INTERNET BLIND TEST: Linear vs. Minimum Phase Upsampling Filters

I. Introduction

Ladies and gentlemen, audiophiles of all ages; you have probably seen pictures like the ones above many times in the magazines, posted online, etc. You know that many DACs these days feature the ability to adjust the way the antialiasing reconstruction filters are "tuned". I remember reading about and becoming fascinated by the different filters back in 2006 with Keith Howard's article on Stereophile. But it wasn't until around 2009 that I noticed Meridian started using minimum phase settings in their equipment like the 808.2 Signature Reference CD player. (I don't know if many other consumer audio devices used a form of the minimum phase filter before 2009; perhaps not as well advertised as Meridian?)

PERSPECTIVE: Poll - Upgraded USB and Sound?

I enjoy visiting the Steve Hoffman Forums for perspective. I think it's probably one of the most balanced places to hang out at. Of course, as in any audio forum, there will be a number of heated arguments here and there, but overall, it's great to see a place where heterogeneous music lovers of various experience levels and beliefs can congregate, share tips, and get advice... It's certainly one of the more vibrant audio communities out there!

Recently there was an interesting poll on whether USB cable upgrades can improve a system's sound quality. Titled "The Great USB cable debate poll" (full disclosure, I took part and posted a comment as well), it ran from February 22 to March 8th before it was closed. In total, it received 415 votes, gathered 36 pages of responses and the outcome was:

About 1/4 felt that upgraded USB cables make a difference, and 3/4 did not. Surprised?

ANALYSIS: DSD-to-PCM 2015 - foobar SACD Plug-In, AuI ConverteR, noise & impulse response...

Noise characteristics of PCM vs. DSD - image found here.

In my post last week looking at the various DSD-to-PCM converters, Solderdude Frans made a good suggestion... Let's have a look at the newer SACD plugin which has superseded the DSDIFF plug-in as the converter of choice these days for foobar. Also, it was suggested by Yuri Korzunov, the author of AuI ConverteR 48x44 to have a look at his converter package as well.

ANALYSIS: DSD-to-PCM Conversion 2015 - Windows & Mac OS X

Impulse Response: One of the talking points from back in the day as a selling point for DSD... Yup! DSD can better reproduce a 0.000003 second "click". Source: Merging Technologies

I. Preamble

It is amazing how quickly another year has passed. About this time last year, I posted the first comparison of DSD Encoders and Decoders "shoot-out" of sorts comparing Weiss Saracon 01.61-27, KORG AudioGate 2.3.3 and JRiver 19.0.117 in terms of quality - both encoding and decoding fidelity using the RightMark Audio Analyzer software. The idea was to determine which of the three created DSD files from an original 24/96 PCM test signal and then decoded it back to 24/96 in a way where there was as little change in terms of distortion, flat frequency response, and lowest amount of added noise.

Perhaps not surprisingly, the expensive Weiss Saracon software sets the standard as the most consistent DSD encoder that resulted in the best output once decoded. The differences in decoding capability appeared to be very minor (questionable audibility between the 3) but objectively, both Saracon and JRiver 19 were on par and the free AudioGate 2 somewhat "noisier" in terms of the PCM output (I speculated this was due to stronger dithering algorithm).

Well, another year has passed in terms of software upgrades to DSD decoding and I was interested to compare the decoding capabilities as of late. We have brand new versions of JRiver and AudioGate now, plus I didn't get to test foobar with the DSDIFF plugin last year. Plus we now have DSD decoding on the Mac OS X available with XLD and commercially with DSD Master.

MUSINGS: Gone 4K / UHD - A "Look" At Ultra-High-Definition...

This week, I thought I'd take a break from just the audio stuff and discuss a new "toy" I got 5 weeks ago. That's right, as the title suggests, a 4K / UHD screen; it's a computer monitor to be exact:

A view from behind the commander's chair :-). BenQ BL3201PH on the table.

Remember that there's a separate "body" defining 4K movies at the local movieplex - the Digital Cinema Initiative (DCI). They have "true" 4000 pixel horizontal resolution like the 4096x1716 (2.39:1 aspect), or the very close 3996x2160 (1.85:1) resolutions. Whereas for the smaller screens like computer monitors and TV's, we have the UHD "Ultra High Definition" standard defined as 3840x2160 (16:9 / 1.78:1). So although it's not exactly "4K" horizontally, it's close and I guess "4K" is a better advertising catch-phrase than "2160P". Needless to say 3840x2160 is 2x the linear resolution of 1080P or 4x the actual number of pixels.

MUSINGS: Audiophiles "Us vs. Them" (Objectivists vs. Subjectivists) Attitudes and Envy!?

Since I'm stuck at LAX on my way home from a wonderful Spring Break with the wife and kids down in Texas as well as a Caribbean cruise, I thought I'd polish my response to Hal Espen's comment in the last post... BTW, I enjoyed visiting Bjorn's in San Antonio just to see the audio and home theater gear they had on display. Some really nice stuff and it looks like they're upgrading their main demo room to Atmos soon. I appreciated the knowledgeable staff and friendly attitude; taking time to demo the gear even though they knew I didn't even live in the USA.

So Hal, nice comment:

Pure confirmation bias from beginning to end. None of this really exists. : )
You can't have it both ways. Either your blog is about providing the little bursts of brain chemicals that us vs. them skeptics receive when scientism is seen to be crushing audiophilia, or you're going to go wafting into the subjective realm of the subtle and imaginative "classy" pleasures of reproducing music electronically, as you do with evident misgivings here.

Which side are you on, boys? Which side are you on>

Gets right to the heart of some of the heated debates and arguments I suppose... I guess I "swing both ways" in some regards. :-)

2015-02-27: HiFi Centre Grand Reopening...

About a year ago, I reported on the B&W Nautilus demo at the HiFi Centre here in Vancouver. That was at their old location... As of late February, they're now in the new place near Vancouver Chinatown and to celebrate, they had a nice (re)opening event (February 27, 2015). It caught some publicity from the Stereophile web site as well.

I decided to go check it out after work on the Friday and see the new space. For fun, here are a few cell phone snapshots of some of the gear on display. Note that it was well attended and I purposely tried not to take shots with people in them to protect the innocent :-).

Upon entering the main building, we see a Nautilus "shell" display; HiFi Centre has always had a good partnership with B&W:

MUSINGS: Audio Quality, The Various Formats, and Diminishing Returns - In Pictures!

Let me be the first to say that graphs and charts where audio formats are plotted out in terms of unidimensional sound quality ratings are ridiculously oversimplified and can be very misleading! However, they can be fun to look at and could be used as bite-sized "memes" for discussion when meeting up with audio friends or for illustration when people ask about audio quality.

Since they're out there already, let us spend some time this week to look at these visual analogies as a way to "think" about what the authors of these works want us to consider/believe. I'm going to screen capture without permission a couple of these images to explore. As usual, I do this out of a desire to discuss, critique, and hopefully educate which I consider "fair use" of copyrighted material; as a reminder to readers, other than a tiny bit of ad revenue on this blog (hey, why not?), I do not expect any other gain from writing a post like this.

First, here's PONO's "Underwater Listening" diagram released around the time of the 2014 SXSW (March 2014):

PONO: Underwater Listening

Others have already commented on this of course (here also). I don't know what ad "genius" came out with this diagram, but it is cute, I suppose. I remember being taken aback by this picture initially as it's so far out of "left field" (creative?) that I felt disoriented when I first saw this thing...

How audio formats would evoke a desire to compare underwater depths remains a mystery to me. Obviously, there's a desire to impress upon the recipient two main messages - a direct correlation between sampling rate (from CD up) with quality, and to make sure the MP3 format gets deprecated as much as possible (1000 ft?!). On both those counts, this image gets it so wrong, it's almost comedic. Clearly, one cannot directly correlate samplerate and bitrate with audio quality because the relationship isn't some kind of linear correlation. Why would CD quality be "200 ft", and 96kHz "20 ft"? Surely nobody in their right mind would say that 96kHz is 10 times perceptually "better". Sure, there is a correlation such that a low bitrate file like 64kbps MP3 will sound quite compromised with poor resolution, but without any qualification around this important bitrate parameter, how can anyone honestly say that all MP3s sound bad? I might as well say that Neil Young's a poor-sounding recording artist because the Le Noise (2010) and A Letter Home (2014) albums are low fidelity.

MEASUREMENTS: The Intercontinental Internet Audio Streaming Test...

Time to go intercontinental. :-) [Scene from the old movie War Games.]

After the ethernet cable results last week and the absence of any difference, there was discussion about an extreme internet music server test. What if instead of maybe 100 feet of ethernet cable from server to player, we had thousands of miles of cables in between?

With help from Mnyb from the Squeezebox Forum, we were able to orchestrate a test to demonstrate the extremes of measured performance with the server system basically on the other side of the world. He lives out in Västerås, Sweden approximately 100 km from Stockholm. A direct distance of:

MEASUREMENTS: Ethernet Cables and Audio...

Remember folks, this is what an "ethernet frame" looks like. It's data. There is no "music" in there until decoded and prepared for the DAC! Notice the CRC bytes for error detection. (The numbers represents how many bytes for each segment.)

0. Preamble

Hey folks, over the years, I have been critical of high-end audio cables... Previously, I have shown that RCA analog interconnects can result in measurable differences with channel crosstalk changes with long lengths. But the digital interconnects themselves do not result in measurable differences even in terms of jitter (TosLink SPDIF, coaxial SPDIF, or USB). Although my HDMI receiver's DAC isn't as accurate or jitter-free, different HDMI cables don't seem to make any measurable difference either. The only caveat to this being that a digital cable can just plain fail, in which case the distortion to the audio signal has a particular (annoying) characteristic which is clearly audible and not a subtle change (eg. a poor USB cable sound).

So far, I have not seen any further measurements to suggest my conclusions are inaccurate. I have seen audiophile reviewers and forum posters still claim digital cables make an audible difference and when questioned they provide lots of words but no actual empirical evidence. It has been awhile since I've seen any articles claiming objective evidence for cable measurements - haven't come across new ads or audiophile articles although of course I may have missed some.

However, as computer audio expands, there will be opportunities to "brand" more hardware as somehow "audiophile approved" and companies that make audio cables likewise will naturally capitalize on new lines of interconnects / cables... And as expected, cost of these things will be commensurate with "premium" products.

Which brings us to the concept of "audiophile ethernet cables" (see here also, and recent mainstream press exposure of the "madness"). Let me be clear. If I have issues with USB cables, or SPDIF cables, making any significant contribution to audible sound quality (assuming again essentially error-free transmission of data), there is no rational explanation whatsoever that ethernet cables should make any difference. The TCP/IP protocol has error correction mechanisms that allow for worldwide transmission integrity (otherwise Internet financial transactions should be banned!),  and is asynchronous so there is no temporal dependence on exact timing mechanisms (jitter not an issue with adequate buffer to reclock and feed the DAC). So long as the "protocol stack" is functioning as it should between the devices, there will not be any issue. Systematic errors causing audible distortion either means hardware failure or poorly implemented communication software. Therefore the expectation if we were to test or "listen to" different ethernet cables is that there would be no difference.

Since I like to make sure objectively, let us at least run a few tests to see if indeed evidence can be found to support the hypothesis.

MEASUREMENTS: Bob Dylan's "Shadows In The Night" - when 24-bit HRA isn't! (Qobuz)

Of shadows... and hot air...

A reader gave me a tip about the new Shadows In The Night album from Bob Dylan. The allegation is that the 24-bit high-resolution downloads of this album are in fact NOT true 24-bits as claimed!

To start, here's a video to show what the inversion-null should look like with a true 24-bit audio sample:

MUSINGS: The ongoing Vinyl vs. Digital debate...

The always assertive Batman. But assertiveness isn't necessarily correct...

(Just a shortish post this week... I've covered much of this in the past.)

As I mentioned in the comments section of the previous post on HRA, there have been discussions recently again around the sound quality of vinyl compared to CD. I assume it started from this article "Why CDs May Actually Sound Better Than Vinyl" from the L.A. Weekly. Overall, I think it's a good article! Some excellent quotes from veterans in the audio engineering business like Bob Clearmountain and Bob Ludwig. We even have the pleasure of an interview with James T. Russell - the "father" of digital optical media. Folks... These people know what they're talking about, so do not take their comments lightly.

Despite the fact that there's nothing ground breaking in that article, it's no surprise that the vinylphiles are up in a tizzy. Michael Fremer has now dragged out an old 1996 article about "Does Vinyl Have Wider Dynamic Range Than CDs?" (the PDF in the article). Let's talk about this...