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"Zerocap" cables

dincz

dincz

Sep 25, 2010
1,778
1,019
Czech Republic
#1
The first time I came across these, I dismissed them as snake oil, but it seems they work on an established principle (triaxial cable with a driven shield) commonly used in medical equipment and other precision measurement applications.

Patent application here:
http://www.google.com/patents/US8246384

I found a few posts mentioning them but no final verdict. Any opinions? bongomania was planning to do some tests - are you still out there?

EDIT: This may be off topic but didn't know where else to post it - and I thought it relevant in terms of pickup/cable interaction.
 
#5
As a guitar amp builder, tweaker, I'm quite sure this will be of 0, zero, zilch, nada, help to a bass player. The small capacitance in a cable can cut some highs up in the 8-10k and higher range, but it's almost impossible to hear with a guitar, much less bass.

For example, if the input impedance is 1M and a cable has 100pF of capacitance, the roll off frequency would be ~15k. Double that capacitance and you're still about 8k, I don't think you'd hear that.

Where I can hear it on guitar is if you have long cables at the input plus effects loop, where the impedance can be far higher. Honestly, often this has the effect of smoothing out the highs. I run 20' effects loop cables for this reason.
 
#8
Bob-I said:
As a guitar amp builder, tweaker, I'm quite sure this will be of 0, zero, zilch, nada, help to a bass player. The small capacitance in a cable can cut some highs up in the 8-10k and higher range, but it's almost impossible to hear with a guitar, much less bass.


For example, if the input impedance is 1M and a cable has 100pF of capacitance, the roll off frequency would be ~15k. Double that capacitance and you're still about 8k, I don't think you'd hear that.

Where I can hear it on guitar is if you have long cables at the input plus effects loop, where the impedance can be far higher. Honestly, often this has the effect of smoothing out the highs. I run 20' effects loop cables for this reason.
Click to expand...



The problem of rolloff due to cable capacitance occurs when the instrument volume is at about -6db (passive electronics). At that setting, it can be quite noticable. With the volume at "10", not significant.

-
 
#9
megafiddle said:
The problem of rolloff due to cable capacitance occurs when the instrument volume is at about -6db (passive electronics). At that setting, it can be quite noticable. With the volume at "10", not significant.

-
Click to expand...

The rolloff of 100 pf combined with the output impedance of a typical passive bass would be well above the audible range. The tone control in the bass will be a bit more noticeable, depending how the bass is wired.
 
#10
okcrum said:
The rolloff of 100 pf combined with the output impedance of a typical passive bass would be well above the audible range. The tone control in the bass will be a bit more noticeable, depending how the bass is wired.
Click to expand...


100 pF is only about 2 or 3 feet of cable. An 18 ft cable can be as much as 800 pF.

Also, it depends on where the volume is set. The output impedance of P type electronics can be grater than 125 kohm with a 500 K pot (at -6 db). The rolloff is well within the audio range.

-
 
#13
megafiddle said:
100 pF is only about 2 or 3 feet of cable. An 18 ft cable can be as much as 800 pF.

Also, it depends on where the volume is set. The output impedance of P type electronics can be grater than 125 kohm with a 500 K pot (at -6 db). The rolloff is well within the audio range.

-
Click to expand...

That sounds like pretty poor cable. My cheepy capacitance meter says about 10-15pF/foot for most o my cables. The cheep ones can be as high as 40pF/foot.
 
#14
megafiddle said:
The problem of rolloff due to cable capacitance occurs when the instrument volume is at about -6db (passive electronics). At that setting, it can be quite noticable. With the volume at "10", not significant.

-
Click to expand...

True. It can be very noticeable on guitar where the volume pot is 250k -500k. I only calculated assuming the volume wide open.
 
#17
LoveThatBass said:
I have found some cables sound a little better than others depending on the pickups used in a guitar, but I have yet to here a difference on a bass. The snake oil is in the price. That is insane!
Click to expand...
A few years ago, I was one of the beta testers for a hi-end cable put out by Elixir; this cable was also evaluated by Bongomania on his Ovni Labs pages at the same time as the testing. Bongo noted that the Elixir basically defied the overall notion that an expensive cable is really no better than an inexpensive one, particularly when the Elixir is used with a passive bass. I noticed this as well in my testing....switching a bass from active to passive did in fact produce a richer/rounder/mo'betta tone...subtle, to be sure, but it was there.

Naturally, Elixir promptly discontinued the cable after the first production run.
 
#18
Somewhere around 40 to 50 pF per foot is typical for guitar / bass signal cables, regardless of price. George L cables have about 20 pF/ft. It's already been mentioned: Buffer the signal and the problem goes away. The other approach is just to live with it, which is what I do.
 
#19
Bob-I said:
...if the input impedance is 1M and a cable has 100pF of capacitance, the roll off frequency would be ~15k. Double that capacitance and you're still about 8k, I don't think you'd hear that.
Click to expand...
aside from 100pF 20-foot cables being unobtanium, what's the slope of this rolloff? how steep?
Bob-I said:
Where I can hear it on guitar is if you have long cables at the input plus effects loop, where the impedance can be far higher.
Click to expand...
most "effects loops" i'm familiar with are buffered, if not even line-level, rendering cable capacitance moot.
 

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