advertisement


MDAC First Listen (Part 00101001)

Status
Not open for further replies.
Amazing, I was just about to ask about this. Sadly I don't know enough about the USB regen and filtering biz to take part in the conversation and am really just waiting for a conclusion... It seems like it works, and if the isolation principle is applied to the FDAC then I feel like I've just aquired another unknown benefit.

Prior to this all my work has been concentrated on the analogue PCB, as this is nearing completion its only natural that I start thinking about the Digital PCB - and related subjects :)

The SQ is the obvious primary reason to be excited, but actually I'm still really excited about the EQ in the digital domain. Do you think there is a chance we can adjust levels (as many as you can fit) using the buttons on the case and the screen as an indicator?

Yes, a simple EQ will be provided as "basic" DSP function.

Also for DRC, is each speaker treated to its own set of filters? Aaaaaaand, can we save profiles for those who like to move their speakers around?

No idea - I leave the details of the DRC to others... I'll just design the best hardware :)

Do you think realistically there is a chance to have this all done before xmas? it just seems like it's hurtling towards us... :eek:

Working on it EVERYDAY - hit the bed at 4am yesterday (Erh today)... OK I was working on the Detox but... completing the updated Analogue PCB by October is a major milestone!
 
Yup there is a whole new science developing about how we make decisions. There was an Horizon programme about it a little while back. We are a lot less rational than we think we. I've always believed the instinctive part of our psyche has a much bigger influence on our behavior than we give it credit for, and this is one manifestation of it. Are you sitting in my chair?
A nicely done video "Thinking that we know" from Daniel Kahneman - a cognitive scientist & nobel prizewinner not in psychology (dont think there ever was one) but for his work in this field related to economics
 
... I have shown that the USB data stream is heavily modulated by the processing actions of the Host PC - and that a USB Hub device repackages and re-times these USB data packets :) I believe that this is the first time its been shown in an Audio related thread, although technically it will come as no surprise as its very simple to understand the mechanises involved - and to be expected. ...

Great Job done here John!

Thanks and keep up the good work you're doing.

/All the best
Lars

PS: Maybe time to send a link to John Atkinson/Stereophile on how to perform measurements like this. DS
 
Working on it EVERYDAY - hit the bed at 4am yesterday (Erh today)... OK I was working on the Detox but... completing the updated Analogue PCB by October is a major milestone!

Hey man, it's the dream I'm behind not the end product, so don't run yourself into the ground trying to achieve all this - it's meant to be fun :cool:

Also, let me know if you need tetley tea, custard creams or anything significantly stronger... ;) I wish I could contribute in a more meaningful way other just getting excited! *waggles the pom poms*
 
I don't agree, I have shown that the USB data stream is heavily modulated by the processing actions of the Host PC - and that a USB Hub device repackages and re-times these USB data packets :) I believe that this is the first time its been shown in an Audio related thread, although technically it will come as no surprise as its very simple to understand the mechanises involved - and to be expected.

The argument that will rage is how does this modulation mechanism cross into the Analogue domain (with a well designed product it should not)... but I've heard its effects in many instances so its not so important to me ATM... I know what can to be done to attenuate the unwanted signal modulation - that's what I'll work on.

I do know that when a person has a deep seated belief no 'snip-its' of information that might bring into question this belief
John I'm very interested in your results and ongoing research. You know better than me though that a person who believes that the precise characterist of a carrier signal transmitting data over asynch USB are not relevant to the sound in a well engineered dac, is not going to change this view as a result of seeing a change in the carrier signal.
Correlating that change with changes further down towards and ultimately at the dac output would become increasingly interesting of course. Small steps.
I'm looking forward to seeing how the regen/ non regen affects the dac's USB receiver.
 
John I'm very interested in your results and ongoing research. You know better than me though that a person who believes that the precise characterist of a carrier signal transmitting data over asynch USB are not relevant to the sound in a well engineered dac, is not going to change this view as a result of seeing a change in the carrier signal.
Correlating that change with changes further down towards and ultimately at the dac output would become increasingly interesting of course. Small steps.
I'm looking forward to seeing how the regen/ non regen affects the dac's USB receiver.

Adam,

For sure, its true that this modulation should not cross into the Analogue domain for its indicative of less then perfect design :( - but I'll be the first to say I've heard the effect on my designs (and every design I've used)....

But it important to recognise these "limitations" then we can work on understanding the causes and to resolving them.
 
John I'm very interested in your results and ongoing research. You know better than me though that a person who believes that the precise characterist of a carrier signal transmitting data over asynch USB are not relevant to the sound in a well engineered dac, is not going to change this view as a result of seeing a change in the carrier signal.
Correlating that change with changes further down towards and ultimately at the dac output would become increasingly interesting of course. Small steps.
I'm looking forward to seeing how the regen/ non regen affects the dac's USB receiver.

Just a correction - "are not" should read "should not be". This is real-world engineering that's being discussed/analysed not some platonic, unreachable ideal.

Agreed that small steps have to be taken but it is going to be a big ask to get there - firstly to measure a difference in the output of the DAC & secondly measurements that will convince some people
 
Hey just saying it as it is :)

I've was sent the Regen and Jitter Bug by a fellow PFM member :) but without PSU, so these test where performed with a low noise linear lab PSU.

Without doubt, the normally supplied SMPS will be worst - if I get my hands on a unit then I can post the measurements...

John,

My SMPS is sitting in the loft unused. You are welcome to it at least until the Detox appears.
PM me if this is of any interest

Bob
 
First, an understanding of the cause & effect is needed before any definitive statements are made. Noise is such a general term & this needs to be analysed & defined to identify the characteristics of the noise & maybe correlate to the effect on SQ. At that stage we should be in a better position to say what can & can't be done at the PC end, the transmission stage or at the receiving USB device.

As I said to you before there could be something masking this effect from you or indeed you could have a Sony laptop which is blameless as far as noise is concerned - a very unlikely situation, don't you agree? You stated before that this was your Regen test config & not a PC, right? "MDAC and Oppo PM1 fed from Sony laptop running Win 10 and Roon or Jriver".

Yes we need to understand the issue, but It is absolutely definitive that there are so many different pcs with so many variables that you are not going to fix them. The daC needs to cope as far as is reasonably practicable. Dacs need to cope with what is thrown at them.

Ok jk, as I asked you in the other thread, please tell me what is wrong with my setup to cause this alleged masking?

I totally agree it is very unlikely there is anything unusual about my Sony laptop. I don't know what you mean by "test config". It is a normal config for me that I use for everyday listening. What's a laptop if it's not a PC?

You seem to be incapable of accepting my experience is that the regen made only a small difference, smaller difference than that heard between Mdac filters and I can plainly hear those differences.

Perhaps your dacs are unusually sensitive to the problem? :)

You would have also thought that if this usb behaviour does have significant negative effect , as big and negative as you seem to be implying, that designers such as john would have turned their attention to solving it a long time ago as a priority.

We have had how many years of Mdac development and this is a last minute project just prior to release. if it's that big a problem why hasn't john being saying that there is something fundamentally wrong with USB that needs to be fixed for years?
 
Just a correction - "are not" should read "should not be". This is real-world engineering that's being discussed/analysed not some platonic, unreachable ideal.

Agreed that small steps have to be taken but it is going to be a big ask to get there - firstly to measure a difference in the output of the DAC & secondly measurements that will convince some people
I've thought about it, and I really did mean "are not".
 
Perhaps your dacs are unusually sensitive to the problem? :)
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).
 
Yes we need to understand the issue, but It is absolutely definitive that there are so many different pcs with so many variables that you are not going to fix them. The daC needs to cope as far as is reasonably practicable. Dacs need to cope with what is thrown at them.

Ok jk, as I asked you in the other thread, please tell me what is wrong with my setup to cause this alleged masking?

I totally agree it is very unlikely there is anything unusual about my Sony laptop. I don't know what you mean by "test config". It is a normal config for me. What's a laptop if it's not a PC?

You seem to be incapable of accepting my experience is that the regen made only a small difference, smaller difference than that heard between Mdac filters and I can plainly hear those differences.

Perhaps your dacs are unusually sensitive to the problem? :)

You would have also thought that if this usb behaviour does have significant negative effect , as big and negative as you seem to be implying, that designers such as john would have turned their attention to solving it a long time ago as a priority.

We have had how many years of Mdac development and this is a last minute project just prior to release. if it's that big a problem why hasn't john being saying that there is something fundamentally wrong with USB that needs to be fixed for years?
I have heard the Regen (& variations of it) on systems other than my own including a purpose built audio PC & Lampizator DAC.

Some people judge aspects of the sound differently from others & I have no idea what the MDac filter differences sound like.

However, in my experience & others, the Regen difference isn't limited to "some tracks seem to have a fraction less sibilance and with the battery and a fraction less "hard"" as you described it. There was a cleaner presentation to the sound with more solidity to the sound stage - a definite reduction in background noise which meant finer details became more evident - unmistakeable in both setups.

You may not consider these aspects important or noteworthy but it appears that you didn't hear them & that's why I said it appears something is masking your perception of this. What it might be, I don't know - could be your Sony Laptop is putting out such an amount of noise pollution that it is swamping the effectiveness of the Regen; it could be that you have a perfect system already but I doubt it - I simply don't know but I do know you are at odds with other Mdac users experience & my experience in using the same device

Your pleas about engineering, MDac, number of years & "big problem", "fundamentally wrong with USB" is just a lot of hand-waving!
 
I've thought about it, and I really did mean "are not".

Sorry, yes, you are correct - you were stating that people who have this "belief" will not be swayed - which I agree with
"a person who believes that the precise characterist of a carrier signal transmitting data over asynch USB are not relevant to the sound in a well engineered dac, is not going to change this view as a result of seeing a change in the carrier signal. "

What I should have said was that this "belief" is incorrect & not based in reality hence my change to "should be"
 
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).

Yes, Clive, I didn't want to get into my DAC on Johnw's MDac thread but he may well find, as I have that the power supply to the USB2412 hub chip is a critical element in the whole picture. Yes the voltage regulators (TPS7A4700) in the Regen are good but there is a better way to independently power this chip :)
 
I have heard the Regen (& variations of it) on systems other than my own including a purpose built audio PC & Lampizator DAC.

Some people judge aspects of the sound differently from others & I have no idea what the MDac filter differences sound like.

However, in my experience & others, the Regen difference isn't limited to "some tracks seem to have a fraction less sibilance and with the battery and a fraction less "hard"" as you described it. There was a cleaner presentation to the sound with more solidity to the sound stage - a definite reduction in background noise which meant finer details became more evident - unmistakeable in both setups.

You may not consider these aspects important or noteworthy but it appears that you didn't hear them & that's why I said it appears something is masking your perception of this. What it might be, I don't know - could be your Sony Laptop is putting out such an amount of noise pollution that it is swamping the effectiveness of the Regen; it could be that you have a perfect system already but I doubt it - I simply don't know but I do know you are at odds with other Mdac users experience & my experience in using the same device

Your pleas about engineering, MDac, number of years & "big problem", "fundamentally wrong with USB" is just a lot of hand-waving!

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?
 
John,

My SMPS is sitting in the loft unused. You are welcome to it at least until the Detox appears.
PM me if this is of any interest

Bob

Bob,

That would be fun to measure it if only to give people an idea of SMPS switching noise (or not) :)

But something tells me your in the US - and it would not be cheap to post it to me?
 
Status
Not open for further replies.


advertisement


Back
Top