Talking about Crosstalk

[mandym]

Ever since I was a young lad building my Dynakits and Heathkits, I have always been warned by the manuals to keep left and right channel signal wires separate and if they have to cross, make them do so at right angles to each other. This is supposed to minimize channel crosstalk. Since all the manuals specify this, I figured it is very important so I followed them religiously. Maybe to this day, it is still being specified and followed by builders.

Fine BUT, something has been bugging me for a long time. What about the tonearm wires? The left and right channel wires run neck and neck for 8 inches or more, bundled together inside the tonearm!

Which brings me to three questions
A) Is the wiring caveat overstated?
B) Will maintaining max separation between the tonearm wires result in a better sounding tonearm?
C) Am I missing something?

Mandym

[amandarae]

Ever since I was a young lad building my Dynakits and Heathkits, I have always been warned by the manuals to keep left and right channel signal wires separate and if they have to cross, make them do so at right angles to each other. This is supposed to minimize channel crosstalk. Since all the manuals specify this, I figured it is very important so I followed them religiously. Maybe to this day, it is still being specified and followed by builders.

Fine BUT, something has been bugging me for a long time. What about the tonearm wires? The left and right channel wires run neck and neck for 8 inches or more, bundled together inside the tonearm!

Which brings me to three questions
A) Is the wiring caveat overstated?
B) Will maintaining max separation between the tonearm wires result in a better sounding tonearm?
C) Am I missing something?

Mandym

Hello Mandy,



Not to sound too techie here (because I am not!) but here's a nice comment that I read before regarding the subject matter...

If you are not hearing a hum, then you are not getting any crosstalk. The only magnetic field susceptability to really worry about is from speaker cables and power cords to unshielded IC's.

The way I interpret this in simple terms is that it is not necessary to worry about crosstalk between two adjacent, wrapped, bundled, or parallel wires if you cannot hear it. It is only necessary to worry about this if the wires will be place close or near high current carrying wires like PC and speaker cables.

It is also useful to remember that crosstalk decreases as a function of the square of the distance of the cable. Mind you, twisting the cable as X per foot does not really increases the crosstalk numbers (decreases the susceptibility of the cables to far-field signals or cancelling) but generally averaging. Averaging the maxima/minima of the field intensity along the length of the cable so that a point at any given distance from the center is theoretically equal in field strength thus, minimizing field imbalance.

I also read that if crosstalk is already an issue, separating the two cable conductor by close to an inch will increase the figure from 35 dB to 100 dB. But if that is not practical, it is better to have the conductors (phono signal for example) to have a side-by-side wiring configuration( + wires across from each other).

hope this helps.....

[egay]

interesting.
i have a vague understanding so i went for a simplified search and i got Wikepedia's:

In electronics, the term crosstalk (XT) has the following meanings:

Undesired capacitive, inductive, or conductive coupling from one circuit, part of a circuit, or channel, to another.

Any phenomenon by which a signal transmitted on one circuit or channel of a transmission system creates an undesired effect in another circuit or channel.

In telecommunication or telephony, crosstalk is often distinguishable as pieces of speech or signaling tones leaking from other people's connections. If the connection is analog, twisted pair cabling can often be used to reduce the effects of crosstalk. Alternatively, the signals can be converted to digital form, which is much less susceptible to crosstalk.

In integrated circuit design, crosstalk normally refers to a signal affecting another nearby signal. Usually the coupling is capacitive, and to the nearest neighbor, but other forms of coupling and effects on signal further away are sometimes important, especially in analog designs. See signal integrity for tools used to measure and prevent this problem, and substrate coupling for a discussion of crosstalk conveyed through the IC substrate. There are a wide variety of possible fixes, with increased spacing, wire re-ordering, and shielding being the most common.

seems simple enough for me to understand congruent to Amandarae's note: it is something that is undesirable as signals "leak" from one piece of component to the other, causing noise that could drive as crazy .

.e.

[mandym]

Thanks for the replies guys.

Maybe you know that I dabble in DIY tonearms. In my quest for better tonearms, I try to look for areas where I can do improvements so I wanted to get a feel of how important crosstalk is (between channels, not to power carrying lines).

Of course there is hardly any space to allow significant physical separation between conductors inside a tonearm. At least one can shoot for every little bit of gain possible! Who knows, maybe all tonearms are hampered by crosstalk and minimizing it could produce good results. The DIYer is like a treasure hunter, always looking for the mother lode!

Mandym