason, LPS1.2 is not getting enough power? Are you using the LPS1.2 to power something else in addition to Qutest?

[ecwl]

On 8/4/2018 at 3:55 PM, Gdbgdb said:

Can anyone comment on qutest performance vs 2qute?

I have not listened to Qutest but I have listened to most current Chord DACs including Hugo 2 and Hugo which are essentially the volume-controllable versions of Qutest & 2Qute.

First, 2Qute always puts out 3V RMS but Qutest can be set to 1V/2V/3V. I was surprised by how many preamplifiers actually will be clipped by the 3V output. So that might be a factor.

Otherwise, Qutest has 10 element pulse array DAC with a higher order noise shaper so you'll hear more resolution and better soundstage. Qutest also has more taps but more importantly, a different 16fs to 256fs upsampling filter so you'll here better timing, transient and timbre. If it's a choice between Qutest vs a discounted used 2Qute, I would recommend anyone with the money to get the Qutest, assuming your signal chain following Qutest is sufficiently revealing (transparent preamp/amp, no Class D amps).

If you own 2Qute but have the money to upgrade Qutest, I would also recommend upgrading. But if you're happy with 2Qute and don't plan on upgrading, 2Qute is still a great DAC.

 

On 8/4/2018 at 3:55 PM, Gdbgdb said:

Also, how much better is the aurilac vega 2 vs the qutest with an aries streamer?

I have not heard the Auralic Vega G2. I am biased because I think Chord Mojo sounds better than most DACs so I actually suspect I would find Qutest sounds better than Auralic Vega G2. But the other aspect is, if you get Qutest, you don't have to get an Aries streamer. There are many other potential options for streamer.

 

With all that said, some people really don't like Chord DAC sound. So you should probably listen to some Chord DACs, preferably in your own system, before deciding on whether you want one.

[ecwl]

 

9 hours ago, HumanMedia said:

Assuming that ones preamp can handle 3v input, does any particular output voltage sound better?

 

is the highest output voltage the best? (Better signal to noise?)

You get better signal to noise ratio because the DAC by design can put out up to around 5V and the 1V vs 2V vs 3V is a digital volume attenuation.

 

The problem is the assumption that most preamps can handle 3V input. Having encouraged a friend to buy the 2Qute and passing on my old QBD76 to another one, I'm surprised how many preamps clip a 3V input. My 2Qute friend ended up needing a 10dB RCA attenuator to get the best out of the DAC when he switched preamps. I think that's where the 1V vs 2V vs 3V preferences come from.

 

I have paired my Chord DAVE (and even Mojo) with many amps/preamps. I can tell you that the digital attenuation of Chord DAVE/Mojo is always more transparent or at least as transparent as preamps. So if you need a preamp and are buying a Qutest, I would not worry about using 1V output to match the preamp because of the lower SNR compared to 3V. Of course, if you don't need a preamp, you really should switch to a Hugo 2 over keeping your preamp for Qutest. Unless you want a preamp to warm up your sound...

[ecwl]

16 hours ago, HumanMedia said:

Im using the Qutest via USB from an UltraRendu using LMS Server, which sees the DAC as supporting DSD.

 

However with the Qutest it wont play DSD128 or DSD256. It plays DSD64, and PCM up to DXD @ 384khz without an issue but when I try and play DSD128 or DSD256 it reports that the current track is the selected track, but just wont play and time stays at 0.

 

Any hints?

My experience is quite different than yours (and others) based on testing I just did on my Blu2 (which should have the same USB receiver as DAVE/Qutest). Granted, I use Roon.

First of all, I presume you have the latest version of sonicorbiter (v2.6) on your Ultrarendu. When you go to sonicorbiter.com, you can log onto the Ultrarendu and then in the Settings for Roon Ready or Squeezelite, you have the option to select the DSD support between DoP vs native DSD. (I presume you're running Squeezelite mode on your Ultrarendu). In my system, I find that if I were to choose native DSD, I actually cannot get DSD playback at all as Roon wouldn't give me that option. Whereas if I were to choose DoP, I can easily play DSD64, DSD128 and DSD256.

So I can tell you from my system DSD256 with DoP definitely works with Roon. I would suggest double checking your LMS Server settings and  your Ultrarendu settings are correct, both in terms of the Output Mode and the Squeezelite DSD settings.

[ecwl]

47 minutes ago, Northern Light said:

I am in the process of “ditching” my Naim ND5XS for a Qutest. Obviously I’ll need a transport for the Qutest. I now wonder whether it was better to use the Qutest’ USB input, or rather the S/PDIF (BNC) input. Does it make any SQ difference? 

If there is no excessive noise or excessive ground loop noise on BNC/USB, it should make no SQ difference to the Qutest.

But from my perspective, the bigger question is, do you need to sell your ND5XS to help pay for the Qutest? If not, what I would do is to start with getting the Qutest first and then feeding BNC from ND5XS to the Qutest. The reasoning is that it's sometimes hard to decide what kind of new streaming solution you want to use to replace your current one (Naim ND5XS). So instead of making a huge computer audio system change, as well as a DAC change, you're just making one change first. And then you can find time to decide how you want to setup your computer audio system (USB/BNC or even Toslink).

 

 

[ecwl]

3 hours ago, Northern Light said:

Yes, I will be using the monies from selling the ND5XS to co-fund the change of source (Qutest, a transport, linear power supply for the transport and cables). ... This all made me think changing to a more flexible computer-based system with standalone DAC and a transport like DigiOne, micruRendu or SoTM 200 would make sense.

If you’re already committed to upgrading your computer audio system to state of the art, then USB is better than BNC for Qutest because 1) USB is galvanically isolated on Qutest and 2) you have more flexibility for input sampling rate options with USB, e.g. DSD over PCM, 705.6/768kHz, etc.

[ecwl]

1 hour ago, chrille said:

Could someone please advice me of a way to use mine with my headphones and headphone amp withpout connecting either to my since today nonfunctional laptop?

What is the easiest most portable highest SQ  hi res files including dff player solution instead of my big heavy laptop with Audirvana and Pure music?

Whereas I would just consider using an iPhone or iPad. You'll need the Lightning to USB camera adaptor. And you'll need the Onkyo HFplayer app.

In fact, that's what I use when I bring my Chord DAVE to the local head-fi meets. Just using gear I already own. But then most of the time, we just demo using WiFi and Tidal.

Many solutions... Just depends on what your needs are. Like Raspberry Pi is a great (but less portable) alternative as @rhern123 said.

 

Do you stream music or was everything on your laptop? How many GB of music do you have on the laptop? What do you already own for desktop/laptop/tablet/phone? Also, Qutest + headphone amp aren't exactly the most portable setup, so truth be told, even though I'm not sufficiently tech savvy, I would go with @rhern123 solution of Raspberry Pi for cost and flexibility.

[ecwl]

24 minutes ago, chrille said:

But ideally I would like to keep my music-player programs Audirvana and Pure Music  plus all the 4tb of music on my  portable firewire harddrives, not to mention eveything else I have in my laptop.So I might just get another laptop and clone things from this one, if I can't get this one to work with my dacs  via usb any more.

Cheers Christer

If you have 4TB of music on an external HDD, you'll need a PC of some sort, be it Raspberry Pi or laptop or desktop. Unless you want to completely change your setup so that you just have a streamer connected to Qutest and all the music resides on your main desktop PC or in a NAS in your home network.

Ultimately, it sounds like you use your laptop for other things too. If you need a laptop, you need a laptop.

[ecwl]

3 hours ago, chrille said:

There wasn't really anything wrong with my mbp after all

Good to know everything worked out and you don't have to spend extra money.

That said, I sometimes use these opportunities to review my current workflow/setup and think about what upgrades/replacements I would get if something does break. It also helps me to see what I need to save up for.

[ecwl]

2 hours ago, chrille said:

And this time around the little slider  volume was at full level  but the ticking on /off for Sound box was empty and  completetely unresponsive ?

With very limited knowledge of  how things digital, really work, I was thinking this is analogue and should not affect the digital connection. But maybe I was wrong in my assumption?

 

Talking about saving up for, having heard what M-scaling  can do I am a bit tempted to add an M-scaler to my  Qutest based  digital system

Hmmm... You’re right, in theory, changing headphones on an external amplifier should not disconnect your laptop from Qutest. That said, interactions of computers/streamers with USB DACs can change all the time. Obviously, the first thing is to check the USB cable to ensure it’s not coming loose intermittently. But some USB DACs require you to turn on the DAC first before turning on the computer and others vice versa. And then some DACs can’t handle it when your computer goes to sleep and it’s never clear to me on each occasion whether the fault is the DAC or the computer setting. Finally, it is always possible the computer’s USB port is becoming less reliable. There are so many possibilities that it does make troubleshooting very hard. My regular stereo dealer connects his Windows laptop to multiple DACs and every few months I help him figure out why it doesn’t connect to one of the DACs. Sometimes we just uninstall everything and re-install everything and turn things on and off until it works and remember the sequence and make sure the computer doesn’t go to sleep. This is one of the many reasons why I don’t use my laptop to connect to my home stereo. That said, it can always be the 2009 laptop and its USB ports. It may be worthwhile to try plugging in a different port.

 

I personally think M-Scaler is a complete no brainer but apparently, some people on the Head-Fi forums felt the sonic difference is minimal. I plug in the Blu2 to my Mojo (which means I only get 500,000 taps instead of 1 million taps) and the sound difference is super obvious. That said, I personally think that people should skip an external headphone amplifier with Chord DACs for added transparency so Hugo TT 2 might allow you to get rid of the external headphone amplifier. Hugo TT2 vs M-Scaler is a tougher call. I personally suspect M-Scaler is the better bang for the buck in this situation but I haven’t listened to the Hugo TT2 yet...

[ecwl]

1 hour ago, jamesg11 said:

Reservation for me - with a large dsd library - re jumping for Qutest, has been Miska’s question mark:

“I'm not sure how Qutest handles DSD input, but if it is like Mojo (which leaks lot of DSD noise aliased down), then it is better to send it 705.6/768k PCM instead. HQPlayer can give you good DSD-to-PCM conversion”.

 

Resolved only by extended home listening ie purchase, or Miska himself buying, listening, testing!

But this quandary is of course a common enough decision-time experience ...

I think Rob Watts has been quite clear that for Qutest, he decimates DSD to 705.6kHz with a stop band attenuation of 220dB (although not sure at what frequency but I presume around 22kHz) with Qutest. This is definitely different than Mojo.

Whether HQPlayer can give you "better" DSD-to-PCM conversion, I don't know as I don't even know what "better" means. In my mind, it means you like the sound more so it's subjective (or it's more technically accurate to the original analog waveform which is a can of worms on its own because it depends on what parameters you define as "accurate").

But I think it's not a quandry at all. Listen to Chord Qutest in your system using bit-perfect files sent to the Qutest (be they DSD or PCM) and then see if you like the sound. If you do, you can keep on buying your DSDs and listening to them through Qutest. If you don't, there are other DACs.

[ecwl]

40 minutes ago, HumanMedia said:

I am under the impression that the usual strategy for HQPlayer is to upsample everything to the highest DSD the DAC can handle, but with the Qutest the strategy is probably different?

I think asking Miska the best way to play music from HQPlayer to Qutest is a great idea. I suspect he would recommend upsampling/converting everything to PCM768.

 

But similarly, if you were to ask Rob Watts, the designer of Qutest, he would say just play everything bit-perfect into Qutest and skip HQPlayer. Play DSD bitperfect into Qutest and play PCM files bit-perfect with no upsampling into Qutest and let Qutest do all the work. That's what you paid the FPGA in the Qutest for.

 

I think every designer has their preferences and like to incorporate them into their designs. Ultimately, if you own both Qutest and HQPlayer, you can pick and choose what you like best.

 

As a point of reference though, if you go to the Chord DAVE thread on Head-Fi, I'd say of the people who have tried Chord DAVE and HQPlayer, I would estimate 9 out of 10 prefers bit-perfect (including DSD) into DAVE while the remaining 1out of 10 prefers running HQPlayer upsampling to PCM/DSD first. Ultimately, it's about what you want to get out of your musical experience so whatever you like best is the way to go.

[ecwl]

11 hours ago, Ralf11 said:

Thanks much.  RME says they have improved some things in the ADI-2, but I have not heard one.  I do have an Audio Research euphonicisor in my system which may help with 'overly clinical' inputs...

I have listened to the ADI-2 at my local head-if meet. I think it’s an excellent DAC chip based DAC. I personally prefer Mojo to the ADI-2 but I think people are so used to listening to DAC chip based DACs that I can see they might prefer ADI-2.

For me, the “advantage” of ADI-2 is the lower noise floor which creates this extra sense of transparency. This is a result of Mojo’s reference power, noise shaper and the 4-element pulse array DAC. The ADI-2 problem compared to Mojo is the noise floor modulation which makes music sound digital/bright/harsh so smooth, warm vocals or instrumental sounds often sound extra exciting with ADI-2 whereas they sound more natural with Mojo. There is also the transient timing issue so when you hear finger snapping or drum strikes, Mojo is more realistic but ADI-2 still sounds dynamic because even though the strikes are less precise, the noise floor modulation makes it sound more exciting. And by natural and realistic, I mean compared to live unamplified performances.

I have not heard Qutest in any system yet but I’ve listened to Hugo 2 via headphones at a stereo store and it far surpasses Mojo and Hugo and 2Qute in everywhere. Hugo 2 is much closer to DAVE than Mojo. So I suspect Qutest would have the same transparency as ADI-2 and all the advantages of Chord DACs.

 

Ultimately though, when we are spending that much money on ADI-2 or Qutest, you have to like the sound and how it integrates into your system. I’ve seen people swear they prefer their R2R or DSD DACs. And DAC chip based DACs are so ubiquitous (Sonos, iphones, just basically everywhere), I think people are so used to hearing their favorite music with imprecise transients and noise floor modulation from DAC chip based DACs, they are frequently preferred over other types of DAC designs. I think the challenge is that we rarely listen to live unamplified music so we forget what natural realistic music sounds like and the DAC chip based DAC sound is now our reference instead of live music. I definitely think anyone thinking about purchasing a DAC in Qutest price range should audition the Qutest though. If it’s not your cup of tea, don’t buy it.

[ecwl]

18 minutes ago, Ralf11 said:

Thanks ecwl.

 

Besides Matt's question can you also tell us if you heard the RMI & Qutest together in the same listening session?

I listened to my Chord Mojo, my Chord DAVE (no Blu2) and the RMI ADI-2 in the same session off headphones. I have never listened to Qutest. Closest was Hugo 2

[ecwl]

4 hours ago, matthias said:

 

Did you encounter the noose floor modulation also when feeding the ADI-2 directly with higher rate DSD?

Thanks

 

Matt

So nobody in my local head-fi meet upsamples from PCM to DSD512/DSD256. We were all listening straight off the DAC.

 

But more to the issue of noise floor modulation, it is definitely not something that many DAC designers talk about. And there seems to be a lot of people saying it doesn't happen or that when they upsample to DSD512 it solves the problem.

 

Truth is, noise floor modulation can happen at multiple stages. First, it's in the recording stage so it's possible for the original recording to have noise floor modulation, making it sound harsher. Second, it's in the digital playback stage so it's theoretically true that any DAC that takes say 44/16 and upsamples to DSD512 or 64-element 5MHz (Sabre DAC chip I think) can introduce noise floor modulation during the upsampling but I think that's actually exceedingly rare for any competent upsampling algorithm.

 

The last stage of noise floor modulation that can be introduced is at the actual Digital-to-Analog conversion. According to the designer Rob Watts, this happens with virtually all DAC designs for a variety of reasons, ranging from RF noise, jitter from the clock but most importantly, the DAC design itself, be it DSD/R2R/multi-bit PWM/DSD, including most modern DAC chips. The issue is that every time your DAC switches from 0's to 1's, or in the case or R2R DACs 256 to 16 or 18 to 238, there is noise that's generated in the rest of the circuit. Moreover, simple switching from 0 to 1 generates a different noise than switching from 1 to 0. The example Rob Watts give is that let's say you have silence and in DSD256, you can encode it with 101010101010101010101010101010101010 or 11001100110011001100110011001100. Technically they are equivalent int he digital domain but the first sequence would involve 32 switches and the other would involve 16 switches so when you're dealing with an actual DAC circuit, the amount of noise generated by these two sequences would be different. Moreover, the frequency of switching would also be different, generating a different noise pattern, despite being "silent". This is the reason why with loud music, the noise floor tends to be higher and with quieter music, the noise floor tends to be lower, leading to noise floor modulation. In addition, specific to DAC chips, because all the DAC chip elements are so close to each other on silicon, they are much more prone to noise. This is the reason why a lot of DAC designers have moved to discrete elements, ranging from DSD DACs to multibit DACs, like dCS. The solution Chord uses in the Pulse Array DAC is that using the 10-element in Qutest to represent say signal levels of 1-9 (through the noise shaper), the DAC is constantly switching at 104 MHz by flipping either two elements at the same time to maintain the same signal level (switching 0 to 1 in 1 element or 1 to 0 in another element) or only 1 element switches (either 0 to 1 or 1 to 0) to change the signal level (from say 4 to 5, or 7 to 6). As a result, the noise level fluctuation is constant regardless of the loudness of music you're playing. 

 

So in answer to your question at the beginning, no I did not get to listen for noise floor modulation off the ADI-2 with DSD256 or DSD512. But the bigger issue is that by design, ADI-2, as with other DAC chips, would have noise floor modulation regardless of what signals you feed it.

[ecwl]

4 hours ago, buonassi said:

So much so, I'm considering the qutest, or a second hand 2qute at half the price.....

Having listened to Hugo 2 vs Mojo and having a friend own 2Qute, I would say if you can afford it, go for Qutest. There are so many technical improvements from Qutest that the sound quality is far superior. Here are the main ones that I think matter the most. 

Qutest has 49000 taps for 16fs upsampling compared to 2Qute 28000 8fs followed by simple 2x FIR upsampling to get to 16fs. 

Qutest then has an additional WTA filter to get to 256fs whereas 2Qute uses a very simple FIR filter and this contributes a lot to sound quality. 

Qutest has 10 elements and a 11th? Order noise shaper whereas 2Qute has 4 elements with a 5th order noise shaper. 

Qutest can output 1, 2, 3V so it won’t clip your preamp whereas 2Qute only puts out 3V.

[ecwl]

My understanding is that all modern Chord DACs upsample to 104MHz 5-bit before sending the signal to the pulse array DAC to be output at 104MHz (at an obviously lower bit-rate through additional noise shaping)

 

Hugo2/TT2/Qutest/Blu2/M-Scaler all take DSD signals and convert it to 705.6kHz, 24-bit??? before being upsampled to 11.3MHz using another WTA filter and the being upsampled to 104MHz 5-bit.

 

Chord DAVE DSD+ mode takes the DSD signal 2.8/5.6/11.3MHz and converts it to 2.8/5.6/11.3MHz, 24-bit???, does some sort of filtering on the signal and to 11.3MHz and then to 104MHz 5-bit

Rob Watts the Chord DAC designer discontinued the DSD+ mode for Hugo2/TT2/Qutest/M-Scaler/Blu2 because he finds that with an improved decimation filter to convert DSD signals to 705.6kHz, 24-bit???, he finds the DSD files to sound better (which i can attest to based on my testing comparing DAVE DSD+ mode vs Blu2 DSD playback).

 

So the official Rob Watts recommendation is that if you want to listen to DSD files on Chord Qutest, you should just send the file directly to Qutest to get the best sound. Obviously, people can manipulate the file in whatever way they want for playback.