Electronics Theory Question

Rick Collins · Post by **Rick Collins** » 24 Mar 2003 10:09 am

George L. cables come in .155 and .225 sizes; __I have both. I cannot hear a difference in sound, one or the other.

Theoretically is there a loss in signal with the smaller cable? Can you detect a difference?

Many thanks in advance, Rick

Brad Sarno · Post by **Brad Sarno** » 24 Mar 2003 12:49 pm

As I understand it, they have the same wire running thru the core in both models. There should be no percievable difference in tone between the two cables. They both use the same metal in the conductors and also have the same material for insulation and anti-stat. I think it's a psychological thing with the thin cable. Technically speaking, either guage of George L's is a very hi-performance audiophile cable.

Brad Sarno
St. Louis, MO

C Dixon · Post by **C Dixon** » 24 Mar 2003 3:16 pm

Wow,

You came right to the very core of my heart.

Let me expound. All cables that have more than one conductor exhibit "capacity" between those conductors, UNLESS the conductors are soo far apart that they are no longer relative to each other.

I digress: Capacity or better; the resistance (such as a pot in a volume control) is part of ANY capicity. It has a name, That name is called "capacitive reactance". So why did they NOT call it resistance?

Because the resistance is NOT constant over all frequencies. In other words, the HIGHER the frequency going thru the conductors, the more resistance there is to any signal going thru this wire.

Pure resistance is constant over the full frequency spectrum. So, long ago they distinguished between the two by assigning pure resistors as offering resistance and resistance offered by capicitors (and coils)as reactance. But they are both expressed in ohms.

NOw I said all the above to say the following:

The capacitive reactance in any coaxial cable (guitar and amp cords fall into this category) is soooooooooooooo very low at audio frequencies; that for all practical purposes it is nil.

This is why ANY audio engineer worth his salt totally and completely rejects and scoffs at such things as "monstor cables" or the notion that "one loses the highs" with specific cables.

Neither of these claims would EVER survive "triple blind tests" using pros from any musical genre'. (This excludes cables that are extremely long. Because the longer the cable the more capacitive reactance. 99% of guitar and amp cables never fall into this category.)

That is why you can't hear the difference EVEN though there is a big difference in those cables capacity relative to each other. Reason: at audo frequencies it is sooooooo low, regardless of the capicity; as to produce no audible affect. Now at RF (radio frequencies) we have a horse of a different color.

carl

Donny Hinson · Post by **Donny Hinson** » 24 Mar 2003 5:38 pm

I always respect Carl, and what he says. Nevertheless, I do have to disagree with him on this matter. The reason I disagree is that I have some cables (under 15' long) that sound significantly different than the cables I normally use.

Ken Fox · Post by **Ken Fox** » 24 Mar 2003 5:49 pm

I have ran cheap cables on a spectrum analyzer and then compared their response curve to an expensive cable. The audible difference was proven out wih the analyzer every time. Cheap cables, with their high capactive reatance and/or microphonic poroperties exhibited a poor frequency response.

Bobby Lee · Post by **Bobby Lee** » 24 Mar 2003 5:56 pm

Whether you can actually hear the difference depends on your amp and speakers. Some amps simply don't reproduce any sound above 8k. I think the manufacturers assume it's just hiss and noise up there. They may be right, knowing the quality of their components, typical stomp boxes, etc..

------------------
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Bruce Derr · Post by **Bruce Derr** » 25 Mar 2003 11:06 am

I know this has been covered here before, but this seems like a good time to run through it again...

The reactance through the center conductor is negligible even on cheap cables. However, the reactance from the center conductor to the shield is significant, and easy to measure even on high end cables.

Instrument cable, like any coaxial cable, has capacitance between the center conductor and the shield. The longer the cable, the more the capacitance. If you look up the specs of the cable you will find this capacitance specified in picofarads per unit length (usually pF/foot). This value ranges from about 20 pF/foot for low-capacitance cable like the thin George-L cable, to 60 or more. (By the way, high quality does not necessarily mean low capacitance, and vice versa.)

So every time you connect your guitar to an amp you are, in effect, placing a capacitor in parallel with your amp's input, perhaps a couple hundred pF to maybe 1000 pF or more, depending on the cable type and length.

Would you hear a difference between 200 pF and 1000 pF? In a typical setup, it is very likely. If you do the numbers it's easy to see why.

For argument's sake let's assume that your pickup's impedance is 20 kilohms at all frequencies, and that you do not have a volume pedal connected. Also we'll assume that the input impedance of your amplifier is high enough to ignore (a safe assumption).

Because Xc is in parallel with the amplifier input, it essentially forms the bottom half of a voltage divider, with the pickup's source impedance forming the top half. We want the bottom half of this divider to be very high, so that most of the pickup's voltage appears across it, and can then be seen by the amp input.

To illustrate, if Xc is the same as the pickup's impedance, only half of the signal would appear at the amplifier input.

But of course Xc varies inversely with frequency; the lower the frequency the higher Xc gets.

(Xc in kilohms = 1 / (2 pi f C).)

Let's look at the Xc for a 200 pF capacitance, at several treble frequencies, along with the percentage of signal that would appear at the amp's input:

1000 Hz: 796K (98%)
3000 Hz: 265K (93%)
5000 Hz: 159K (89%)
7000 Hz: 114K (85%)

Now for a 1000 pF capacitance:

1000 Hz: 159K (89%)
3000 Hz: 53K (73%)
5000 Hz: 32K (62%)
7000 Hz: 23K (53%)

This is a significant difference that I believe would be audible to most steelers.

Here's the clincher: Add the volume pedal. A pot-type pedal at full volume will add 500K of resistance in parallel and no resistance in series. This has virtually no effect. However, when you reduce the volume, you essentially add part of the pot's resistance to the source impedance of the pickup. Instead of 20K, you might have 100K or more. This raises the source impedance (the top half of the divider), which increases the treble-reducing effect of the cable significantly.

Some folks use a preamp (high impedance input, low impedance output) to help with this problem. However, putting a preamp BEFORE the volume pedal won't solve the problem completely. Although you've isolated the pickup, the pot pedal will still raise the source impedance seen by the cable going to the amp, and the problem will still exist. A preamp is most effective if used at the volume pedal's output. This provides a signal with a low source impedance going into the amp cable, so even a low Xc is high enough to be insignificant.

I've never used an active (electronic) volume pedal like the Hilton, but the main reason they sound better than a pot pedal is certainly because of the low output impedance, which negates the effect of the cable's capacitive reactance on the treble frequencies.

(Sorry for the long post; I didn't realize it would get so big when I started it!)[This message was edited by Bruce Derr on 25 March 2003 at 11:16 AM.][This message was edited by Bruce Derr on 25 March 2003 at 11:20 AM.]

Buck Grantham R.I.P. · Post by **Buck Grantham R.I.P.** » 30 Mar 2003 8:00 pm

All I know is that with the small George L cable I seem to get more highs .

John Macy · Post by **John Macy** » 30 Mar 2003 8:56 pm

quote

"This is why ANY audio engineer worth his salt totally and completely rejects and scoffs at such things as "monstor cables" or the notion that "one loses the highs" with specific cables.

Neither of these claims would EVER survive "triple blind tests" using pros from any musical genre'. (This excludes cables that are extremely long. Because the longer the cable the more capacitive reactance. 99% of guitar and amp cables never fall into this category.)"

Well this audio engineer must not be worth his salt cause I have sat through many blindfold tests of various cables where all in attendance heard the difference between them...

C Dixon · Post by **C Dixon** » 31 Mar 2003 8:53 am

The author of that quote did not say blindfold tests. He said "triple blind tests". And I doubt very seriously that you ever sat thru sophisticated tests like those performed by RCA labs at Princeton. I personally have never seen the extremes they went thru to make sure there was NO "subjectivity" in the tests.

They insisted on knowing the real facts; totally void of ANY human tendencies. That is why they insisted upon triple blind tests. Since these are the ONLY tests known that are 100% reliable.

carl

[This message was edited by C Dixon on 31 March 2003 at 10:55 AM.]

Ernie Renn · Post by **Ernie Renn** » 31 Mar 2003 9:02 am

I've used both sizes of George L cable, (under the Lawrence name in the 80's,) and I don't hear any difference inthem. However I do prefer the smaller cord. It's easier to manage. Especially when wiring a rack system. It'll fit thru smaller openings than the larger cable.

I also have a few mid-90's Fender cords, (they were given to me.) They don't sound anywhere near as good as the George L cables do.

Just my two cents...

John Macy · Post by **John Macy** » 31 Mar 2003 12:35 pm

Double, triple, quadruple-whatever. I hear it, and most of my peers hear it.

At one session, one of my second engineers swapped out the cable while we were at lunch during a vocal session without telling us. Interesting thing--both the artist and myself noticed the change sonically. I don't know the multiple of the blindfold count on that, but...

Rupert Neve tells an interesting story about a Neve console delivered to AIR Studios shortly after he sold the company. Seems Geoff Emerick was complaining that 4 of the 48 channels in the console did not sound right. The new owners of Neve could not figure it out and finally called Rupert back to figure it out. It turns out there were 4 transformers inproperly terminated that was causing an anomally at 58K, way, way above the normal range of human hearing, but Geoff caught it. So it hearing a difference in cables does not seem so far fetched...