Saturday, 22 June 2019

MUSINGS and LISTENING: On Absolute Polarity / Phase... (And on the joy of the modern audiophile.)

Hey guys and gals, I thought for this post we'll spend a bit more time on the topic of "absolute polarity". As you can see from the post last week in the comments, our man in Japan Yamamoto2002 posted a link to his page where he has an interesting test signal for all to listen to.

If we look at the test signal he used, it's an asymmetrical waveform where half of it appears to be a standard sine wave, the other half has been "flattened" off which results in numerous harmonics if we are to display it on an FFT. One of the files is simply the inverted version of the other to test whether this polarity change is audible. Notice that the waveform is bandwidth limited, and there is no "ringing" after going through a digital filter.

Saturday, 15 June 2019

MEASUREMENTS: Topping D10 DAC. (And a few words on "absolute polarity / phase".)

Hey guys, getting busy around here as I'm preparing for summer holidays coming up in a couple of weeks :-).

I did want to post a "quick" report however on the Topping D10 DAC (<US$90) I got last week... It's for an upcoming project of sorts which I'll post on over the months ahead. What I wanted was a DAC that could be powered off USB, reliable with Window and Linux compatibility, that's reasonably portable, and of course of high signal accuracy.

Notice the DAC manual shows some AP measurement graphs... I guess Topping believes in showing objective accuracy :-). Nice.

Saturday, 8 June 2019

GUEST POST: Why We Should Use Software Volume Control / Management by Bennet Ng. (Plus discussions on resampling options, true peaks, etc...)

I received an invitation from Archimago to write something about volume control. While I am of the opinion that digital and analog volume controls can coexist to achieve an ideal gain stage, this article is mainly about PCM digital volume control.

The basic conclusion we can say regarding digital volume control is that as long as the playback device has higher bit-depth than the file source, it is possible to losslessly reduce the volume of a file until the playback device's bit-depth limit is reached. For example, with an ideal 24-bit device, it is possible to playback a 16-bit file 48dB lower without losing quality, because one bit has about 6dB of dynamic range (the exact formula of bitdepth and dynamic range is 6.02*n-bits + 1.76).

Saturday, 1 June 2019

POLL RESULTS: Music streaming service adoption among audiophiles in 2019...

Click on image to zoom.
Yeah, I know. Music streaming as a subscription model is the latest "revolution" for music lovers. This is why I decided to put up the recent poll in mid-March while we were concurrently also running the blind test as reported on in the last few weeks. Above, you see the overall results based on the visitors to this blog.

Remember that for the poll, I allowed voters to select up to 3 options. As a result, even though there were 616 respondents, a total of 809 selections were made. This means that up to ~30% of people selected more than 1 option and these are represented in the percentages above.

Saturday, 25 May 2019

BLIND TEST Results Part 4: "Do digital audio players sound different playing 16/44.1 music?" - Subjective Comments. Final thoughts on blind testing and critiques.

As we close off discussions and posts around the Internet Blind Test of devices playing 16/44.1 music, I want to publish some of the subjective comments from respondents who undertook this test... Impressions in the respondents' own words about the test when they submitted their results to me.

Remember that these are subjective. Human perception, especially when differences are at the margins of our perception are of course tough to describe. And when we compound that with the limited utility of words to describe ephemeral experiences (even with codifying the terminology as was attempted years back), it's no surprise that meaning can often only be conveyed as impressions. It's great to see the respondents trying their best and in many instances, I certainly appreciate the impressive use of language to express the experiences. Let's have some fun with these!

Saturday, 18 May 2019

BLIND TEST Results Part 3: "Do digital audio players sound different playing 16/44.1 music?" - Listener Results.

Thanks for the patience everyone. We are now into Part 3 of the report on the Internet Blind Test on the audibility of 16/44.1 digital playback using various devices. In Part 1 we talked about the test procedure itself and unblinded the devices (ASRock Z77 Extreme4 motherboard, Apple iPhone 6, Oppo UDP-205 as ethernet DAC, and Sony SCD-CE775 playing a burned CD-R).

Last week in Part 2, we reviewed the objective measurements of the 4 devices. I hope the readership recognizes the importance of doing this to set the context of what we're looking at this time as we dive into the results from the blind test respondents. As with many things in life, it is only with having facts at our disposal first, then we can make comparisons and develop ideas based on this foundation of knowledge.

Saturday, 11 May 2019

BLIND TEST Results Part 2: "Do digital audio players sound different playing 16/44.1 music?" - Relative objective performance. [And a few words about "Legends"...]

Last week, I revealed the four CD-resolution / 16/44.1 playback devices I used for this blind test. (By the way, if you want to have a listen to the original 16/44.1 track excerpts used, I added a link as an addendum to the post last week.)

While I'm still doing some counting, calculations, and writing the summary of the data, I think it's best this week to start by having a better look at those devices and seeing what objective results tell us about them so we can hypothesize what we might find when we examine the blind test results.

While it may be controversial to some in the audiophile world, I think we should keep our minds open to the idea that science and technology for digital audio playback has already surpassed the human auditory system. As discussed years ago, the human perceptual and cognitive systems do not have infinite resolution. I'm of course not discounting that the ears and mind have excellent abilities when it comes to appreciating miniscule differences, yet I think we have to remain humble; even if we believe we have "golden ears". Also, even if we don't believe measurements capture everything, it's not unreasonable to accept that the vast majority of what is heard can already be quantified in terms of fidelity to the source. This is why I think we need to explore the objective performance first... Then we can see if the subjective preferences from the respondents line up with expectations. I think for many of the well-respected audio engineers that design our hi-fi gear, this sequence makes sense. Ensure that the measurements are decent first, then verify and tweak with subjective listening.

Over the years, I've measured most of these devices in the blind test separately with different ADCs. For this post, let's run each one through the RME ADI-2 Pro FS and compare objectively using the exact same "measuring stick". For completeness, here's what the measurement chains look like with each player/DAC:

Saturday, 4 May 2019

BLIND TEST Results Part 1: "Do digital audio players sound different playing 16/44.1 music?" - Devices Unblinded! (Plus unusual exuberance & bias in the media?)

Thanks everyone for taking the time and efforts in performing the blind test which we started back in late January!

I officially closed off my survey from submissions May 1st (I promised April 30th, but gave a few hours more for stragglers from different time zones). I trust the 3 months provided plenty of time for everyone who wanted to perform the test to do so. I'll leave the blind test samples available for download for now and will take the files down in the near future.

You can read about the reason I ran this blind test in the previous post, but in a nutshell it's because of this poll result which I think reflects general audiophile perceptions on the question:

Saturday, 27 April 2019

MEASUREMENTS: Experiments in audio component grounding - using a bus bar & HumX. And on the last The Cranberries album, on audio quality legacy...

You may remember a number of years ago, I talked about reducing interference I was experiencing with my Emotiva XSP-1 pre-amp. The issue had to do with the audio system picking up interference and noise through the pre-amp's "Home Theater Bypass" unbalanced RCA input when connected to my AV receiver. This "HT Bypass" mode is used as a conduit for the front channels and subwoofer out when the AV receiver is in use, typically when I watch movies with multichannel sound.

While this was a bit of a hassle for me, sometimes out of these hurdles and limitations, one is provided with opportunities to explore things like the 8kHz USB PHY packet noise which seeped into my system from the TEAC UD-501 DAC (not an issues these days with my Oppo UDP-205). Playing with things like the Corning Optical USB 3 extender allowed me to lower the noise level. Furthermore, I was also able to show that different USB hubs affected the severity of that 8kHz noise. Remember that much of this investigation was prompted in those days when devices like the AudioQuest USB Jitterbug and the silly single-port-hub known as the UpTone Audio USB Regen were being hyped up by certain websites and forums. To this day, I have not seen any evidence that this stuff improved things like noise level and jitter with reasonable asynchronous USB DACs.

Saturday, 20 April 2019

A Look (and Listen) to some audio gear in Taiwan and Singapore...

Image result for window shopping

Hey everyone, as discussed recently, I had an opportunity to visit Asia over the Spring Break. Since it is "audio show season" with AXPONA in Chicago last week and Munich High End coming up in May, perhaps it's a good time to post up some images and descriptions of what I found in Asia this time.

While it was a family vacation, I found time to do a little bit of "window shopping" myself and check out the audio gear and stores overseas.

Thursday, 11 April 2019

COMPARISON: Roon DSP speed - Intel i5-6500 vs. Intel i7-7700K... (and the value of Intel Speed Shift!)

As mentioned, a little while back when I wrote about Roon, I was about to receive a "drop in" Intel i7-7700K CPU for my Server machine which runs Roon Core. I was able to find the i7-7700K used for a decent price and I didn't feel like dismantling the machine and upgrading the Z170 motherboard since the newest CPUs now need a Z3XX series board. Furthermore, for me, one of the least interesting "jobs" one has to manage as a technophile is reinstalling the operating system and software again... I try my best to avoid this mundane task :-(.

Note that if I were to rebuild my Server these days, I'd probably consider something like the very affordable Core i5-9600K with 6 cores. In fact, for most applications, this CPU will beat out the i7-7700K which I suspect would apply when using Roon for DSP as well.

Saturday, 6 April 2019

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.