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 Post subject: Re: Rickenbacker cap .0047mF - What is the cut off frequency
 Post Posted: Sun Oct 30, 2011 6:55 am 
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iiipopes wrote:
With the fundamental of the low E string being 80 Hz....


Actually 41hz. 82hz would be the first harmonic.


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 Post subject: Re: Rickenbacker cap .0047mF - What is the cut off frequency
 Post Posted: Tue Nov 01, 2011 1:31 pm 
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Joined: Fri Oct 21, 2011 12:43 pm
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Hi coolhandjjl!
Thanks for your input, same question to you:
Which guitar/bass was it?
Did you use the ric-o-sound mono? Was this Bridge PU only on the swich?
Do you know what pots it was?


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 Post subject: Re: Rickenbacker cap .0047mF - What is the cut off frequency
 Post Posted: Tue Nov 01, 2011 1:39 pm 
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Hi iiipopes!
Can you explain what the 90deg does to the sound? I suspect that in combination
with the neck PU you get a combfilter, with some frequncies canceled/reduced?
But brindge only would be no effect?


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 Post subject: Re: Rickenbacker cap .0047mF - What is the cut off frequency
 Post Posted: Tue Nov 01, 2011 1:50 pm 
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iiilpopes: With the fundamental of the low E string being 80 Hz....
coolhandjjl: Actually 41hz. 82hz would be the first harmonic.

Hi coolhandjjl! I guess you're a bass player? Maybe iiilpopes plays the guitar?
I'm a guitarplayer myself.


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 Post subject: Re: Rickenbacker cap .0047mF - What is the cut off frequency
 Post Posted: Tue Nov 01, 2011 2:04 pm 
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laban1 wrote:
Hi iiipopes!
Can you explain what the 90deg does to the sound? I suspect that in combination
with the neck PU you get a combfilter, with some frequncies canceled/reduced?
But brindge only would be no effect?


You're right, it's a comb filter between the two pickups under normal conditions (and I'm glad to see someone else using that terminology). The 90-degree shift takes the signals into perpendicular phases where they cannot do said comb filtering. Want to prove it to yourself? Here you go: solo the neck pickup, then go to both pickups with the cap bypassed. The sound, even in the low end coming from the neck pickup, changes a lot. It gets scooped by comparison. Now try the same thing with the cap in. With both pickups on the neck pickup's inherent sound will still be there, and you're getting some highs in there from the bridge pickup. But the signals aren't filtering each other out so this configuration still has that "soloed pickup" sound to it, which is a really cool thing about the 4.7 nF HPF capacitor. I think it also explains why this setup can sound so huge, because you're getting the full breadth of two pickups at once, minus the fundamental that would normally come from the bridge pickup (which the neck pickup replaces with no problem).


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 Post subject: Re: Rickenbacker cap .0047mF - What is the cut off frequency
 Post Posted: Wed Nov 02, 2011 12:20 pm 
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Thanks cassius987! That sounds very interesting, think I'll do the mod.
Can't help to ask: What about that shift?
I think if it would be 180 deg thay would cancel completely, and 90 is half way, wouldn't that be more cancelling than without cap?

OR since the PU:s is a bit apart, the string is in fact in different phase over the PU's, and
the shift with the cap correct this partly, so the PU is more in phase with the cap than without? Keep posting!


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 Post subject: Re: Rickenbacker cap .0047mF - What is the cut off frequency
 Post Posted: Wed Nov 02, 2011 12:39 pm 
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laban1 wrote:
Thanks cassius987! That sounds very interesting, think I'll do the mod.
Can't help to ask: What about that shift?
I think if it would be 180 deg thay would cancel completely, and 90 is half way, wouldn't that be more cancelling than without cap?

OR since the PU:s is a bit apart, the string is in fact in different phase over the PU's, and
the shift with the cap correct this partly, so the PU is more in phase with the cap than without? Keep posting!


Two perpendicular signals can't really do much phase cancelation as they are not oriented properly to do so. Cancelation happens in parallel phases--0 or 180 degrees, etc. You are right that the pickups are slightly out-of-phase with each other spatially, hence the role a pickup position plays in voicing a pickup. Basically with the cap in, there is no signal cancelation--or enhancement--really happening between the two pickups because the phases are perpendicular. The evidence for this is very audible.


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 Post subject: Re: Rickenbacker cap .0047mF - What is the cut off frequency
 Post Posted: Wed Nov 02, 2011 9:31 pm 
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It's really rather simplistic to say that a capacitor introduces a 90 degree phase shift. In reality, it's somewhere between 0 and 90 degrees.

<Nerd Mode>

Take the case of the 0.0047uF cap in series with the pickup signal and a resistor (the volume control) to ground. This is a classic first order RC high pass filter because it blocks low frequencies and passes high frequencies.

When the input is constant or has very slow changes, the capacitor acts like an open circuit. That is, it draws very little current, and so very little voltage is dropped across the output resistor. So slow frequencies on the input are nearly stripped from the output.

When the input is very quickly changing, the capacitor draws as much current as possible (i.e., it is a short circuit), and so the circuit response is set primarily by the resistor. Hence, these fast frequencies are copied nearly perfectly onto the output.

This open-capacitor-at-low and short-capacitor-at-high explanation of the filter’s magnitude response can be extended to explain its phase response as well.

At low frequencies, the open-circuit-like capacitor draws so little current across the resistor that the voltage across the capacitor is all of vin. Because Ic = Cv′c and Vc ≈ vin, then the capacitor current is in quadrature (i.e., 90◦ out of phase) with the input. However, because the output is taken across a simple resistor, it is just a scaled version of the capacitor current. So the output has a 90◦ phase shift for low frequencies (i.e., frequencies where the capacitor is in complete control of the current).

At high frequencies, the short-circuit-like capacitor does not restrict the current, and so vout ≈ vin, and there is no phase shift.

The phase response for intermediate frequencies smoothly connects these two extremes.

</Nerd Mode>


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 Post subject: Re: Rickenbacker cap .0047mF - What is the cut off frequency
 Post Posted: Thu Nov 03, 2011 10:13 am 
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coolhandjjl wrote:
iiipopes wrote:
With the fundamental of the low E string being 80 Hz....


Actually 41hz. 82hz would be the first harmonic.

Yes. @41.2 Hz on bass, I was referencing guitar @82.4 Hz.


Last edited by iiipopes on Thu Nov 03, 2011 10:17 am, edited 1 time in total.

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 Post subject: Re: Rickenbacker cap .0047mF - What is the cut off frequency
 Post Posted: Thu Nov 03, 2011 10:16 am 
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cjj wrote:
The phase response for intermediate frequencies smoothly connects these two extremes.

And this is what is the indispensible ingredient for true jangle, as the highest frequencies beyond the resonance peak of the pickup tend to fall off anyway.


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