Balanced interconnect with 2 x 75 ohm coax cables? - diyAudio
Go Back   Home > Forums > Source & Line > Analog Line Level

Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 7th February 2012, 04:56 PM   #1
diyAudio Member
 
Join Date: Mar 2011
Default Balanced interconnect with 2 x 75 ohm coax cables?

Just wondering if this could work well.

Assuming I have a DIY DAC with a balanced output, and I wired it to send the output to 2 x RCA sockets. At the other end is a DIY amplifier with the same sockets and wiring.

GND to sleeve of both RCA's

+V to tip of one RCA

-V to tip of other RCA

[x2 - so there would be 4 RCA sockets for balanced stereo]

Any good?

Last edited by judderod; 7th February 2012 at 05:01 PM. Reason: clarification of channels
  Reply With Quote
Old 7th February 2012, 05:05 PM   #2
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
Unconventional, but should not cause any particular issues, just make sure all RCA jacks are grounded to the same ground point.
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 7th February 2012, 05:13 PM   #3
DF96 is offline DF96  England
diyAudio Member
 
Join Date: May 2007
Slight possibility of a ground loop because of the two parallel screens.
  Reply With Quote
Old 7th February 2012, 05:16 PM   #4
diyAudio Member
 
Join Date: Mar 2011
Quote:
Originally Posted by DF96 View Post
Slight possibility of a ground loop because of the two parallel screens.
I was thinking of leaving the output end of the shield disconnected. Both devices would share the same mains ground.

If that would help, I'm just guessing here.
  Reply With Quote
Old 7th February 2012, 05:26 PM   #5
DF96 is offline DF96  England
diyAudio Member
 
Join Date: May 2007
You would then need excellent CMRR. Why are you using RCA with balanced connections? And why a pair of coax instead of a twisted pair?
  Reply With Quote
Old 7th February 2012, 06:15 PM   #6
diyAudio Member
 
Join Date: Mar 2011
Quote:
Originally Posted by DF96 View Post
Why are you using RCA with balanced connections? And why a pair of coax instead of a twisted pair?
Hopefully this won't go OT as I'm sure there are others with differing opinions on this but the main reasons are:

1. I cannot find any solid siver conductor XLR plugs or sockets for less than thousands of $'s. There are solid silver RCA plugs and sockets available for a lot less.

2. I cannot find a solid silver-cored shielded twisted pair available on the market for less than about $100/m. I am currently using a solid silver-cored coax for single ended audio that costs a lot less than that (and sounds great I might add).

Here's the idea:

Click the image to open in full size.

I figure there might need to be some combination of resistors and/or capacitors between A, B and GND on the amplifier side? I'm no good at design, only theory and implementation so thanks for any help
  Reply With Quote
Old 7th February 2012, 08:02 PM   #7
mjf is offline mjf  Austria
diyAudio Member
 
Join Date: Jan 2009
Location: Austria
perhaps you can try this out with two pairs of cheap rca - cables (equal lenght, sitting tightly together...... with short pieces of heatshrink or so ).
  Reply With Quote
Old 7th February 2012, 08:26 PM   #8
avcllc is offline avcllc  United States
diyAudio Member
 
Join Date: Feb 2007
Location: Connecticut
FYI, James Bongiorno used the two RCA sockets in a balanced cable connection in his Sumo line of amplifiers (circa. 1980's), preamp to power amp. This was before consumer electronics has balanced XLR connectors and associated circuitry.
  Reply With Quote
Old 7th February 2012, 09:24 PM   #9
diyAudio Member
 
Speedskater's Avatar
 
Join Date: Sep 2002
Location: Lakewood, Ohio
The shield or in this case the two shields are not audio ground. They should only be connected to the chassis's. Not being part of the audio circuit, ground loops are not a mater of concern.
As "mjf" symmetry is necessary for a good balanced analog interconnect. So both cables (equal lenght, sitting tightly together...).
__________________
Kevin
  Reply With Quote
Old 8th February 2012, 12:09 AM   #10
avcllc is offline avcllc  United States
diyAudio Member
 
Join Date: Feb 2007
Location: Connecticut
Default XLR to RCA Balanced cables

You are indeed correct the signal+, and signal - are the center conductors of each individual coax, and the shields are chassis ground. I tend to agree with Jan Didden, that the use of a shielded twisted pair with Cannon XLR connectors work best for balanced connections. I was just pointing out that the use of two coaxial cables with RCA connectors was used in a production amplifier back in the '70's.
A good reference for connector wiring can be found on Rane's pro-sound website under tech notes section. They also explain pin 1 grounding in a balanced interconnect.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Using 75-ohm digital coax cable for regular 2-ch analog audio? Glowbug Digital Source 7 12th May 2008 06:27 AM
ssabripo's DIY Interconnect cables: $200 cables for 1/10 th the cost! ssabripo Everything Else 3 26th October 2006 02:33 PM
interconnect cables dsmkwan Parts 3 29th May 2006 11:15 PM
Looking for affordable, good sounding, balanced interconnect cables Peter Daniel Solid State 11 19th June 2004 06:15 PM
Are 75 ohm digital video and audio cables the same? diamdiam Digital Source 8 2nd March 2004 03:52 PM


New To Site? Need Help?

All times are GMT. The time now is 03:18 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2