Sunday, March 23, 2014

I have seen data sheets for Burr Brown PCM63 and PCM1702 that call them Sigma Delta.  Never the PCM 1704.  Maybe marketing changed, but all three of these dacs are are now known as PCM dacs, not sigma delta dacs.  They all feature dual collinear dacs summed together.  These collinear dacs uses the same ladder in opposite directions, hence canceling out error.

Here is the official data sheet on PCM 63.

I actually have a DAC that uses these, an Aragon D2A2, currently not working (some electrolytic in power supply failed and leaked).  I loved the fact that it has HDCD, but I hated the fact that the input selector goes back to position 1, which I couldn't use, after every power outage.  I had it wired in for the disk player (then, a Denon 2900 which lacked HDCD) and the Sonus input (to de-code HDCD discs), and the Dish receiver (to get Dish music).  The Dish connection (via Toslink) often sounded underwatery for some reason, so I quit using it and had to run Dish audio through an isolation transformer to fix a ground loop I had then.  (Little did I know, my whole house was ungrounded then.)  Getting HDCD was always problematic too (of course Sonos had to be on max level).  I rarely did the Sonos thing with it, too much hassle.  And before I knew it (a few years after I got it in 2007 or thereabouts) it died (20012?) with leaky capacitor in the power supply.   My Aragon 8008 BB from that same era is still doing fine.

Anyway, I do need to get D2A2 fixed.  It really is nice.  And now I know ladder dacs are interesting.

I saw StephenSank on bragging that his Pioneer DV-AX10 uses PCM1704, but that's not what the Pioneer website says, so I posted that to this blog about 1704's.  It turns out earlier ones, or something like that, used 1704's (it's shown in a 2000 service manual) but later Pioneer switched to Analog Devices (as one person saw when opening one).

Here's a great list of which DACs us which DAC chips.

Most of those are nearly unobtanium, or ultra expensive even now.  I saw the Levinson 360 going for $3100, and the Wadia's sell for still more.  Now, 14 years later.

An assemblage 3.1 sold for $1350 late last year.  Those are nearly unobtanium, it looks like.

On Sunday I bought an Onkyo RDV-1, which features two 1704 dacs, and apparently clock developed by Apogee.  It has SPDIF coax and toslink inputs, and can be used as a DAC.  One reviewer in 2012 found it better sounding as a DAC than his Schiit BiForst.  I am hopeful that it will at least allow 96kHz input (most likely it will not allow 192kHz input given the date of manufacture, but 96kHz spdif was common by 2000, and especially since Onkyo went so far as to get collaboration with Apogee, there is a good chance the input will allow 96kHz.).  Details have been hard to find on the web.  This was a DVD-Audio player made to the highest standards to compete with the top multichannel players of Sony, Denon, Toshiba, and others.  It was replaced far too soon with the RDV-1.1, which added SACD (what I now call modulated noise) capability, and the collectible 1704's were replaced with early sigma delta's by Wolfson.  The 1.1 lacked the external inputs too.  Onkyo apparently bowed to market pressure and the Sony SACD juggernaut.  Here's a blurb from the blog linked above:

Integra Research's RDV-1 DVD, DVD Audio, and CD Player
05/14/01 - The Integra Research RDV-1 is a THX Ultra certified DVD player that combines professional audio and video circuitry features to extract the ultimate performance from DVD, DVD Audio, and CDs -- including CD-R recordable disks. It can also function as an outboard D/A converter for other source units. The RDV-1 was designed from the ground up to set new standards for DVD performance and quality; the D/A converters and power supply alone make this product stand out from the competition. The RDV-1 uses 192kHz/24-Bit DAC to provide the most accurate DVD-Audio playback possible. The DAC uses a Vector Linear Conversion (VLC) system with a low jitter Master Clock developed by the professional audio firm, Apogee Electronics, of Santa Monica, CA. The Apogee clock all-but eliminates jitter and provides for the highest quality digital conversion available. The Vector Linear Conversion system completely eliminates the ""sonic unevenness"" inherent with conventional conversion methods.This low-jitter digital clock circuit was first developed by Apogee for the professional music recordingindustry, and is at the very heart of the best equipment used to make the master recordings for music. Now, Integra Research and Apogee have used the same technology to play these recordings back at home. Jitter is the measure of the lack of rhythm between digital sound samples. Unfortunately, the human ear and brain are very sensitive to these tiny timing irregularities. Jitter of just a few nanoseconds can compromise digital audio performance by interfering with the brain’s ability to perceive a stereo soundstage. By using the Apogee clock, the RDV-1 minimizes jitter and insures each digital sample arrives in perfect step with all the other samples. With all the digital signals zipping around inside a DVD player, there is a lot of potential for these signals to go where they do not belong. To circumvent these problems, Integra Researchhas developed high-quality dual power supplies to provide inherent DC stability and ensure that no traces of digital artifacts enter the audio paths or analog ground. The Integra Research RDV-1 is also state-of-the-art when it comes to video. It has progressive scan video output for a smooth, flicker-free image, and compatibility with digital-ready TVs that can upconvert video signals. The video playback system uses a 27MHz/10-Bit video D/A conversion with four times the accuracy of conventional 13.5MHz/8-Bit systems. In addition to a full complement of optical and coaxial digital outputs, the RDV-1 has a multichannel analog output (DB-25) for simple single-cable hookup of multichannel applications.

96kHz is all I need right now, since everything else I have runs at 96kHz, except I can use my Lavry AD10 to resample higher rates from my Denon 5900 or Oppo back down to 96kHz, so it can run through my Tact and 2496 DCX.

I figured out finally how I can get digital output for the midrange to run through a real ladder DAC (and not the reasonably good, but still sigma delta AKM, inside the DCX.  The answer is, bypass the DCX for the midrange!  I wonder why I had never thought of this before.  I can use a DEQ to create whatever crossover I want by combining parametric EQ's !  And the 2496 DEQ does have digital output.  And it can crucially add the needed time delay so I can time align my speakers, as before.  Actually, one could create a super DCX this way with three DEQ's.  But I think it's only worth bothering with for the midrange (which is 80Hz to 20k on my Acoustats, so it's really almost everything except deepest bass and super extreme highs), because it is a bit more hassle than using the DCX, as well as being more expensive (drop in the bucket compared with other solutions, like the $1000 digital output upgrade for the Behringer, which is no longer listed on a mod website, and I wonder if it handles the muting that the DCX needs properly).

So with my spare DEQ, and the new Onkyo, I can upgrade to full ladder DAC in the midrange.

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