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Digital Inputs


dreamwhisper
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What digital input do you use?  

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  1. 1. What digital input do you use?



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ok, I'll say it.. I see "digital input" and I think somoene's getting a finger in their ass.

there's plenty of other places to stick a finger: nose, mouth, ears, and yes, ass

I know because I conducted a poll about it on Head-Fi

unfortunately, too many of them already had their head stuck up their ass

leaving no more available inputs

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I'm using RCA output from my SB3 to BNC input on my DAC. I don't know if this nullifies the benefits of BNC or what (anyone know?), but I figured my DAC has BNC so might as well use it.

Assuming the BNC in your gear is actually providing a good impedance match, you will have one less reflection from impedance mismatch, which can only be a good thing.

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Assuming the BNC in your gear is actually providing a good impedance match, you will have one less reflection from impedance mismatch, which can only be a good thing.

Cool. Thanks for the info.

I think BNC is also just a really cool interface. No wear and tear on the jacks and connectors and they snap on/off really easily, but still stay connected securely.

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Just make sure you get 75 ohm BNCs as opposed to 50 ohm, which seem to be more common (used for oscilloscope leads, etc.). When looking at connectors over time, I have noticed that many of the boutique BNCs are actually 50 ohm, but moar gold plated. :palm:

Furutech--probably 50 ohm

FP-3-117.jpg

Vampire--also appears to be 50 ohm

VAMPIRE-56013.jpg

Cardas--appears to be 75 ohm, though can't tell for sure

GRBNCR.JPG

Trompeter 50 and 75 ohm shown in thumbnails: 50 ohm on left, 75 ohm on right.

post-432-12951155562393_thumb.jpg

post-432-12951155563138_thumb.jpg

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50 ohm is faster and thus moar bettar, right?

I dunno. Faster could mean more reflections, though if your reciever and cable are rated at the same impedance, Ohms law should cancel that out perfectly and make reflections a non-issue. Since that's not an issue, then yeah 50 Ohm seems like it would be better as long as nothing comes about from the frequencies and possible interference. I'm completely an amateur with digital electronics, so this should be read in that light.

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I dunno. Faster could mean more reflections, though if your reciever and cable are rated at the same impedance, Ohms law should cancel that out perfectly and make reflections a non-issue. Since that's not an issue, then yeah 50 Ohm seems like it would be better as long as nothing comes about from the frequencies and possible interference. I'm completely an amateur with digital electronics, so this should be read in that light.

I have often wondered what would happen if you used a cable impedance matched to an RCA connection, and switched out 75ohm termination resistors at either end for whatever resistor is appropriate......

From my understanding, that would work extremely well, without having to resort to BNC connections. Anybody smarter than me care to comment?

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I don't know that you could come up with a characteristic impedance that would cover all RCAs. The spdif standard is 75 ohms, but if you changed the transmitter and receiver matching as well as the cable/connectors then sure, you could use anything you wanted.

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I don't know that you could come up with a characteristic impedance that would cover all RCAs.

True. I assume though, possibly incorrectly, that there is at least a ballpark figure that is probably a bit closer than the 75 ohms that most coax and transmitter/receivers would use.

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I also believe that RCA connectors, while not having a standard impedance they try to conform to, are also not constant impedance connectors. That is to say, they may be say, 30r at one spot, but 50r at another. I believe I have seen the impedance of RCA connectors generalized in the 30-40ohm range. Also, they arnt really made as RF connectors, so probably have issues there.

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