Can a cable be too short?

[amirm]

It sure seems like it. Easy to read document here on S/PDIF cable considerations: http://www.positive-feedback.com/Issue14/spdif.htm. And a bit about what modding a source can do to improve things.

 

[DonH50]

Of course, perfectly match the source, cable and load and the reflection problem goes away... It also glosses over that there will be a reflection from the triple-transit time eventually no matter the cable length (though a longer cable might attenuate more), and probably never at a "good" time for the receiver. Finally, using a PLL to recover the clock, the designer can control the loop so that reflections are well outside the PLL's loop bandwidth so they are effectively "ignored". Not a complete panacea, since if there are a lot of significant reflection terms you'll end up with an average of primary and secondary edges creating the clock.

I should note that many are probably aware of those "magic" frequencies, or in this case cable lengths, that cause the reflections to cancel at the receiver.

 

[Speedskater]

In Bob Cordell's new book "Designing Audio Power Amplifiers", he writes about how a normal audio circuit and a power, interconnect or speaker cable can become a tuned radio frequency circuit to RFI interference.

 

[amirm]

How good is that book? Years ago I went looking for amp design books as I was designing one for cars and I couldn't find anything decent.

 

[Vincent Kars]

A short cable:

 

[Speedskater]

How good is that book? Years ago I went looking for amp design books as I was designing one for cars and I couldn't find anything decent.

Bob Cordell's new book "Designing Audio Power Amplifiers" is definitely a good book! It's a 600 page technical work, but with very little math or formulas! Treat it as a number of short stories on whatever interests you that day rather than reading it cover to cover. I'm not designing an amplifier so I'll skip the chapters on SPICE and bias circuits. Everything is shades of gray and about compromises and trade-offs.

 

[DonH50]

Shades of gray, welcome to The World of Design! Seriously, another book to add to my list, thanks! - Don

 

[amirm]

Amp design is bewildering. Every subcircuit has dozen+ variations. And you not only have to worry about performance, but reliability. Thank heaven for computer simulation. In the old days, it would take a long time just to build and test one variation. Only to find it smoke out because you mis-wired one component.

 

[DonH50]

I miss the smell of mica in the morning...

 

[garylkoh]

My sister calls it "letting out the magic smoke" when I blow up large electrolytics.

 

[amirm]

Hehe .

 

[rhyno]

i would actually pose the question differently:

in a particular application, if the length of cable is of certain size or smaller, wil the inherent character of the cable inpose its flavor on the signal or not?

i dont know, but i'd betcha its the case for ACs, ICs, SC, and dig cables in that order (note: connector quality is always heard. there's always a connector...i'm just talkign using oyaide plugs w/ belden wire will sound as good as Stage 3 if the connectors & gauge are the same).

 

[booboobaer]

I own Purist Audio Design cables, no others. I asked Jim Aud the designer about power cables , speakers cables, suggested length and this is what he said. On power cables he suggested that they be at LEAST six feet long (something about capacitance). On speaker cables he said the ideal length was 9 feet long. I don't pretend to fully understand the physics of it but I sure trust Jim. These cables are amazing. Happy New Year!