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MDAC First Listen (part 00110100)

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Ian,

JohnS breakdown of PSU noise is simplistic but the "Type 2" noise is largely caused by the Class Y capacitor in SMPS.

While the iFi PSU might have low output noise between output terminals (no reason to doubt this is there claimed noise is not that hard to achieve) - however I strongly suspect it does not between output terminals and Ground due to the leakage current of the Class Y Cap (which JohnS refers to as Type II noise) - I agree with John that this is the most "damaging" and critical within an audio system.
 
JohnW said:
Ian,

JohnS breakdown of PSU noise is simplistic but the "Type 2" noise is largely caused by the Class Y capacitor in SMPS.

While the iFi PSU might have low output noise between output terminals (no reason to doubt this is there claimed noise is not that hard to achieve) - however I strongly suspect it does not between output terminals and Ground due to the leakage current of the Class Y Cap (which JohnS refers to as Type II noise) - I agree with John that this is the most "damaging" and critical within an audio system.
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Heey, that's not right criticising a competitors product without any evidence. imo you should either measure it and show your measurements or withdraw your accusations.

I also think ifiAudio, who do not promote their products here, should be offered the right to reply.
 
AndyU said:
Heey, that's not right criticising a competitors product without any evidence. imo you should either measure it and show your measurements or withdraw your accusations.

I also think ifiAudio, who do not promote their products here, should be offered the right to reply.
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Maybe this thread and all the other mdac threads should be in the trade discussion area, after all its just product promotion?
 
muzzer said:
Maybe this thread and all the other mdac threads should be in the trade discussion area, after all its just product promotion?
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nah, it doesn't bother me that they're here, they've been here so long they are a part of the place. But if you are going to slag off a competitor you should have more than supposition. Accusing iFi Audio of making deliberately deceptive measurements and just trying to "pull the wool over buyers eyes" without any facts is completely wrong and out of order.
 
AndyU said:
Heey, that's not right criticising a competitors product without any evidence. imo you should either measure it and show your measurements or withdraw your accusations.

I also think ifiAudio, who do not promote their products here, should be offered the right to reply.
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Andy,

Yes - your correct I've not measured the PSU and would be more then happy to - that said you can see the effect of the leakage current in Amir's tests.

The criticism is not levelled at iFi but SMPS in general - I've never measured a "floating" SMPS that did not have high leakage current again I refer you to the following paper on the problems of designing a low leakage SMPS:-

http://archive.eetasia.com/www.eetasia.com/ARTICLES/2004NOV/B/2004NOV16_POW_TA.pdf?SOURCES=DOWNLOAD
 
AndyU said:
Accusing iFi Audio of making deliberately deceptive measurements and just trying to "pull the wool over buyers eyes" without any facts is completely wrong and out of order.
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I based my comments on the Mains hum components in Amirs test AND iFi own post saying that these where due to Amirs "incorrect measurement set-up" as it had been Grounded - but this is a reality in almost all audio systems and the Ground currents will be present and will result in the same observed "system" noise.

I see these "Ground currents" day in day out on the lab bench.... so theres no "black magic" here - just leakage current!
 
JohnW said:
Andy,

..
The criticism is not levelled at iFi but SMPS in general - I've never measured a "floating" SMPS that did not have high leakage current again I refer you to the following paper on the problems of designing a low leakage SMPS:-

http://archive.eetasia.com/www.eetasia.com/ARTICLES/2004NOV/B/2004NOV16_POW_TA.pdf?SOURCES=DOWNLOAD
Click to expand...

Your criticism, and your accusation of deliberate deception, were directly and explicitly levelled at iFi

JohnW said:
..
iFi measured there PSU with the "Earth" lifted on the AP measurement system - if the "load" device / system (audio system) is Earthed (as most systems are) then I'll expect you will have much the same results as Amir measured.

iFi must know this and are just trying to pull the wool over buyers eyes...
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Like I said, you should produce the evidence that iFi have deliberately deceived their buyers, or withdraw your accusation. Being "95% sure" isn't good enough for making an accusation like that against a competitor.
 
Andy,

I make it clear that:-

1. I've not measured the iFi but based my interpretation on Amires measurements and iFi OWN explanation of his results.

2. I make it VERY clear "That I'm 95% certain" I would measure typical SMPS leakage currents due to the Class Y Cap - its left to the reader to decide for themselves - KNOWING I have not measured a unit.

So based upon these criteria, I stand by my comment that if as I suspect the iFi PSU (as with MOST SMPS) does have "significant" Leakage current then they are hiding this fact by talking about the low noise across the output terminals but not IME the more important Ground noise due to Leakage current.

Its this "leakage current" that causes so many headaches with computers when connected to audio systems via USB (think MDAC / CDQ etc).

I'd be more then happy to correct myself if I get a unit to measure - but until then I'll stand by my comments based on Amires measurements and iFi own explanation of his results AS THEY HAVE ALL BUT ADMITTED TO THE LEAKAGE CURRENT ISSUE IN THERE EXPLANATION - you would understand this if you had an understanding of the issue at hand here (Sorry I'm really REALLY I'm not trying to be rude here, but I just want to get the point across that this leakage current is a real issue in any "System").

In iFi's long winded and to me condescending answer where they are trying to be rather too clever and "blind people" with too much information and pointless pictures of the Ghost Busters and CSI etc. - they goto great lengths to talk about how important "Measuring Noise requires full Galvanic Isolation" - where in reality within the context of a practical HiFi system this is a pointless assumption / requirement as there will always be multiple Ground points - and the VERY LAST THING YOU NEED is a device injecting Earth leakage current - which is the issue at hand here with SMPS largely due to the Class Y capacitor.

If iFi spent time talking about the Leakage current/ Class Y Cap etc, then I'd have full respect for them and not be left feeling that they where in my words "trying to pull the wool over peoples eyes"... They could have just said that to meet EMC requirements as with 99% of SMPS our PSU has Leakage current that can cause issues in Grounded Audio / measurement system (as with Amires case) - not trying to blindside everyone with such a misdirection of a post.

NOW AGAIN I'VE NOT MEASURED A UNIT TO CONFIRM THE LEAKAGE CURRENT - but base my comments on a "professional" interpretation of Amires results and iFi subsequent explanation...

Its simple - what iFi are saying is that there PSU has low noise when measured with a perfectly galvanically isolated test system - but when the "system" is Grounded (as most HiFi systems in the real world are) then I suspect one can expect to see results like Amires "incorrect" test setup revealed.

Ground noise in any system is always a headache - and why I STRONGLY recommend the use of balanced signal transmission - but any balanced system never has perfect noise rejection especially at higher frequencies - so limiting circulating leakage currents is your first defence... and why I so strongly dislike the use of SMPS in any audio system...

So I think its far to say that based upon my understanding of the measurements results and iFi explanation, the iFi PSU is low noise UNLESS used with a HiFi system with a connection to Ground....

I also don't plan to make a standalone PSU product like the iFi so I have ZERO reason to speak negatively about there products - but certainly would not recommend ANY SMPS to be used with my own designs. On the MDAC2 we goto lengths to isolate the "leaky" Digital input side with the analogue domain with an isolation barrier - but "Isolation" is only attenuation in the practical world...
 
A small update to those wanting "streaming" support on FDAC/MDAC2, I'm afraid native support for RoonBridge / HQPlayer NAA won't be legally possible (or at least be at a risk of a lawsuit) as neither has a license that would permit a 3rd party (John's company) to distribute the binaries. Other software (squeezelite, shairport-sync) has either a compatible permissive license (GPLv2/GPLv3) or is "public domain".
I've emailed both over the last month and got "we are mostly fine with it" replies, which unfortunately isn't enough from a legal POV.

Of course DIY solutions are always possible, it's just that the official software probably won't have those.
 
I guess there's no problem for owners to install the software themselves - just that we cannot ship MDAC2's with the software pre-installed?
 
I just ordered the V2 pre-production Detox Chassis - if all is good with the sample then we will goto first detox production.
 
Jiri,

We ordered the RPi3 for you before New Year but Farnell is out of stock - then we found a slightly more expensive part# with SDcard, Case and PSU - so I ordered this yesterday for your development.

We have the CM1 modules (SoDIMM socket etc.) - and we are working on the PCB design.
 
jirij said:
A small update to those wanting "streaming" support on FDAC/MDAC2, I'm afraid native support for RoonBridge / HQPlayer NAA won't be legally possible (or at least be at a risk of a lawsuit) as neither has a license that would permit a 3rd party (John's company) to distribute the binaries. Other software (squeezelite, shairport-sync) has either a compatible permissive license (GPLv2/GPLv3) or is "public domain".
I've emailed both over the last month and got "we are mostly fine with it" replies, which unfortunately isn't enough from a legal POV.

Of course DIY solutions are always possible, it's just that the official software probably won't have those.
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jirij,
That is shame, but at least RoonBridge is easy to install as long as there is no dependencies missing.

HQPlayer NAA might not be so relevant now, because the Roon 1.3 will have DSD upsampling and parametric EQ and more. It should be released some time in January acording to this
which is discussed on the Roon forum here
 
JohnW said:
I guess there's no problem for owners to install the software themselves - just that we cannot ship MDAC2's with the software pre-installed?
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Exactly. The licenses are visibly aimed at end users, not distributors.

JohnW said:
Jiri,

We ordered the RPi3 for you before New Year but Farnell is out of stock - then we found a slightly more expensive part# with SDcard, Case and PSU - so I ordered this yesterday for your development.

We have the CM1 modules (SoDIMM socket etc.) - and we are working on the PCB design.
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You could have just used a cz shop to get it next business day. :)
http://rpishop.cz/kategorie/283-raspberry-pi-3-model-b-64-bit.html (>5 in stock)
Doesn't matter that much though, FDAC is still quite some way away.

For MDAC2, I hope to use mostly off-the-shelf distribution, so besides a small modification for DSD, there shouldn't be any software needing "development", hopefully.

Rune said:
jirij,
That is shame, but at least RoonBridge is easy to install as long as there is no dependencies missing.

HQPlayer NAA might not be so relevant now, because the Roon 1.3 will have DSD upsampling and parametric EQ and more. It should be released some time in January acording to this
which is discussed on the Roon forum here
Click to expand...
It won't be so easy to install on the minimal OS, but it should be possible to prepare the environment for it, so that it is reasonably easy for end users (you) without the need to build the OS image from scratch. For example ext4 OS image support in addition to the read-only compressed squashfs.
 
Rune said:
HQPlayer NAA might not be so relevant now, because the Roon 1.3 will have DSD upsampling and parametric EQ and more. It should be released some time in January acording to this
which is discussed on the Roon forum here
Click to expand...
Interesting, it's always good to have competition from a consumer viewpoint. I'd be very surprised Roon's first attempt at a DSP engine can upsample/convolve as well as HQP. And be totally gobsmacked if it runs on a NAS!!! :eek:
J River has DSD upsampling too, and a free trial version, but not in the same league as HQP.
 
jamjar784 said:
Interesting, it's always good to have competition from a consumer viewpoint. I'd be very surprised Roon's first attempt at a DSP engine can upsample/convolve as well as HQP. And be totally gobsmacked if it runs on a NAS!!! :eek:
J River has DSD upsampling too, and a free trial version, but not in the same league as HQP.
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It is not supposed to run on a NAS! The best way to run Roon is to have a dedicated i3-i7 NUC as your Roon Server and your music files where ever you want them.

I do not expect the first attempt of DSD upsampling/convolve to be as advanced as HQPlayer that is not why I use Roon but it is nice to see it added and it will work better from a usability point of view.
 
WRT HQPlayer NAA I'm not keen on any upsampling / downsamping based on our test here of software resampling - Not one of the samplers Jarek "enabled" sounded better then "direct" - this is through Lab speakers and our small twin ESS DAC!
 
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