A look at the music library: How much DAC intersample overhead is enough? True Peak analysis of genres in an eclectic digital collection.

In a recent article about Linn DS streamers, I touched again on intersample peaks ("True Peaks") as I measured the DAC hardware. In the comments section, there was further talk about this topic so this got me thinking over the last few weeks to spend some more time on this but from a different angle.

For those who are not aware of what "intersample peaks" are, recall that DACs implement filters to ensure accurate reconstruction of the waveforms (unlike the jagged-looking NOS DACs which some audiophiles still subjectively appear to prefer). Typically this is done through oversampling whereby 44.1kHz (ie. CD samplerate) might be increased by something like 8x (352.8kHz) while applying a low-pass filter that cuts off content beyond the 22.05kHz Nyquist frequency. The DAC will interpolate to create those extra upsampled datapoints. In this DSP process, some of the reconstructed "intersample" points might have >0dBFS values. If these "True Peak" values are too high beyond the limits of the digital filter or output level of our DACs, the samples will "clip", resulting in extra distortion in the playback.

For this post, instead of considering from a hardware measurement viewpoint what kind of overhead a DAC can handle, let's consider from the music content side by using a relatively large music library - my library of thousands of albums - and consider just how much overhead peak we might find and "need" based on the commonly-owned music genres in an audiophile's collection.

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.

HOW-TO: Roon 2.0 with ARC released, running Android ARC on Windows. Roon's "grace period". And how about more audiophile remasters of music from the '80s onward?

The big news this week among the audiophile channels I think is that Roon 2.0 has been released which allows remote access to your Roon Core when on-the-go. Nice, it's about time considering that I've been streaming off Logitech Media Server for ages to my phone and at the office! The app that allows access remotely is something called Roon ARC - available for 64-bit Android in Google Store and for Apple devices.

This is a nice step forward and now I can listen to my music on the smartphone. However, I want to also play the music at my office on the Windows 10 computer. However, when remote desktop streaming was discussed with the company, the official answer has been "Roon ARC is mobile device-only application". Well, that's not a completely acceptable answer, I'm afraid. :-(

For the time being, you could run the Android app in Windows with BlueStacks 5 - 64-bit Android 9 Pie edition. Here's a look...

MEASUREMENTS: Roon 1.6 Upsampling Digital Filter Options & A Discussion on "Signal Path" Quality...

As discussed last month, I've started using Roon as my main music player for the sound room recently. Back in the days of Roon 1.2, many users performed upsampling using HQPlayer. While HQPlayer integration is still available (go to Settings --> Setup to access the installation option), since version 1.3, Roon has incorporated its own DSP samplerate conversion which I suspect would be completely adequate for the majority of users.

I was curious about the upsampling digital filter options available in Roon. If you look at the "Sample Rate Conversion" control panel, we see the four main "Sample Rate Conversion Filter" settings:

On the left panel, notice that Roon allows you to select the different DSP options and add various filters to the "chain" (left lower panel). "Headroom Management" is always available if needed which basically means you can set the amount of attenuation you want to use to prevent clipping while doing the DSP processes. Default setting is a very reasonable -3dB.

HOWTO: Integrating WavPack 5-compressed DSD into Logitech Media Server (LMS).

piCorePlayer streaming WavPack-compressed DSD128 (1-bit, 5.6MHz) to TEAC UD-501 from recent nightly version of Logitech Media Server 7.9.1.

As I mentioned last time, it's great to see that DSD compression and metadata tagging are available in the form of WavPack 5. Starting from the post by michaelvv on the Squeezebox Forum, I decided to spend more time on getting WavPack-DSD working in LMS and managed to get it working quite stably installed on a Ubuntu Linux (currently 16.04 LTS) virtual machine in the Windows Server 2016 computer that serves as my repository of data, movies, and music. For a description of the initial software install, have a look at my HOWTO: LMS + BrutefirDRC Plugin post from last year. The hardware these days is my Intel i5-6500 server machine described here.

MUSINGS: On DSD, tagging, compression and conversion... Time for WavPack 5.

Many moons ago (back in 2013), I discussed DSD audio. While over the years I've talked about DSD from a a number of different angles (eg. JRiver realtime conversion listening, PCM <--> DSD conversion, conversion 2015, equipment DSD playback measurements like PonoPlayer / TEAC UD-501 / Oppo BDP-105 / Oppo Sonica DAC), concerns from that very first discussion about DSD still irks me these days!

The main issue is simply this: the lack of ability for gear and software to support both tagging and data compression when dealing with DSD. This IMO truly has been a ridiculous state of affairs for so many years! Despite years of cheerleading in the industry and even smaller sales outfits like NativeDSD Music already putting files out there for consumers, the relative inelegance of it all is rather silly.

As usual, I find it rather baffling that the typical mainstream audiophile press remains silent on deficiencies like this. To me, it is issues like these, while perhaps not "sexy" nor provides the press something to market to consumers, that when addressed can actually move the hobby forward. Unlike yet another megabuck product that provides a few minutes of eye-candy at best and affects the few, "infrastructural" changes can affect the many. Yet another example of the myopia of the audiophile press and an inability to muster any leadership in changing the industry and hobby in meaningful ways.

MEASUREMENTS: Roon 1.2 (with Intel NUC 6i5SYH)

NOTE: I know that just a couple weeks ago, version 1.3 of Roon has been released and I'll perhaps look into that a bit later once some of the initial bugs are stamped out and the system matures a little. Clearly 1.3 has a few new interesting features but the basic bit-perfect playback function I trust would be the same which is what I'm aiming at exploring in this article.

Over the last few years, I have already gradually made my way across the different audio ecosystems that most audiophiles find themselves interested in. Starting with the venerable Squeezebox / Logitech Music Server system (eg. Touch, Transporter), to standard Windows PC and Mac OS X playback, to questionable software (like JPLAY and the JPLAY update), to even just as questionable OS tweaks (eg. Fidelizer), to more recently looking at DLNA streaming using low power devices like the Raspberry Pi 3 and ODROID-C2.

For today and the next few weeks (let's see how this goes), let's spend some time on Roon, another computer audio system much lauded in the audiophile press and see if we can make a few measurements and comment on some observations and thoughts...

MUSINGS: On the Digital Music Collection, Metadata Tagging, and Hygiene...

 Happy New Year everyone! I hope the holidays went well and you're ready to take on 2017.

Today, I thought I'd spend some time talking about something extremely important and one which I'm surprised I don't hear more about looking around forums and audiophile watering holes... It's the topic of how one creates a collection of music. The difference between a collection and just plain hoarding is of course the discipline of organization involved in the collector's hobby. The collector knows what he/she has. The collector has mastery over the collection. Though responses may be variable, I believe a friend or even complete stranger would be able to appreciate the time and dedication that a collector has put into achieving this mastery as opposed to a sense of revulsion when faced with the hoarder (this is honestly the feeling I get when looking at this "collection").

Over the years, I have seen a handful of articles like this one which also introduces one to Picard, the free MusicBrainz software that will do the job in an automated fashion. If I were to start putting a new collection fresh today, I'll probably do something like this and grow from there, adding customizations, and checking accuracy along the way. However, I have been collecting CD's since the 1980's and over the years, especially after 2004, I have migrated all the "physical" music over to my music server. Through the years, although I have gone through multiple hardware servers, the data from the music collection really has not. It has been essentially rip once into a lossless format, and the CDs packed up in storage thereafter. As the years go on, I suppose like every collector, one develops a unique way to archive the albums, manage the directory structure, and a way to tag the files in a fashion that "works" for oneself.

Let's start the new year with a look at one way to manage the music collection (my idiosyncratic way :-). It has served me well and maybe some of what I do will resonate with you as well...