Cat5e Line Level Standards? - diyAudio
Go Back   Home > Forums > General Interest > Everything Else

Everything Else Anything related to audio / video / electronics etc) BUT remember- we have many new forums where your thread may now fit! .... Parts, Equipment & Tools, Construction Tips, Software Tools......

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 13th April 2009, 05:21 PM   #1
diyAudio Member
 
Join Date: Apr 2009
Default Cat5e Line Level Standards?

Hi All -

I found an ancient thread about Cat5 line level audio, and decided I'd start a new thread instead of resurrecting the old one.

I'd like to use an existing cat5 run through my attic to send line level audio through my house. I have a few questions for anyone who has done this already:

1 - Is there any sort of standard about which cat5 wire color goes with what channel?

2 - My plan was to use solid color wire for signal and the striped line for sense... this will let me run 2 channels (left and right) on one cable. Is this what other people have done? I'm worried about sending audio down a single conductor wire...

3 - Does anyone have a Bode plot of their completed signal, from before the balanced driver to after? If/when I get this project done I will grab a few data points, but it would be nice to know what kind of frequency response a single conductor has across ~20m.

Thanks
Jordan
  Reply With Quote
Old 14th April 2009, 12:22 AM   #2
diyAudio Member
 
Join Date: Mar 2006
Location: South East
From what I know:

1. No, there is not standard for audio. Only for networking.

2. I would not recommend your plan in conductor implementation. The point of the Cat5 is that its twisted pair, so it'll block out interference. Subsquently, you will want to specifically use them in their color coded pairs. Ex: org & org/white = left pos & left neg. Then blue & blue/white = right pos & right neg. Use the pairs *together*.

3. I would think the frequency response would be just fine over that length. Maybe only the signal wouldn't be as strong.

John
  Reply With Quote
Old 14th April 2009, 12:52 AM   #3
infinia is offline infinia  United States
diyAudio Member
 
infinia's Avatar
 
Join Date: May 2005
Location: Californication
Hi
see link http://en.wikipedia.org/wiki/Category_5_cable
For a Cat 5 twisted pair the cutoff frequency is around 50KHz for 100m length, so should be OK for line level audio up to 20m.

Zo is spec'd at 100 ohms. So for single ended drive use 100 ohm source resitance as well as a 100 ohm terminating resistor.
Using differential circuits will give an additional 6 dB of SNR and heaps more CMRR. So now the 2 source resistors will be 1/2 Zo or 50 ohms each and the receive end s/b 2*Zo or 200 ohms.
__________________
like four million tons of hydrogen exploding on the sun
like the whisper of the termites building castles in the dust
  Reply With Quote
Old 14th April 2009, 01:10 AM   #4
diyAudio Member
 
scott wurcer's Avatar
 
Join Date: Jan 2004
Location: cambridge ma
Quote:
Originally posted by infinia
Hi
see link http://en.wikipedia.org/wiki/Category_5_cable
For a Cat 5 twisted pair the cutoff frequency is around 50KHz for 100m length, so should be OK for line level audio up to 20m.

Zo is spec'd at 100 ohms. So for single ended drive use 100 ohm source resitance as well as a 100 ohm terminating resistor.
Using differential circuits will give an additional 6 dB of SNR and heaps more CMRR. So now the 2 source resistors will be 1/2 Zo or 50 ohms each and the receive end s/b 2*Zo or 200 ohms.
You misread the meaning of "cutoff" frequency. Read the reference [4] for an explanation.
__________________
Silence is so accurate.
  Reply With Quote
Old 14th April 2009, 01:30 AM   #5
infinia is offline infinia  United States
diyAudio Member
 
infinia's Avatar
 
Join Date: May 2005
Location: Californication
Quote:
Originally posted by infinia
Hi
see link http://en.wikipedia.org/wiki/Category_5_cable
For a Cat 5 twisted pair the cutoff frequency is around 50KHz for 100m length, so should be OK for line level audio up to 20m.


The cuttoff of 50 KHz is using a high impedance load (open termination) so is worst case. Using the proper matching described above, you can use Cat 5 well into video frequencies.
__________________
like four million tons of hydrogen exploding on the sun
like the whisper of the termites building castles in the dust
  Reply With Quote
Old 14th April 2009, 02:45 AM   #6
diyAudio Member
 
zigzagflux's Avatar
 
Join Date: Oct 2006
Location: Charlotte, NC
The use of 100 ohm (or 75 ohm) source and terminating resistors is for transmission lines at very high frequencies; it does not hold true for audio. General rule is zero (or small as possible) source resistance, and large (as possible) terminating load resistance.

This idea continues to rear its ugly head in audio circles, but doesn't belong. If you are talking about transmitting a few MHz SPDIF signal, okay, but emphatically not audio signals.
  Reply With Quote
Old 14th April 2009, 03:02 AM   #7
Mr Evil is offline Mr Evil  United Kingdom
diyAudio Member
 
Join Date: Aug 2004
Location: Behind you
Quote:
Originally posted by zigzagflux
The use of 100 ohm (or 75 ohm) source and terminating resistors is for transmission lines at very high frequencies; it does not hold true for audio. General rule is zero (or small as possible) source resistance, and large (as possible) terminating load resistance.

This idea continues to rear its ugly head in audio circles, but doesn't belong. If you are talking about transmitting a few MHz SPDIF signal, okay, but emphatically not audio signals.
Might it not be helpful on long runs to add a Zobel network to set the impedance to the correct value at RF, if only to help absorb noise?
__________________
https://mrevil.asvachin.eu/
  Reply With Quote
Old 14th April 2009, 03:05 AM   #8
infinia is offline infinia  United States
diyAudio Member
 
infinia's Avatar
 
Join Date: May 2005
Location: Californication
Quote:
Originally posted by zigzagflux
The use of 100 ohm (or 75 ohm) source and terminating resistors is for transmission lines at very high frequencies; it does not hold true for audio. General rule is zero (or small as possible) source resistance, and large (as possible) terminating load resistance.

Why? I think source resistors are quite useful, esp. using op-amps to drive reactive loads like twisted pair or even coax. You have to be extra careful using zero ohm sources to drive audio unless it's designed to. Granted you have a 3 dB power loss but at line level it's not a huge concern.


I see nothing wrong with using twisted pair for line level audio. In my mind its the right way. If done properly it can be cheaper than, and with performance rivaling coax.
__________________
like four million tons of hydrogen exploding on the sun
like the whisper of the termites building castles in the dust
  Reply With Quote
Old 14th April 2009, 03:20 AM   #9
diyAudio Member
 
Join Date: Apr 2009
Quote:
Originally posted by calee4nyaboy
From what I know:

2. I would not recommend your plan in conductor implementation. The point of the Cat5 is that its twisted pair, so it'll block out interference. Subsquently, you will want to specifically use them in their color coded pairs. Ex: org & org/white = left pos & left neg. Then blue & blue/white = right pos & right neg. Use the pairs *together*.

John

Good call - so I'd do left-force +/- on the green-solid/green-striped wires, left-sense +/- on the orange-solid/orange-striped wires, etc.
  Reply With Quote
Old 14th April 2009, 03:20 AM   #10
diyAudio Member
 
Join Date: Mar 2006
Location: South East
Quote:
Originally posted by zigzagflux
The use of 100 ohm (or 75 ohm) source and terminating resistors is for transmission lines at very high frequencies; it does not hold true for audio. General rule is zero (or small as possible) source resistance, and large (as possible) terminating load resistance.

This idea continues to rear its ugly head in audio circles, but doesn't belong. If you are talking about transmitting a few MHz SPDIF signal, okay, but emphatically not audio signals.

Yeah, I was kinda confused by all that talk too. Arent you supposed to just solder RCA ends to each twisted pair and call it a day?
  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
Convert Line Level to Electric Guitar Level miallen Solid State 4 16th May 2010 01:22 PM
CAT5e Cable fun! Line level. Pano Everything Else 3 25th March 2008 08:32 AM
speaker level input vs line level question crippledchicken Subwoofers 4 17th July 2007 03:36 AM
lesser of two evils, high level -> line level, digital volume control mazurek Solid State 3 19th November 2006 12:25 AM
how to bring down line level signal to preamplifier level deji Solid State 15 15th April 2004 04:13 PM


New To Site? Need Help?

All times are GMT. The time now is 02:14 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