Another question to fuel the resistance

[frets]

Oh boy, Are you guys ready to ban me from the forum yet with my insipid questions? I know I need to read the electronics tutorial; however, I don’t think this will be in there. And I’ve yet to get John’s Guitarfreak to work because I only have Excel 2003.
I’ve asked this question in a roundabout manner about two weeks ago. But I understand the topic far better now. Well, a bit better.
Q: Does a Capacitor in Parallel with a resistor comprise a lo pass or hi pass RC filter. Given the voltage is traveling simultaneously through both when they are parallel, how does that simultaneous “flow” effect frequency in Hertz? For example, you have a .039 capacitor and put a 270k resistor in parallel with the Cap. This is what I erroneously referred to previously as “Resistor between the Capacitor’s Legs” . If the signal that hits that combination on the hot side does it result in a lo pass or hi pass filter as the signal travels through the .039/270k combination either limiting or passing thru frequencies? Thank you for your clarification.

[JohnH]

There is a version of GuitarFreak for Excel 97-2003. Just scroll down the first post

Your RC pair could be used as part of a low pass or a high pass circuit. Depends how its wired. into a circuit.

The capacitor has an impedance that falls with higher frequency. In this case, it will be of similar magnitude to the resistor at 15 hz. Below this, the pair will act more like the fixed resistor, and above it, it will tend to act more like the capacitor.

There's a lot more to tell!

[frets]

John, for the example below, I have a push pull tone pot.  The parallel cap/resistor combo is .033/39k.   It is attached at dpdt lug 1 (hypothetical C1, C2 connections to the pot are in place) and the parallel is grounded to the pot with all other wiring necessary to make it a functioning pot in place. The pot is pulled up and rotated; thus, activating the cap/resistor combo.  The signal is hitting the cap and resistor at the same time, what type of cut would this situation be in terms of cut and frequency?
Thanks for helping me understand this.

[frets]

Is there anybody out there that can answer my question in the previous thread? To make myself clearer, when a resistor is placed between the legs of a capacitor in order to generate a particular tone; I.e. soldered as the tone capacitor on a tone pot, is is a lo cut, hi cut or what? I am interested because the signal is passing through the capacitor and resistor at the same time and then traveling to ground.
Again, resistor between the legs of a capacitor, a A500k pot - the resistor cap combination is soldered to the pot as a tone pot, in layman’s vernacular, what is transpiring? Let’s say a .047/40k. Lo or hi or what?

[JohnH]

if that pair is connected from hot to ground, it will reduce highs. I'd call that low pass

[frets]

Hey John, Sorry to be so late in responding. I’ve read up a lot on this issue in terms of generalities regarding RC and RLC. What they are, what they do, etc.. I appreciate your response. And it’s getting me closer to comprehending.

Recently, I mistakenly put two values, Resitor/Cap and calculated Hz on a online calculator. It made no realistic sense in terms of a guitar. Did the same taking the pickups into account in an RLC calculator and soon found that one did not make sense either.

I have entered the above in a high pass calculator and learned that this method revealed a realistic frequency as combined. Like the 047/40k. I think....However, how would one “know” the tone tweak in order to construct an RLC in a guitar that landed around 800Hz or 2000Hz, or 150Hz, etc., etc. How can one use these circuits to “microbrew” a specific tone? A “Custom Designer” of hitting a favored small tone spot through the utilization of Resistors and Capacitors in Parallel? A good example of this would be the Rothstein Midrange. How did they know a .0022 with a 1M would give them the result they were seeking?

[newey]

You can, I believe, model this situation using JohnH's Guitarfreak software, producing frequency curves to show the frequencies that you want.

There is also the trial-and-error method, which does not need to mean soldering and resoldering different options. You can construct a cap/resistor "substitution box" external to the guitar as test various combinations. The caps and resistors are cheap enough that it won't hurt your wallet too drastically.

[JohnH]

Ok so in a simple filter comprising an R and a C, you can configure it in a few ways to cut highs and pass lows or cut lows and pass highs. The frequency where tbe cutting starts to happen is around the frequency where the impedance of the capacitor equals that of tbe resistor.

1/(2Pi.frequency.capacitance) = R

so, frequency = 1 / (2Pi.R.C)

So if you double the capacitance or the resistance, this 'corner' frequency will halve. Its a soft rounded transition though.

If an inductance is involved, the C interacts with the L to make a resonant dip or hump at a frequency where


1/ (2Pi.f.capacitance) = 2.Pi.f.L

Those kind of statements give a clue to what happens but don't reveal a basis for much deeper understanding. To do that, you need to consider numbers in a 'complex number' plane, Resistances are measured horizontally and capacitive and inductive impedances are measured down and up respectively. Adding them up is like a pythagoras calculation. With a few more techniques on this basis you can understand any complicated RLC network (such as an entire guitar).

[frets]

John and Newey,
I really appreciate the suggestions and am so thankful for the formulas. I can get into that. I’m going to do a little math with this and also use John’s software. I think a basic table outlining the effects per salient combinations would be helpful, if not interesting. I’ll be back.

[frets]

Would some good soul provide the link to John's Guitar Freak?  I want to load it on another computer and just cannot find it on the forum. Duh
Thank you !

[sumgai]

Just used it a moment ago, in another answer to someone.....


Here ya go: John's Guitar Freak

HTH





sumgai

[frets]

Thanks Sumgai !!

[sumgai]

(Text deleted due to explanations below. Post not deleted to provide continuity for the following responses.)

[frets]

Sumgai, This is over my pay grade; but, if one wanted to determine how frequency is affected by a cap and a resistor, it seems John’s formula does that. Right? I know that’s not your issue with it; however, yours requires the frequency to be “known” apriori. My simplistic inquiry was just about how frequencies can be nudged by RC’s and RCL’s. I’m still going to plug in values into your formulas utilizing a mean frequency for a given cap by itself within an apriori circuit before it is nudged by an RC or RCL . If that’s appropriate.

[frets]

Sumgai,
Bare with me...
Using your formula for extracting the value of a resistor needed to achieve a particular desired frequency, one would insert the desired frequency into the equation (1/2Pi*frequency)/C? So, say I want to arrive at 800Hz, and I’m using an .022 Cap, would the Resistor required = 57090.90909 Ohms or 57k?

[sumgai]

frets,


Here's what happened above. John's formulas are correct.  At first glance, one compared to the other looks like a proof that R = 1/frequency, but that's not the case, for various reasons. What I did a few postings ago was to get all mathematical, and then stop short of finishing how John's formula is correct.  I deleted that text, because there was no reason for it.  John observed the K.I.S.S. principle, and I did not.  Consider me properly scolded.

Now, leaving my mis-statements alone, let's plug your values into the correct formula.  R = 1/(2Pi*frequency*C) gives us 6.28 * 800 * 0.000000022 (0.022uF), which yields 9047.5 Ohms.  A 10KOhm resistor should do the trick.  If not, if more accuracy is required, then two or more resistors may be lashed together in series and/or parallel as needed.  Sorry if I put you through a rough time, mea culpa.

HTH

sumgai

[ashcatlt]

Is this basically just a resistor parallel to the capacitor in an otherwise normal tone configuration? Like, there's a "pot" wired as a variable resistor between the hot output of a magnetic pickup (or combination thereof), and the top of the cap/resistor parallel thing, with the bottom of that parallel thing going to "ground"?

Then it's essentially a low pass filter. How the resistor will affect things does depend on absolutely everything else, but I would expect it to cause a bit of reduction in the very highest frequencies and a small but measurable reduction in the broadband output. I haven't done the trig part, which is where resonance throws its curve balls, but the math is pretty easy.

Everything useful is a voltage divider. The top half of this voltage divider is pretty big but relatively flat at low frequencies, but gets big (heads toward infinity) fast at high frequencies. The C is really big (heads toward infinity) at lower frequencies, but is parallel to the R. Low frequencies are attenuated some because it's no longer "kinda big" over "infinity" but rather "kinda big" over "really big". At higher frequencies where C starts to look smaller, it being in parallel to R just makes it even smaller, so now it's "starting to get big fast" over "getting smaller faster".

Again, the trigonometry might (probably will) dictate a resonant peak right at the point where broadband attenuation turns into low pass, but that's what GuitarFreak is for.

[Deleted]

XC = 1 / (2 x Pi x F x C)
NOTE C will be in 0.001 for Milli 0.000 001 Micro, 0.000 000 001 Nano, 0.000 000 000 001 for Peco
and its called Inductance Reactance (I had to correct myself {Impedance}) measured in Ohms

XL = 2 x Pi x F x L

if i recall right that Z = naaa its gone im going to have to google it

dam i was right about the Z formula

Z = SQR(R^2 + (XC-XL)^2)

i would suggest reading about this than taking it to a forum 
and to take FORMULA as RULES not to be QUESTION
i should use this formula for light system to bring the phase back in .. Lights being XL 

[thetragichero]

impedance: it's complicated

[frets]

Thanks to all with a special thanks to Sumgai and John who have answered exactly what I wanted to know in a broad swath, 30,000 foot manner - which is all I needed. Thanks Sumgai for making it real.

[sumgai]

frets,


Yer welcome!







sumgai