Cable myths, or truths?

[Magnus Danielson]

>>>>> "MSP" == Matthew S Padden <mattp at mindless.com> writes:

 MSP> Hi..

Hi Matthew!

 MSP> Now, this is something that's bothered me for years, and which I
 MSP> think is absolute fantasy. Pick up any hi-fi mag and you'll see ads
 MSP> for DIRECTIONAL CABLE. (ie one end to CD player, other end to amp) 

 MSP> Am I missing something here, or is this utter nonsense? The only
 MSP> explanation I can think of is transmission line theory, but that
 MSP> surely doesn't affect audio frequencies....... 

To the best of my knowledge (there have been people trying to convince
me of the oposite) this is just as you said, utter nonsense.

Above a certain level, cables should not create much of a noticable
effect on a normal amp and speaker (or line level stuff, which should
be even simpler).

There are cases when the amplifiers/output buffers are so bad, that
they will not be capable of seeing the reactive impedance that a cable
becomes when you have an impedance missmatch. Such amplifier will
distort at much lower levels (and much lower output power) than when
they look into a proper resistive load. This can all be explained by
carefull study of the voltage and current curves that the transistors
(or tubes for the tubeheads) see, one must also make this study for
various phase differances between voltage and current at the output to
see the differances... this is BTW a great way to learn how amplifier
really works (and not works).

To put it very brutally: Some amplifiers ("Good Hi-Fi Amps") simple
can't drive the cables! Let's now also ask how well they will drive
your speakers and you migth get the hang of it...

As for line level signals it is also common, since line level signals
is the signals that God forgot about, the engineers just mumble
througth and the users get mad about... (OK, I am exagerating a
little, but sometimes it is all too true to be healthy... )

Also, since many poweramps are built the way they are can this
reactiveness disturbe the feedback loop in the amplifier... now we
have a error signal introduced into a feedback loop and the output
stage is starting to get nonlinear on us... there is all chances that
this will go on for some time before getting more quite...

There are ways go come around the worst of these problems, and one
migth learn to build amplifiers to avoid them.

So in my view, it is not necessarilly the cables that is the fault,
but the system of amp, cables and speakers that needs carefull study
in order to seek the problem.

In a professional PA is the cables among the least of the
problems... and there they usally will have to cary an amp or a
few...

My experience is that studying and dimensioning the system using just
simple and sound electrical engineering skills add a few drops of
simple and sound acoustical engineering and you have come a very long
way to a good sound... there isn't much of the hokus pokus stuff which
is around the Hi-Fi market... that's all about getting to your pocket
and while there digging deeeeeeeep!

That is my 2 cents worth on the subject, but I hope is saves you more ;)

Cheers,
Magnus