SACD Player/Transport Choices

I have a very different perspective, not being based in North America!

First, when I play SACD I use more than 2 channels.  The European way of sending digital audio uses purpose designed HDMI technology which supports a huge array of formats and channels. HDMI includes Ethernet, almost as an afterthought!

On the other hand, I2S was designed in 1957 to allow two integrated circuits on a board to communicate 2-channel 16-bit PCM encoded audio. To communicate between boards, I2S developers have borrowed the HDMI connectors and cable, but not the rest of the technology.  Why anyone would throw away most of the channels recorded on a SACD is beyond me.

I have a couple of universal disk transports which play SACD along with 4k Blu-Ray, DVD and CDs.  These transports output via two HDMI cables, one exclusively for audio.  In this mode, they obviously rely on an external DAC.

One of my transports is an ultracheap Sony - about $250 - and it is only a transport.  My other unit is a Reavon for about 10 times the price.  Amazingly, it contains two Burr-Brown DACs but they are a complete waste for SACD.  SACD is down converted to CD quality - something I found immediately noticeable.  As a transport outputting HDMI, the Reavon is fine.

Some of the Dolby Atmos multi-channel recordings, delivered on Blu-Ray Audio-only disks, are absolutely stunning.  I am mainly referencing the Norwegian www.2L.no label. These disks play natively on each of my transports.

@mahler123 

The Reavon universal players are very similar to the Oppo and use the same 'System on a Chip" for controlling the device, but have inferior DACs which cannot handle DSD natively - they down-sample to 16-bit PCM.

@faustuss 

The Reavon 110 and 200 universal disk players can absolutely output native DSD, over one or both of their HDMI outputs

@faustuss

Not sure if you are referring to the Reavon universal disk transport / players, but the UBR-X110 I mentioned is a pure transport and its outputs are digital only - 2 x HDMI, 1 x coax digital and 1 x optical digital.  It transports SACD natively over HDMI.

The UBR-X200 on the other hand does add two Burr-Brown DACs, one for two-channel analogue playback and one for multi-channel, including SACDs.  These DACs are inferior to the ESS Sabre DACs in the Oppo, in particular because they cannot natively process DSD.  They down-convert to CD quality!  So in my book, the DACs in the 200 are a waste of money, especially when compared to the DAC-less 110.  Both are excellent transports.

HDMI is a digital standard, but that does not stop others from trying to push analogue down the cable.  The Dometic analogue TV cameras in my motorhome connect to the display head using an HDMI cable and standard connections, which are particularly unsuitable for in-vehicle installations.  There is a rugged HDMI connector made specifically for in-vehicle use, but Dometic don't use it.  This is an unnatural act, in my opinion, like using HDMI cable for I2S 

@dinov 

I am not aware of any other SACD transports, just players. It’s the proprietary nature of SACD that make a transport difficult to make without some sort of special connection like McIntosh provides

I earlier gave two examples transports that natively spin SACD disks , one a cheap Sony, the other a Reavon.  Both use one of the most widely standards for high speed digital communication, HDMI.

Reavon shares its SOC (System On a Chip) with Oppo and newer players

@bergenma

Great questions that probably bother silver disk fans! 

I bought a Reavon UBR-X200 on a whim after my Marantz Universal Disk Player (UDP) carked it.  Just went to a couple of HiFi shops nearby, The first told me I did not want to play SACDs (I have hundreds) and the second had just taken delivery of their first Reavon, which I had never heard of.  I bought it anyway, because functionally it appeared to do everything I wanted.  

There was also the Reavon UBR-X100 but it did not support SACD at all.  The UBR-X110, which functions as a SACD transport, had not reached the market at that time.

My main left and right channels were played through Quad electrostatic speakers (2905) powered by a Krell class A amplifier (KSA-80) with an 18" Velodyne subwoofer.

My Reavon is connected by one of its HDMI outputs to my Audio Visual (AV) preprocessor, a Marantz AV8802.  The Marantz tells me exactly what is being input including the connector, format and bit rate.  The Reavon absolutely can output DSD 5.1 (Direct Stream Digital) natively over HDMI, as well as PCM from Pure Audio Blu-rays, Dolby Atmos, etc.

I also hooked up the seven analog output pairs to the Marantz using RCA connectors, as well as the two channel analog output using balanced XLR connectors.

The HiFi store promised me that CD playback would be as good as my venerable Sony player over balanced XLR, that Pure Audio would be as good as my old Marantz UDP, and that SACD analog output would be as good or better than the Marantz.

No problems with CD and Pure Audio playback, but when I switched to SACD I got full volume white noise (or pink?).  The manual was wrong!  Once sorted, the multi-channel SACD sound was way below what I was used to.  I checked the specifications of the two-channel and multi-channel Burr Brown DACs.  Neither mentioned DSD which is a good indication they cannot natively process DSD.  I wrote to Reavon and they confirmed multi-channel DSD is down converted to CD quality PCM.

The two-channel Reavon DAC has better specifications, so I thought 2-channel DSD might be down converted to a higher resolution PCM but no, still just CD quality.  No review that I have read mentions this, but to me the poor sound quality was almost instantly apparent.

My Marantz AV8802 on the other hand has 8 AKM 2-channel DACs similar in specification to the ESS Sabres used by Oppo.  They process DSD natively. Using the Reavon as a pure transport works a treat when the Marantz is doing the analog conversion.

By the way, changing the output formats on the Reavon is painful: the machine has to be restarted.  Now I just leave it on HDMI output, no problems.

I don’t know how good the Reavon UBR-X110 is - the power supplies are not as advanced as the X200 for a start.  The addition of a 3-mm thick steel baseplate makes both machines feel like quality though!

There are other derivatives now on the market including Magnetar which use the same Mediatek System on a Chip (SOC).  I believe Cambridge Audio has one as well.  Pioneer seem still active, as is Panasonic but pride stops them offering rival Sony’s SACD format!  There was also a Chinese-brand but I have forgotten its name.

I have a couple of very cheap Sony UDP transports, but I have not done a direct comparison.  I suspect they are just as good, sonically.

Does I2S support multi-channel DSD?  Until recently I had never heard of I2S which dates back to 1957.

My final thought is that the value-for-money offered by big manufacturers like Sony and Denon/Marantz far exceeds what niche manufacturers can offer, unless they piggback on others R&D, such as the Mediatek SOC.

@bergenma 

but given the guts of the X110 are inferior to the model you have

To be fair to Raevon, most of the internals of the X110 and X200 are identical.  The X200 has the addition of analogue audio outputs and it looks to me that the power supply has been upgraded to suit analogue, with a well shielded toroidal transformer.

Both boxes have a pretty low component count which should enhance reliability of the electronics.  The MediaTek chips are in the highest classification of integrated circuit densities.

The Magnetar UDP800 is essentially a Raevon X200 without the second Burr Brown DAC, which delivers 7.1 and 5.1 channel analogue over RCA interconnects.  Raevon and Magnetar are a bit like Marantz and Denon - sister companies.

According to Reavon’s website

"DSD is natively transported via HDMI as a fully digital signal up to 5.1 multichanel"

But the website also claims

"The best possible picture and sound technologies for an incredible home cinema experience"

Down-converting SACD to CD quality on analogue playback is not the best possible sound technology but full SACD quality is delivered over HDMI to a suitable DAC or pre-amplifier. No disc player should output full volume noise though

@faustuss

Now that you have educated yourself, you may be able to appreciate that when we say that a transport delivers Direct Stream Digital (DSD) natively over High-Definition Multimedia Interface (HDMI), we really mean it!

DSD

To be absolutely clear, DSD is a brilliantly simple way of encoding sound waves.  Each successive bit indicates whether to notch the digital sound pressure level up or down by one quantum, when compared to the real analogue sound pressure level, Silence is represented by an endless series of (up, down) at Megahertz rates.  Rising sound pressure will have more ups than downs, while falling has more downs than ups.  The analogue to digital conversion should not be more than half a quantum out. 

Moreover the quantisation noise can be removed by passing the bit stream through a gentle low-pass filter rolling off in the MHz region.  In principle the output can be played as an analogue signal without further processing except for a volume control!

Conventionally geeks refer to ups as 1 and downs as 0 in the digital domain.

PCM

By contrast, Pulse Code Modulation (PCM) samples the sound pressure level about 44,000 times per second (using CDs as an example).  At each sample, it measures the sound pressure level on a linear scale from about -32,000 to +32,000.  This range can be encoded into 16 binary bits (0 or 1) where each bit represents twice the level of the previous bit.

PCM cannot encode frequencies higher than half the sampling rate, and the low pass filters needed to remove digital noise must operate close to audible high frequencies.

Binary

You can see how this works by counting in binary using your fingers.  Using only the four fingers on your left hand, you can count from decimal 0 to 15.  The first finger represents 0 or 1, the next 0 or 2, then 0 or 4 etc.  You add up all the fingers to get the decimal equivalent. Keep going with the four fingers on your right hand and you get anywhere from decimal 0 to 255.  (This is the range of one computer byte, and looks like part of a four byte Internet Protocol version 4 address, eg 192.255.1.201)

Add in four toes from each foot, giving you 16 bits, and you can count from 0 to 65535.  Or -32767 to +32768 if one finger represents the - sign, which is handy because sound waves go both up and down from silence (0).  Why didn’t our Neanderthal relatives invent counting this way?

PCM linearity

So what is the issue with PCM?  Well, the most significant bit represents a value 16384 times bigger than the least significant bit.  At some point, when the sound pressure rises by 1, all fifteen lower bits switch off and the biggest one switches on.  It is almost impossible to manufacture any analogue device, like a resistor, to this degree of accuracy.

Imagine feeding every number between -32767 and +32768 in sequence to a Digital to Analogue Converter (DAC). Ideally the output would increase with every sample – known as a monotonic increase.  But resistors cannot be made accurate enough.

Philips knew this from the get-go, and just used the top 14 bits in their early CD players.  It gets even more ridiculous with high resolution at 24 bits, which needs 256 times more accuracy still, or 32 bits which needs 65,536 times the accuracy in order to resolve every bit.

Sigma-Delta

Enter the sigma-delta technique.  If you take the difference between consecutive PCM  levels, you can in theory add or subtract that many quanta to get from one sample to the next. So in effect, you convert the differences between consecutive sample to a local DSD stream.  It is easier to add a number of near-identical charges than to accurately trim a resistor.

It is similarly easy to create a PCM sequence from a DSD stream – just count the net number of ups and downs over 64 bits (for DSD64) and add or subtract from the previous sample.  But you cannot go the other way without guessing where each up or down should fit in time.  You lose information.  This is why a DAC that handles a DSD stream natively is better than a DAC chip that needs DSD to be externally converted to PCM.

Transporting digital formats

Any digital format can be chunked up into packets.  The packets can be any size.

If you want to send say a DSD stream over I2S, just chunk it up into 16-bit chunks and push each chunk into the pipeline.  The receiving end has to know what format is being delivered so it can unpack the chunks into a new stream identical to the original DSD stream.  It is not really over but inside and nothing is lost. 

The network technology can be anything that supports chunks (known as packets).  Internet Protocol, Ethernet, Universal Serial Bus (USB); anything will do if it is error free and fast enough.

On the other hand, if the DSD stream has to be converted to the two-channel 16-bit PCM samples I2S expects, then the timing detail gets lost and most likely the conversion will not be monotonic.