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-   -   Cap values... (http://www.talkbass.com/forum/f38/cap-values-956267/)

 cnltb 02-07-2013 03:37 PM

Cap values...

What would a 0.47 pf cap sound like in a 51 style p bass compared with two 0.22 pf ones?
Thanks!

 line6man 02-07-2013 03:47 PM

I think you mean 0.047uF. PicoFarads are a few orders of magnitude smaller.

Two 0.022uF caps in series make 0.011uF. Two 0.022uF caps in parallel make 0.044uF.

 jeffmensch 02-07-2013 03:52 PM

If the caps are connected in parallel, the capacitance is additive (0.22 pf + 0.22 pf = 44 pf). Since the 0.47 pf is larger, the high frequency cutoff is shifted down slightly reducing a bit of the high end. This can make the bass frequencies to be perceived as more prominent. It may be hard to distinguish the change unless you have really good ears.

.047µF = 47nF (.47µF or .47pF both wrong) is the normal P51 capacitor ...
TWO .022µF parallel would sound nearly the same.

I AM NO ELECTRONIC TECHNICIAN!

But as far as I remeber, it's a little bit tricky ...
While two resistors in parallel mode mean hald value (R = 1/R1 + 1/R2)
the value of two parallel capacitors are added. So, 22nF + 22nF are nearly 47nF.

The sound surely varies from brand to brand, type to type +++ ...

EDIT: Both were much faster than me!

 line6man 02-07-2013 04:24 PM

Quote:
 Originally Posted by Cadfael (Post 13846186) But as far as I remeber, it's a little bit tricky ... While two resistors in parallel mode mean hald value (R = 1/R1 + 1/R2)
This is incorrect. That will give you the inverse of "R." You need to find the inverse of the sum of the inverses to get the total of parallel resistances, impedances and inductances, and series capacitances.

In other words, CTotal=1/([1/C1]+[1/C2]+...[1/Cn]). (If you're a math guy, you can throw in "∀n∈N" to get technical.:hyper:)

SORRY!

1/R Total = 1/R1 + 1/R2

 line6man 02-07-2013 07:55 PM

Quote:
 Originally Posted by Cadfael (Post 13846558) SORRY! I had already been a bit too drunk? 1/R Total = 1/R1 + 1/R2
People do it all the time on this forum. No big deal. :hyper:

I've done worse things after drinking.:hiding:

 cnltb 02-08-2013 02:32 AM

Wow...
Thanks VERY much for your input so far!

now if someone had the facilities and time to post sound samples of the two options ( one of two parallel 0.022 and one of a 0.047) that would be great!!!:)

 Meddle 02-08-2013 05:47 AM

Quote:
 Originally Posted by line6man (Post 13846142) I think you mean 0.047uF. PicoFarads are a few orders of magnitude smaller. Two 0.022uF caps in series make 0.011uF. Two 0.022uF caps in parallel make 0.044uF.
This looks correct.

If they are in parallel, and you can claim to hear a difference between a 0.044uF and 0.047uF cap then you are a savant.

 SlingBass4 02-08-2013 06:16 AM

IMO & IME cap values are like horseshoes and hand-grenades. Close...but not exact. The variables of woods (age, weight, composition) plus pups may not always match with the sound one hears in their head. I've sat with a tech and gone through a half dozen caps before arriving at my choice. Often times not even close to where I thought I was going. It's a subjective topic that can only be answered by taking time and experimenting to insure totally fulfilled potential and satisfaction. Just sayin'...

Quote:
 Originally Posted by cnltb (Post 13848476) ...now if someone had the facilities and time to post sound samples of the two options ( one of two parallel 0.022 and one of a 0.047) that would be great!!!:)
A graphic tone-diagram might show differences - but would at the same time say nothing ...

SlingBass4 showed the right way ...

 Meddle 02-08-2013 06:36 AM

You are trusting these caps to be <1% tolerance as well. Thats why old PIO capacitors can sound 'warm' or 'sparkly'... because their values are nothing like what they are reported to be.

 Rip Topaz 02-08-2013 06:48 AM

So based on all of this, my SCPB has a really nasty treble bite to it. Right now there's a .047 cap in there.

Would swapping to a .1 cap allow me to tame that high end harshness?

 FunkMetalBass 02-08-2013 08:09 AM

Quote:
 Originally Posted by cnltb (Post 13848476) Wow... Thanks VERY much for your input so far! now if someone had the facilities and time to post sound samples of the two options ( one of two parallel 0.022 and one of a 0.047) that would be great!!!:)
The problem is that the values are never exact, so they could have the same capacitance, or the .047 could have less actual capacitance than the two .022's. Even if you got them exact, I think the cutoff frequency would only differ by about a semitone.

 Meddle 02-08-2013 04:45 PM

Quote:
 Originally Posted by Rip Topaz (Post 13848765) So based on all of this, my SCPB has a really nasty treble bite to it. Right now there's a .047 cap in there. Would swapping to a .1 cap allow me to tame that high end harshness?

Try 250k pots first.

I also have a Dearmond Jet Star II that I permenantly wired with the pickups in series and with something like a 0.001uF capacitor wired over the output jack. Just tames enough transient peaks to make the tone 'smoother'.

As for FunkMetalBass, I would be wary of saying a semitone cutoff frequency change would occur because the cutoff happens over such a wide range of frequencies in such a gradual manner. That is like saying that once you turn down the tone control everything above the 7th fret of the G suddenly vanishes but if you have a 0.002uF difference then you can hear the 8th fret.

 FunkMetalBass 02-08-2013 06:18 PM

Quote:
 Originally Posted by Meddle (Post 13851878) As for FunkMetalBass, I would be wary of saying a semitone cutoff frequency change would occur because the cutoff happens over such a wide range of frequencies in such a gradual manner. That is like saying that once you turn down the tone control everything above the 7th fret of the G suddenly vanishes but if you have a 0.002uF difference then you can hear the 8th fret.
In this case, I'm only considering the tone control as a LPF (by that I mean when the tone is rolled all the way down) as that's when the difference in cut-off frequencies is going to be most noticeable since the cut-off will be steeper.

EDIT: In fact, it should be fairly uniform across the entirety of the pot's rotation. Since resistance and inductance can be held constant between the two circuits, the ratio of the two cutoff frequencies is based entirely on the ratio of their capacitors; that is .044/.047 = 1:1.06818, and the ratio of semitones is 1:1.05946. My claim about one semitone difference still stands.

 SGD Lutherie 02-09-2013 03:00 AM

Quote:
 Originally Posted by cnltb (Post 13848476) now if someone had the facilities and time to post sound samples of the two options ( one of two parallel 0.022 and one of a 0.047) that would be great!!!:)
Why would you want two parallel .022µF caps?

No one will have sound clips because no one would do that.

You wont hear the difference from a .047µF cap.

 cnltb 02-09-2013 03:42 AM

Quote:
 Originally Posted by SGD Lutherie (Post 13853856) Why would you want two parallel .022µF caps? No one will have sound clips because no one would do that. You wont hear the difference from a .047µF cap.
Well... someone HAS done that :).
I have a GREAT sounding '51 style P bass with two parallel .022 caps and I was wondering wether I might get even better results if I put a single .047 in there.
And since we all know what often happens when someone asks a "should I, shouldn't I..." question, I put mine the way I did.
Thanks again for all the input- I learned something here, which is a good thing ! :-)

Fender hasn't done this "ex factory" ...

BUT GIBSON DID!
The Gibson EB2 from 1958-1970 had two 22nF parallely wired!
It had three 22nF capacitors all in all - two wired parallel to 44nF at the tone pot and a third one in the "tone switch circuit" ...

The Epiphone Rivoli Bass from 1965 had this, too!

EDIT: Maybe they made this to get less capacitor "mix errors" by unskilled workers???
The worker got three capacitors with the same value - so he could not mix the .047 and .022µF capacitor. "One here, two there" is easyier than reading the value ...

 khutch 02-09-2013 08:50 AM

Quote:
 Originally Posted by Meddle (Post 13851878) As for FunkMetalBass, I would be wary of saying a semitone cutoff frequency change would occur because the cutoff happens over such a wide range of frequencies in such a gradual manner. That is like saying that once you turn down the tone control everything above the 7th fret of the G suddenly vanishes but if you have a 0.002uF difference then you can hear the 8th fret.
Cutoff frequency is a precise engineering term. It is the point where the response has fallen 3dB (usually, you can use another value as long as you specify it). So it is correct to say that the cutoff changes by a semitone and incorrect to say that it occurs over a range of frequencies. What you are referring to is the steepness of the skirt of the tone response. That is relatively gradual on typical tone circuits. The cutoff frequency is effectively the point where the passband ends and the stopband begins.

Ken

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