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The Border Patrol DAC - Maybe linearity in a DAC is bad ... Spitballing

Hi Everyone,
I've been thinking about a few things related to DAC's and how they behave and how we hear. Also thinking about a couple of audiophile comparisons I've heard and how we interpret what we hear.

Let's talk about this simple measurement called linearity.

In a DAC what we mean is that as the magnitude changes the output changes the same amount. That is, if the signal says "3 dB softer" you want to get exactly 3 dB softer output on the jacks.

And with modern, top tier DACs this is usually really good until around -90 dB where noise becomes the limiting factor.

For a long time I felt that a DAC which allowed me to hear the decay of a note, so that it fades instead of stops suddenly was the mark of a truly excellent sounding DAC.

I'm wondering if what I'm actually hearing is compression? Lack of linearity.

The reason I bring this up is that I was reading a long article about the complexities of reviewing a DAC from Border Patrol. One of the main failings, from measurements, is that it is really not linear at all. Sounds don't get softer fast enough. And ... low and behold, Herb Reichert actually makes many comments about how much more he can hear with this DAC than with others.

I'm going to link to a critique of the "scandal" so you all can get a better look:


https://parttimeaudiophile.com/2019/01/06/border-patrol-dac-revisited-audio-fur/


Also, take a look at the linearity charts in the original review. Honestly, awful. Not up to what we expect in state of the art DACs today, but ....


https://www.stereophile.com/content/borderpatrol-digital-analogue-converter-se-measurements

What do you all think? Do we need a compression feature in DACs so we can hear more details? That would make more sense to me than a lot of the current fad in having multiple filter types.

Best,
E

erik_squires
erik_squires OP
5,268 posts
 
If the Border Patrol is manipulating the output signal to mimic a compressor, than it is not surprising that many listeners would like the effect. An analogy would be upping the contrast slightly in a video signal.

I don't think they are manipulating it so much as going with old school designs to make it happen. Based on the Stereophile measurements, I'm not even sure they know what they did. If they had, the L and R channels would be better matched.


nonoise's avatar
nonoise
4,382 posts
 

From the Stereophile review, a rebuttal from the first reviewer:

In order to answer that question, I have purchased and studied at least 80 genuine (analogue) “master tapes” taken directly from the archives of RCA. Many of them I played back on the exact Ampex machines they were recorded on (which I also purchased). Virtually all of them sounded VERY “pleasing good” and therefore, by your definition, must ALSO have sounded accurate good. In truth, I can’t remember hearing too many bad sounding master tapes.

For my reviews I always use high-res “master” files supplied to me by the recordist for that purpose. When I finished my BP/BM comparison, I told JA about my own “alarming audiophile episode” with Macy Gray’s HDTracks album “Stripped,” wherein the BP DAC reproduced pretty much exactly what I heard sitting behind the binaural head at the former church in Greenpoint and the Benchmark DAC3 which did not even get close. It conspicuously stripped away a huge amounts of what I and David Chesky know is on the recording.

I use Chesky recording sessions to review headphones because I can compare what I hear live to the sound coming off the so-called “mike feed.” The Border Patrol DAC reproduced the church walls, the reverb, the positions on the floor where the musicians were standing, and all the subtle breathiness of Macy Gray’s voice. With the Benchmark, the majority of that information (which is definitely on the master file and appears via David’s $100K MSB DAC and via my Holo Spring DAC) disappeared !!! Your neutral DAC “stripped” away information that is unquestionably on the master file. Not to mention the BM DAC made it sound hard cold and harmonically threadbare. I call this subtractive distortion. Did you measure any of that?  


It’s all in the ear of the beholder.

All the best,
Nonoise
erik_squires OP
5,268 posts
 
Nonoise:
Yes, and this part in particular catches my eyes:
I use Chesky recording sessions to review headphones because I can compare what I hear live to the sound coming off the so-called “mike feed.” The Border Patrol DAC reproduced the church walls, the reverb, the positions on the floor where the musicians were standing, and all the subtle breathiness of Macy Gray’s voice. 

I am wondering if this is not indeed compression, and that we like compression.

Best,
E

nonoise's avatar
nonoise
4,382 posts
 
Erik:
Don't let the objectivists hear you say that. They would consider it blasphemy and subject you to something jagged, or worse.  😄

All the best,
Nonoise
gwbeers
62 posts
 

These "meters vs. ears" discussions always remind me of the film-to- video evolution of the early seventies. I owned a well established film/video studio in Manhattan. I always got a kick out of the debates between the film directors and the video engineers. The video eng. would point to his monitors and scopes and prove the image was “picture perfect” in hue and luminence. “And you can see the threads on the buttons of his shirt!” And the director would scream “no-one can walk into a dimly lit room, open a window blind to sunshine, then crawl under a bed and not have a single shadow on them! The video eng. relished the technology and the film director looked for realism and emotion. I admit I like the dancing needles on McIntosh gear but, I find my enjoyment with the listening and pay little attention to the meter readings.


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