Watts Up...?
Mar 31, 2016 at 1:31 AM Post #61 of 4,684
Hi Rob,
Very interesting stuff, thanks.

A topic I am keen to hear an expert explore is that of digital filters.

What are the pros and cons of the different filter types? Can pre-ringing effect the brains ability to process? Does post ringing sound more natural? What was your decidion making process in going with a linear phase filter (correct me if I'm wrong on that) with the popular Chord products you developed?

In addition, while not really a topic for discussion I did have a question as well -

Does Chord have any plans, or would you like to see them, evolve the Mojo project into a digital audio player?

The number of photos I see with high end DAPS having their expensive circuitry bypassed into a Mojo via digital output boggles my mind. It seems to me that you have the hard work done with a miniature yet highly regarded DAC and amp circuit in the Mojo. Why not capitalise on the growing market for high end DAPS and make a mojo player?

I plan to do a blog post about digital filters but it will be some time coming, as I hope to publish some measurements to show the time domain problem.
 
But I have a little tease for you. A perfect sinc response infinite FIR filter will perfectly reconstruct the original bandwidth limited analogue signal - without any change whatsoever - no pre ringing or post ringing, it is mathematically identical except displaced in time. But such a filter has an infinite amount of pre and post ringing, so looks nothing like the original impulse?
 
How can you explain that paradox that a filter that won't change the original signal at all has an infinite amount of ringing? This is actually a very important question as the whole audio industry in trying to minimize ringing has got the filter question completely and utterly wrong.
 
Rob
 
Mar 31, 2016 at 2:18 AM Post #62 of 4,684
Just to clarify a bit. As you probably know, I am independent of Chord, and so on this blog I am talking strictly personally. This blog is primarily about talking about my engineering that goes into Chord products. I am at liberty to talk about WTA, noise shaping, pulse array etc as I own that intellectual property (IP). But I may not be at liberty to discuss Chord products, as it may involve Chord IP, or it may be commercially sensitive to Chord, and so I generally can't talk about future Chord products. But I can talk about future Chord projects - Davina is classed as a project, as its about testing my ADC IP. Davina will also be a product, but when I talk about it its as a project. Also the digital power amp is a project too, so I will be talking about that as well, even though that will end up as a product too (when we get around to coming up with a name).
 
It does not have to be just about the tech, we can also talk about music, recordings, and any other subject.
 
I hope that clarifies, Rob
 
Mar 31, 2016 at 2:56 AM Post #63 of 4,684
Just to clarify a bit. As you probably know, I am independent of Chord, and so on this blog I am talking strictly personally. This blog is primarily about talking about my engineering that goes into Chord products. I am at liberty to talk about WTA, noise shaping, pulse array etc as I own that intellectual property (IP). But I may not be at liberty to discuss Chord products, as it may involve Chord IP, or it may be commercially sensitive to Chord, and so I generally can't talk about future Chord products. But I can talk about future Chord projects - Davina is classed as a project, as its about testing my ADC IP. Davina will also be a product, but when I talk about it its as a project. Also the digital power amp is a project too, so I will be talking about that as well, even though that will end up as a product too (when we get around to coming up with a name).

It does not have to be just about the tech, we can also talk about music, recordings, and any other subject.

I hope that clarifies, Rob


Great clarification Rob.

Curious, what's your take on the reports of different sources sounding different feeding a DAC. I know your stance on RF noise in the signal chain affecting sound and it's one of the cases for using an optical connection, but recently (just last night) I did hear a difference between two sources, both connected optically to the Mojo and both sources are from the same company on different ends of the price scale. One source sounded warmer and had more depth. The other source was brighter and brought many instruments forward, particularly female vocals, hi hats and cymbals, as well as piano notes and acoustic guitar. The depth was essentially flattened from one source while sounding brighter.

I only discovered this as my battery was low on one portable source while I was listening and I connected my other source with the same optical cable and I was taken back that I heard any difference at all considering there is no user DSP (EQ or otherwise) active. Up until this point I've never really been able to discern any real difference between sources. I spent the following 2 hours testing different tracks using the ETHER C and the results were consistent across the different music. I know your expertise may not be in file decoding from a source, but I suspect you have an idea. I'd be interested in your thoughts on the subject.
 
Mar 31, 2016 at 3:09 AM Post #64 of 4,684
Great clarification Rob.

Curious, what's your take on the reports of different sources sounding different feeding a DAC. I know your stance on RF noise in the signal chain affecting sound and it's one of the cases for using an optical connection, but recently (just last night) I did hear a difference between two sources, both connected optically to the Mojo and both sources are from the same company on different ends of the price scale. One source sounded warmer and had more depth. The other source was brighter and brought many instruments forward, particularly female vocals, hi hats and cymbals, as well as piano notes and acoustic guitar. The depth was essentially flattened from one source while sounding brighter.

I only discovered this as my battery was low on one portable source while I was listening and I connected my other source with the same optical cable and I was taken back that I heard any difference at all considering there is no user DSP (EQ or otherwise) active. Up until this point I've never really been able to discern any real difference between sources. I spent the following 2 hours testing different tracks using the ETHER C and the results were consistent across the different music. I know your expertise may not be in file decoding from a source, but I suspect you have an idea. I'd be interested in your thoughts on the subject.

 
Hmm - sounds like most likely explanation is that its not bit perfect files. Even if a single stage of gain scaling happens, it will make a big difference to the sound - see my earlier post about my -301 dB test. If data is not properly handled when its adjusted, it will lose depth, and if really bad truncation, will also sound harder.
 
Normally if the optical is not bit perfect you will get drop-outs as it falls in and out of lock, so I don't expect its the optical connection.
 
Rob
 
Mar 31, 2016 at 3:38 AM Post #67 of 4,684
Rob, both Davina and your digital amp project seem to me that they will have the potential to be landmark products as they could well result in a level of performance never before achieved. It would seem to me that Davina has the potential to have the broader impact as all systems would benefit, Chord or otherwise, while your digital amp will only benefit owners of the DAVE. Is that correct?

Of the two projects, which is the bigger priority? Which one will be the bigger challenge?
 
Mar 31, 2016 at 3:46 AM Post #68 of 4,684
Hmm - sounds like most likely explanation is that its not bit perfect files. Even if a single stage of gain scaling happens, it will make a big difference to the sound - see my earlier post about my -301 dB test. If data is not properly handled when its adjusted, it will lose depth, and if really bad truncation, will also sound harder.

Normally if the optical is not bit perfect you will get drop-outs as it falls in and out of lock, so I don't expect its the optical connection.

Rob


I agree Rob, which is what has me stumped as both sources should be bit perfect and they are playing the same files, and aren't being up/down sampled. It's not the optical connection, that's fine. Perhaps the manufacturer of the devices (same manufacturer, different tier products) isn't completely transparent regarding any DSP being used to achieve their sonic signature at different price brackets. Thanks for the reply. I'll check your post in the DAVE thread as well.

Another question, what genre do you find the best for testing music? I prefer live, smaller venue, acoustic performances as I can usually relate to the space. Orchestrational music I find difficult to assess given the large space and variables with mic placement.
 
Mar 31, 2016 at 4:00 AM Post #69 of 4,684
Changing subject...
 
First time i really become aware of sound quality of recorded music was in a rehearsal room watching a band of friends. I headed home scratching my head thinking: why drums don't sound like this on recorded music?
 
To this day i still think that live drums trump recorded drums (even if the tracking, mixing and mastering is very good as on Rolling Stones "Black And Blue" album) and i was wondering if this has to do with mics capabilities. After all mics are what turn live sound into electricity.
 
What is the dynamic range of a studio mic (SM57s, Neumann...) and what is the dynamic range of a snare drum when hit hard?
 
Mar 31, 2016 at 5:05 AM Post #70 of 4,684
  Changing subject...
 
First time i really become aware of sound quality of recorded music was in a rehearsal room watching a band of friends. I headed home scratching my head thinking: why drums don't sound like this on recorded music?
 
To this day i still think that live drums trump recorded drums (even if the tracking, mixing and mastering is very good as on Rolling Stones "Black And Blue" album) and i was wondering if this has to do with mics capabilities. After all mics are what turn live sound into electricity.
 
What is the dynamic range of a studio mic (SM57s, Neumann...) and what is the dynamic range of a snare drum when hit hard?


To add to your question, just how capable are the current ADCs used in this process? I guess not good enough... hence the Davina project. Does this mean that all analogue master tape transfers will need to be redone when Davina comes into being?
We tend to concentrate on the equipment used to reproduce digital music, because we are in control of that. What happens in the studio we have to accept as someone else's choice.
 
Mar 31, 2016 at 6:13 AM Post #71 of 4,684
 
To add to your question, just how capable are the current ADCs used in this process? I guess not good enough... hence the Davina project. Does this mean that all analogue master tape transfers will need to be redone when Davina comes into being?
We tend to concentrate on the equipment used to reproduce digital music, because we are in control of that. What happens in the studio we have to accept as someone else's choice.


Yep. Converters are key as well.

If you can get a hold of the japanese 2011 SHM-SACDs of the Rolling Stones key albums...they are a flat new transfer from the master tapes carried out with top notch converters from Abbey Road studios. The sonic improvement is obvious in terms of purity, clarity and openness. A real treat for any Stones fan.
 
Mar 31, 2016 at 10:23 AM Post #72 of 4,684
 
To add to your question, just how capable are the current ADCs used in this process? I guess not good enough... hence the Davina project. Does this mean that all analogue master tape transfers will need to be redone when Davina comes into being?
We tend to concentrate on the equipment used to reproduce digital music, because we are in control of that. What happens in the studio we have to accept as someone else's choice.

 
There was a lot of talk on Head-fi at one point about Mike Moffat's "Super Analogue" ADC used in some MFSL recordings.  In theory, one of those recordings played back with an R2R DAC offers much improved sound fidelity because it's an R2R ADC into an R2R DAC.  I've listened to some of those recording vs the non MFSL versions on my R2R DAC's and haven't noticed much difference (though I suspect others with better ears might?).
 
Curious how this plays into the Davina subject.
 
Mar 31, 2016 at 12:20 PM Post #73 of 4,684
Rob,
 
I think you wisely chose the key topic to start which is some thoughts on listening to music via electronics
 
One of the areas of great debate in the industry is the impact of really good algorithms for reducing files below redbook (e.g. AAC at 256, etc.) compared with Redbook.  Conversely, a similar area of controversy is whether resolutions above redbook (say 24-88 or higher, of DSD of various flavors) really can add something to the musical reproduction chain.
 
So some ways of addressing that would be helpful. 
 
Personally I find that it takes an extended listening session to really hear some differences as resolutions go up from psychoacoustic reduction to redbook to "hi res"; which conflicts with the concept of A-B testing.
 
Your take on this or some thoughts on how to approach this would be great.
 
By the way I spent some time at CES with your reps and they were really great to speak with.  I also demoed the Mojo afterwards for a bit and was very impressed.
 
Mar 31, 2016 at 12:34 PM Post #74 of 4,684
Well, with proper drivers and use of WASAPI and ASIO one can output direct to a DAC so this issue raised with PC downconversion is taken off the table.
 
Maybe it is the kid glove approach that makes the difference, but hi res versions of Miles Davis Kind of Blue (especially HD Tracks at 24-192) and Beck's Sea Changes sound pretty amazing to me.   But others would disagree. 
 
I know that some people equate louder with better and AAC files are the winners in their A-B testing as my experience shows that bit reduced files tend to be somewhat compressed.  So volume leveling results in a slightly louder overall experience.
 
Mar 31, 2016 at 12:40 PM Post #75 of 4,684
I'm trying to find a post (not sure if it was Rob's or not) I recall reading, about a year ago, which was very insightful on the topic of legitimacy (or otherwise 
wink.gif
) of 24/192, but it is, thus far, eluding me.
 
I'm also mindful that it'd be bordering on 'Sound Science' forum territory, so perhaps it is apt that I've been unable to locate it!
 
 

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