Review and Measurements of PS Audio PerfectWave DirectStream DAC

[LTig]

For filtering the DSD stream output yes, when converting the PCM there is a very steep linear phase filter applied which works really well judging from the measurements. So for PCM the reconstruction filtering is digital and the output filter is a post filter, similar function to that of a SD DAC.

Are you sure that the low pass behind the interpolation stage in an upsampler can be called reconstruction filter? AFAIK the reconstruction filter always is analog and behind the DAC chip.

I may be wrong though and would be glad for a link which corrects my view.

 

[Herbert]

Almost no setup in our homes will meet Amirs measuring conditions. My house is 100 years old an misses mains ground. The gear would even measure worse. As far as I understood, for 6k you will get no
EMI RFI filter, right ? Gosh, this was standard in early compact disc players !

 

[LTig]

As engineering quality, yes. As audibility quality, yes and no (yes only in the extremes). They are not synonyms. There is no consistent inference or correlation that can be derived about audibility experience from the equipment comparison tables published after every measurement based on SINAD, for example despite knowing anything else.

Agreed, one has to read the review before a decision. But this is also true for Stereophile reviews. Just read what they wrote in the article Recommended Components: 2019 Fall Edition.

I recall having seen a formular which weighs the different harmonic components to get a number which shall better represent the audibility of harmonic distortion. Regarding hum and noise an A-filtered value may also better represent SNR.

Maybe ASR should also use such numbers (separate for HD and SNR) for ranking of components. Why separate: if the numbers are bad such a unit may still work fine in certain circumstances. Bad SNR for example is no problem if you never listen loud and/or your speakers are ineffective. Bad HD may be no big deal if you listen to LPs only.

 

[LTig]

[..]
So, regarding, just addressing the input side of equation, transformer vs "electronic balanced"(transformerless) inputs, it's quite trick to design a direct balanced input circuit that does not complicate the harmonic structure of the distortion, and it takes, IMO, VASTLY less of the thus "disharmonic" distortion to be audible than a transformer's simple even-order harmonics. As long as the transformer is properly loaded by the succeding circuit, and is, of course, well designed, it's fairly close to impossible for it to be the cause of "bad sound" in any way. On the output side, choice between xfmr & xfmr-less is a heck of a lot more complicated, and xfmr is not very often the better choice.

I think I got it:

• On the input side the designer has the loading of the xfmr under control and can ensure that it is proper.
• On the output side this is not the case. The designer does not know what the user connects to this output. And it is not necessary to use xfmr in any output if all inputs have xmfr.

BTW, am I the only one here who finds the build quality & component choices in this dac quite bad for a $6k unit? For someone who blathers on & on about how important clean & abundant power is, Mr. McGowan's dac has a completely mundane & unimpressive main power supply, and power supply support among the circuit stages is nearly negligible, and of very base level quality. Seems like they blew the budget on custom chips & software and had little left for the rest of the build.

Probably the money was blown in listening tests and looking for a cheaper xmfr .... But you should not underestimate the costs of software development.

 

[solderdude]

Are you sure that the low pass behind the interpolation stage in an upsampler can be called reconstruction filter?

Pretty sure.
Only the very first CDplayers (no oversampling) had steep analog reconstruction filtering. Philips and later designs that had oversampling had part of it in the upsampling filter and a less steep analog reconstruction filter after the DAC.
This was possible because the DAC always operated at the same freq. 44.1 or its multiples.

Current DACs need to have a variable frequency filter for each different sample rate it would need to shift frequency to Nyquist.
This is practically impossible to make with pure analog reconstruction filters.
Digital and or switched capacitor filters can do this.
In case of OS DACs the reconstruction filter is in the oversampling part (as to not get mirror images) which should be steep to work well.
The question could be at what point (frequency) one can still consider it part of the reconstruction filter.
The oversampled output (in case of R2R) can be less steep and only need to 'smooth' the signal (partly reconstruction one could say) so steps are gone.
For DS that output frequency is yet much higher and the post filter only needs to remove the non essential noise.
In this case, AFAIK, the output is not DS (with a few bit levels) but a DSD stream (1 bit) at a very high frequency.
One that doesn't pass the transformer anyway and an extra capacitor is used so the transformer doesn't get much HF to begin with.
So only 'post filtering' to remove DSD switching frequency, which for DSD doubles as a reconstruction filter.
Don't know this for certain (that PS works that way) but is what I would do if I wanted to design in a similar way for some reason.

 

[LTig]

Are you sure that the low pass behind the interpolation stage in an upsampler can be called reconstruction filter?

Pretty sure.

Wikipedia says:

... the output of a DAC requires a low-pass analog filter, called a reconstruction filter - because the output signal must be bandlimited, to prevent imaging (meaning Fourier coefficients being reconstructed as spurious high-frequency 'mirrors'). ​

But ...

In case of OS DACs the reconstruction filter is in the oversampling part (as to not get mirror images) which should be steep to work well.

... if the main task of a lowpass filter in an upsampler is to remove mirror images then it may also be called reconstruction filter. See again Wikipedia:

Thus, the reconstruction filter smooths the waveform to remove image frequencies (copies) above the Nyquist limit. In doing so, it reconstructs the continuous time signal (whether originally sampled, or modelled by digital logic) corresponding to the digital time sequence. ​

 

[digititus]

I don't like the man's presentation style in the least, and I certainly don't trust his subjective listening impressions. However, I can tolerate him long enough to listen to/read his comments on functionality on the odd occasion, but only if I can't find such information elsewhere...

Darko is part of the business model. They need shill's to sell their wares. He is that shill. Just take a look at his top recommendations. Enough said.

 

[AudioSceptic]

Wasn't Ed the guy with the platterless turntable? So the record would be able to bounce around as it spun? Classic!

Not really platterless, just a tiny platter that supported/clamped just the record label. AT had a similar idea with the Sound Burger <https://www.vinylengine.com/library/audio-technica/at-727-sound-burger.shtml>

 

[GrimSurfer]

It is not right to make personal mockery, much less compare someone with a terrorist!!!

A little humor directed Ted's way is better than the truth: The man appears to be an unbridled hypocrite, which is the worst charge one can levy against another person.

He denigrates people based on age when he himself is clearly elderly and, in light of this and his career path, is almost certainly affected by hearing loss.

He questions a person's objectivity while he is in the employ of a company whose products he defends.

He dismisses technical shortcomings of his designs by attempting to belittle or dismiss those who point them out.

He touts a very expensive product whose measured performance is well below that of far more affordable alternatives.

If anything, my use of humour was a little too soft. Had I been objective, my criticisms would have been much more cutting and cruel.

So lighten up, @maty . My earlier post was being easier on him than he deserved. Besides, the parallels between the two are interesting at a certain level of abstraction.

Be honest: My [darkly humorous] point about non-ferrous component cases sailed over your head, didn't it?

 

[Bliman]

Agree.

The methodology is so key to the results and conclusion/s and I have seen questions asked:

https://www.superbestaudiofriends.o...c-deconstructing-amirs-hack-job-part-ii.6449/

I like this site but there is always that looming question about Amir's testing setup (not just which model AP) and methodology.

Amir says he can't write a bible for every product and that is perfectly understandable (obviously) but unfortunately the devil is always in the details.

That applies to Amir, to manufacturers (who leave out all the details sometime deliberately), to everyone.

That worries me.
I have come here because I wanted another tool in search of best value/performance gear.
Me personally doesn't know half what is written here. But I used his measurements to know how good a product is. Just like magazines use words to describe how good a product is.
But now I read on this other site that maybe the measurements are not done in the right way. This leads to a situation where I don't know what to believe anymore. Because I don't know all these technical stuff.
So it would be great if Amir would address these points.
Now it seems like there can be more different measurements taken and that the analyzer was not calibrated right. And we are again back at the start. Because then we have to choose whose measurements we believe. This is frustrating for someone with little knowledge.

 

[Bliman]

Oh yeah and I really really don't like the ad hominem attacks on this site and on the psaudio site. That is totally unnecesary and is pretty harmfull. We can always discuss things. It is very easy to get in a mudfight.

 

[Frank Dernie]

IMO, digital has been more accurate since it’s first commercial incarnation.

My experience too.
I have made recordings as a hobby for over 50 years and the first time I heard a recorder output indistinguishable by ear from the microphone feed was the first digital recorder I used.

 

[FooYatChong]

Because then we have to choose whose measurements we believe.

I had the same doubts in the sound good/measure good debate.

But in the rare cases where manufacturers publish their measurements, Amir's measurements usually confirmed them and if not, an explanation was found. So at least Amir knows how to do these measurements.

 

[LTig]

Now it seems like there can be more different measurements taken and that the analyzer was not calibrated right. And we are again back at the start. Because then we have to choose whose measurements we believe. This is frustrating for someone with little knowledge.

If @amirm's analyzer was not calibrated correctly then all other DACs and amps he has measured before and after the PS DAC should show similar bad performance. This is not the case as far as I can see. At least until September 10th (2 weeks ago) his analyzer was OK, see the measurements of the Monoprice Monolith THX 887 where the analyzer came close to its own limits. I'm sure that when @amirm remeasures one of the DACs in his possession the results would be very close.

 

[Ron Texas]

PS: imo, ad hominem attacks here are not better than the ones directed at Amir elsewhere. Let the measurements speak for themselves.

You think that bit of satire is an ad hominem attack? Get off your high horse and remember I was the one who defended our host.

 

[SIY]

But now I read on this other site that maybe the measurements are not done in the right way.

There was really no substantive criticism. And Amir has never hesitated to share project files so anyone can examine his results.

FWIW, we've both measured the same sample of at least two different pieces of gear and gotten essentially identical results.

 

[pkane]

Oh yeah and I really really don't like the ad hominem attacks on this site and on the psaudio site. That is totally unnecesary and is pretty harmfull. We can always discuss things. It is very easy to get in a mudfight.

IMHO, age is extremely relevant to a discussion with anyone who claims to have exceptional hearing abilities. It is important to know that designers that eschew measurements for listening tests rely entirely on their hearing, and it is a fact that hearing deteriorates with age. It is not a personal attack to discuss the age of a DAC designer who says he designs by listening. Posting his photo here may or may not be considered a personal attack, but that depends on whether you think he looks funny, and is thus, subjective

 

[Ron Texas]

I can't believe nobody has commented on the questionable hearing capability of influencial Darko

https://darko.audio/the-darko-dac-index/

well, indeed always aligns with the price tag.

I always thought Darko's claims here were absurd.

 

[pozz]

@audimus Have you looked at existing psychoacoustic research? TBH, I think you should start another thread since this isn't really about the reviewed device at this point.

 

[SIY]

Posting his photo here may or may not be considered a personal attack, but that depends on whether you think he looks funny, and is thus, subjective

I would have commented on it except that my Arizona drivers license arrived yesterday and the photo of me on it was... mock-worthy as well.