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MDAC First Listen (Part 00101001)

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BE718 said:
A definite reduction in background noise. Really! I suggest you make some measurements - oh sorry I forgot, your a dac designer who doesn't even posses a spectrum analyser :p.

I mention the Mdac filters as it is a reference that people can relate to, particularly on this thread. You are judging my experience with a Mdac and you haven't even heard one if you don't know what the filters sound like.

Why is it hand waving to point out the bleeding obvious?


So this is a "night and day" type revelation is it? Or shall I attach some different cliched hyperbole?
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Stop being a prat & drop it - if you can't describe what you hear without resorting to measurements then it's what I suspected all along - you don't allow yourself to hear anything that measurements don't tell you. I asked you this before but you avoided answering - have you ever heard anything that you couldn't measure?
 
clivem2 said:
I have heard a Regen with one of JKs DACs. It does make a difference but it makes far less difference with his DAC that it does with my Metrum Octave mkII. I suspect this is because the JK DAC USB receiver is powered by battery where as my Octave uses Vbus power (or iFi iUSB Power and now a linear PS into the Regen).
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Yes that would makes sense, usb bus power is not going to be good.
 
jkeny said:
Stop being a prat & drop it - if you can't describe what you hear without resorting to measurements then it's what I suspected all along - you don't allow yourself to hear anything that measurements don't tell you. I asked you this before but you avoided answering - have you ever heard anything that you couldn't measure?
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Is there anything inaccurate I have said? it's you that won't accept my experience.

Measurements have nothing to do with it. The background noise levels haven't changed in any appreciable manner. You description is inaccurate.

Now who is being a prat?

However I will gladly drop as I don't want to waste my time and disrupt the thread conversing with you.
 
BE718 said:
Yes that would makes sense, usb bus power is not going to be good.
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You'd think. But as I understand it in order to galvanically isolate the usb receiver section from the rest of the dac you have to use the usb bus to power it (or at least some other sort of external 5v supply). That's what the Fdac is going to do as i understand it (correct me if I'm wrong John).
 
BE718 said:
Is there anything inaccurate I have said. it's you that won't accept my experience.

Measurements have nothing to do with it. The background noise levels haven't changed in any appreciable manner. You description is inaccurate.

Now who is being a prat?

However I will gladly drop as I don't want to waste my time and disrupt the thread conversing with you.
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Great!!

What I find a lot is a major disconnect between psychoacoustics (which is auditory perception just so there is no confusion over the term) & how they relate to measurements. Lots of people think that a perception of a reduction in background noise means that there is a measureable reduction in the level of noise across the board - they interpret auditory perception descriptions literally & equate this to a measurement - hence the "night & day" phrase bandied about & the usual smugness about how this should be so easy to measure

There are many reasons why there might be a perceived reduction in background noise which do not entail the actual reduction in background noise measurement (or at least a standard FFT of such a measure)
 
JohnW said:
Hi Fred,

Sorry your post got missed - No the FDAC only has a single RCA output but I can hand mount a second for you if your remind me when I'm about to ship your unit :)
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Thank you very much!
Then 2 pairs RCA and one pair XLR. Thats fine for my 3way activ system ;-))
 
John,

If I read it correctly, you mentioned that the Jitter/RF noise on the USB bus is leaking to the analog domain via the IC/chip handling the USB (and house keeping) on the MDAC. Do you foresee this being fixed somehow on the FDAC digital board?

Also, since USB seems to have all these issues, do you think the HDMI input on FDAC (if there is one) would be better input from a PC? Or are we looking at similar issues? After all, HDMI (and display port for that matter) was designed with Audio in mind (unlike USB) and should have better spec for handling these kind of issues. Or not :)

As always, very grateful for all your hard work.
 
jkeny said:
Great!!

What I find a lot is a major disconnect between psychoacoustics (which is auditory perception just so there is no confusion over the term) & how they relate to measurements. Lots of people think that a perception of a reduction in background noise means that there is a measureable reduction in the level of noise across the board - they interpret auditory perception descriptions literally & equate this to a measurement - hence the "night & day" phrase bandied about & the usual smugness about how this should be so easy to measure

There are many reasons why there might be a perceived reduction in background noise which do not entail the actual reduction in background noise measurement (or at least a standard FFT of such a measure)
Click to expand...

So I was correct, the description is inaccurate.

You are the one saying this is making a huge difference to the sound, it has nothing to do with measurement.

ok, please explain these many reasons.
 
jadidih101 said:
John,

If I read it correctly, you mentioned that the Jitter/RF noise on the USB bus is leaking to the analog domain via the IC/chip handling the USB (and house keeping) on the MDAC. Do you foresee this being fixed somehow on the FDAC digital board?

Also, since USB seems to have all these issues, do you think the HDMI input on FDAC (if there is one) would be better input from a PC? Or are we looking at similar issues? After all, HDMI (and display port for that matter) was designed with Audio in mind (unlike USB) and should have better spec for handling these kind of issues. Or not :)

As always, very grateful for all your hard work.
Click to expand...

The issue will remain on the FDAC, the FDAC however has an isolated USB section so this offers some attenuation (but the reality is that at 1GHz the attenuation is very low), once the RF is internal to the enclosure its a loosing battle.

Ideally the digital PCB would be designed into a fully screen enclosure with local individually screen sections - think of a lump of aluminium milled with individual sections, then the PCB mounted on top, with each circuit section in its own milled area, then filtering between each section.

I'll design the Detox along these lines, its chassis milled from a small solid lump, with individually isolated internal sections. We can use the cheap vendor I visited in China as price is more important then 100% cosmetic perfection for the Detox... it also allows me to trial the vendor... but I fear Mickey Mouse QC...

Same issue with RF applies to the HDMI.... :(

Lets get the Analogue PCB completed first then and Detox into production and then consider if we go crazy with the FDAC digital PCB mounted into a milled lid :).... if I design the PCB with this in mind, then it can be an option....
 
adamdea said:
You'd think. But as I understand it in order to galvanically isolate the usb receiver section from the rest of the dac you have to use the usb bus to power it (or at least some other sort of external 5v supply). That's what the Fdac is going to do as i understand it (correct me if I'm wrong John).
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Yes correct - but in a perfect world this section should still be cleanly powered as any noise will find its way into the rest of the design.

For this reason alone (Clean 5V PSU), the Detox is a good idea for the FDAC.
 
jadidih101 said:
After all, HDMI (and display port for that matter) was designed with Audio in mind (unlike USB) and should have better spec for handling these kind of issues. Or not :)
Click to expand...

HDMI was designed for video (including audio data). You cannot transmit audio data via HDMI without at least a steady black picture.
 
jadidih101 said:
Also, since USB seems to have all these issues, do you think the HDMI input on FDAC (if there is one) would be better input from a PC? Or are we looking at similar issues? After all, HDMI (and display port for that matter) was designed with Audio in mind (unlike USB) and should have better spec for handling these kind of issues. Or not :)
Click to expand...
(USB was also designed for audio, quoting one of the original Goals from the 1996 draft - "Full support for real-time data for voice, audio, and compressed video")
 
fusion5 said:
HDMI was designed for video (including audio data). You cannot transmit audio data via HDMI without at least a steady black picture.
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If it is coming from a PC, the picture part would be what is on the screen/desktop, I guess.

Anyhow, John said that it would have the same issue as USB for RF, so this is beside the point.
 
jirij said:
(USB was also designed for audio, quoting one of the original Goals from the 1996 draft - "Full support for real-time data for voice, audio, and compressed video")
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Thanks, I had forgotten that. I remember now when USB displays came out. The refresh rate was so bad nobody really used them. I guess the audio part was for PC quality speakers and not really for HIFi stuff.
 
Something I would like to understand from those who hold this position - there is now an acceptance that the VBus isn't fit for purpose for powering USB audio devices & it's accepted that external power is usually better (which wasn't the view of some of these people in 2013) but yet when it comes to the data signal the USB device it is contended that the USB device should be able to deal with all possible distortion of this signal.

Why don't these people also insist that the USB device should be capable of using the VBus & dealing with all the crap on it? The crap on the VBUS & ground was well known almost from day 1 - yet this signal waveform distortion has only been known about recently (1 day :))

Any good explanation?
 
@JohnW are other resources in your team (e.g. Dominik) already working on software/interfaces, or is that not possible until the digital board has been designed?
 
fred sonnen said:
Thank you very much!
Then 2 pairs RCA and one pair XLR. Thats fine for my 3way activ system ;-))
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In order for that to work the FDAC would have to process and convert 6 channels, but it can only handle 2. For a 3 way system you also need 2 slave units.
 
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