GUEST POST: A Raspberry Pi Music System that Punches Above its Weight - Wax by Jeffrey Barish

[Hey everyone, the community of Raspberry Pi audio applications has grown tremendously over the years! SBC's similar to the Pi running on Linux OS are almost ubiquitous inside streamer components these days. Jeffrey Barish recently contacted me about his novel software which looks like a fantastic system for managing a music library that imports art, rich metadata, and other information that can be run in a small all-in-one box with DAC output! Here's his write-up and introduction to Wax.]

Using a Raspberry Pi as the basis for a music system is not novel. Raspberry Pi OS is based on Linux, so at least 20 audio player programs should be compatible. If you listen only to pop and you are satisfied with a program that allows you to simply select and play an album, then you will probably be satisfied with almost any of these programs. However, if you are a serious music lover – and especially if your collection includes classical music – then you are probably looking for more.

Serious music lovers like to know something about the music they are playing. They like to know the identities of the artists performing the music. These capabilities are available in some proprietary solutions, but those products are expensive, they might require additional components (e.g., a DAC or disk drives), and some require that users pay an ongoing fee. This article describes a new program for the Raspberry Pi that provides an inexpensive solution with these and many more capabilities.

Pacific Audio Fest 2024: Part III - parting thoughts, audiophile education, speaker:amp price ratio & the future?

Hypothetical scene in Seattle...

Another year, another Pacific Audio Fest in the annals of audio shows. Looking back, this show would be the 6th of this sort I've attended and subsequently discussed on this blog over the last decade, let's see:

Vancouver Audio Show 2015

Vancouver Audio Show 2016

Rocky Mountain Audio Fest 2019 - final RMAF
[Pandemic Years]

Pacific Audio Fest 2022

Pacific Audio Fest 2023

It's interesting reviewing some of those others over the years. I think most audiophiles will recognize that over time, not really much has changed, has it? Sure, the companies come and go, we've seen the ebb and flow of themes both in this blog as well as at the shows (for example, jitter was more of an uncertainty when AudioQuest introduced their JitterBug device in 2015). We've seen the rise of "high-end" computers and streamers (also discussed here), and these days I noticed that the companies are not as aggressive in the marketing as these products mature. Streaming may have reduced the need for local libraries, or simply that consumers themselves are comfortable with digital audio quality, the lack of sonic difference (and the "Bits Are Bits" reality).

The Dolby Atmos Music Target Curve. And on being an audiophile "tonmeister".

[For the post this week, let's take a pause from the Pacific Audio Fest 2024 discussions (last 2 weeks). Next week we'll have a Part III discussion about audio shows.]

Standardization is generally good.

I've discussed in previous posts that Dolby Atmos defines loudness characteristics for recordings and this has helped preserve dynamic range in multichannel/Atmos albums following their guidelines. Likewise, we can benefit from standardization of the frequency response as this will allow us to better "translate" the sound from the studio into our sound rooms. This idea is not new for audiophiles. The ill-fated (with good reason) MQA promised that we could experience the "sound of the studio", but they never could deliver in a large part because there was never any standardization for essential parameters like the frequency response, among other failings. In the same way, back in the day (~2014), this was the promise of hi-res audio by Neil Young and Pono that you would somehow get the "finest digital copy" and this would represent the sound the artists intended from the studio; clearly they overpromised and under-delivered by 2015.

It's one thing to standardize between the studio and home ("inter-system") playback, but it's also important to standardize "intra-system" - that is, between all the speakers in your set-up when you're doing multichannel such that each speaker is calibrated to the same timbre. This is important in a multichannel layout since we do not want "objects" moving through space changing tonality because of mismatch between speakers around the listener. The Dolby Atmos Music Target Curve is Dolby's recommendation for the music studio frequency response. This curve evolved from the X-Curve, an 'X'perimental frequency response based on some early empirical work exploring the performance of actual theater sound systems starting in the 1970's, and evolved over the years. See this paper for more details, note some similarity of the Dolby Atmos Music Target Curve to the SMPTE 202M - 1998 X-Curve.

As with all things in audio, nothing wrong with asking whether this curve is the "best". 🤔

Pacific Audio Fest 2024: Part II. [About that MACHINA DYNAMICA, and mental health. 🫣]

PAF'24 - the balcony shot on a Sunday afternoon as things start to wrap up...

So let's continue with the September 6-8, 2024 Pacific Audio Fest show-and-tell (Part I last week) at Seattle. These are my visits to the rooms on Sunday September 8th. You've probably seen from my previous show reports that Sundays tend to be less busy than Fridays and Saturdays. Often this is not a bad day to visit because it means that the crowds are smaller, you'll be able to linger a bit longer to enjoy the music, are more likely to be able to request music, and the reps are easier to access if you have questions (or concerns). It's also a good day to make deals since many rooms would rather sell you the gear than pack stuff up and take home that evening. I know some folks scored some barely used room treatments.

Let's spend some time on Wing 2 of the main floor, and then the larger 2nd Floor "Cascades" rooms to finish off. As with last week, all prices are in US dollars unless specified otherwise.

Pacific Audio Fest 2024: Part I. [And expensive speaker cables unanimously turned down in a blind test?! 😕]

This is the third year for the Pacific Audio Fest which first started in 2022, basically after the COVID-19 pandemic reopenings. I think the first 2 years of the show were quite similar in size but this third show is clearly a smaller event with fewer display rooms and less stalls in the Marketplace. Correlated with that, I also noticed fewer headphone set-ups to try out.

To be honest, while I think this probably was disappointing for some, I only had a couple of days to visit anyways so this actually worked out driving into Seattle on Saturday morning, stayed a night, and got home by later afternoon Sunday having felt like I spent enough time in each room, even visiting a few of the rooms a number of times to compare.

So, let's have a peek at some audiophile eye-candy and consider the goods out on display this year. Let's be honest, one of the most important specs whenever doing any shopping is the asking price. Unless specified otherwise, all prices are in USD.

The show ran from September 6-8, 2024 at the SeaTac DoubleTree Hilton which is the same as in previous years. I spent the 7th and 8th "hitting the rooms". Let's go!

AS WE HEAR IT: Moving forward as audiophiles & a plea for higher dynamic range music (to Epica). [Plus highest DR Oasis - Definitely Maybe.]

Well, this weekend is Pacific Audio Fest 2024 and I figure since it's nearby in Seattle and they've decided to make it every 2 years (next in 2026), I'll pop down for a look and listen for a couple days. It's fun staying incognito for the most part as a "more objective" audiophile even if this might not be the prevailing culture at these shows to get a sense of how the megabuck systems perform, what's potentially exciting, and observe the trajectory of the hobby. Given the busyness of work these days, I'll just take my time this year on the show reports with pictures, sharing some thoughts over the next couple weeks.

For this post, it's time for an "As We Hear It" article based on reader E-mails.

I. First Watt Amplifiers & Progressing as Audiophiles

June 26, 2024

Hi Achi:

Your blog took me here (ie. E-mail address) and thanks for all your wonderful work to make the audiophiles' world a better place. Here is my little story.

I have been an audiophile for as long as I can remember. But only recently decided to get serious about the equipment side of things. Thanks to the YouTube channel called Audiophiliac by Steve Guttenberg, I quickly decided to get a pair of Magnepan speakers. That was wonderful, due to planar construction, the transparency and soundstage is amazing. 

Part II: Fosi Audio V3 Mono Amp; Class D + PFFB, TI TPA3255 - Retail box with single 48V/10A power supply and filter. [Power, Distortion, and Subjective Impressions.] And on rejoicing over "Solved Problems" in audio.

Gotta love those Nordost-like flat speaker cables from AliExpress. The 90° locking banana connectors are a bit on the large side however. 😉

As we saw last week in Part I, I started reviewing the Fosi Audio V3 Mono amplifier, early August 2024 retail release, in the form of the stereo with 48V/10A power supply kit. We've already had an extensive look externally and inside the device, seen the benefit of PFFB for load invariance as well as discussed a couple of the issues I ran into (inverted polarity and the ground noise with 2 amps connected to one battery).

This time in Part II, let's proceed deeper into the measurements to explore the amount of power this little amplifier can provide, some details on distortion characteristics, and as usual, ending off with subjective impressions and summary of the product.

Part I: Fosi Audio V3 Mono Amp; Class D + PFFB, TI TPA3255 - Retail box with single 48V/10A power supply and filter. [With initial measurements.]

Over the last few months, I've been hearing a lot about this Fosi Audio Mono V3 (~US$140) amplifier which is typically sold as an individual unit with 48V/5A power supply, or as dual amps with 48V/10A supply, DC filter, and splitter cable (currently ~US$280).

I have already seen a number of reviews and YouTube videos typically with the pre-release product supplied by the company; honestly guys, many of the reviews seem superficial with essentially "Trust me, bro!" opinions rather than presentation of facts. For this review, let me grab the 2 amps + single 48V/10A kit from the Amazon retail pipeline to have a look at the final product. This review is not sponsored by Fosi Audio. With measurements, I believe this would be as bias-free as a review can be.

As you might already be aware, this inexpensive amplifier represents an evolution of their TI TPA3255 Class D "chip amp" product line. The company incorporated community feedback and developed this as a monoblock design (through Kickstarter funding, as usual due diligence needed when participating in crowd-funding) with no volume control so as to optimize resolution, accepts true balanced (XLR/TRS) input, and also incorporates Post-Filter Feedback (PFFB) to lower output impedance (increase damping factor) for load independence.

The company publishes a power rating of 240W into 4Ω, 1% THD; 120W into 8Ω. That should be more than enough for most reasonably efficient speakers of normal load, in normal smallish listening rooms.

Let's take a good look...

SUMMER MUSINGS: What are the most important audio components? Domains / dimensions of the audiophile pursuit.

[Available as audio podcast summary.]

The other day, I came upon another common question we run into within the audiophile forum communities. The thread topic on the Steve Hoffman Forums read: "What is more important? The quality of the source devices or the quality of the amp and speakers?"

Among the pages, in response to the question, there was this one listing items as such:

1 (tie). Source material, i.e. the recording, the mix and master, etc.
1 (tie). Speakers
3. Your hearing
4. Analog source playback device
5. Your room
6. Your mood
7 (tie). Digital source playback device
7 (tie). Amplification

A good list to start with! Let's spend some time in this post thinking more about this, adding more details, and broadening it out. Clearly, this (and variants of this) topic is one of those "classic" big-picture questions that demand a more nuanced and complete take. Specifically, let's make sure to contextualize the response with what I believe are relevant dimensions or domains to include.

2.5Gbps Ethernet in the Sound Room... (D-Link DMS-106XT & GigaPlus S25-0802 2.5G Smart Switch). And a quick peek in the Headphone Bar & Red Cat Records.

On occasion, I get a kick out of reading the audiophile media's review of ethernet switches. These are perhaps some of the most hilarious pseudo-infomercials out there as companies try to justify their highly expensive network switches in the hopes of capturing the interest of the few audiophiles who still somehow do not realize that there's no benefit to these devices (even Paul McGowan agrees, imagine that!).

Feel free to check out the reviews of such things like the Silent Angel Bonn NX Pro Ethernet Switch (asking US$4000!), or filters like the Network Acoustic Muon Pro (asking £1,329.17!). There are also now Chinese companies that make these things for audiophiles - Gustard N18 (US$370 - only 2 ethernet ports + 1 gigabit SFP) and N18 Pro (US$530 - 5 ethernet + 1 gigabit SFP) for example; sure, they're cheaper but that's still quite a bit for what you get which is just a nice looking ethernet switch with integrated power supply and an essentially meaningless 10MHz clock input! (Timing is essential inside the DAC for precise conversion to analog output, not the network switch.)

A few years ago (2020), I talked about the Netgear Nighthawk S8000 as a great choice for a high quality ethernet switch which affords features including port priority. Hey, it's still a great little switch and I see that sometimes there's still stock available on Amazon.  Over the years, I've upgraded my home network beyond 1Gbps (and update here) so I figured let's find faster switches to try out for the sound/media room.

Here are two easily available and not expensive options: the D-Link DMS-106XT (US$200), with 10GbE high-speed port to connect to your main network plus 5 x 2.5GbE ports for downstream devices with user-defined port priority, and the very inexpensive GigaPlus S25-0802 2.5G Smart Switch (US$80), an 8-port 2.5GbE switch with 2 x 10Gbps SFP+ for those who want to use fiber networking, or possibly 10GbE RJ45 multigigabit transceivers (some very inexpensive like this).

Both are fanless - essential for the sound room.

AudioVero Acourate v3.1 - room correction with bass pre-filtering and Inter-Channel Phase Alignment (ICPA).

After writing the post on Audiolense recently, I thought it would be good to have another peek after a few years now at AudioVero's Acourate (€416 non-EU countries); the latest version 3.1 released in June 2024.

For years, Acourate has been the room-correction filter toolbox I've used (at least since 2016, updated 2019, plus discussion on partial correction in 2021). Now that it has been half a decade plus a pandemic (!) since the step-by-step 2019 update, let's look at the latest version which has brought with it changes in the user interface as well as the Inter-Channel Phase Alignment (ICPA) feature released in version 2 which I had not discussed previously.

Before getting started, a big thanks to Mitch Barnett of Accurate Sound for his YouTube video a couple years back using Acourate 2 showing the technique around pre-filtering and ICPA. I've taken inspiration from his video, applying it to my home set-up, and converting those steps into a written blog format for the current Acourate version. If what I'm doing here is not clear, make sure to also check out the video since Mitch might have already covered your questions/issues there.

Let's get started!

SUMMER MUSINGS: Defining "subjective" and "objective" audiophile evaluations.

Hey everyone, I thought I'd make a "quick" post in response to this comment in the recent "SUMMER MUSINGS: On the perils of subjective opinions in High-End Audio (dCS v. GoldenSound)" article:

SY 24 July 2024 at 13:07

Could I beg and plead with you to join me in refusing to misuse the term "subjective" to mean "uncontrolled?" Something can be subjective and absolutely valid and rigorous (e.g., subjective reactions made with basic ears-only controls) or subjective and absolutely invalid (e.g., subjective reactions made with peeking, preconceptions, and non-auditory inputs).

Subjective =/= uncontrolled. So much fuzzy thinking has arisen because of that conflation of terms.

Greetings SY,

Sure! I agree with you that "subjective" (when referring to audio hardware reviews specifically) is simply a reference to the form of evaluation and does not imply whether the evaluation is valid or invalid, nor whether controls were applied or not. Certainly some subjective opinions are clearly valid if the difference is obviously detected by the listener. I trust no audiophile worth his street credibility would have difficulty telling the difference between AM mono and FM stereo sound quality for example and will accurately point to the stereo FM playback being of higher fidelity.

Indeed, subjective reviewers listening under controlled conditions also can produce highly valid reports. I hope I have not confounded that over the years. For clarity, let me expand the position in some (pedantic) detail for those who like reading this stuff. 😉

SUMMER MUSINGS: On the perils of subjective opinions in High-End Audio (dCS v. GoldenSound).

Every once awhile here in audiophile-land we see our share of drama.

There was MoFiGate a couple years back when vinyl collectors panicked about DSD256 data corrupting their precious analog remasters, Tekton (Eric Alexander) v. Erin recently due to legal threats for calling into question a speaker design, we've seen silly hyped Pono/Neil Young claims a decade ago, and of course the painfully prolonged MQA episode which was just a mess (as summarized years ago).

Well, in the last week we have something a bit different; the dCS v. GoldenSound lawsuit threat due to unhappiness about a YouTube DAC review from late 2021. I'm not going to rehash the stuff here because there were clearly many missteps in dCS's communications as explained in GoldenSound's video and here's the dCS response where the company "fully acknowledge that some of the emails shared by GoldenSound were unacceptable and we addressed and acknowledged this in subsequent communications".

I trust they'll figure it out between the various players on the two sides. As with the domestic conflicts of others, I'm not particularly interested in the details as to who said what unless personally involved. Likewise, some of the technical details regarding the external clock, DSD resampling, seem to be side distractions from the concerns around the review; no need to spend time with these minor digressions.

Instead, I was more curious about that original dCS Bartók DAC/headphone amp YouTube review by GoldenSound that came out on December 31, 2021. What was it that made dCS or their representatives so upset? Is there something about the review itself we can/should learn from?

Seating variations, multi-seat correction & multichannel DRC. The audio "sweet spot".

A look at the rear of my room and the sofa seating - surround speakers, LP rack for a little bit of diffusion room treatment. For best practice, it's important to not sit too close to the back wall. I have 3' between the couch and the LP rack, and the rack is about 17" deep before that back wall. 

Before putting the UMIK-1 microphone away after using Audiolense XO as discussed last time, I thought it would be interesting to explore in greater detail what happens with frequency response and time-domain performance as we sit off the "sweet spot" where the measurements were collected and correction calculated for.

In the image above, I've put a meter stick on my listening couch to identify the seating positions 1 and 2-feet to the right and left of that sweet spot so I can take detailed measurements of what happens to the sound coming from the 5 main speakers at those positions with and without DSP turned on.

Multichannel Digital Room Correction with Audiolense XO. And "What's your budget?".

As you might recall from over the years, I strongly believe that one of the most important things one should try as an audiophile seeking high-fidelity - after having a decent sound room, and getting good equipment - is to consider the use of room correction. It could be as simple as frequency-domain EQ correction for larger bumps and dips (as discussed with the Behringer DEQ2496 hardware back in 2013-2014, device measurements here), or the much more sophisticated frequency and time-alignment of filters created by software like AudioVero's Acourate (and 2019 update) capable of much higher resolutions.

The power that one has to optimize and customize the sound runs well beyond most hardware upgrades other than wholesale speaker replacements and changing sound room! The change one can expect with room correction dialed in is astronomical compared to all the snake oil tweaks, cables, hi-res DAC/streamers, even amplifiers you might want to throw at your system.

These days, I've increasingly been converting multichannel content over to my Roon server, typically 5.1 SACDs and DVD-As but also Bluray rips, ideally lossless TrueHD with 7.1 channels. Unfortunately, Roon is currently unable to decode codecs like EAC3-JOC (lossy multichannel/Atmos) or TrueHD (lossless, based on the MLP codec) so the content typically gets transcoded to multichannel FLAC-compressed PCM which can handle up to 7.1.  

Although Acourate can be used for multichannel filter creation, the manual procedure here is unfortunately quite involved and more than most audiophiles would like to get their hands dirty with! Which is why today's post is going to be about multichannel digital room correction using Juice HiFi's Audiolense XO (€390, currently version 6.21). I see that there is the less expensive Audiolense Surround which I suspect could be enough for many users, and if all you need is 2-channel stereo, there's Audiolense 2.0.