1kHz Test Tone: Does increasing the number of PCM values really matter? And Stereophile's "still listening" to the community (so they say).

Hey there audiophiles, lots happening in life to keep me busy these days as we enter summer 2025, so let's do another little follow-up of a topic based on reader comments.

In the previous post, there was a comment by Mister MB about the 1kHz test tone and the idea that it would be good to use tones that employ more PCM values as quoted from Ken Pohlmann's book Principles of Digital Audio (currently 6th Edition, 2011, from page 81, emphasis mine):

"Digitally generated test tones are often used to measure D/A converters; it is important to choose test frequencies that are not correlated with the sampling frequency. Otherwise, a small sequence of codes might be reproduced over and over, without fully exercising the converter. Depending on the converter’s linearity at those particular codes, the output distortion might measure better, or worse, than typical performance. For example, when replaying a 1-second, 1-kHz, 0-dBFS sine wave sampled at 44.1 kHz, only 441 different codes would be used over the 44,100 points. A 0-dBFS sine wave at 997 Hz would use 20,542 codes, giving a much better representation of converter performance. Standard test tones have been selected to avoid this anomaly. For example, some standard test frequencies are: 17, 31, 61, 127, 251, 499, 997, 1999, 4001, 7993, 10,007, 12,503, 16,001, 17,989, and 19,997 Hz."

Certainly a good point to think about. However, if we look at actual hi-res DACs these days, and the way we're running 1kHz tests to show routinely >100dB SINAD, would we actually see significantly different results depending on how we create these test tones, specifically whether more or less PCM codes are being used in the signal sent to the DAC?

Well, while I still have the Topping DX9 on my testbench, let's have a look at the analog output from the device with a few ~1kHz test tone variants.

Follow-up: Topping DX9 DAC tests. And reduction in the ability to comment on the Stereophile website.

Topping DX9 DAC sitting on Linn Klimax DS/2 which we'll talk about another time.

Hey guys and gals, thanks for the comments and feedback over the years on this blog. It really helps to refine the testing and of course explore broader ideas about audiophilia and what it is we're after in this hobby. I think it's important that we're free to discuss and critique not just the hardware, but also the ideas (including the philosophy and psychology) that "we" as individuals believe in. There's so much unsubstantiated audiophile cultural beliefs out there based on myths such that everything should be up for examination regardless of who says what. It's not unusual to find that audiophile review "high priests" are wrong, and some "heroes" of the audiophile world are nothing more than false prophets.

It's also good to get feedback suggestions on the published measurements, for example in the recent series on the Topping DX9 flagship DAC (based on rare AKM AK4499EQ chip), Nick in the Part III comments suggested that I consider this:

"Hi Archi,

Prior to version 5.40.78 beta rew had a gross error in IMD vs Level plotting, the results were underestimated by about 12 dB. It looks like the version you used has this error.

IMHO there are not enough performance measurements at high frequencies for a complete picture. If still available, it would be very interesting to see THD (without noise) vs frequency performance, accurate THD measurement at 10kHz and wideband fft (without weighting) with a weak signal such as the signal for the DR test.

Thanks!"

Excellent feedback and suggestions Nick, let's focus on checking this out in this post!

Roon in 2025, 10 years on: Sound quality, thoughts, and suggestions. And an increasingly AI-generated Internet.

Notice it has been "10 Years" for Roon as per the top left.
Roon 1.0 was released May 2015.

Obviously, it's impossible to get on all the discussion forum about the myriad subtopics in this audiophile hobby. However, I do get newsletters in my inbox and I see frequently asked questions that inspire many of the topics addressed here.

If we've come across each other on the audio forums (places like Steve Hoffman's site, or Audiophile Style), you'll notice that I often will respond with links to articles on this blog. I've posted more than 600 long-form articles already, the vast majority digging pretty deep into the audio topic. One of my intentions over the years is for this to be a repository of information, articles I can use as "landmarks" when I engage in discussions with fellow audiophiles; how I understand the hobby including big-picture philosophy, psychology, the debates. Contained within these pages are the thoughts, character, understandings of "Archimago the anonymous audiophile from the early 21st Century" with contributions from guest posters. Familiarity with these articles I think will provide a good starting point for "rational audiophiles", without necessarily going too deeply into technical details.

Apart from discussing individual products, broadly, I think we've covered many of the usual issues raised in audio circles already, much of it analyzed with data to seek out the facts, rather than mere opinions. Feel free on the main page of this blog to use the "Search This Blog" widget as I suspect you'll find articles addressing many questions.

So, coming back to a frequently asked question, for this post, let's think about Roon software in 2025 (currently version 2.51 build 1534). In a recent Roon forum newsletter, I saw this question posed by Eric_Pell:

"I am wondering for years why the most expensive app in the world of hifi and high end only has a sound quality which is only ok. If you compare Roon with JPLAY i think JPLAY has only a few people to develope (sic) software and improve sound quality. But here the difference. What is Roon doing to improve sound quality and do they compare with JPLAY or not?"