Topic: Sony PCMD 100 Can Toslink In be Changed to Spdif?

[ghibliss]

I am interested in knowing if one can simply change the input connector on this recorder from it's current mini Toslink to a two pin connector to support Coaxial spdif input.  I read that the Toslink receiver simply consists of an opto coupler and an IC which converts the light pulses to a voltage which has the same spec as spdif ie .5 - .6 volts with a .2 minimum according to wikipedia.  I am trying to get feedback from Sony on this now as I would much prefer to use a locking style connector over the toslink connector to eliminate the possibility of cable pull out during recording a show.  There is ample room inside the recorder for a connector as the toslink receiver is fairly large.

The specification for the toslink input connector has to meet eiajCP1201 which is an industry standard specification for toslink connectors.  The output is simply on three legs to the pcb VCC (5 Volts), Ground, and V Out which is Spdif In.   

I have not been able to locate a schematic of the Sony recorder so if someone has one it might answer the question that i have!

[kleiner Rainer]

ghibliss,

the TOSLINK receivers I know are integrated into a stereo minijack (3.5mm Dia.). The output is CMOS level going directly into the DSP. For a well made SP/DIF input you need an input transformer to isolate the input signal and a pulse forming circuit to feed the differential low level signal into the DSP.

Here are some informations about SP/DIF and TOSLINK, including converter schematics:

http://www.epanorama.net/documents/audio/spdif.html

It seems easier to me to use a SP/DIF to opto converter. The TOSLINK connectors I used kind of locked into the jack, so I never had a connection separate. Maybe I am conditioned by my cassette tape days to keep mechanical shock and vibration from affecting my recorders...

Greetings,

Rainer

[ghibliss]

Here are two toslink connector specification sheets from Sharp and another manufacturer from China. They all look virtually identical as far as pin out and specifications.  If you scroll down to the last page of the first document you will see the diagram displays that pin 3 is SPDIF in .  If you look at the bottom of page 3 it says:

"The DLR1151-1 light receiving unit satisfies EIAJ CP-1201 digital audio interface standard." Applications:

Descriptions
The light receiving unit is a standard-package product with connector and opto-electric component packaged with PD and drive I/V amplifier IC. The function of unit changes the light signal into electrical signal.
The unit is operated at single +5V and the input signal is TTL compatible. The DLT1151-1 has a
maximum operating speed of 16 Mbps.

Applications:

Audio equipment

Digital optical data link

MD

Sound card

Do you agree that since the description of pin 3 is "SPDIF in" that the signal is no different than if it was directly from a SPDIF cable rather than via a Toslink connector which then translates the pulses of light to a TTL voltage and presents it as SPDIF to the PCB? 
 

[kleiner Rainer]

Do you agree that since the description of pin 3 is "SPDIF in" that the signal is no different than if it was directly from a SPDIF cable rather than via a Toslink connector which then translates the pulses of light to a TTL voltage and presents it as SPDIF to the PCB? 
 

No, I don´t. You are mixing up different levels of the OSI Layer model. S/PDIF describes the data structure of serial audio data. Coax and TOSLINK are two different ways to physically transmit it. Closely related is the AES/EBU way to transmit serial audio data - the physical interface is slightly different to the consumer coax connection, but the data representation is close, but not equal, as many tapers found out to their disappointment.

The coax S/PDIF output signal is an AC signal. The LSI chip expects a voltage <0.8V as low and >2V as high (if it is TTL-compatible). This is a minimum required voltage difference of 1.2V. A conformant S/PDIF coax output is required to deliver 0.4V peak-to-peak as a minimum. See the problem?

Again: http://www.epanorama.net/documents/audio/spdif.html

The TOSLINK receiver and transmitter in my PCM-D50 connect directly to the audio LSI chip - I expect a similar solution in the D100. Wiring a coax S/PDIF input without ESD protection and pulse forming straight to the LSI chip is a sure way to disaster.

But - its not my recorder. Feel free to experiment. Report back if it works - or not.


Greetings,

Rainer

[ghibliss]

Thanks for the very thorough explanation Rainer! I am not planning on cannibalizing a recorder before I have a complete understanding of how it works first.  If it cannot be converted then it will not be done.  I simply have a preference for SPDIF over Toslink because of the locking style connectors.  I am able to use either one with the a/d mic preamplifier that I use so it is not a problem either way. I will let you know what Sony says if they get back to me with any enlightening information on this topic.