Chord Qutest question ...

[Mike Hanson]

One of the reasons for such with off-board SMPS is that they all, for reasons of EMC regs - tend to have a small class Y cap, usu c 2.2nF, from output back to Mains side - across the output switch. Makes the emissions graph nice, but injects leakage current.

That's up to 0.1mA of mains leakage current (on UK mains) - harmless but as you say disturbing in terms of 'touch'.

When you realise the effect of such a current might have in generating 50/100Hz/+, +, + intermod voltages across the length of shared-impedance in say a meter+ of interconnect and all in-series connections inc plugs (say 1-10ohms for all included resistances, for decent-gauge cables... worse for others) - that utterly ruins the potential SNR and for reasons that have nothing to do with how good the DAC is! At 10ohms for the interconnect - pessimistic but possible for some daft designs - you've just limited the maximal achievable SNR at 3Vac out of the dac to just -69dB (!)

It is also why toslink is probably best - because then you do not have leakage currents from the DAC's SMPS (any dac!) and your laptop's (any laptop/ PC/ NUC!) in contention. It breaks that galvanic path, and for no penalty. Tie the two electrically using USB - who knows what is going on, and no -it's not as clean a sound, even with a 'fixed' 5v supply (says a MoJo user since they came out...)

So - no: I am not surprised that even daft-simple linear PSUs can be found beneficial - from their lack of such large common-mode leakage currents. Yet this will be incredibly context-dependant.

The only caveat is the optical S/PDIF interfaces are occasionally included as "checkmarks" in the design. I've encountered multiple devices where the optical option sounded shockingly worse than the coax. Also, S/PDIF interfaces are also typically limited to 192KHz, and often start glitching beyond 96KHz.

If I'm stuck with S/PDIF, then I've experienced the best results with AES/EBU (if available).

However, I prefer to use USB, which supports data rates up to 768KHz. There's the possibility of problems with noisy power wires coming from the source, but an inexpensive Topping HS02 usually nips that in the bud. If it's really bad, one could stretch to a DDC to do USB-to-I²S. There are a many of those available, across a wide range is prices.

 

[Linear]

I had a 2Qute, thought it was a bit bright, a change of interconnect's helped but it was still a bit too shiny for me. I changed it for a Topping, which I thought sounded better.

 

[adamdea]

One of the reasons for such with off-board SMPS is that they all, for reasons of EMC regs - tend to have a small class Y cap, usu c 2.2nF, from output back to Mains side - across the output switch. Makes the emissions graph nice, but injects leakage current.

That's up to 0.1mA of mains leakage current (on UK mains) - harmless but as you say disturbing in terms of 'touch'.

When you realise the effect of such a current might have in generating 50/100Hz/+, +, + intermod voltages across the length of shared-impedance in say a meter+ of interconnect and all in-series connections inc plugs (say 1-10ohms for all included resistances, for decent-gauge cables... worse for others) - that utterly ruins the potential SNR and for reasons that have nothing to do with how good the DAC is! At 10ohms for the interconnect - pessimistic but possible for some daft designs - you've just limited the maximal achievable SNR at 3Vac out of the dac to just -69dB (!)

It is also why toslink is probably best - because then you do not have leakage currents from the DAC's SMPS (any dac!) and your laptop's (any laptop/ PC/ NUC!) in contention. It breaks that galvanic path, and for no penalty. Tie the two electrically using USB - who knows what is going on, and no -it's not as clean a sound, even with a 'fixed' 5v supply (says a MoJo user since they came out...)

So - no: I am not surprised that even daft-simple linear PSUs can be found beneficial - from their lack of such large common-mode leakage currents. Yet this will be incredibly context-dependant.

Am I right in thinking that this is mainly going to be an issue with single ended interconnects as current flowing through the shield of balanced differential cables has a job doing any harm?

 

[Tony L]

I notice some Chord DACs have a phono-stage-like ground terminal on the rear panel, e.g. the 2Qute (eBay), DAC64 (eBay). Is this the reason? My only experience of this is from Macbooks, and there using the longer grounded cable for the Apple PSU adapter stops it.

PS No connection to the auctions, just using some pics from an advertising affiliated source!

 

[martin clark]

Am I right in thinking that this is mainly going to be an issue with single ended interconnects as current flowing through the shield of balanced differential cables has a job doing any harm?

Yes that is correct - but how 'good' balanced interfaces are, is also matter of quite some precision. It's easy to get ...sub-optimal.
Bill Whitlock of Jensen transformers wrote a few interesting things on the latter - rather than waste space here, PM me an email address if its of any interest.

For my own Mojo - I modified a standard 5v wallwart with a bit of copper tape that ties output 0v to mains Earth: that, optical interconnect from macbook pro (used with the earthed extension cable) and no chassic potential differences whatsoever... took five minutes. One of these years I might build an LPSU, but the mojo then has internal smps to boost 5v to 8.4 to charge the battery. and having replaced the battery after 6yrs use - easy diy - there's no significant diff between running off internal battery, and 5v usb supply connected, via headphones anyway...

NB the optical still sounds better / fuller/more refined than usb, but I'm only feeding 44.1Khz/16bit, mostly.

 

[20hzFlat]

Thanks, good of you to post that and pleased to accept your apology.

As it happens I’m fairly centrist on the objective/subjective divide. I’m interested in measurements, how things work and why they sound as they do but also feel that in the end it is whatever brings my favourite music to life as though it is being played in my living room which I choose to use. My signature on the now defunct Wam was something like “it’s what you think you here that really matters”, and that’s a product of what I actually hear and can be measured and verified and how my mind interprets it to recreate the illusion of music. It’s complex, particularly when you take the whole chain into consideration; original performance (assuming it exists) - recording - hifi equipment - listening room - listener. I’m lucky, in that after years of faffing about I have a couple of systems that now work very well for me.

edit: oops, missed out the all important listening room.

Totally agree in terms of enjoying it and measurements for that matter. In fact I'm hugely into room measurements, not so much equipment as Im heavily into room acoustics and understand the importance of how it effects the sound. I went down the acoustics rabbit hole about 5 years ago and it has been a continuous addiction since. My listening room is heavily treated with huge amounts of absorption and a health dose of diffusion to top it off. Ive spent years learning the principles and science behind it. As for equipment I am not chasing or trying to fix a poor sound as you suggested. I am curious as to what things can do or cant do for that matter and want to try them for myself rather than rely of a lot of folks opinions who have never tried things, only reading and repeated what they have heard. Take the Qutest for instance, folk argue till they are black and blue, quote Mr Watts i.e power Supply etc. I decided I shall try it for myself out of curiosity to know for sure, same with cables, fuses etc. I thought id try them for myself to settle my curiosity and for experience.

 

[Tim Jones]

My MCRU/Longdog LPSU arrived this morning, and I look forward to testing it with my Qutest when I get home from work.

 

[hifi-dog]

You will like it I’m sure..

 

[Thegreatroberto]

When I had my quietest, I spent too much time trying to hear differences in the filters. A complete waste of my time. Still convinced that just the lamp changed colour and that was it.

 

[camverton]

When I had my quietest, I spent too much time trying to hear differences in the filters. A complete waste of my time. Still convinced that just the lamp changed colour and that was it.

It’s pretty damn subtle isn’t it. Switching between them and comparing the sound I couldn’t hand on heart claim hearing any difference. The funny thing is, however, that in the long term I did prefer one filter over another for listening to music, and it was a different filter when used with different partnering equipment and speakers. Of course the different colours on the filter button have a different effect… Which is annoying because currently I prefer the ”sound” of the white colour but don’t like the look of it!

 

[Tim Jones]

It's a definite improvement, perhaps 10-15% on my Fidelio-Meter. Not entirely night and day, but it certainly takes the slight grain of the cooking SMPS out of the upper registers and makes everything more hear-through.

It's staying.

 

[James Evans]

When I had my quietest, I spent too much time trying to hear differences in the filters. A complete waste of my time. Still convinced that just the lamp changed colour and that was it.

Maybe you should have turned it up a bit

 

[Thegreatroberto]

Maybe you should have turned it up a bit

Haha. I'm sure I did crank it up .