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Hifiman HM-801 RMAA Tests - Page 44  

post #646 of 795


 

Quote:
Originally Posted by b0dhi View Post

Correct me if I'm wrong but that PCB looks like its been soldered by hand. There's even a pair of bridged pins on the top left.

 

The two channels are virtually crammed up against each other, which, if the layout isn't effective, would explain the cross-talk. The digital side of the PCM1704s have power decoupling ceramics bypassed with smaller yet further away ceramics, which is just a waste of parts for a package having the parasitic inductance of a SOIC20. The bottom channel seems to be missing a (useless as mentioned) bypass cap.

 

That said, there is use of high quality parts around the DACs and analog stage.

 

Definitely hand soldered for all the through hole components (a bit excessive use of solder, but at least they're nice and shiny and not dull looking cold solder joints), and quite a few of the SMD parts. 

 

b0hi, the shorted pins on the PCM2706 chip are 25 and 26, (ZGND and AGNDL). 

http://focus.ti.com/lit/ds/symlink/pcm2707.pdf
 

-Ed


Edited by Edwood - 5/30/10 at 5:18pm
post #647 of 795

Quote:

Originally Posted by nick_charles View Post





Actually it is by no means certain that many people would be able to hear the roll-off. Experiments back in 1978: "Sampling-Frequency Considerations in Digital Audio" , TERUO MURAOKA, YOSHlHlKO YAMADA, AND MASAMI YAMAZAKI provides evidence that a roll-off can be as low as 15K before it is reliably audible, a hard cut-off at 20K, 18K and 16K was not reliably audible (p < 0.05) by any of the 31 trained subjects and only some of them detected the 14K cut-off , in my own experiments I was unable to detect anything above a 13K roll-off, but I am 51 so that is explicable.


Sorry, I should remember there are age groups and those with hearing loss on the forums.  Nonetheless I have hearing up to a bit above 17K, so the roll-off is relatively noticeable under scrutiny for me at least.

 

@immtbiker

 

If you like the way the player sounds that's fine - that's subjective.  You can feel it's the best sounding, the thing is the best at reproducing a signal it is not - hence it is inaccurate.  There is no debating that fact unfortunately.

 

I don't care if it sounds like it's able to gloss over mastering flaws or sounds more revealing than listening to a live band - if it's not accurate it's not what was intended for you to hear.

 

Personally, I think for $800 they could have done a lot better honestly.

 

Also, this:

 

 

 

Quote:
I was at CES this year, and there were many chinese manufactures who wanted to buy it, reverse engineer the technology,

and try to come out with something competitive . That speaks volumes about the HiFiMAN. It is a compliment.

 

Sounds more like they have an idea of how much it actually costs to build, but they know there's plenty of room to under-cut and sell to "audiophiles" who claim it's the best thing since sliced bread.

 

So in reality if it says anything it says there's demand and money to be made.  That's all really.

post #648 of 795

...and the Manley Steelhead is worth $7000? 

 

Whether I agree with you or not, I always pose the question to people who say that something is too expensive, "How

do you know how much money went into R&D and manufacturing"? Industry standard for markup is typically 100%.

Again, I'm not disagreeing with you, but it is up to every consumer to decide whether or not something is worth the asking price.

 

Are any of the better amps that we buy, really worth the msrp price?

 

I'm sure other products will come out in my buying history that I will like better, but right now, the 801 sounds better than

anything  else that I have heard, right out of the headphone jack. I can't prove it, I can only state my opinion.

post #649 of 795
Quote:
Originally Posted by Shike View Post

Sorry, I should remember there are age groups and those with hearing loss on the forums.  Nonetheless I have hearing up to a bit above 17K, so the roll-off is relatively noticeable under scrutiny for me at least.

 

Have you done a DBT to determine for sure that you can hear the roll-off and that it's not just because you know there is one? 

 

Sorry, couldn't resist.
 

post #650 of 795

Quote:

Originally Posted by immtbiker View Post

...and the Manley Steelhead is worth $7000?

 

Probably not.

 

Quote:

Whether I agree with you or not, I always pose the question to people who say that something is too expensive, "How

do you know how much money went into R&D and manufacturing"? Industry standard for markup is typically 100%.

 

Well the circuit design has other issues, so obviously it seems not a lot of R&D went into it or major oversights were made.  The parts aren't exactly exotic so they're easy to source in decent quantities.  Oh, and it seems like it's still hand soldered in China - extremely cheap source of manufacturing.

 

Quote:

Again, I'm not disagreeing with you, but it is up to every consumer to decide whether or not something is worth the asking price.

 

Are any of the better amps that we buy, really worth the msrp price?

 

Sure, it's always up to the consumer . . . however, I've seen choices that "consumers" make that repulse  (look at stupid fads that wouldn't die in the past - there's your proof).

 

As for the amps being worth MSRP - depends on the amp honestly.  One of the worst cases of price gouging was the Gain Card, which was praised up and down till someone popped open the chassis to find an opamp.  People became furious they had been duped into buying such an amp for $3K - and yet they didn't have a problem till they knew what it was they actually purchased.

 

Obviously, some companies seem a bit more in line with common (and often considered fair) pricing structures than others.  $800 for a NOS DAP just doesn't seem to scale well - it's more an example of they're the only ones in the market (with a NOS DAP design), so what are you going to do about it?


Quote:
Have you done a DBT to determine for sure that you can hear the roll-off and that it's not just because you know there is one? 

 

I used the recorded files like everyone else, but after Nick said there was an issue with phasing I bit my tongue since arguably the results were no longer valid.  A fair question though actually.

post #651 of 795
Quote:
Originally Posted by Shike View Post

Obviously, some companies seem a bit more in line with common (and often considered fair) pricing structures than others.  $800 for a NOS DAP just doesn't seem to scale well - it's more an example of they're the only ones in the market (with a NOS DAP design), so what are you going to do about it?


Judging by the oscillator frequency it looks like this is an oversampling DAC after all.

post #652 of 795

Quote:

Originally Posted by b0dhi View Post


Judging by the oscillator frequency it looks like this is an oversampling DAC after all.


Can you highlight in the image?  I'm not seeing it.

 

If it is an oversampling design than I fail to see why they even bothered with the slow-roll off.

 

EDIT:

 

nvm, see it now.  An oscillator at 24.576 . . . with a DF1704 sitting right next to it.


Edited by Shike - 5/31/10 at 5:35am
post #653 of 795
Originally Posted by Shike View Post

 

If it is an oversampling design than I fail to see why they even bothered with the slow-roll off.

 

Oversampling isn't responsible for the ringing, it's the filter implementation. You can prefectly reproduce the high-frequency characteristic of a NOS DAC (in the audible range) with oversampling – as Wadia shows.

 

And BTW, it's the sound that counts, not the measurements. Many (actually most) amps and DACs measure perfect yet sound significantly different (to my ears at least).

.


Edited by JaZZ - 5/31/10 at 6:48am
post #654 of 795

Quote:

Originally Posted by JaZZ View Post

Oversampling isn't responsible for the ringing, it's the filter implementation. You can prefectly reproduce the high-frequency characteristic of a NOS DAC (in the audible range) with oversampling – as Wadia shows.


I understand that - oversampling is there to avoid aliasing.  I think we've already had this conversation of why oversampling is pointless in this instance though.  One could have gone NOS and used the slow roll-off anyway - both the ringing (which is questionably audible) and the aliasing would be attenuated without even needing to oversample.

 

It seems redundant honestly.  Maybe I should have phrased it as "why even bother oversampling".

 

 

Quote:
And BTW, it's the sound that counts, not the measurements. Many (actually most) amps and DACs measure perfect yet sound significantly different (to my ears at least).

 

And there's DBTs that have shown different, but that's really besides the point.

post #655 of 795
Originally Posted by Shike View Post

I understand that - oversampling is there to avoid aliasing.  I think we've already had this conversation of why oversampling is pointless in this instance though.  One could have gone NOS and used the slow roll-off anyway - both the ringing (which is questionably audible) and the aliasing would be attenuated without even needing to oversample.

 

It seems redundant honestly.  Maybe I should have phrased it as "why even bother oversampling".

 

You're missing the point. Oversampling is the technically best implementation of an anti-aliasing low-pass filter independent of the filter characteristic. It enables the use of very few analogue filter components. There's no benefit from pure analogue filtering, if that's what you understand by NOS. Actually the term NOS is mostly used for completely filterless DACs which have the benefit of renouncing analogue filters with their signal-corruption potential after all. And since there are no higher frequencies than 22 kHz in the signal which could interact with the music signal in the form of aliasing (if it has passed a corresponding low-pass filter in the ADC), the only downside is ultrasonic noise which could do harm to voice-coils and maybe some electronics components.


 

And there's DBTs that have shown different, but that's really besides the point.

 

I don't do DBT for comparing gear, and luckily it's very hard to compare different DAPs that way. If I like the sound of a component better than another in real life, the purpose is served. You can't always get away with the DBT argument. I have different DAPs with different sonic characteristics – not even clearly better or worse – which are absolutely consistent. You can doubt that as long as you want!  

.


Edited by JaZZ - 5/31/10 at 9:14am
post #656 of 795

 

Quote:

If it is an oversampling design than I fail to see why they even bothered with the slow-roll off.

 

I'm a little puzzled by the slow roll-off. The DAC already implements a brick-wall filter so there's no point in the slow roll-off. It doesn't reduce Gibbs phenomenon since the filter slope is very high anyway, due to the brickwall. I can only guess that either it's a poorly implemented analog filter (unlikely) or it's intentional (also unlikely).

 

It's also possible that the guy that measured the FR, even though it was sampling at 96khz, had an anti-aliasing filter around 22khz in the recording chain.

post #657 of 795

Quote:

Originally Posted by JaZZ View Post

You're missing the point. Oversampling is the technically best implementation of an anti-aliasing low-pass filter independent of the filter characteristic. It enables the use of very few analogue filter components. There's no benefit from pure analogue filtering, if that's what you understand by NOS. Actually the term NOS is mostly used for completely filterless DACs which have the benefit of renouncing analogue filters with their signal-corruption potential after all. And since there are no higher frequencies than 22 kHz in the signal which could interact with the music signal in the form of aliasing (if it has passed a corresponding low-pass filter in the ADC), the only downside is ultrasonic noise which could do harm to voice-coils and maybe some electronics components.


I'm not talking about pure analog filtering, I'm saying the filter didn't even need to oversample.  NOS does not mean completely filterless DAC, without a filter you'd be begging for tweeter damage as you even mention.

 

NOS just means it doesn't oversample - and usually either has a brick wall filter (uncommon today with complaints of ringing) or slow roll-off.  It doesn't matter if it's digital or analog.

 

In fact, judging by your earlier arguments wouldn't this be the worst solution since it's adding pre-ringing with little to no benefit?

 

@b0dhi

 

It's either intentional or an oversight, the slow roll-off is a feature that can be enabled/disabled in the DF1704 (a digital filter).

post #658 of 795

Quote:

Originally Posted by Shike View Post

@b0dhi

 

It's either intentional or an oversight, the slow roll-off is a feature that can be enabled/disabled in the DF1704 (a digital filter).


Ah yes, that looks like the best explanation. df1704rolloff.png

Matches up pretty well from memory.

post #659 of 795

 

Originally Posted by b0dhi View Post

 

I'm a little puzzled by the slow roll-off. The DAC already implements a brick-wall filter so there's no point in the slow roll-off. It doesn't reduce Gibbs phenomenon since the filter slope is very high anyway, due to the brickwall. I can only guess that either it's a poorly implemented analog filter (unlikely) or it's intentional (also unlikely).

 

It's also possible that the guy that measured the FR, even though it was sampling at 96khz, had an anti-aliasing filter around 22khz in the recording chain.


The latter is imaginable – but I doubt that there's an ADC with a 22-kHz anti-aliasing filter at a sampling rate of 96 kHz. If it's a feature of the player, it is a technical flaw in my book. At least it's a missed chance of deriving advantage from the smooth roll-off.
 


 

Originally Posted by Shike View Post


I'm not talking about pure analog filtering, I'm saying the filter didn't even need to oversample.  NOS does not mean completely filterless DAC, without a filter you'd be begging for tweeter damage as you even mention.

 

NOS just means it doesn't oversample - and usually either has a brick wall filter (uncommon today with complaints of ringing) or slow roll-off. It doesn't matter if it's digital or analog.

 

It doesn't need oversampling, true, but there's no benefit from renouncing it either. Oversampling is the best, simplest and cheapest filter implementation, so it makes no sense not to use it. Wadia DACs use it – despite (in your understanding) their smooth treble roll-off.


 

...In fact, judging by your earlier arguments wouldn't this be the worst solution since it's adding pre-ringing with little to no benefit?

 

Yes, certainly – not specifically because of the pre-ringing, but because of the still high amount of ringing. Another reason for not being interested in this player. But I'm rather confident that I would appreciate its sound quality nonetheless despite the not so glorious technical data. They simply don't tell the whole story. Believe me!
.

post #660 of 795
Quote:
Originally Posted by JaZZ View Post

 


The latter is imaginable – but I doubt that there's an ADC with a 22-kHz anti-aliasing filter at a sampling rate of 96 kHz. If it's a feature of the player, it is a technical flaw in my book. At least it's a missed chance of deriving advantage from the smooth roll-off.
.


Agreed. But when dealing with oversampling there's always some trade-off. If you use slow roll-off you get higher aliasing. Less aliasing, more Gibbs. And it's not even certain to what extent either of these are audible (if at all). All these (and many other) "issues" would very cleanly disappear if music was recorded at 192khz in the first place. This is a much better solution, IMO, than the very sophisticated research needed to properly address the "audibility" question. Why answer a question when you can render it moot instead?

 

Sigh.

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