RE: What I have been told is...

Posted by PAR on March 4, 2016 at 16:26:47

In Reply to: What I have been told is... posted by John Marks on March 3, 2016 at 19:05:25:

Please forgive my scepticism but " RCA plug that by definition cannot be 75 Ohms because of its physical dimensions." applies almost equally to the average BNC plug and socket. They too cannot maintain the correct spacing between conductor and dielectric to the contacts so as to preserve the desired impedence characteristic. In fact if you spend time reading the manufacturer's specifications (where properly defined; I seem to remember Neutrik are good at this) for typical BNC's they are quoted as having an impedence of 50 - 75 ohms. One of the few (only?) BNCs currently manufactured that meets the correct 75 Ohm impedence (according to the manufacturer) is made by Canare and is physically much larger than those we are all used to so as to house the necessary dielectric.

However my scepticism continues further as even if one uses true 75 Ohm connectors and cable it all comes adrift as soon as the signal passes on from the connectors. Its route to the actual input receiver is most commonly via a length of generic hookup wire. Fortunately this is short. But then again then so is the average home audio digital interface so the relevance of absolutely correct impedence is minimal.

Similar arguments apply to most "110 Ohm" XLRs and interfaces.

Oh, BTW I have lengths of Belden 75 Ohm cable terminated with the correct 75 Ohm Canare connectors. Sounds awful!

This post is made possible by the generous support of people like you and our sponsors:

Follow Ups Full Thread

Topic - AES/EBU digital 110 ohm characteristic impedance - Duster 18:40:57 03/3/16 (19)

RE: AES/EBU digital 110 ohm characteristic impedance - Thorsten 19:38:09 03/9/16 (3)

RE: AES/EBU digital 110 ohm characteristic impedance - noway 06:48:19 03/24/16 (1)

RE: AES/EBU digital 110 ohm characteristic impedance - Thorsten 06:57:23 03/25/16 (0)

RE: AES/EBU digital 110 ohm characteristic impedance - 91derlust 12:57:29 03/21/16 (0)

RE: "...one might think that a rather strict tolerance is required..." - genungo 00:51:05 03/7/16 (0)

What I have been told is... - John Marks 19:05:25 03/3/16 (13)

Let's be careful going forward... - Chris Garrett 22:11:52 03/6/16 (0)

RE: What I have been told is... - PAR 03/4/1616:26:47 03/4/16 (1)

I agree with many of your points--especially what happens behind the back panels. - John Marks 16:40:26 03/4/16 (0)

RE: What I have been told is... - John Elison 19:40:28 03/3/16 (9)

I am running out the door. - John Marks 13:04:59 03/4/16 (8)

Thanks! I think I found a better link, though.... - John Elison 13:57:07 03/4/16 (7)

RE: Thanks! I think I found a better link, though.... - flood2 18:57:32 03/6/16 (5)

RE: Thanks! I think I found a better link, though.... - John Elison 19:50:26 03/6/16 (4)

You can measure this with a Time Domain Reflectometer - Tony Lauck 10:42:40 03/7/16 (2)

RE: You can measure this with a Time Domain Reflectometer - John Elison 22:18:08 03/7/16 (1)

RE: You can measure this with a Time Domain Reflectometer - flood2 14:59:42 03/8/16 (0)

You're welcome.. - flood2 20:25:19 03/6/16 (0)

That's what the math looks like! - John Marks 16:31:35 03/4/16 (0)

Follow Ups

RE: What I have been told is... - PAR 03/4/1616:26:47 03/4/16 (1)

I agree with many of your points--especially what happens behind the back panels. - John Marks 16:40:26 03/4/16 (0)

RE: What I have been told is...

Post a Message!