Maximum cable length for I2s?

Ryssen · 27th June 2010, 08:52 PM

Been searching the forum on this subject,and some say after 10cm the signal gets worse,use LVDS for longer cables.And some say LVDS is overkill...that I2s can bes used for longer length.
Opinions on this?

Sandor · 27th June 2010, 10:13 PM

I used 75 cm (about 3 inches) long cables to connect my modded cdplayer to my TDA1541-based dac. Cables were self-made using RG59 coaxial cable and BNC connectors. Observed at the scope, the signals at the dac end looked good, and almost identical to the ones at the player end. No problem, good sound.
Reagrds.
Paul

glt · 27th June 2010, 11:09 PM

75 cm or 7.5 cm?

SoNic_real_one · 28th June 2010, 01:30 PM

Depends of the output/input impedances. If they are low and adapted with the cable, then you don't need LVDS for 2-3 feet.
I would suggest twisted CAT5E cable with 100 ohms resistor on the receiver side. And of course with the I2S output buffered to be capable of driving that load.

Ryssen · 28th June 2010, 08:45 PM

Quote:

And of course with the I2S output buffered to be capable of driving that load.

How is such a buffert constructed?

Voegelchen · 28th June 2010, 09:02 PM

Use 74HC(T) or 74AC(T) 244/245 buffers...
- clock lines can beterminated by using 100 Ohms and 100pF in series (so the DC-resistance isn't that low) and
- data lines with 220 Ohms to Vcc and 330 Ohms to GND (see SCSI), perhaps coupled via 100pF to the line.

!! But LVDS is preferrable !! or you must a 100MHz (minimum !) scope to check if termination is ok.

Don't forget, that the MCLK must be treatened as an analog signal ! (else you would get jitter problems and therefore noise or FM modulated to the signal (not detectable by common used notch filters analyzers !)

Voegelchen · 29th June 2010, 09:26 AM

pics for better understanding. The value of C depends on the frequency to be terminated

27th June 2010, 08:52 PM	#1
Ryssen diyAudio Member Join Date: Dec 2003 Location: Sweden--> Here	Maximum cable length for I2s? Been searching the forum on this subject,and some say after 10cm the signal gets worse,use LVDS for longer cables.And some say LVDS is overkill...that I2s can bes used for longer length. Opinions on this?

27th June 2010, 11:09 PM	#3
glt diyAudio Member Join Date: Oct 2004	75 cm or 7.5 cm? __________________ www.hifiduino.wordpress.com

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Optical and Coax cable length?	Maniac	Acoustic Fun	4	28th November 2009 12:17 PM
Maximum low-level line length?	jdgonko	Everything Else	2	12th February 2008 03:07 AM
Long cable length - SPDIF or analogue?	johnm	Digital Source	5	14th August 2007 09:17 PM
AES/EBU coax cables sensitivity to cable length?	miksin	Digital Source	9	15th August 2006 12:16 PM
Digital Cable Length	fmak	Digital Source	39	27th March 2003 04:23 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	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

27th June 2010, 10:13 PM	#2
Sandor diyAudio Member Join Date: Mar 2004 Location: Milan	I used 75 cm (about 3 inches) long cables to connect my modded cdplayer to my TDA1541-based dac. Cables were self-made using RG59 coaxial cable and BNC connectors. Observed at the scope, the signals at the dac end looked good, and almost identical to the ones at the player end. No problem, good sound. Reagrds. Paul

28th June 2010, 01:30 PM	#4
SoNic_real_one diyAudio Member Join Date: Jan 2008 Location: Virginia	Depends of the output/input impedances. If they are low and adapted with the cable, then you don't need LVDS for 2-3 feet. I would suggest twisted CAT5E cable with 100 ohms resistor on the receiver side. And of course with the I2S output buffered to be capable of driving that load.

28th June 2010, 09:02 PM	#6
Voegelchen diyAudio Member Join Date: Jun 2010 Location: Germany and www.aca-vogel.de	Use 74HC(T) or 74AC(T) 244/245 buffers... - clock lines can beterminated by using 100 Ohms and 100pF in series (so the DC-resistance isn't that low) and - data lines with 220 Ohms to Vcc and 330 Ohms to GND (see SCSI), perhaps coupled via 100pF to the line. !! But LVDS is preferrable !! or you must a 100MHz (minimum !) scope to check if termination is ok. Don't forget, that the MCLK must be treatened as an analog signal ! (else you would get jitter problems and therefore noise or FM modulated to the signal (not detectable by common used notch filters analyzers !)

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)