does firewire cable length affect anything

Posted: Wed Feb 27, 2008 12:21 pm

I connect my presonus firepod to my powerbook via firewire, of course. The way my desk is setup though, it's a bit of an inconvenience with the firewire cord only being about 3 feet long. Just wondering, if i went up to an 8 foot or so firewire cable, will i experience any negative side effects?

Note that i also run my 500gb external hard drive daisy-chained with the firepod, and that most of my sessions are run off the external. I know it can sometimes be recommended to transfer the sessions onto the computer's hard drive to work on them, but i haven't had any troubles in the past running things as i have.

so.....what of a longer firewire cord?

Posted: Wed Feb 27, 2008 12:33 pm

There shouldn't be any issues at all. I doubt there would be any problems even at 50 feet or more. You might need a repeater (if there is such a thing for firewire)at 50 feet but the only thing that degrades is the strength of the signal(and possibly added latency). At such a short run though, it's a non issue.

Posted: Thu Feb 28, 2008 12:45 pm

I don’t think you will have any problem going from 3ft to 8 feet.

Simply put the longer the cable the greater the chance of data packets getting corrupted by RF inference, or slew issues.

However most firewire the difference between 3ft and 8ft will be small.

Keep in my the digital data streams traveling down the firewire copper are running much faster then serial communications

Firewire 400-transfer rates up to 393 MBit/second.

Firewire 800- transfer rates up to 786 MBit/second.

USB 2.0 Hi speed- 1.5, 12, and 320 MBit/second.

The faster they run the easier it is for them to get corrupted by difference in wire impedance. The wire acts like an RC circuit which effectively distort the data waveform. Look at the picture on the link below:

http://en.wikipedia.org/wiki/Slew_rate

There is a reason most cables are less than 15 feet.

Long story short you should be fine.

Posted: Fri Feb 29, 2008 4:17 am

I have recently had a similar problem - the technical limit for Firewire is around 4.5M (15 feet).

I bought a repeater firewire cable (I think it's limited to 400 Firewire) to add some distance and it works perfectly with my MOTU 828 MkII - I'm now running it at longer distance with no problems.

HTH

Posted: Fri Feb 29, 2008 6:40 am

My experience has been that firewire lengths of greater than 15' do not hold their connection. After 3-4 seconds the connection is dropped.

But I've found no difference between 3' and 15'.

Posted: Fri Feb 29, 2008 9:31 am

Well there you go. I have been fully corrected and probably deserve a good flogging for that bit of missinfo. I'm so ashamed.

Posted: Fri Feb 29, 2008 7:05 pm

Hi,
I switched from the stock 3 foot cable to an 8 foot for my Firepod and the latency went up by .5. So, now the lowest I can set the latency is 2.0 (which is not bad at all). I did this months ago and have not noticed any probs... just get a really nice cable if you can. Hope this helps.

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