Optimal SPDIF cable length for OR5

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JPS

  • Jr. Member
  • Posts: 21
Optimal SPDIF cable length for OR5
« on: 30 Mar 2012, 05:49 pm »
Dear Steve,

In the Off Ramp 4 manual you recommend for the S/PDIF output:
The cable attached to this connector should be at least 1.0m in length, but minimize the length beyond that. 1.5m is usually perfect and will work best with other gear.

For best results with Off Ramp 5, would you recommend 1m or 1.5m length?


audioengr

Re: Optimal SPDIF cable length for OR5
« Reply #1 on: 30 Mar 2012, 06:03 pm »
Dear Steve,

In the Off Ramp 4 manual you recommend for the S/PDIF output:
The cable attached to this connector should be at least 1.0m in length, but minimize the length beyond that. 1.5m is usually perfect and will work best with other gear.

For best results with Off Ramp 5, would you recommend 1m or 1.5m length?

For best results, 1.5m length.

That's what I use.

Steve N.

JPS

  • Jr. Member
  • Posts: 21
Re: Optimal SPDIF cable length for OR5
« Reply #2 on: 30 Mar 2012, 08:36 pm »
Thanks!

serengetiplains

Re: Optimal SPDIF cable length for OR5
« Reply #3 on: 31 Mar 2012, 04:36 am »
Steve, what is the length at which one begins to get reflections?

audioengr

Re: Optimal SPDIF cable length for OR5
« Reply #4 on: 31 Mar 2012, 04:59 am »
Steve, what is the length at which one begins to get reflections?

You will always get reflections.  The question is whether the first reflection, which is the highest amplitude, will reach the destination at the critical time when the edge is sampled by the receiver.

It depends on the edge-rate.  Faster edge-rates will cause the receiver to detect the edge earlier, allowing the use of a shorter cable.  The first reflection can arrive earlier without affecting the detection of the edge.

1.5m is just a good rule-of thumb because it will cover edge-rates from about 20nsec to 1nsec.  The round-trip flight-time of a 1.5m cable is about 13-14nsec.  If the edge is past the half-way mark after this time is elapsed, then it will not be affected by the first reflection.

My S/PDIF output, when driving a low-loss cable achieves about 4nsec risetime, so there is plenty of time for the receiver to detect the edge before the first reflection.  If there are other impedance discontinuities within the receiving DAC, then there may be other reflections that return earlier, such as those from circuit board traces or wiring that is not 75 ohms.  In this case, the faster the risetime is, the better.

Steve N.


 

jb26

  • Jr. Member
  • Posts: 90
Re: Optimal SPDIF cable length for OR5
« Reply #5 on: 31 Mar 2012, 06:08 am »
Do you have a similar rule of thumb for USB cables to the 1.5 for the SPDIF cables?

audioengr

Re: Optimal SPDIF cable length for OR5
« Reply #6 on: 31 Mar 2012, 03:56 pm »
Do you have a similar rule of thumb for USB cables to the 1.5 for the SPDIF cables?

Yes, same rule.

Steve N.

jimiles

Re: Optimal SPDIF cable length for OR5
« Reply #7 on: 23 Apr 2012, 12:38 am »
Speaking of S/PDIF cables; I saw folks talking up the Revelation Audio USB cables in a recent thread.  Are folks also liking their S/PDIF cables?   

audioengr

Re: Optimal SPDIF cable length for OR5
« Reply #8 on: 23 Apr 2012, 03:08 am »
Speaking of S/PDIF cables; I saw folks talking up the Revelation Audio USB cables in a recent thread.  Are folks also liking their S/PDIF cables?

I have not heard their S/PDIF cable yet.  I have heard the I2S and had customers report on the USB cable only.

The Ridge Street Audio Poiema S/PDIF is a good cable.

Steve N.

jimiles

Re: Optimal SPDIF cable length for OR5
« Reply #9 on: 1 May 2012, 07:38 pm »
I'll report back on the Revelation Audio Labs S/PDIF cable once I recieve it.  The Ridge Street cable is undoubtedly awesome, but frugality dictates that I at least entertain a sub-$1000 option first.

kyrill

Re: Optimal SPDIF cable length for OR5
« Reply #10 on: 21 Dec 2012, 04:23 pm »
hi Miles
Any news on yr new SPDIF cable?

Watthead

Re: Optimal SPDIF cable length for OR5
« Reply #11 on: 9 Jan 2013, 06:18 pm »
This 1.5 meter rule sucks. I understand it, and I respect it, makes sense. But it sucks because i gotta buy 1.5 meter long coaxial cable. And the "cheapest" versions normally are the 0.50 long ones. But 1.5 can cost 3 times as much. We're talking about difference between $300 and $900 in some cases. Sucks.