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).

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