SPDF Questions

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mtl777

Member
2007-10-02 7:12 am
Hey guys, I have a couple of questions on SPDIF:

1. What is the maximum input signal voltage level that an SPDIF input (i.e., most common consumer SPDIF equipped gear) can handle?

2. I want to make an SPDIF cable and I wonder if I should splurge on a more expensive Canare RCAP-C series RCA connector which Canare claims to be a "75 ohm RCA Connector" where one of the applications they listed is for "SPDIF Digital Audio". Will I get better electrical performance if I use this connector rather than an ordinary Neutrik RCA connector that is not rated 75 Ohms? Or is Canare's claim just a marketing gimmick and there is really no 75 Ohm rated RCA, unlike BNC which comes in 50 and 75 Ohms?

Any help would be much appreciated. Thanks! :)
 

mtl777

Member
2007-10-02 7:12 am
Thanks very much guys! :)

Regarding the Canare RCA connector being 75 Ohms, I received a reply from another forum that it is virtually impossible to make an RCA connector rated for 75 Ohms. The connector's impedance is determined by the outside shell diameter, the inside pin diameter, and the insulation dielectric properties. The outer shell is too small relative to the very large diameter of the center pin to make 75 Ohms impedance.

So Canare's claim is just a clever play of words to make it appear that their RCA connector is 75 Ohms - in other words, a marketing gimmick. A deeper look at the specs sheet of the connector reveals that what Canare really means is that the connector has "standard 75 Ohm construction". All this means is that a 75 Ohm coaxial crimp tool that is used for 75 Ohm BNC connectors will also work for this connector. The connector actually has a separate pin for the inside wire which is just like the ones for BNC connectors. That way, you can strip your coax, and crimp the center pin, and then insert the whole thing into that RCA connector and crimp the outer sleeve exactly as you would for a BNC connector. That's all. So it's not really a 75 Ohm rated connector but a connector that follows standard 75 Ohm BNC cable construction procedure. Clever, huh!
 
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