24/192 over SPDIF - already possible?

Hi,

I recently saw this on Accuphase DP-510 web page: "coaxial input can handle audio data up to a sampling frequency of 192 kHz and 24-bit resolution":

http://www.accuphase.com/model/dp-510.html

I prevously thought that only 24/96 signal could go through SPDIF coax? My upsampler has dual AES (I think) lines for this kind of signal, as nothing else could handle 24/192 back in the day - it was made in 1999.

Does anyone know about this?

 

Yes, 24/192 has been supported by both SPDIF coax and Toslink for a long time. What is an 'upsampler'? Do you mean a DAC? You mention 'dual AES' but to my understanding AES is a single line digital connection. Could you mean the balanced XLR analog outputs on a DAC which use the same type connectors as an AES cable. It is similar in the difference between RCA connectors being used on both analog interconnects and digital coax cables.

 

That is most likely a limitation of the DAC hardware.

My Electrocompaniet ECD-1 from 2002 can only handle 24/96 signals as well, although it upsamples internally to 24/192.

 

There was a recent thread on TOSLINK limitations ... http://www.stevehoffman.tv/forums/showthread.php?t=279987

The S/PDIF spec (IEC958) originally only covered sample rates to 48K, and most interface cables and transceivers weren't designed for a very wide bandwidth. To maintain low clock jitter, some of the companies that first started using S/PDIF at higher sample rates used the duplex configuration you describe, with the higher rate signal multiplexed across the two cables, each operating at the lower rate. At first, some companies did this for 96K, but I think once there were 96K transmitters and receivers they all went to single lines up to 96K.

Note that in addition to audio data, the interface carries an embedded `bit-clock' at 64 cycles per frame, and synchronising patterns for deriving a sample rate clock. For a sample rate of 48kHz the embedded clock is at 3.072MHz.

Cheap TOSLINK really doesn't have the bandwidth for high sample rates if you want to maintain low jitter on the recovered clock, but it will still work. Coax has some of the same bandwidth issues and requires careful terminations, but doesn't have that built-in limitation of the plastic cable.

Characteristics Standard IEC958 "Digital audio interface" from EBU (European Broadcasting Union) details:
Audio format : linear 16 bit default, up to 24 bit expandable
Allowed sampling frequencies (Fs) of the audio: 44.1kHz from CD 48 kHz from DAT 32 kHz from DSR One way communication: from a transmitter to a receiver.
Control information:
V (validity) bit : indicates if audio sample is valid.
U (user) bit : user free coding i.e. running time song, track number.
C (channel status) bit : emphasis, sampling rate and copy permit.
P (parity) bit : error detection bit to check for good reception.
Coding format: biphase mark except the headers (preambles), for sync purposes.
Bandwidth occupation : 100kHz up to 6Mhz (no DC!)
Signal bitrate is 2.8Mhz (Fs=44.1kHz), 2Mhz (Fs=32kHz) and 3.1Mhz (Fs=48kHz).

 

Interesting. So you guys say that 24/192 via coax cable is old news? How come there are no more pieces of kit that can take 24/192 signal via their coax inputs? Dacs or players with digital inputs, whatever.

To my knowledge, even current dCS dacs support 24/192 only through firewire or USB digital inputs. Or the above mentioned dual AES "pipes", which is what they used to use before fireware was born.

 

There are quite a few DACs that support 24/192 via S/PDIF, either Toslink or coax; perhaps more than via USB, since good USB boards for 24/192 are pretty recent (for example, the Rega DAC can only accept 24/192 via S/PDIF, and the NuForce DAC-9 just got its USB input upgraded).

 

That's correct on the dCS side of things. My Paganini only currently supports 24/96 via USB but does the dual AES as you mentioned. Im using the Debussy to get 24/192, fed by the clock of the Pag.

They are promising a new USB board any day though...

Glad that baby is modular!

 

WARNING: THREAD HIJACK

It frankly pisses me off that by the time the music I want to listen to in 24/192 will be available, i will be as dead as Debussy (I love Debussy too, you understand).