Digital Cable questions-regarding 75 ohm

I finally bought my first streamer.
The Aurender N100C-A huge step up…I’ve come to the conclusion that I like the Coaxial out over the USB.
Here is my question- From what I’ve read a true 75 ohm digital cable provides the best results. Also- To get a true 75 ohm transfer, it should have BNC connectors. RCA’s connectors apparently aren’t compatible? I understand they in some way don’t provide what BNC connectors do.

My questions- Is the above true? Some of the cables I’m considering have BNC to RCA adapters. Is this any better than RCA to RCA ? My Dac has a BNC in. Would I use the adapter on the steamer end (rca out) and then run the BNC end directly into the DAC ?

My gut tells me that if use a quality digital cable…its not going to degrade the sound regardless of the connectors.

Also- If someone could explain the clocking differences between the USB in --as opposed to the RCA or BNC in ----on the DAC

Any and all help would be greatly appreciated.

This is one of the few forums left that you can get great answers without getting all the snarky comments.

Thanks in advance.

Also- Can someone explain the differences

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In an ideal world all of the connection between a 75 ohm transmitter and a 75 ohm receiver would be 75 ohms. Then any reflections of the signal can be perfectly canceled and they won’t interfere with the wanted signal. Any discontinuities in the impedance (e.g. a RCA connector) will cause reflections in the signal and those reflections (and reflections of reflections) will interfere with the signal, sometimes making it higher than it should be and other times lower. In principle, in the limit, the reflection could exactly cancel the signal.

With 75 ohms all along the path the length of the cable doesn’t matter very much, but the effect of reflections depends a lot on cable length.

Degradation of the signal, even if it doesn’t cause bit errors, can cause more jitter whose effects depend a lot on the equipment involved.

BNC / RCA adapters will just add more impedance discontinuities.

The practical effect of all of this is system dependent, some will never hear it, to others it’s more obvious (tho subtle.)

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I had used a small set of Coax cables- the original Illuminati Orchid cable (coax) sounded the best to me at the time (probably back in 2010). Orchid is currently sold by Kimber.
Manufacturer have different claims- For example- The Nordost digital cable is BNC only, and they say to use a true 75 ohm bnc to coax adapter and it will do the trick.
With the modern dac like DirectStream- I would favor sources that output usb or I2S connectors - and use coax for secondary type sources where sound don’t matter as much- I planned to add a bluetooth receiver with digital coax to Directstream, so “lesser” cables (for my application) won’t matter as much. I hope you find the best coax cable for your Aurender.

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Congrats on your new player. I recently bought an A10 Music Server. I am very happy with it thusfar. Sound quality is excellent.

This is a great question and one I’ve have myself regarding mixing the connectors. I’ve often wondered if you can use the BNC on one end and the RCA adapter on the other when a BNC was not present.

The dimensions necessary for an RCA connector dictate that it can’t truly be 75 ohms. I have seen RCA connectors “advertised” as 75 ohm, connectors, but as far as I know, it’s not REALLY possible. Because of this, there WILL be internal reflections (see Ted’s post above), but how the equipment handles this can vary quite a bit.

Most modern electronics handle this well, but it’s still debated “how well.”

BNC connectors (some) are designed as true 75 ohm connectors. If you REALLY want to maintain the 75 ohm, you would have to replace the rca receptacle in the equipment and run true BNC between. Not worth it in my opinion, but to each his own.

Blue Jeans cable has a good explanation here:

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So this means the whole Nordost BNC to RCA is not that efficient? I also struggle finding a DAC with a BNC input as well. Only RCA and optical / toslink.

I think the Ayre DACs only use BNC for SPDIF … QX-5 Twenty Streaming DAC | Ayre Acoustics | Streaming Music System

I understand the Directstream MkII DAC won’t have BNC inputs (unless there’s a late change in plans).

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Not sure what you mean by “efficient,” but yes, there will be reflections because of the impedance mismatch between the connector, cable, and designed impedance of the circuits.

Does it REALLY make a difference? In the grand scheme of things, with any reasonably designed DAC, I would say “no,” but as stated, if you REALLY want to eliminate the mismatch, the only way is to replace the RCA receptacle in the equipment with the proper impedance BNC - or use AES/EBU if available (assuming you want to stay with S/PDIF.

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The Ayre has AES/EBU (which is S/PDIF in balanced form).

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Forgot to mention. Most DACs only come with RCA connectors, and most source equipment use RCA. Unless BOTH sides use BNC, there really is no benefit for the DAC to use BNC.

Another issue is that even if the source and DAC uses BNC, the propensity for “audiophile” cable companies to create ‘non-compliant’ cables ‘for the sake of sound’ would most likely then result in the CABLE not being 75 ohm even if the connectors are.

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