Musical Fidelity MX-DAC Review (Balanced DAC)

[Jimbob54]

The Pro-ject Pre Box DS2 Digital measured 107dB SINAD, costs ~$900, and got the golfing panther. That has more functionality though, and I think Amir liked the all-around competence.

Agreed. Had it just been a dac in that same box, or maybe just a dac and headamp, I think it might have got as I suggested. The phono inputs make it something different.

 

[Nfalck]

It’s not broken at all. It’s audibly transparent and not $3,000. Linearity 3 dB down at -116 dB is not broken. Median SINAD is not broken.

@amirm, this does not deserve a headless panther.

Shhh we're supposed to focus on technical performance 100 db down, not whether we like how it sounds.

 

[rdenney]

In re all the discussions of "audibility," I think it's likely that some sounds that are inaudible may nonetheless be perceptible. Otherwise why would DAC filters that don't even engage within the audible range affect the perceived sound quality? And even @amirm has acknowledged that filters can affect how a DAC "sounds" (which I think involves things other than those in the 10Hz-18kHz range).

Audibility is the standard of perceptibility, unless you believe that these products emit ectoplasm. Of course, we might be swayed in our perceptions by what we see, but that's in the realm of delusion (however benign in any given case) rather than engineering. How does a manufacturer design something to achieve what is inaudible? What measurements do they use? How do they select components? How do they lay out the circuit boards? How do they route wires? Are they limited to "try this and then listen for a week with my golden ears and then try something else until it gets better", do you think any manufacturer at any price point would actually do that?

But if there really is a "perceptible" difference, controlled listening tests should demonstrate it. I'd bet that for every ASR reader with the skills to hear how deficient this DAC is relative to the best on the market, there will be a dozen or more that could not. I'd be one of them.

Rick "at least for the simple conversion of a digital stream to analog audio" Denney

 

[charleski]

In re all the discussions of "audibility," I think it's likely that some sounds that are inaudible may nonetheless be perceptible.

This is an important issue in psychopysiology which cannot be dismissed out of hand. Unfortunately it’s also a very complex issue. If you want to find out some more about the concept of implicit perception there are a number of review articles available. One such which is freely available can be found here. It’s not a ten-minute read, but that’s just the way things are. It’s rather old, but it’s free and should be sufficiently authoritative.

I thought about summarising some of the main findings, which are based on results from medical and psychological research over the past century (this is not a new concept). But that would just make this post way too long. The primary characteristic is that they are all quite gross findings, because those are the ones that have stood up to repeated enquiry. But they do certainly exist. There definitely are elements of memory and perception that can function without awareness of that function.

But that doesn’t mean that we can jump to unwarranted conclusions about the rest of the perceptual system. It doesn’t mean we can assume such elements exist in other forms. The presence of implicit perception needs to be robustly demonstrated if we’re to use it to explain certain auditory phenomena. This is especially true as there are many other explanations for many of these phenomena. And we should never dismiss the extent of neural plasticity, especially in situations involving directed training.

This all boils down to what science is really all about: “Nice idea, now go and prove it.”

 

[MaxBuck]

This is an important issue in psychopysiology which cannot be dismissed out of hand. Unfortunately it’s also a very complex issue. If you want to find out some more about the concept of implicit perception there are a number of review articles available. One such which is freely available can be found here. It’s not a ten-minute read, but that’s just the way things are. It’s rather old, but it’s free and should be sufficiently authoritative.

I thought about summarising some of the main findings, which are based on results from medical and psychological research over the past century (this is not a new concept). But that would just make this post way too long. The primary characteristic is that they are all quite gross findings, because those are the ones that have stood up to repeated enquiry. But they do certainly exist. There definitely are elements of memory and perception that can function without awareness of that function.

But that doesn’t mean that we can jump to unwarranted conclusions about the rest of the perceptual system. It doesn’t mean we can assume such elements exist in other forms. The presence of implicit perception needs to be robustly demonstrated if we’re to use it to explain certain auditory phenomena. This is especially true as there are many other explanations for many of these phenomena. And we should never dismiss the extent of neural plasticity, especially in situations involving directed training.

This all boils down to what science is really all about: “Nice idea, now go and prove it.”

I agree with what you're saying about proof. But as pointed out in the evaluation of "Havana Syndrome" for US Embassy employees, even radio-frequency emissions have the ability to cause malaise and even actual illness. And again: if superaudible frequencies are unimportant to listening pleasure, why does @amirm test DAC filters that don't affect the "audible frequencies?" For that matter, why do manufacturers include them?

 

[amirm]

And again: if superaudible frequencies are unimportant to listening pleasure, why does @amirm test DAC filters that don't affect the "audible frequencies?"

Because I got tired of not testing them and have people ask for them!

 

[MaxBuck]

Because I got tired of not testing them and have people ask for them!

Obviously that's not the true reason. You've expressed a strong preference for "brickwall" filters and opined that filters must suppress the signal to zero by 22 kHz. Why does it matter? These things all operate in the realm of the "inaudible."

 

[rdenney]

I just wrote a long thesis on dithering, antialiasing filters in digital cameras, and so on. Too much. Summary: There's no harm in removing what can't be heard and isn't part of the intended signal anyway, on the off-chance that might occasionally interact noticeably and therefore negatively with what can be heard.

It wasn't what they heard that caused those embassy officials to be affected by extreme RF.

Rick "noting that microwave RF is used to cook food" Denney

 

[charleski]

if superaudible frequencies are unimportant to listening pleasure, why does @amirm test DAC filters that don't affect the "audible frequencies?"

Because intermodulation with aliased tones in the output stage has the potential to affect performance in the audible range. Many, but not all, DACs with poor filtering show rising distortion in high frequencies.

For that matter, why do manufacturers include them?

Because they’ve become fashionable and including them leads to more sales. The primary goal of any successful manufacturer is always going to be to sell more of their product.

 

[Sheriff1972]

In my experience, removing any out of band noise that can potentially slew limit the input stage of the following amplifier is a good thing...

 

[sarumbear]

Obviously that's not the true reason. You've expressed a strong preference for "brickwall" filters and opined that filters must suppress the signal to zero by 22 kHz. Why does it matter? These things all operate in the realm of the "inaudible."

You need to learn more about the subject before using words like "obviously" and think that Nyquist–Shannon sampling theorem is an "opinion". They say ignorance is bliss but reading posts like yours is a pain in the...

Besides, telling @amirm that he is hiding the true reason is downright rude.

 

[AnalogSteph]

That being said, a "fast rolloff" filter of the traditional kind is all you really need for a DAC in practice. With little actual signal energy above 20 kHz being present in real-life source material, there is little reason to be making compromises in-band (e.g. periodic passband ripple in FIR filters) or substantially increase filter complexity and group delay just to be able to get any last bit of aliasing knocked down to nothing. At fs = 44.1 kHz, -6 dB at 22.05 kHz going down to near filter ultimate by about 24.1 kHz (= 44.1 kHz - 20 kHz) is perfectly fine. Even if the alias of a 20 kHz full-scale signal is "just" 50-60 dB down, it's not going to bother any amplifier, at least not any more than the 20 kHz tone itself.

The ADC side is substantially more critical when it comes to filter performance (not to mention it may be degraded by clock jitter as well). Even so, 100% "correct" filters were never a big hit and mostly recommended for measurement applications; I don't think any more such chips have been made since the CS5397 from the late '90s, well, not until the fairly recent ESS ADCs with their various filter choices.

 

[617]

It's amazing how people revert to treating amir like a cult leader or conspiratorial mastermind instead of some dude who provides data and his own opinions for free.

I have said it before and will say it again; mere consumers are not capable of having productive technical discussions the way hobbyist diyers and actual researchers are.

Besides maybe cables, there is no less consequential category of audio equipment than a DAC. None of them sound different. These ratings which draw so much ire are only interesting to people who take pleasure in seeing how close to the theoretical minimum noise and distortion manufacturers can approach. What are we at now, -124db? That's pretty cool, but that's all it is. Sort of sad to think that we may never see actual 24 bit audio in our lifetimes.

The problem with including filter measurements is that it perpetuates a fiction that they matter, in the same way that speaker measurements matter. Frankly I think Amir should stop including these insane measurements (has anyone heard the ESS hump??) Or at least include a caveat that everything here is inaudible.

 

[Rottmannash]

I have a Pana Plasma from 2010 in my exercise room; its picture is outstanding. It does look tiny, even though at one time it "filled" my living room wall.

I have one of those too. Don't know what to do with it. Don't want to throw it away so it sits alone, unplugged in the spare bedroom.

 

[sarumbear]

I think Amir should stop including these insane measurements (has anyone heard the ESS hump??) Or at least include a caveat that everything here is inaudible.

The same patronising stance, again: should!

Why? What gave any of us the right to demand what @amirm should do? If we are not happy with what he says, ignore it. Nobody is forcing us, nor there is any legality involved in what he says that requires a caveat.

(Beggars belief!)

 

[PeteL]

You need to learn more about the subject before using words like "obviously" and think that Nyquist–Shannon sampling theorem is an "opinion". They say ignorance is bliss but reading posts like yours is a pain in the...

Besides, telling @amirm that he is hiding the true reason is downright rude.

Audible differences between DAC Filters is a valid question. Nobody has questioned the sampling theorem, you bring that up. The question was, how is a filter preferable to an other if they sound exactly the same under all circumstance, If Amir says that the only reason he measure them is because he is tired of people asking. Maybe it does matter, maybe it don't, but the question hasn't been answered.

 

[sarumbear]

Audible differences between DAC Filters is a valid question. Nobody has questioned the sampling theorem, you bring that up. The question was, how is a filter preferable to an other if they sound exactly the same under all circumstance, If Amir says that the only reason he measure them is because he is tired of people asking. Maybe it does matter, maybe it don't, but the question hasn't been answered.

There’s no question to be answered. As I said, read the theorem to see the answers you are chasing.

 

[PeteL]

There’s no question to be answered. As I said, read the theorem to see the answers you are chasing.

Maybe you didn't read what was the question? The sampling theorem tells us about signal restitution in D-A in the most theoretically perfect way. It doesn't say anything about audibility of conversion artifacts.

 

[pkane]

The sampling theorem tells us about signal restitution in D-A in the most theoretically perfect way. It doesn't say anything about audibility of conversion artifacts.

The way I read the sampling theorem, it most certainly does. It says that when the signal frequency is under 1/2 the sampling rate, the sampled waveform can be reconstructed perfectly. This means that there are no artifacts to be audible. Don't know about you, but that's what I want from my DACs. Lazy filters or NOS-type DACs with no filtering are just messing with the recorded signal, distorting it.

 

[PeteL]

The way I read the sampling theorem, it most certainly does. It says that when the signal frequency is under 1/2 the sampling rate, the sampled waveform can be reconstructed perfectly. This means that there are no artifacts to be audible. Don't know about you, but that's what I want from my DACs. Lazy filters or NOS-type DACs with no filtering are just messing with the recorded signal, distorting it.

your statement is rigorously true, but again, that wasn't the question.