|Impulse Response: One of the talking points from back in the day as a selling point for DSD... Yup! DSD can better reproduce a 0.000003 second "click". Source: Merging Technologies|
I. PreambleIt is amazing how quickly another year has passed. About this time last year, I posted the first comparison of DSD Encoders and Decoders "shoot-out" of sorts comparing Weiss Saracon 01.61-27, KORG AudioGate 2.3.3 and JRiver 19.0.117 in terms of quality - both encoding and decoding fidelity using the RightMark Audio Analyzer software. The idea was to determine which of the three created DSD files from an original 24/96 PCM test signal and then decoded it back to 24/96 in a way where there was as little change in terms of distortion, flat frequency response, and lowest amount of added noise.
Perhaps not surprisingly, the expensive Weiss Saracon software sets the standard as the most consistent DSD encoder that resulted in the best output once decoded. The differences in decoding capability appeared to be very minor (questionable audibility between the 3) but objectively, both Saracon and JRiver 19 were on par and the free AudioGate 2 somewhat "noisier" in terms of the PCM output (I speculated this was due to stronger dithering algorithm).
Well, another year has passed in terms of software upgrades to DSD decoding and I was interested to compare the decoding capabilities as of late. We have brand new versions of JRiver and AudioGate now, plus I didn't get to test foobar with the DSDIFF plugin last year. Plus we now have DSD decoding on the Mac OS X available with XLD and commercially with DSD Master.
To maintain an "apples to apples" comparison as best I can, I will use the Saracon 01.61-27 encoded DSD file of a 24/96 test signal with each of these decoders. I think this is fair given that Saracon produced excellent results last time as an encoder plus it is an "industry standard" used in many professional studios.
Let us have a look at the decoders I will be testing:
1. foobar with DSDIFF 1.4 plugin [Windows]. foobar2000 does not need any introduction as a freely available Windows music player. It's stable. Sounds fantastic. Is bitperfect. Is extremely feature-rich. And as witnessed by the myriad plugins like DSDIFF, very extensible. The DSDIFF plugin has been around as version 1.4 since 2011 by kode54. Decoding was set to 24/96 PCM, WAV output.
2. KORG AudioGate 3.0.2 [Windows]. AudioGate got an upgrade in June 2014 to version 3. It's no longer "free" like before where you can do conversions after just allowing Tweets from your account. I'm going to test with the output set at 24/96, "High Quality", no dithering. Let's see if the noise floor is better than AudioGate 2.
3. JRiver Media Center 20.0.87 [Windows used, Mac and Linux also available]. Upgrade from version 19 to 20 has introduced some new features (one of which I'm most interested in I'll talk about another time). Don't know if DSD decoding has changed... We shall see! For the test this year, I decided to stay with the default "safe" 24kHz low-pass filter like last year. Remember, you do have a choice: go to Tools --> Options... --> Advanced --> ... Configure input plug-in ... --> DSD input plug-in...
4. X Lossless Decoder (XLD) 20141129 [Mac OS X]. Freely available audio tool for Mac users. As of the 2014/11/09 release, it has the capability of decoding DSD files. Let's see how this newcomer compares! Again, decoding target was 24/96, I used higher quality "SoX VHQ Linear" resampling. Since the options allow easy adjustment of parameters like decimation and quantization, I will test both the default (8:1 decimation, 24-bit integer quantization) as well as higher quality (8:1 decimation, 32-bit floating point). [Decimation correlates to the output samplerate, so 8:1 for DSD64 is 352.8kHz output which then gets resampled by SoX to 96kHz.]
5. DSD Master 1.0 [Mac OS X]. Thank you to Richard at BitPerfect Sound Inc. for letting me give this program a spin (US$29.99 on the AppStore)! As per the company namesake, these are the same guys who brought you BitPerfect for the Mac. I actually downloaded this program in late 2014, unfortunately it took me awhile to get to the testing... After migrating to Windows in the last 2 years, I just haven't been using the Mac nearly as much. As with the other programs, I've set DSD Master to do all processing back to 24/96. Write as a WAV file. No gain applied. I see DSD Master can handle up to DSD256. One interesting feature is the DSD Hybrid mode where the DSD data is retained along with PCM conversion - large file sizes to be expected, and you will need BitPerfect 2.0 to play through iTunes to a DSD DAC.
For completeness, I will also post up the results for Weiss Saracon 01.61-27 which I obtained last year as the standard for comparison. (I borrowed Saracon to test last year so have not kept up as to whether there have been updated versions since.)
II. ResultsHere are the summary results (to keep the tables smaller, I separated the Windows and Mac software used):
|Windows DSD Conversion|
|Mac DSD Conversion|
If we compare the software updates, we see that there has been a substantial change with KORG AudioGate 3 compared to version 2 in terms of noise level; I'm seeing about a 10dB improvement compared to last year. If my suspicion is correct, perhaps they were using a stronger dithering algorithm back in version 2. The result is now much more in line with the other conversion packages.
As for JRiver 20 vs. 19, there has been little change; about 1-2dB difference. Note that JRiver posted fantastic numbers last year already so the slight improvement is actually very impressive!
Let's now look at the newcomers to this round-up...
Foobar DSDIFF did okay overall. Good performance and about the same as AudioGate when decoding the test signal. Hey, it's free :-).
XLD on the Mac provided good results as well. As you can see comparing the 24-bit integer to 32-bit floating point calculations, there was no difference. Any difference between 24-bit and 32-bit processing would be below the precision of the final 24/96 WAV file and RightMark's calculations. Therefore, if you use this program, you might as well stick with 24-bit integer calculations as it's faster.
Finally, we have the DSD Master software. Excellent quality output converting DSD64 to 24/96. Very low noise level and high dynamic range essentially the same as the much more expensive Weiss Saracon. (Remember, this is all relative since we're talking about noise levels below -130dB!)
Let's have a look at the graphs:
|Windows DSD Conversion - Frequency Response|
|Mac DSD Conversion - Frequency Response|
On the Mac, I see that neither XLD nor DSD Master perform much low-pass filtering - at least not within 48kHz.
Here are the noise level graphs:
|Windows DSD Conversion - Noise Level. Slight irregularity in the DSDIFF noise floor at high frequencies.|
|Mac DSD Conversion - Noise Level [note XLD tracings exactly the same so only the purple 32-bit tracing showing up]|
III. ConclusionsAs I suggested last year, I believe that DSD --> PCM conversion is transparent. I'm measuring the distortion added by both PCM (24/96) --> DSD64 [via Saracon] as well as DSD64 --> PCM (24/96) steps and as you can see, there is nothing showing up of concern. Fidelity is maintained beyond any DAC's analogue output I am aware of except for all that ultrasonic stuff peaking at about -85dB if filtering is not applied. Speaker system / headphone playback would add more distortion than this (at least within the audible frequencies).
You might be asking - what about subjective listening?
Bottom line: No need to worry about the sonic output from any of these converters IMO. Conversion algorithms and software look mature with little difference between them. The only significant choice is whether you want to have a low-pass filter in the conversion process (I do so I'd prefer Saracon or JRiver). I know some people claim they can hear qualitative differences between conversion programs beyond just level differences... Maybe. I'd certainly be impressed if anyone can show positive controlled, blinded listening test results given the minute changes I see/hear while doing these tests!
So guys, what do you think about the state of DSD these days? It really looks like the "push" has fizzled lately... Other than more DACs supporting native DSD playback, there seems to be little news out there. Anyone actually buying many DSD downloads?
As I wrote back in April 2013 (On SACD & DSD audio...), there are many factors working against DSD audio if the goal is to expand beyond just a small audio-geek niche format. It appears my concerns around the need for a modern file format that provides full tagging and data compression persists...
Psssstttt... Coders... Want to be famous? Pull together some code to create an open source ID3 taggable compression CODEC for DSD (.fdac? Free DSD Audio Codec - how about just .dac format). Get the guys at JRiver and foobar2000 to support it, and make sure it runs in Linux for music servers. I bet this format would become widely used among the guys ripping their SACD's and those who rip LPs into DSD! Make sure to support compression of DSD128+ as well just in case hi-res DSD becomes available (as far as I know the old Philips ProTECH DST Encoder could only handle DSD64)...
Until next time, have a wonderful April and hope you're enjoying the music!