Variable capacitor circuits

[audioguru]

This is that we have to do is this

.05uf with a 22K in parallel the frequency range is ?

An allpass filter's output will be 90 degrees at 146Hz.

.047uf with a 10K in parallel the frequency range is?

An allpass filter's output will be 90 degrees at 340 Hz.

.01uf with a 100uf in parallel the frequency range is?

One must be a resistor.

The phase-shift changes with frequency, it is nearly 180 degrees at 1/10th the tuned frequency and nearly 0 degrees at 10 times the tuned frequency. Calculating the phase-shift of different allpass filters in series boggles my mind. Google's links have already calculated them for you.

The formula for most electronic RC circuits:

 

[mstechca]

Changing the capacitor and changing the resistor in a RC circuit does exactly the same thing.

No its doesn't

what do you mean NO?

The Capacitor Value changes the frequency Range

uh, no. The capacitor value is a number. Audioguru pointed out a good equation for finding out the frequency based on a resistor and a capacitor.

a .01uf can only phase shift so many frequencys range so u have to change the .01uf to another value like a .47uf to change the frequency range

NO! a capacitor is not a device that changes the frequency range. If it was that, radios wouldn't exist!

The resistor can't go past the .01uf frequency range without changing the .01uf to another value like a .47uf to get a different frequency range with different phase shifts

Your theory has blown me away. In other words, it doesn't make sense.

100k with a .01uf is different than a 100k with a .47uf phase shift network whats the difference?

First of all, Let's remove "phase shift" out of your vocabulary because it is screwing you up.

Secondly, the absolute, most ridiculous simple time formula, while ignoring all detail, enhanced factors is:

Time = resistance * capacitance

Now, that is true to an extent because a capacitor stores charges, but not instantly. the value of the capacitor can determine the amount of charge a capacitor can hold.

Now a resistor in series with it limits the current entering the capacitor. and the less current there is entering the capacitor, the longer it takes for it to charge.

Of course, the other gods could elaborate more, but thats where the R * C comes from in audioguru's equation.

Frequency is 1 / time.

Now if you wanted a frequency range, you will have to continually play with your resistors, and capacitors, and follow Audioguru's equation over and over again.

 

[audioguru]

You asked for it. In Google's link about allpass filters, there is a complicated cascaded bunch of allpass filters: "This circuit will produce two outputs, which will remain 90 degrees out of phase with each other from 20 Hz to 20,000 Hz with a phase error of less than +/- 1 degree."

 

[mstechca]

I'll never build that circuit.

Audioguru, is that the way they gave the schematic to you, because I can't read 1/2 the writing.

And while we are on the discussion on filters and capacitors, I think I have discovered something interesting with my superregen design. It turns out that it has a band-pass filter, and a band-reject filter. It seems that I am constantly tuning the band-reject filter, and leaving the band-pass filter alone.

I'm going to tune them BOTH with a varactor and I do hope and pray to god that I get full success, because then there will be NO filter stopping the signal from reaching the speaker.

Walters, I hope you do understand what we are saying here.
In fact, in my tone transmitters, I have to use simple time equations as well.

BUT when it comes to HF, VHF, or UHF work, the equation changes when dealing with an inductor and a capacitor.

 

[audioguru]

Audioguru, is that the way they gave the schematic to you, because I can't read 1/2 the writing.

It's a schematic that is too small and is drawn with a lousy schematic-drawing program. I can see most of it on my big high-res LCD monitor.
They have another one using fewer allpass filters, but it works only between 100Hz and 10kHz.

What would be the effect of this circuit for sound? If you had one speaker at zero degrees and another speaker at its 90 degrees then I think your brain would think that the leading phase occurs 1st, that the sound comes from that direction and that it is louder when it is not. Big deal effect!

If you displayed it on a 'scope as an X minus Y display, then it would make cool modulated circles. The size of the circles would depend on the instantaneous volume of the signal.

For years my 'scope displayed X minus Y for stereo signals. I think they were cooler-looking than circles. :lol:
One time I caught Toronto's CBC FM station transmitting stereo out-of-phase. Mono was nothing but low-level distortion and loud echoes. With stereo the phase-detector in my brain went beserk. Their engineer said "oops" it was on the tape that way and he didn't have a switch to correct it. :cry:

 

[walters]

Thanks alot guys for the help

C1 through C12 all have different cap values in parallel with a 100K
What does this do?

If C1 through C12 all had the same values like .01uf what would change the phase shift?

 

[audioguru]

C1 through C12 all have different cap values in parallel with a 100K
What does this do?

Only a few of the capacitors are in parallel with a 100k resistor. Selected resistor values were calculated together with the different capacitor values to make a range of allpass filter frequencies, to cover the entire 20Hz to 20kHz frequency range.

If C1 through C12 all had the same values like .01uf what would change the phase shift?

If the capacitors and the resistors all had the same values then each stage would be tuned to the same frequency and have 90 degrees phase shift. The output would have 8 times 90 degrees= 720 degrees at that frequency, 8 times 180 degrees at 1/15th that frequency and 8 times 0 degrees at 15 times that frequency.

 

[walters]

I think the capacitor changes the phase/frequency combination because of this example its long but i have to do it to explain

have the Cap "FIXED" and the resistor in parallel "Variable"

.01uf with a 100K in parallel = X frequency and phase degree X
.01uf with a 90K in parallel= Y Frequency and phase degree Y
.01uf with a 80K in parallel= Z frequency and phase degree Z'
.01uf with a 70K in parallel= A' frequency and phase degree A'
.01uf with a 60K in parallel= B' frequency and phase degree B'
.01uf with a 50K in parallel= C' frequency and phase degree C'
.01uf with a 40K in parallel= D' frequency and phase degree D'
.01uf with a 30K in parallel= E' frequency and phase degree E'
.01uf with a 20K in parallel= F' Frequency and phase degree F'
.01uf with a 10K in parallel= G' frequency and phase degree G'



.015uf with a 100K in parallel = X frequency and phase degree X
.015uf with a 90K in parallel= Y Frequency and phase degree Y
.015uf with a 80K in parallel= Z frequency and phase degree Z'
.015uf with a 70K in parallel= A' frequency and phase degree A'
.015uf with a 60K in parallel= B' frequency and phase degree B'
.015uf with a 50K in parallel= C' frequency and phase degree C'
.015uf with a 40K in parallel= D' frequency and phase degree D'
.015uf with a 30K in parallel= E' frequency and phase degree E'
.015uf with a 20K in parallel= F' Frequency and phase degree F'
.015uf with a 10K in parallel= G' frequency and phase degree G'


.047uf with a 100K in parallel = X frequency and phase degree X
.047uf with a 90K in parallel= Y Frequency and phase degree Y
.047uf with a 80K in parallel= Z frequency and phase degree Z'
.047uf with a 70K in parallel= A' frequency and phase degree A'
.047uf with a 60K in parallel= B' frequency and phase degree B'
.047uf with a 50K in parallel= C' frequency and phase degree C'
.047uf with a 40K in parallel= D' frequency and phase degree D'
.047uf with a 30K in parallel= E' frequency and phase degree E'
.047uf with a 20K in parallel= F' Frequency and phase degree F'
.047uf with a 10K in parallel= G' frequency and phase degree G'


.22uf with a 100K in parallel = X frequency and phase degree X
.22uf with a 90K in parallel= Y Frequency and phase degree Y
.22uf with a 80K in parallel= Z frequency and phase degree Z'
.22uf with a 70K in parallel= A' frequency and phase degree A'
.22uf with a 60K in parallel= B' frequency and phase degree B'
.22uf with a 50K in parallel= C' frequency and phase degree C'
.22uf with a 40K in parallel= D' frequency and phase degree D'
.22uf with a 30K in parallel= E' frequency and phase degree E'
.22uf with a 20K in parallel= F' Frequency and phase degree F'
.22uf with a 10K in parallel= G' frequency and phase degree G'


.001uf with a 100K in parallel = X frequency and phase degree X
.001uf with a 90K in parallel= Y Frequency and phase degree Y
.001uf with a 80K in parallel= Z frequency and phase degree Z'
.001uf with a 70K in parallel= A' frequency and phase degree A'
.001uf with a 60K in parallel= B' frequency and phase degree B'
.001uf with a 50K in parallel= C' frequency and phase degree C'
.001uf with a 40K in parallel= D' frequency and phase degree D'
.001uf with a 30K in parallel= E' frequency and phase degree E'
.001uf with a 20K in parallel= F' Frequency and phase degree F'
.001uf with a 10K in parallel= G' frequency and phase degree G'


220uf with a 100K in parallel = X frequency and phase degree X
220uf with a 90K in parallel= Y Frequency and phase degree Y
220uf with a 80K in parallel= Z frequency and phase degree Z'
220uf with a 70K in parallel= A' frequency and phase degree A'
220uf with a 60K in parallel= B' frequency and phase degree B'
220uf with a 50K in parallel= C' frequency and phase degree C'
220uf with a 40K in parallel= D' frequency and phase degree D'
220uf with a 30K in parallel= E' frequency and phase degree E'
220uf with a 20K in parallel= F' Frequency and phase degree F'
220uf with a 10K in parallel= G' frequency and phase degree G'


100uf with a 100K in parallel = X frequency and phase degree X
100uf with a 90K in parallel= Y Frequency and phase degree Y
100uf with a 80K in parallel= Z frequency and phase degree Z'
100uf with a 70K in parallel= A' frequency and phase degree A'
100uf with a 60K in parallel= B' frequency and phase degree B'
100uf with a 50K in parallel= C' frequency and phase degree C'
100uf with a 40K in parallel= D' frequency and phase degree D'
100uf with a 30K in parallel= E' frequency and phase degree E'
100uf with a 20K in parallel= F' Frequency and phase degree F'
100uf with a 10K in parallel= G' frequency and phase degree G'


20uf with a 100K in parallel = X frequency and phase degree X
20uf with a 90K in parallel= Y Frequency and phase degree Y
20uf with a 80K in parallel= Z frequency and phase degree Z'
20uf with a 70K in parallel= A' frequency and phase degree A'
20uf with a 60K in parallel= B' frequency and phase degree B'
20uf with a 50K in parallel= C' frequency and phase degree C'
20uf with a 40K in parallel= D' frequency and phase degree D'
20uf with a 30K in parallel= E' frequency and phase degree E'
20uf with a 20K in parallel= F' Frequency and phase degree F'
20uf with a 10K in parallel= G' frequency and phase degree G'


How do i find out the frequency and phase degree for each frequency?
Which formulas do i use please to find the answers?

 

[audioguru]

How do i find out the frequency and phase degree for each frequency?
Which formulas do i use please to find the answers?

I showed you the formula to determine the center tuned frequency of an allpass filter where its phase-shift is 90 degrees.
I showed you a graph showing that the phase-shift is nearly 180 degrees at 1/10th its tuned frequency and nearly 0 degrees at 10 times its tuned frequency.
I would just look at the graph to determine the amount of phase-shift at a frequency, by using a ratio of my frequency with the frequencies shown on the graph.
If you want a more detailed formula then look at allpass filters on Google.

 

[walters]

Thanks for the help

05uf with a 22K in parallel the frequency range is ?

An allpass filter's output will be 90 degrees at 146Hz.

Whats the frequency for 10 degrees?
Whats the frequency for 20 degrees?
Whats the frequency for 30 degrees?
whats the frequency for 40 degrees?
Whats the frequency for 50 degrees?
Whats the frequency for 60 degrees?
Whats the frequency for 70 degrees?
Whats the frequency for 80 degrees?
Whats the frequency for 90 degrees?
Whats the frequency for 100 degrees?


Quote:
.047uf with a 10K in parallel the frequency range is?

An allpass filter's output will be 90 degrees at 340 Hz.

Whats the frequency for 10 degrees?
Whats the frequency for 20 degrees?
Whats the frequency for 30 degrees?
whats the frequency for 40 degrees?
Whats the frequency for 50 degrees?
Whats the frequency for 60 degrees?
Whats the frequency for 70 degrees?
Whats the frequency for 80 degrees?
Whats the frequency for 90 degrees?
Whats the frequency for 100 degrees?

How did u get the frequency and the 90 degrees?
What formulas do u use to get the frequency at the other degrees please?

 

[audioguru]

How did u get the frequency and the 90 degrees?
What formulas do u use to get the frequency at the other degrees please?

I showed you the formula to calculate the tuned center frequency of an allpass filter where the phase-shift is 90 degrees: 1, divided by (2 * pi * R * C).
For other amounts of phase shift you can change the center tuned frequency, look at the graph or look in Google for a detailed and complicated formula.

 

[walters]

1, divided by (2 * pi * R * C).

This is only for the "center frequency" only and how do u know its 90 degrees? with this formula

How do i "transpose" this formulas so i can get other frequencys and phase degrees ?

Like whats the phase degree at 100hz
phase degree at 200hz
phase degree at 500hz

What formulas do i use to get the phase degrees ?

 

[i_build_stuff]

I think that phase shift circuit is actually meant to be part of an SSB modulator...

One method that I don't think anybody mentioned yet is to use an op-amp to "amplify" the capacitance of a varactor using the Miller effect. The only limitation is the total amount of charge this "capacitor" can hold--the voltage across the capacitor is multiplied by the same gain that its C value is, and this voltage can't be any higher than Vdd - Vin (or less than Vss - Vin, depending on the polarity of Vin).

 

[audioguru]

how do u know its 90 degrees? with this formula

Look at the graph.
Look at links about allpass filters in Google.

How do i "transpose" this formulas so i can get other frequencys and phase degrees ?

Look at the graph and make a ratio with its tuned center frequency and yours.

What formulas do i use to get the phase degrees ?

Look at links about allpass filters in Google.

 

[mstechca]

I think 2 * pi in the equation converts radians into degrees.
Isn't pi also 90 degrees, or no?

And Walters, What do you intend to do with phase shifts anyway?

You seem to be asking all sorts of questions, and I just don't know exactly how you use our answers. Are you having us do 1/2 your school work?

 

[audioguru]

Are you having us do 1/2 your school work?

Which school teaches the history of ancient guitar effects?
I think "flanging" was discovered "a few hundred years ago" by the Beatles, when two tape players weren't quite syncronized. Later, when every guitar player on earth bought bucket-delayline ICs to make the effect electronically, nobody bought the ICs anymore so most Semi companies stopped making them.
I am surprised that nobody makes a fuzz IC with famous guitar players' names on the pins to be shorted to ground for their particular kind of severe distortion. :lol:

 

[walters]

Yes this formula 1, divided by (2 * pi * R * C).
doesn't work for getting other phase angles/degrees and different "input"
frequency

I need a formula that will take any "input" frequency and the RC time and give me the phase degree for the input frequency with the RC time what formula is this please?

 

[audioguru]

Yes this formula 1, divided by (2 * pi * R * C).
doesn't work for getting other phase angles/degrees and different "input"
frequency

I need a formula that will take any "input" frequency and the RC time and give me the phase degree for the input frequency with the RC time what formula is this please?

The articles about allpass filters in Google might have a formula for you.

 

[walters]

yea i been looking there is some many formulas but i need this one only to get the answers for phase shift frequencys and degrees

 

[_3iMaJ]

yea i been looking there is some many formulas but i need this one only to get the answers for phase shift frequencys and degrees

I don't know how you plan to understand electronics with out first understanding basic mathematics.