AuraEngine: Perfectionist off-line mega-tap digital filtering - with hybrid-phase transient detection & blending.

As you know, while digital oversampling filters have been around for ages (4x oversampling available back in the '80s), audiophiles probably got more interested in digital filters thanks to Bob Stuart, and Meridian by 2009 talking about "apodizing" filters. DACs started allowing different filter options. And spin-offs like MQA took things too far utilizing poor designs through the 2010's (and still looking for a reason to exist).

Years ago now, I spent quite a bit of time talking about digital filters across articles like this and contemplating things like pre-ringing here. There were also discussions of using the intermediate phase setting as a compromise. And we even ran a blind test to compare strong pre-ringing vs. no-pre-ringing minimum phase settings.

While I think I've exhausted my time exploring such things at the base level, ever-more-precise filtering options have been available for audiophiles to use. HQPlayer has many realtime software-based playback settings including DSD transcoding. Companies like Chord/Rob Watts have taken their stand on using ultra-tap-length linear phase filters (to the point of extreme IMO).

Off-line upsampling of high precision can also be achieved using software like Pan Galactic Gargle Blaster (PGGB) in 2021 -  I see they have a PGGB+ version now with DSD and up to "ludicrous" 256-bit processing.

Well friends, it's 2026 and the other day I was contacted by Toxa Dev about his new ultra-accurate upsampling system called AuraEngine (current version 1.2.2) available on Github; full source code published and freely released for non-commercial use. You can also download and run the pre-built Windows portable app here. Notice that there are three downloads available: Starter 1M-taps, Standard 10M-taps, and Reference 30M-taps. Pick your level of obsession err... weapon against weak upsampling!

Crosstalk Cancellation/Ambiophonics: Updated CTXMatrix Lite with standalone processor & 60° speaker angle support.

Significant changes in the UI from the previous CTXMatrixBeta release.

I want to remind 2-channel "immersive sound" lovers about the potential for using stereo crosstalk cancellation (XTC) / ambiophonics playback to enhance the 3D soundstage. You might have already heard of uBACCH in the audio magazines and on forums - why not try a similar effect for free (or through a small coffee donation)?!

You might recall, last year STC contributed a post on CTXMatrixBeta DSP for Windows. Well, it's great to see that he has continued to develop the software with updated user interface and abilities, this latest edition renamed CTXMatrix Lite, currently at version 1.3. It now includes a standalone processor which I'll spend some time discussing in this post, along with the 64-bit VST3 plugin as shown above that can be used in JRiver, Audirvāna and DAW software like Reaper.

Furthermore, there is now a VST3 plugin for Linux. Since I primarily use Windows for my music listening and processing, I'll stick with the Windows variant here with the hopes that some of this will be applicable. In my discussions with STC, he's aware of interest from Mac OSX users.

Perhaps the most important update in the last few months is that there is now improved support for standard ~60° stereo speaker angle (typically, the recommendation is 20-30° in ambiophonics). As a result, one should have a much better experience with the effect on most set-ups. In particular, hopefully more desktop computer music lovers will give this a listen without needed to move the speaker position and explore what you might be missing in your existing music library.

[If you run a miniPC streamer in the sound room like I do, CTXMatrix can easily be used like with HAF X-talk Shaper DSP discussed a couple years ago.]

Happy New Year! And a thank you to the Lyrion Music Server folks for renewing the life of my Squeezebox Radio. ☺️

Hope you're all having a wonderful Christmas-New Year Holiday season!

On Christmas morn 2025, as I relaxed in the sitting room waiting for the rest of the family to get ready for some holiday festivities, listening to holiday music, I could not help but marvel at the fact that my little Logitech Squeezebox Radio sitting over the fireplace, released back in 2009 continues to go strong all these years later. The Squeezebox products including the Radio were some of the first devices I posted about with measurements in the early days of this blog.

I think it's an obvious reminder that even though time flies, music preferences and artists change, hardware gets upgraded and new technologies show up at our homes, the ability to enjoy music need not be tied into the hardware obsessionality that can consume audiophiles. We can derive much joy out of even a simple mono "radio" device like this.

Although Logitech got out of Squeezebox hardware production way back in 2012, they continued the official MySqueezebox.com servers until March 2024. I actually didn't even notice this change as I've been using my own Logitech Music Server (LMS) home system since something like 2008.

While LMS development has stopped, it's great to see that the good folks have continued to work on this venerable music streaming system as Lyrion Music Server.

Stereo Crosstalk Cancellation (XTC) / Ambiophonics: Introducing CTXMatrixBeta, a Free VST3 Plugin with XTC Calibration. [Guest post, STC.]

Greetings audiophiles!

As you may recall, Archimago and I (STC) wrote the previous article from October 2023 on stereo crosstalk cancellation (XTC). If you're not familiar with the topic, I recommend a look at that to familiarize yourself with the principles behind the technique.

I now want to introduce CTXMatrixBeta, a free 64-bit VST3 plugin that brings Ralph Glasgal's vision with freely accessible Ambiophonics for all to try. (In the near future, I'm planning to work on adding support with surround channels for the "Domestic Concert Hall" [DCH]. The ideas and logic are ready to implement.)

Regarding CTXMatrixBeta, by harnessing intuitive ear-based calibration, this plugin aims to deliver precise XTC, empowering enthusiasts to experience the immersive, lifelike sound of their 2-channel recordings with unmatched clarity.

Mega-taps upsampling: Remastero's Pan Galactic Gargle Blaster (PGGB) software. (Broadly on audiophile software & the noise boogeyman.)

This article came about after I received an E-mail from an audiophile friend who saw this Audiophile Style thread in praise of "math and magic". It links to a piece of software by a site called remastero, and the program itself is called "PGGB" (Pan Galactic Gargle Blaster), obviously referring to The Hitchhiker's Guide To The Galaxy with the main author named Zaphod Beeblebrox (who in the book is also the ex-president of the Galaxy). Cute, and of course the number "42" features prominently here and there.

In the past, we have talked about "audiophile" software that supposedly affect sound quality. Years ago, we talked about bit-perfect players (Windows, Mac) and really how "bit-perfect" is simply "bit-perfect" regardless of what software is used. We discussed questionable programs like JPLAY. Then there are the OS tweaks like Fidelizer. Neither JPLAY nor Fidelizer made any difference in my testing or listening.

That is not to say software doesn't make a difference at all. With the computing power we have these days, we can certainly perform highly precise filtering and DSD-PCM transcoding - like with HQPlayer. 

The idea with PGGB is that this is software that will take (in batch) various tracks you have and convert these to upsampled versions like 24/384 or 32/705.6 or even higher. In the process, applying very strong filtering (eg. on the order of >200M-taps sinc filter for some of the tests we'll run here, very impressive big number, right?). Furthermore, the website states that the software can apply settings for various levels of "transparency", apply HF noise filtering, uses noise shaping, adjusts gain monitoring for intersample overs, deal with convolution filters, and an apodizing setting. That's a bit of stuff so I won't promise that we'll hit on all these here. My intent is to at least have a good look at the foundation of the upsampling effect and the EQ function.