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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

Showing 9 responses by erik_squires

erik_squires OP
16,677 posts
 
In the Stereophile 2nd opinion review the reviewer specifically mentions that the Border Patrol sounds like the Benchmark, but with a vintage tube compressor inserted.

Good find, I missed it.

Also, given the difference in non-linearity and difference in listening experiences, I wonder if a major problem is manufacturing consistency in the R2R DAC?

Best,
E



erik_squires OP
16,677 posts
 
Anyway, I don't know anythiung for sure, I'm just spit balling about compresion, and air and dynamics.

I used to think more air = more linear. I'm not sure now. :)

erik_squires OP
16,677 posts
 
Apparently I like the decay and transparency of a typical DAC because I felt the Border Patrol sucked the life right out of my system.

If I interpret this as a loss of dynamics, it would be too much compression.

It’s not that it’s literally removed, but rather that the resolution of one is superior, allowing to hear deeper and wider into the soundstage, thus capturing the extremely minute character of the reflections off the walls of the venue. 


Which would be easier to hear with compression, not expansion.


erik_squires OP
16,677 posts
 
@kalali

Don't you think these effects could be explained by compression?

Best,
E


erik_squires OP
16,677 posts
 
I agree, that ears matter.

I do want to kind of emphasize that when I posted this thread I was using "linearity" as a very specific measure.

I don't mean to rehash all things about all measurements.

But, what if specifically, with DACs we prefer some compression at the bottom? Why not?

What if this is in fact correcting a problem in the ADC end?
erik_squires OP
16,677 posts
 
He is quite adamant that he heard musical information that was present on the master file and subsequently conveyed convincingly with the BP .

Yep, and looking at the measurements, the lack of linearity is an interesting clue, one which supports a hypothesis I have suspected before I even heard of the BP DAC:
DAC’s are too linear. Very linear DAC’s cut off faster. DAC’s with compression are more revealing, without the frequency response aberrations associated with "revealing" speakers.

I’m going to try to prove this in 2019. :)

Best,
E


erik_squires OP
16,677 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

erik_squires OP
16,677 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.


erik_squires OP
16,677 posts
 
But I do not think we can measure what Herb R. says is 'human sounding musical pleasures'.


In this case, I actually genuinely think we can. My hypothesis is that he is enjoying the compression at the bottom of the dynamic range.

I'm going to see if I can prove this. :)

Stay tuned.

E

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