[ajreynol]

I was fortunate to have a dealer who did a very fair part-x and I wouldn’t have got as much on eBay.

I wish I could find a dealer like that. I made 3 calls and they were all talking about like 25% of the value of the item.

 

[dawktah2]

Irrespective of the last few comments, I still welcome members' views on the positive/negative impact of different PSU on their Qutest and any expert opinions (Rob) on the matter. I'm keen to maximise the performance of my DAC and if pairing it with the right PSU is the best way to do this, then I'd like to know.

Is this like buying a Centenario and someone saying you need to change the exhaust?

 

[Rob Watts]

@RobWatts,

Ok, I understand how a high quality power supply affects an amplifier. I understand how a clean power supply affects noise. Mr. Watts can you explain how power supply affects a DAC? Then Mr. Watts explain how it could affect the Qutest.

I'm 52 and not that technical, as a surgeon I just look at things differently. You can PM me if you feel will derail thread.

Irrespective of the last few comments, I still welcome members' views on the positive/negative impact of different PSU on their Qutest and any expert opinions (Rob) on the matter. I'm keen to maximise the performance of my DAC and if pairing it with the right PSU is the best way to do this, then I'd like to know.

The accepted wisdom is that linear PSU's are the best, and that switchers are the worst, and I too bought into that prejudice some 5 years ago. But with the Hugo 1 project, my first portable DAC, you absolutely have to use switcher regulators from an efficiency POV.

And here is what is strange - the switchers sounded much better than the linear regulators - and - the DAC measured better too. Now the measurements were easy to understand, and its down to FPGA core noise being much lower with switchers than with linear, due to efficiency issues. But the improved sound quality? That was actually down to lower RF noise.

RF noise is a massive problem in audio, and like a fungal foot infection in the wet, is pernicious and almost impossible to remove; the effects from 100 kHz to many GHz are very audible. The technical reason for the sensitivity is down to noise floor modulation - and this is an effect that one can simulate and easily measure. Indeed, my DAC's are the only DAC's at all (any price) that show zero measured noise floor modulation. The strange thing about noise floor modulation is that it does not matter how small it is, careful listening tests exposes it as very audible. In large amounts it shows up as grain, glare and hardness; in small amounts it adds brightness and suppresses timbre variation - in that warm instruments sound unnaturally bright too.

So why would switchers sound warmer and richer than linear regulators? A switcher must employ an RF filter - and today RF filters are very effective (with SMD chip components) at removing both the switching components and the incoming RF noise from the mains and other circuits. So when you buy a switcher PSU you are getting an effective RF noise filter too; but a linear supply is completely open to RF from the mains. And today, RF in the house is a massive issue with a huge number of RF sources from kHz to 5 GHz.

So do not make the assumption that a high end audiophile linear supply is better than a humble switcher; it's probably much worse, with considerably more RF noise. Also, RF is a problem in that some actually like the SQ from RF noise; it adds an edge to the sound, which superficially it's easy to enjoy - particularly when doing AB tests - but when it comes to actually enjoying music you will find the richer and warmer sound of low RF more musical, enjoyable and with less listener fatigue.

Having said all that, it is a complex area - and it's technically possible that a switcher may interfere with a RF sensitive power amp or headphone amp. My view is for one to try a USB battery bank - and if you can hear no change (in my system I can't) then forget about upgrading the PSU - as any change in SQ is due to more RF noise from the linear supply actually making it sound brighter and worse. A USB battery source will give the lowest possible noise and the best SQ.

 

[flyte3333]

So when you buy a switcher PSU you are getting an effective RF noise filter too; but a linear supply is completely open to RF from the mains.

Hi Rob, does this mean the transformer isolation of linear PSU's are generally ineffective from filtering RF from mains?

For those following his CA Forum posts, John S has measured SMPS's and linear PSU's and found (of those he's measured, i.e. not every PSU on the planet) SMPS's generally have higher leakage currents than linear PSU's. SMPS's generally have what he calls 'high' and 'low impedance leakage' currents. And he's found linear PSU's generally only have lower leakage, which are easier to filter inside DACs - digital isolators and even ethernet transformers apparently do a great job at filtering these low impedance leakage currents. He says he's made up his own testing gear to measure this stuff.

In addition, I thought leakage currents also play an important role in RF interference?

I know your DACs themselves do a great job internally filtering RF, right at the USB power input (ferrite isolation) and after the input.

As you said it's complicated stuff and probably difficult to over simplify and there are multiple things at play.

While I don't lose sleep over it I do find learning about this stuff very interesting!

And I fully agree your DACs are some of the least sensitive to power supplies of DACs I've had in my system but in my case, mostly for headphone use for me.

Appreciated

 

[Rob Watts]

All PSU's are transformer coupled, and innately provide negligible RF isolation, as the interwinding capacitance on the transformer is too large. To get rid of RF you must have effective RF filtering, and that means a complex multistage filter. But even simple SMPS filters are better than no filters that are often in linear PSU's.

And yes leakage currents at the switching frequency is an issue - but the switching frequency is actually very low, of 50 to 100 kHz typically. This noise a DAC PSU is quite able to deal with - even simple DAC's - but its 1MHz to several GHz that is the larger SQ problem, and that's the area when you need extensive RF filtering.

Another point - my lowest noise source that is mains driven is my lab switched mode PSU - and this has much lower measured noise than a linear PSU and negligible leakage currents.

 

[Romi54]

I connected an Ifi iPower to the Qutest and it sounded less hard, a bit warmer and less stressful.

Unfortunately, the Ifi broke after an hour ....

 

[flyte3333]

All PSU's are transformer coupled, and innately provide negligible RF isolation, as the interwinding capacitance on the transformer is too large. To get rid of RF you must have effective RF filtering, and that means a complex multistage filter. But even simple SMPS filters are better than no filters that are often in linear PSU's.

And yes leakage currents at the switching frequency is an issue - but the switching frequency is actually very low, of 50 to 100 kHz typically. This noise a DAC PSU is quite able to deal with - even simple DAC's - but its 1MHz to several GHz that is the larger SQ problem, and that's the area when you need extensive RF filtering.

Another point - my lowest noise source that is mains driven is my lab switched mode PSU - and this has much lower measured noise than a linear PSU and negligible leakage currents.

Thanks Rob.

As a backdrop to all this, I've been told by another expert that EU regulations will soon/eventually make linear PSU's non-viable, and this will force a global change.

So with this forced change, I guess it's reasonable to expect lots of fast improvement and innovation going forward in switching PSU's (and amps...).

It sounds like you're already ahead of most in that area.

 

[Triode User]

As a backdrop to all this, I've been told by another expert that EU regulations will soon/eventually make linear PSU's non-viable, and this will force a global change.

Interested, were you told of the logic behind this?

 

[flyte3333]

Interested, were you told of the logic behind this?

Nope, I wasn't told the background to mentioned EU regulations.

I was just discussing SMPS's vs linear PSU's with them and they said it didn't matter what advantages linear PSU's had because longer term, these regulations (I assume related to power consumption) will force everything to switching PSU's (and amps) and we'll see even faster innovation in these areas.

I'm just reporting what I was told by someone who I respect to be in the know. I'm not claiming this as fact, so I'd be just as interested as you in this background info.

Is there any truth/accuracy to this EU regulations stuff @Rob Watts ? Or has someone been telling me porkies

 

[flyte3333]

Interested, were you told of the logic behind this?

A quick Google lead me to this. I don't know if it's related as it relates to external PSU's but maybe it is related. Hopefully Rob can share if any of the above I mentioned has any accuracy to it.

https://ec.europa.eu/energy/en/topi...gy-efficient-products/external-power-supplies

To re-iterate, I wasn't told that linear PSU's would be outright banned. I was told that the regulations would instead make linear PSU's non-viable, long term... And the main point of our discussion was that this would drive even faster innovation in switching PSU's (and amps), than there already is, again longer term, i.e. years ahead not months.

 

[Triode User]

A quick Google lead me to this. I don't know if it's related as it relates to external PSU's but maybe it is related. Hopefully Rob can share if any of the above I mentioned has any accuracy to it.

https://ec.europa.eu/energy/en/topi...gy-efficient-products/external-power-supplies

To re-iterate, I wasn't told that linear PSU's would be outright banned. I was told that the regulations would instead make linear PSU's non-viable, long term... And the main point of our discussion was that this would drive even faster innovation in switching PSU's (and amps), than there already is, again longer term, i.e. years ahead not months.

Many thanks. So the one word summary is efficiency.

As an aside and reading that link I wonder if items such as the PS Audio power regenerators will get caught in the requirement as they certainly add significant energy loss to the chain (they get quite hot). But that is a distraction to the thread and just idle curiosity.

 

[flyte3333]

Many thanks. So the one word summary is efficiency.

Your one word is nicer but 'emissions targets' may tell a little more of the story, albeit with an extra word. All related of course.

As an aside and reading that link I wonder if items such as the PS Audio power regenerators will get caught in the requirement as they certainly add significant energy loss to the chain (they get quite hot).

That may come under 'power transformers' ?

https://ec.europa.eu/energy/en/topics/energy-efficiency/energy-efficient-products/power-transformers

A good question to pose to Paul on the PSA Forum. He's very open and may shed light on if it applies to them and if so, he may even give timelines.

 

[Triode User]

That may come under 'power transformers' ?
https://ec.europa.eu/energy/en/topics/energy-efficiency/energy-efficient-products/power-transformers
A good question to pose to Paul on the PSA Forum. He's very open and may shed light on if it applies to them and if so, he may even give timelines.

That link includes this text, "These requirements mainly cover minimum energy efficiency levels of transformers with a minimum power rating of 1kVA that are used in 50 Hz electricity networks or in industrial applications." So you may be right. Although I do occasionally dip into the PSA forum I doubt me bringing this up there will add anything to the party.

An interesting diversion though and thanks for your responses.

 

[dac64]

As a backdrop to all this, I've been told by another expert that EU regulations will soon/eventually make linear PSU's non-viable, and this will force a global change.

OT: I heard this couple of yeas ago! My first impression was those monster EU made pure class A will be gone with the winds!

However, these can be made outside EU, and their biggest market wasn't EU at all!

 

[flyte3333]

OT: I heard this couple of yeas ago! My first impression was those monster EU made pure class A will be gone with the winds!

However, these can be made outside EU, and their biggest market wasn't EU at all!

Ha agreed, some companies may be able to get away with possibly ignoring the EU market.

But not all. And for those, I can't imagine you'd make a particular model device for the EU market (using switching PSU's or amps) and another model for the 'rest of the world' (using linear PSU or Class A amplification). Those can be significantly different designs. I guess this is why this person thinks long term (years ahead, not months) this will force global changes.

I'm really only (harmlessly) guessing now. I really don't know and don't pretend to know.

But yes, let's let the rest of the convo go back to Qutest