The Truth And Myth Of Cables..

there is a fact of manufacturers to say that their interconnects are directional, fine i agree, but the problem lies is in what direction or how does it become that, simple they will say "follow the arrow" i have to get in trouble with this thread because i am going to say this : the maiin hart and by-passing of signals is the pre-amp , being integrated or seperate, the sources are some as "IN OR OUT" the interconnect if is based on a 3 star earth, witch means that one end it has a earth to the rca or other and the other end has only two connecting cables it means simply that the 3* earthing should always follow the flow, others will have to create their own, nando.

 

I've got a Toslink optical cable that has its directionality marked.

I'll be impressed if anyone can explain that one.

 

o.k. i will not speak dutch, thank you bottlenec, optical or digital connects have no direction, however , analogue cables as i explained have, if you have (for example) a cd player and a cd recorder and you want to make a copy from a cd that a friend lent you via coax or tosslink, those cables have no direction, where analogue has, and also the connection between transport and d.a.c. the connector is the same as a normal rac, it will do the same job as anybody saying O. NO YOU HAVE TO HAVE A DIG..CABLE, bull s...t the termination of a digital cable must be at least 76 ohms, rca's are not,sorry wife is ill and i have nothing to do, regards nando, p.s. try BNC termination

 

Nando... you might want to re-do your first post.

It looks double dutch to me..

 

actually .....my digital cables are dirrectional but its to do with buffering resistor ....

I've heard slight changes depending which way round its used.

the buffer is to con the reciever chip into thinking it an ideal load ...seems to work quite well !

 

hi peter, rac as i mention are 60 ohms terminated, the influence there exists to a point, but the true resistance of a digital coax cable is the termination end, not rca's they limit to 60 ohms , the bnc termination is of 76 ohms, problem lies in the cable joining such connection there for copper in conjuction with a well measured width of ferrite will do it , "for all it's worth" nando.

 

What do you mean by fooling it in to thinking it has an ideal load? You mean you put a resistor in to make up for the cable not being true 75 ohm impeadance or something?

There should already be a terminating resistor across the line of either 75 ohm or 110 ohm for S-PDIF and AES/EBU respectively, so if that’s what you mean, I don’t see why you would want to also add another one to the cable which would half the effective termination resistance.

I don’t mean this to sound like I am picking fault with the cable, just interested how you choose the resistor value or exactly what you are doing with it.

 

yes thats it .....

you'd be suprised at some of the resistor values on the reciever chips I've seen/measured. Its not strictly impedance matching....but they sound better than the identical cable without.

The digital reflections created by poor or mismatched impedances which I think nando is referring to can be eliminated by adding a pulse transformer ...but the cables not elegant.

As to the value ....I try to get the whole shebang to about 125 ohm but settle for 60-80 ohm if I don't know the gear ...oddly two resistors seem better than one [ie 2 x 30 in series from sig to ground]....for which I've not the foggiest.