MUSINGS/HOW-TO: Raspberry Pi 4 "Touch" Audio Streamer, and CRAAP settings! ;-) The decline of public feedback, virtual showrooms, value-added content and Darko Audio?

Left - Raspberry Pi 4B, Right - Raspberry Pi 3B. Heatsinks installed on both boards.

Back in August, I wrote an update on building and running the of Raspberry Pi "Touch" audio streamer with RoPieee software. The article was still written with the Raspberry Pi 3B(+) in mind.

Well, on Prime Day recently, I was able to get a Raspberry Pi 4, 4GB "Starter Kit" for a price I could not resist. It's nice to have all the parts including the appropriately sized heatsinks, ready-to-use microSD card, and 5V/3A USB-C power supply. For now, I have no need for the Pi 4 case and the micro-HDMI cables can go in my box of miscellaneous cables.

For audio streaming purposes, a basic 2GB Pi 4 kit (<US$55) would be even cheaper and works just as well. Given the minimal difference in cost, no point going with a 1GB model although that would still be fine - remember the Pi 3 was limited to 1GB. There is also an 8GB Pi 4 but that's a huge amount of memory for just an audio streaming "appliance"!

Musings/Measurements: quasi-Spinorama "qSpin" & the KEF LS50 bookshelf loudspeaker...

Auditioning the KEF LS50 Black Edition, powered by SMSL SA300 Class D amp on computer workstation.

With autumn here, sunlight hours reduced and looking towards the rainy months ahead, I thought it would be good to start expanding measurements and be a bit more "serious" with evaluating loudspeakers.

As you know, speaker measurements have been done since the start of the audiophile hobby and there are all kinds of ways to get the job done to varying levels of precision and reliability. Stereophile has been doing this for years with John Atkinson's use of the MLSSA (DRA Labs) system as he summarized in this review which formed his 1997 AES paper. More recently, it's great to see Audio Science Review's use of the Klippel Near Field Scanner (NFS) for many speaker measurements already!

For many of us interested in speaker performance, probably introduced to the ideas with Floyd Toole's book Sound Reproduction - Loudspeakers and Rooms (first edition 2008, now in 3rd edition 2017), there has been a rise in loudspeaker measurements using the "Spinorama" technique. This measurement method plus its standard representation of data has since becoming codified in the ANSI/CTA-2034-A "Standard Method of Measurement for In-Home Loudspeakers" (you can get a copy of the current CTA-2034-A R-2020 here), first published in 2015.

Further Explorations into "Intersample Overs" - Resampling/Downsampling & De-Clip by Charles King

Greetings everyone. It's great to interact with some of you over the years around contents I've posted in this blog. As you perhaps know, recently, I talked about resampling hi-res audio files in my article on "Post-Hi-Res" with the idea that the vast majority of albums we download as supposedly high-resolution content simply do not warrant the file size or bitrate. As such... I routinely just bring them back to 16/48 or 16/44.1.

Here's an interesting comment by Charles King on this and his explorations of the topic:

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Hi Archimago,

I was a bit taken aback on reading your 25 July post in which you talked about a need to guard against intersample overs when downsampling hires files. I've collected quite a few albums in hires over the years, often to check if I could hear any difference (I can't, and have given up on that) or to see if they provided better mastering (occasionally true, though in some notable cases the mastering is audibly worse). Since I don't want to litter my long-term storage with gigabytes of useless data I end up downsampling these to 16/48 in Adobe Audition (which is rated as having one of the better resamplers) and then compressing to variable-rate AAC (which is transparent to me).

HOW-TO: CD Pre-Emphasis & Using SoX De-Emphasis. (And the decline of physical media with vinyl revenue > CD now.)

Have you ever ripped or downloaded an old music CD that just sounds way too harsh? Sounding like the EQ is accentuated with too much treble?

Back in the day, a number of CDs were processed with pre-emphasis used and we can see at least a partial list of pre-emphasized albums here. Typically these would be early CDs from the mid-'80s although as per the list there are also a number from the late '80s and even early '90s.

In those early years, DACs were incapable of true 16-bit resolution and noisy analogue brick-wall filters added high-frequency distortions. As a means of improving signal-to-noise, they boosted the high frequency content and corrected the tone on playback (see this Hydrogen Audio FAQ on Pre-emphasis). As you're probably aware, a CD doesn't just contain the 16/44.1 audio data but have encoded within each "frame" 8 bytes of CIRC error correction and another byte of "subcode" data which can be thought of as "control data"; like a precursor to today's much more complete metadata. One of the subcodes is the "pre-emphasis flag". When activated, a CD player will engage its "de-emphasis" circuitry/filter. These days, DAC chips themselves can implement digital de-emphasis as part of basic functionality.

MEASUREMENTS: RME ADI-2 Pro FS R Black Edition as DAC.

 

Well friends, it's time to publish some measurements of my new RME ADI-2 Pro FS R Black Edition ("FS R BE") unit as DAC. For background, refer to the Preview from August and a couple weeks back, I had published results discussing the ADC function.

As you might be aware, since 2018, I've been using the older RME ADI-2 Pro FS ("Pro FS") for ADC and DAC duties in my measurements. It has performed like a champ and in fact, given that the ADC function is almost identical between the two units, there's certainly no reason to retire the "Pro FS" from measurement duties.

What we know is that as a DAC, the "FS R BE" should perform better than the "Pro FS" due to the fact that the internal AKM chip has been upgraded to the AK4493 from the previous AK4490. On paper, this represents a +5dB improvement in SNR and +1dB improvement in THD+N so we're not looking at Earth-shattering differences in specs numbers. Let's see if we're able to measure these differences on the test bench and identify any other changes to the DAC's performance along the way...

As We Hear It: Thoughts from an audiophile friend on assembling his sound system.

Every so often, I have the pleasure of having friends and readers add their thoughts to these pages. The other day my buddy whom I visited at the end of 2019 (a.k.a. "linnrd" online) sent me this discussion piece. Back in December when I visited, I invited him to take the opportunity to write about his equipment and how he came to this interesting collection of gear. Well, he delivered...

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A Complex Path to Simple Sound

Audio systems are generally an assemblage of products from different manufacturers. While significant R&D resources go into designing the various pieces that make up a system, it is left to the consumer to deal with the "R&D" of system design from "soup to nuts", as it were. The popular audio press is more oriented to singing the praises of individual components instead of educating and helping the reader actually assemble a decent combination of the aforementioned. Perhaps this a result of whom they view as customer and who as the product. A graveyard visit allows one to see much touted wonders such as Shakti Stones and the green CD marker (Ed: also see Harley's extensive investigation in Stereophile in 2004 amounting to nothing of course), to name just two, with the rotting corpse of MQA lying in wait for a plot (in both senses of the word!). 

Unfortunately, the self-proclaimed experts actively ignore existing knowledge and science and make it extremely difficult to fix this fundamental problem of the spread of misinformation by also subscribing to junk science. In other words, they are really messing up the S:N ratio of information transmission. As Bill Whitlock from Jensen says, reiterated in a recent discussion: "It often feels like an uphill battle to educate in a world of marketing deception and self-appointed experts."

MEASUREMENTS: RME ADI-2 Pro FS R Black Edition as ADC.

About a month ago, I posted this preview of the RME ADI-2 Pro FS R Black Edition AD/DA converter. It has been a wonderful month of simply listening to this device without a care around performing measurements. For listening, I have it set up as per the image in my sound room with the Raspberry Pi "Touch" running RoPieee previously discussed.

So far, from a subjective perspective, it has been a joy to listen to music with this machine.

Alas, as a "more objective" audiophile, it came time to have a look at the performance for this device to check if I'm missing any significant limitations. Over the years, I've discussed limitations to human hearing as well as the idea that many of our audio electronics these days have surpassed human auditory perception such that while measurements of DACs or amplifiers can show limitations, often these are beyond the resolution thresholds of human hearing/perception. Remember that while not all measurable anomalies need to be chased after when the goal is simply to be able to enjoy music, technical "ideals" are useful for devices one may want to use as a "reference".

So to start, today let's just focus on the ADC side of this RME device. Remember that the RME ADI-2 Pro FS R Black Edition (again, let me just call it the "FS R BE" for short) is an evolutionary step from the ADI-2 Pro FS ("Pro FS") that I started using 2 years ago. Consider this article as building on some of what we already know about the Pro FS as an ADC from 2018 with requisite repeated tests comparing the two machines and using today's software.

SUMMER MUSINGS: Modern Tech Life; obligatory home computer mechanic - NVMe replacement, WiFi Router. And thoughts about "high end", high priced DACs and value (Recent Darko & Sircom).

I was actually planning to just take a little break this week but given that it's almost September, I'll be away for Labour Day and school's starting for the kids with likely some virtual elements, I thought I'd just pen a not-too-long post not so much about audio but rather the highly computer-dependent world we're living in (with a bit about audiophile stuff to end).

SUMMER MUSINGS: The Soundroom - speaker layout, vibration control & correction. (And importance for the subjective reviewer!)

I thought before summer's over, it was time to "shoot the breeze" again and talk generally about a very important topic that affects all of us audio enthusiasts with what I hope are some practical suggestions from my own "journey" here at home.

The image above of a room set-up came from an article back in 1960 entitled Room Acoustics for Stereo by Abraham B. Cohen (Electronics World, January 1960 - make sure to also check out Part 2 here from February 1960). This was a time when many homes were still transitioning from the monophonic single-channel era to the bold new world of stereophonic "3D" playback with an opportunity to virtually experience an actual soundstage in the comforts of the living room. Those must have been exciting times, perhaps comparable in my lifetime to the late '90s with the release of AC3/DTS receivers providing discrete multichannel home theater.

As you can see from the pair of articles, already back in 1960, the groundwork had been laid out for what constitutes conditions for good "stereorama" sound. Best practice tips to achieve a sense of realism, the variables related to speaker placement in a room, angles to target for from the sweet-spot, distance between speakers and orientation like toe-in. Room characteristics like absorption characteristics of materials, reverberation time, room layout were discussed as well; all this informed by decades of professional recordings and studio design that came before.

RETRO-MEASURE: Pioneer SX-880 receiver (1978). And the amplifier "THD Wars" of the '70s?

Back in the 1970's, Pioneer among various Japanese brands like Sansui, Sony, Yamaha, and Technics brought popular, budget-conscious audio gear to the masses. With the prices of solid state components dropping, these amplifiers powered many college parties and brought music into the homes of many audiophiles of that generation.

Check out this ad from back in the day featuring the Pioneer SX-780 (45Wpc):

Nice to see that the idea of "high-fidelity" featured prominently rather than some nebulous idea of "high end" audio. Today, let's measure and discuss the sound of the last in the Pioneer SX-800 series of receivers, the Pioneer SX-880 featuring up to 60Wpc into 8Ω. The SX-880 came out in 1978 with a retail price around US$425. Thanks to a large part to central government mismanagement... err... inflation, this would be about US$1700 2020 dollars which would buy a rather advanced multichannel receiver like the Denon AVR-X4500H these days.

DIY: Raspberry Pi "Touch" Audio Streamer (2020) and RoPieee - US$160. Spectral tilt, educational articles, and anti-audiophoolery...

It has been awhile since I built my Raspberry Pi "Touch" Streamer discussed back in 2017. We're here now in 2020 and I had the need to put another one together. Since 2017, I've been using Roon more than Logitech Media Server (LMS) in my sound room so I thought I'd focus on installing RoPieee for this article although piCorePlayer remains my preferred software for LMS use (I still have LMS running on a Linux VM on my Server machine for remote playback of music away from home).

Build price for this simple Pi USB streamer is very reasonable. Based on Amazon US$ prices at the time of writing:

Raspberry Pi 3 B+ - $42
AC Adapter 5V/3A with switch (microUSB for Pi 3) - $10
Official Raspberry 7" touchscreen - $64
SmartiPi Touch 2 case - $30
SanDisk 64GB microSD - $13 

RoPieee software - donation-ware download, your choice "standard" or "XL"

Grand total of <US$160 for this USB audio streamer with 7" touchscreen.

PREVIEW: RME ADI-2 Pro FS R Black Edition AD/DA Converter

Look what showed up at my door (finally!) the other day. This is the latest hardware update to the RME ADI-2 Pro line of converters, the RME ADI-2 Pro FS R "Black Edition" - quite the mouthful! Let's just use "FS R BE" for the rest of this article for short in reference to the name.

Currently, the street price is around US$2,000.

Back in mid January, RME debuted this latest iteration of the ADI-2 Pro at NAMM 2020. Since 2018, I have been in contact with Matthias Carstens (co-founder of RME) off and on about the ADI-2 Pro FS that I have been using for measurements on this blog. Shortly after NAMM, I contacted Matthias about getting an upgrade as I could use two of these ADI-2 Pro devices - one for the soundroom and another for my test bench - when the company starts shipping these.

SUMMER MUSINGS: Post Hi-Res Audio. Why hi-res is often not for the best. Resampling, dithering and de-clipping.

It has been a good summer around here thus far with time off, working around the house, and of course time to enjoy the warm weather for a bit. Here in Vancouver, the late fall to early springs are typically dark and rainy so I'm happy to catch a few photons when I can :-).

With the pandemic, this will certainly be an unusual summer/year. Unless things change substantially, this will be the first year in 2 decades that I won't be traveling off the continent for vacation or work - heck, I can't even visit the USA at this point without at least 2 weeks of self-quarantine back in Canada. In that spirit of staying put and cleaning up this year, I thought I'd talk about a few related items that have been on my mind pertaining to my music library.

A few months ago, I wrote an article about remembering that for home audio, we must always think about the big picture triad of PRODUCTION - REPRODUCTION - PERCEPTION. So often, we in audiophilia spend disproportionate amounts of time on the hardware aspects of reproduction (what's new? how do these devices measure/perform?), or speak of subjective perceptual experiences. Much of that I think is a reflection of what our magazines, online sources, and forum topics revolve around. Maybe that's what the Industry also wants us to think/talk about. We so often forget that in fact, a huge amount of what we perceive - or can perceive - has already been "baked into the cake" from when favourite recordings left the studio (or perhaps specifically the mastering engineer's workstation).

OWNER'S COMMENTS: Pass Amp Camp Amp (ACA) 1.1 by Mitch Barnett

[What follows are comments from Mitch Barnett, the owner of the Pass Amp Camp Amp 1.1s that I listened to and measured. I appreciate Mitch's input on the matter, it's a great example of how owners of the ACA might put them to use in one's system, recognizing one's needs.]

Thanks Arch for the great time with your family for a fun night of good food, wine and of course music and movies. Great job on the objective measurements and subjective listening impressions, “It actually sounds good…” with the caveat of not asking too much from the amp. In my mind, this is the dichotomy between objective measurements versus what sounds good to our ears.

MEASUREMENTS: Pass Amp Camp Amp (ACA) 1.1. The crossroads between objectivism and subjectivism, and reconsidering von Recklinghausen.

Back in 2012, Dana Brock, Nelson Brock, and Mark Cronander (aka Variac) organized an "Amp Camp" in Northern California at the Brock's ranch. Nelson Pass, well known among audiophile circles, contributed with one of his designs and I'm sure they all must have supervised the participants as they went about soldering and building those first kits. The result was a simple, solid-state, Class A amplifier to take home. This amp was of course the Amp Camp Amp (or ACA) which we'll be talking about and measuring here.

You can see Pass' article introducing the amplifier with schematics and measurements. What a great idea! There is no substitute for the value of experience and the memories of building something, especially while sharing with a loved one; regardless of the subjective or objective performance of the final product.

The ACA has developed a healthy following over the years - check out the long-lived discussion thread on diyAudio. Nothing official, but I heard over the grapevine that there have been >2000 kits sold, suggesting conservatively >2500 actual stereo amps out there with no accurate way to estimate non-kit PCBs, unofficial "clones", or just completely DIY builds with the published schematics.