Living Room System

Wednesday, July 2, 2014

Converted DSD sounds threadbare

The Denon DVD-9000 will not play SACD.  So how do I play SACD on new living room system?

I tried using Oppo BDP-95, which is supposed to convert SACD's to PCM (if you select that option, which I did) and give you 88.2kHz PCM out both digital outputs and HDMI.  Playing Weather Report SACD, I only seemed to get 44.1kHz through the HDMI, and it had a very pure sound, I thought at first, but then later felt was threadbare, as if the whole thing were a synthesized realization.

Well, of course, Weather Report does use a lot of synths.  But then I played Weather Report on the Denon 5900 (re-sampled by the Lavry AD10) and it sounded much more real, I felt, as if missing information had been restored.

The magic is in the noise.  If you convert DSD to PCM, you eliminate much of the noise.  When you play an SACD, the noise is there, big time, but gets largely filtered out.  A tiny tiny bit of that noise remains.  Now this noise is not random, it is highly correlated with the recorded signal.  So that tiny bit of extra noise you get when listening to SACD or DSD when converted directly, not through PCM, is not just noise, it's information from the original event.

So SACD/DSD playback actually relies on its own high frequency "noise" to sound real.

Perhaps I could get some of that when I get the 88.2kHz conversion.  If I can't get that, I might have to keep the Denon 5900 in the living room for SACD's, or get another SACD player.



Saturday, June 28, 2014

Hydrogen Audio are Good

I like Hydrogen Audio objectivists.  I am often disappointed with myself that I'm not an audio objectivist by their standards, or perhaps any.

One thing for sure, if you don't like spending money on unproven things, don't follow my approach, which pretty much guarantees that.

Arnold B. Krueger, despite his fame, works tirelessly and sympathetically to help find the best explanations for everything.  He is not the kind of in-your-face or casually hurtful person you might suspect from his reputation and his avatar.  But he is not the kind to surrender to subjectivism either.  He sticks to his reason, and I respect that.

I like doing what I do anyway.  I do focus a lot on things objectivists like, such a speakers and room acoustics.  But I also (waste?) a lot of time with electronics whose levels of performance should not be required for satisfactory reproduction.

I know that such things may not be important AT ALL.  I just enjoy working them anyway.  I try not to make big claims (but sometimes I do anyway, such as my recent war against sigma delta).  Whatever I might say, you can be sure that I do also always harbor considerable doubt at my own ideas.

I stay away from things where I have no understanding of how it's supposed to make things sound better, look better, or be more fun.  I think that is the wrong approach to audio.  If you don't have a hypothesis you are exploring, can understand roughly, or measure, I don't think it will be easy to make progress in a sound improving direction.

Many people think "science" is all about observation.  But actually, it always has to start with a plausible story.  Without a story, it's just all shots in the dark.






Tuesday, June 24, 2014

Jitter in new Toslink/SPDIF link

Now that I've finally implemented a digital link from the kitchen Mac computer to the living room stereo, I'm a bit worried about jitter.  So far I haven't noticed any loss of digital lock, or any bad sound (in fact, it sounds better than anything) but as an audiophile with obsessive tendencies (like most) I nevertheless worry about such things (though not as uselessly as some people, I like to think).

The link is not as simple as I might like.  At minimum, it has to convert the Toslink output of the Mac (conveniently combined with the headphone jack) into coax to run across about 65 feet of coax to the living room (50ft running through ceiling reaching wall jacks, and an additional 15 feet of patch cords…or the ceiling wire might also be 75 ft, I provided both lengths to the electricians and don't remember what they actually used).

Probably most of the degradation would come from conversion into Toslink inside the mac, and then conversion from Toslink to coax, and maybe in the Toslink cables themselves.

But actually, it's more complicated than that, because I need to run the Toslink from the Mac into at least a 3 way splitter.  Currently I use a INDAY 4 way Toslink splitter, which splits off one line for the living room (which gets converted to coax as described above), one line for the kitchen system (a Yamaha AV receiver), and one line for the hard drive recorder (which only accepts analog inputs, so therefore goes through an EMU audio interface repurposed as a DAC).

As I said, everything seems to work perfectly, but the line going to the living room has to pass through these interfaces:

1) The Mac Toslink output
2) 1 foot very high grade plastic Toslink cable
3) INDAY active splitter
4) 12 foot high grade plastic Toslink cable
5) MAudio CO2 converter
6) 2 foot precision coax
8) 50 feet in-wall coax with F terminations
9) F-to-RCA adapter
10) 6 foot RG-6 patch cord with RCA terminations
11) RCA-to-RCA barrel adapter
12) 6 foot Monster Video 3 patch cord with RCA terminations

Now the easiest thing to fix would be 9-12, I can simply get a 10 foot precision video cable terminated with F connector on one end and RCA on the other.  I will be ordering that next month.

But what actually worries me more are the Toslink conversions.  First the digital signal is emitted through a Toslink LED in the Mac.  Count that as 1 hop.  Then in the INDAY splitter, the digital is received and retransmitted.  Count that as 2 hops.  Then, in the CO2 adapter, it goes through one more Toslink receiver.  So count this as 4 optical "hops."  A minimal Toslink connection involves only two hops: sender and receiver.  Each optical hop limits rise time and therefore makes jitter possible.

I could easily change this by running the Toslink from the Mac through a different kind of splitter.  The best kind is the one that I haven't yet found, which would have two optical outputs and one coax output.  Instead, the typical kind of "splitter/converter" has one coax output and one optical output.  That would work just dandy for the living room connection, which would be reduced from 4 hops to 2 hops.  But meanwhile, it would increase the number of hops for the kitchen receiver from 4 to 6, because I'd still have to use the INDAY splitter on the Toslink output of the first converter to get the two Toslink outputs that I need, and likewise the number of hops to the EMU audio interface would increase to 6.  They might not even work with that many hops (though, I expect they would), but at best they would see increased likelihood of jitter, despite the use of very short 1 foot very high grade Toslink cables.

The MAudio CO2 can be used as that new kind of splitter/converter.  By changing some switches, I could change it to take Toslink input and produce both Toslink and Coax outputs.  And there are also other similar splitter/converters available, including one from Calrad.  (MAudio no longer makes the CO2, but there is a Calrad replacement which can also be used as one Toslink to Toslink and Coax.)

But I have seen nothing doing exactly what I want: 1 Toslink to 2 (or 3) Toslink and 1 coax.  There are other variations, however.  Calrad makes an adapter that takes Toslink input and gives as output 1 Toslink, 1 Coax, and one stereo output.  With that unit I would put living room at the minimum of 2 optical hops, and keep the kitchen receiver at 4 optical hops (where it is now).  And I would eliminate the need for the EMU interface.  But that's also a rub, because I doubt the DAC in the Calrad adapter would be as good as the one in the EMU interface (which is professional grade, >110dB S/N, etc) and would also lack the convenient volume control.  Plus, I'd need to use a stereo audio isolation transformer on the analog outputs because otherwise I'd be connecting the grounds of my kitchen hard drive recorder and my living room audio system (very undesirable!).  That isolation transformer would not be as perfect as the optical isolation now used, AND it would further slightly degrade the analog audio sent to the hard drive recorder.

There might be some sort of switch that would do the trick.  This one looks like it might work, except it's unclear whether it actually converts Toslink to coax or merely switches Toslink to Toslink and Coax to Coax.  Plus it's way overcomplicated for what I need, since it also switches and distributes 4 component video inputs, though surprisingly inexpensive also (which raises other doubts).

And I haven't even begun to consider adding yet another digital link to the master bedroom.  I could easily add that on to the system I have now (simply by adding another CO2 converter to the currently unused 4th Toslink output of the INDAY splitter) but it would not work with any of the other adapters or switches I've mentioned so far.

In assessing new digital audio distribution strategies, it might be useful to measure the digital transmission system itself or the jitter it produces.  Here's the best discussion of measuring jitter I've seen.

Here are some very expensive digital analyzers I won't be buying.

Here's a long discussion of transports and jitter--but also looks closely at the SPDIF and Toslink interfaces.

Here's a discussion of Jitter that claims audibility based on AES analytics (not ABX testing) to 120pS for 16 bit and 20pS for 20 bit.  (The ABX testing shows much lower sensitivity up to 10nS, 100 times larger.)  Here's a further discussion of the importance of characteristic impedance by the same author (Steve Nugent of Empirical Audio).

Here is Toslink vs Coax measurement, and the coax is said to be 7 times better.

Here is MSB paper on jitter.

FINALLY, I found what I need, a Toslink splitter with extra coax output, the Inday TLDA-22.

Actually, what would be really perfect would be if it had two galvanically isolated coax outputs, so I could send coax digital to two different rooms.  Given that two galvanically isolated outputs would be pretty hard to do anyway, one coax output is ok.

Monday, June 23, 2014

Dirac

Here's a review of Dirac pc-based equalization system and other equalization systems.

Interesting.  However I wouldn't like having to run everything through my Mac for correction.

My last time around (in 2010) with automated room eq didn't turn out well.  Optimizing the center room sweet spot made the room boundaries in a huge boom zone.  Next time, I plan to only correct the subwoofer bass, and I plan to do a multipoint correction which takes into account boundary positions as well as the current less central sweet spot.  I still plan to use the DualCore DSPeaker to do this.  It's hard to know how the DSPeaker algorithms compare with Dirac, but DSPeaker is sure more convenient for me.

Other software for room eq includes Audiolense, Acourate, and REW.  REW creates filters that you load onto a PEQ device (I still have the one they suggested in factory box).

Here's a quick summary of DRC, Acourate, Audiolense, Ultimate Equalizer 2.0 HT, Dirac, and MathAudio.




Sunday, June 22, 2014

Audiophile Information Model

A musical event, either live, or the sum total of pre-recorded takes, consists of a very large amount of information, though perhaps much of it redundant.  A produced album consists of a huge reduction in the original information, but presumably selected or translated as to concentrate the musical information from the redundant, and have a particular style.

Listening to a recording, and audiophile gathers information of many kinds, originating from the recording,  constructed (interpolated or stylized) mentally from information in the recording, and caused by the interaction between the recording and the reproducing system.

In no single listening can all the information be fully gathered originating from the recording, in each listening only a subset of information originating from the recording is actually gathered, and the subset gathered on successive listenings differs, though usually with large central overlap.  But while the subset of information gathered originating from the recording may vary little, the impact on mental reconstruction may be discontinuously huge, because the construction process is itself highly discontinuous and non-linear.  The information gathered resulting from interaction with the reproducing system may also vary only slightly, but have large discontinuous impact upon mental reconstruction.

Now many audio reproducing systems are simplifying systems.  They simplify the information available from the recording.  A classic and ubiquitous way is by limiting frequency response.  Few reproducing systems do not restrict frequency response in some way, though most ubiquitously in the very deep bass.  So while we may hear to 20 Hz and feel to 16 Hz, few reproduction systems do a good job of reproducing the octave below 32 Hz.  Meanwhile, systems with 32 Hz response may have high end response to 22kHz, which is actually a violation of a longstanding rule of frequency response bandwidth limiting…low frequency restriction should be matched by high frequency restriction to sound balanced, and response to 20kHz corresponds with low frequency response to 20Hz.

But simplification in other forms is actually more serious.  Most of these are simplification by obscurity.  Resonances draw attention to themselves and their intermodulations with the music, but obscure adjacent details.

Systems involving dynamic compression are another type.  The worst of those can simplify by reduction.  MP3 is an example of such a system, the missing information is simply gone.

I maintain that DSD is such a dynamic compression system, as are all PWM and delta sigma systems.  They often rely on reduced human sensitivity to high frequency dynamic range.  Canonical DSD has 1 bit of resolution at 64fs, which means little more than 65^2 possible states at 20kHz.  Redbook 16 bit 44.1kHz digital has 65536^2 possible states at that frequency.

Now you can see from the vast amount of information potentially available at just one cycle of the highest frequency we can hear…we can never hear it all, but only a subset.  But if there is vastly reduced information in the recording itself, then more overlapping subsets of information may be heard on each listening.  Ultimately making it boring.




Monday, June 16, 2014

More evidence from a big test and upgrade

Now believing that ladder DACs are better than Sigma Delta DACs, I am disappointed by the fact that the way I was playing high resolution media necessarily involves passing through one set of sigma delta DACs.  Those are the Burr Brown 1790's in my Denon 5900 universal disc player.  The analog output of that player gets resampled to digital (via a professional grade Lavry AD10 analog to digital converter) for level, crossover, and eq processing, and converted to analog the last time by the Burr Brown 1704's in my Onkyo RDV-1 operating as a DAC.

Onkyo RDV-1 (on bottom) running as DAC
Unfortunately, I can't simply play DVD-Audio discs on the RDV-1 and use it as a DAC at the same time.  Even if I were to give up the crossover and EQ parts of my system (and therefore the subs and super tweeters), I would still have no way to set the level on the RDV-1 output.  I use no analog attenuators (and I generally find that passive attenuators make the sound dark, dead, and closed-in).  The RDV-1 is simply connected to my main power amp via short audiophile grade interconnects.  As complicated as my system looks, the analog domain past the digital converters is very simple--just wires connecting to a well designed amplifier.

But what I could do, and what I did, was take the RDV-1 offline for awhile (Saturday and Sunday) and  use it as the analog source for the Lavry AD10, and record the Lavry digital on my Alesis Masterlink.  I could then burn those new digital files to a DVD-Video disk at 24/96, and play that in the Denon using digital output.  In the whole process, I would be using the ladder DACs in the RDV-1 twice, first for making the new digital files, and finally as my main system DAC.  And I would not be using sigma delta DACs at all, all other transfers would be digital.

Recording tracks on the Masterlink was a relearning experience and it took quite a bit of time to record tracks in groups of three, burn them to CD24 discs with the 24/96 digital information unaltered, and copy them to my Mac mini.  After I had copied over about 6 songs from the DVD-Audio of Santana Supernatural, it occurred to me that rather than burning DVD's with the new digital files to play on the Denon 5900, it would take about the same effort or less to create a SPDIF digital connection from my Mac to my living room system.  And then, I would also be able to play other digital files from the Mac without burning discs…including the Audiogon Sampler I just downloaded from HDTracks over the last week (but without any actual means to play it).  And then I could get more albums from HDTracks, possibly including the official high resolution files from Santana Supernatural, which are likely to be even better than my resampled versions.  (I will NOT be getting any DSD files, which I have no means of playing and I strongly believe are inferior anyway.)

So that was the big upgrade--I added Hirez file playing capability to my living room and kitchen systems.  I had been behind the curve a few years on this.  To allow the Mac to actually play high resolution audio files, I downloaded and installed Amarra Hifi for $49.  If the Mac natively plays high resolution files at all (and I'm not sure it does anyway), it does so by resampling them to 44.1 kHz and 16 bit resolution.  Amarra bypasses that operation and makes the Mac play back files up to 96kHz in their native sampling rate, and in bit clear fashion so all the bits get through.  The digital connection uses my new in-wall network, which has a Belden RG-6 line running from the kitchen to the living room.  I take the Toslink output from the Mac, run it through a 12 foot Toslink cable, convert to coax with a M-Audio CO2, then run through 75 ohm coax cables and a couple F-to-RCA adapters, and plug that into my Tact preamp as one of the coax digital inputs.  I had all the needed cables and adapters on hand, though I also needed to use one RCA barrel connector to join two RCA terminated 75 ohm cables.  I should get better quality cables cut to the correct length later.  Even with the adhoc whirring, the digital connection from Mac to living room works perfectly, and there is no detectable ground loop though the CO2 is powered in the Kitchen through it's own transformer which has a two wire AC connection.  Though some audiophiles may frown at such a "complex" system because of all different wires, I see only a direct digital connection without any synchronous or asynchronous conversion or modulation.  The clock being used is the one in the Mac Mini, and bit buffering is done right there--by hardware and Amarra, and that is the best possible place.

I wasn't actually expecting to be able to play Hirez in the kitchen, but to my delight the Yamaha 5790 receiver takes the 24/96kHz digital input and plays it just fine.  I have never heard such good sound being played in the kitchen.  I also understand iTunes much better, and that I can simply select a bunch of songs and put them into a playlist.  If you don't play from playlists, iTunes will simply proceed to play every song available, which could be dangerous.  And adding songs to iTunes is most simply done just by clicking on them.

Playing the new Hirez files, the added resolution from bypassing the sigma delta converters in my Denon 5900 was obvious.  There is much more resolution now!  Sometimes I felt the highs were a bit strident, and the brass extra brassy, but the sound was much more interesting and involving and worth putting up with the blemishes.  Better cabling might help the stridency.  It had a neutral and transparent sound with layer upon layer of stuff going on in audio that was audible for the first time.  By comparison, the original path through the 5900 was like rose colored glasses--it always had the passion, and it always sounds pleasant, but it's missing many of the details.  That's the signature of sigma delta converters, and what would be expected from the information loss that is inevitable from them.

One thing I hadn't been expecting was the newfound bass tightness.  Although sigma delta converters should work fine in the bass, they might work "too well."  I think they were halving the bass sometimes, working like a subharmonic synthesizer.  Now the bass is deep and tuneful at the same time.  Far more tuneful.

Of course the differences I'm describing are the differences between starting with the Denon 5900 and the new Onkyo RDV-1.  The differences could be caused by other aspects of the circuitry.  But I think both of these machines are well engineered, and that most of the differences come from the differences between the digital to analog converters they use, which are fundamentally different (though ironically both made by Burr Brown).




Saturday, June 14, 2014

Sonos Line-In levels

I use the line-in feature of my Sonos system more than anything else.  It's incredibly convenient and sounds good.  The main things I listen through Sonos line-in are my two FM tuners (Kenwood KT-6040 and Pioneer F-26) which are set to Jazz/Indie KRTU and Classical KPAC.

But I often wonder about setting the input level.  Unfortunately Sonos provides no visible feedback of clipping through the line input.

Well here is what Sonos Support says about the line input levels.  Interpolating for levels 3-5 and 7, here are the max input levels as best I figure them now:

2.2V  Level 1 (low)
2.0V  Level 2
1.8V  Level 3
1.6V  Level 4
1.4V  Level 5
1.2V  Level 6
1.1V  Level 7
1.0V  Level 8
0.8V  Level 9
0.6V  Level 10

My Kenwood KT-6040 specs say output is 0.8V at 100% FM modulation.  Since modulation can go a bit higher than 100% in practice, this corresponds to a max output of about 1.0V, which was a standard line level before CD players were introduced (CD players have output of 2.1V).  Allowing a further bit of headroom, I've just set the Sonos to Level 5 which is 1.4V.  Previously I had been using Level 1 or 2, which is a waste of dynamic range.

It often takes a few minutes to get used to higher resolution, and that was true when I changed from Level 2 to Level 5.  But there is no audible clipping or harshness, just more information.