small stone "colour switch"

[markphaser]

Thanks George Giblet for correcting me and adding your information to the questions because i need the help

Does a phase shift *pitch shift* the notches? how does it pitch shift the notches?

Does a phase shift oscillator LFO pitch shifts the notches?

LFO is that it changes the *position* of the notches

What is this "positions" of the notches? what u mean by the "positions"

The DC offset changes the "positions" of the notches also but whats the main difference please?

[markphaser]

The number of notches=  by the number of stages

Notch depth means ?

[bioroids]

The number of notches=  by the number of stages

Number of notches = number of stages divided by two

Notch depth = how much the "notched" frequency is eliminated, you can measure it in dB, but I think on phasers the notch is supposed to be infinite (that is, the frequency totally disapears. That is, if the input has that frequency present, it will not be at the output).

This is very well explained at The technology of phasers an flangers at GEO http://www.geofex.com/Article_Folders/phasers/phase.html

You should read it, as it is very clear (that's where I learned the little I know )

Miguel

[George Giblet]

Some questions have been covered.

> Does a phase shift *pitch shift* the notches? how does it pitch shift the notches?

Notches themselves don't cause pitch shift. The notch is caused by the all-pass signal cancelling out the dry signal at particular frequencies (the 180deg  mentioned in previous post).  If the notches are not moving in time, ie. there is no LFO and a fixed manual control/offset, there is no pitch shift.

The pitch shifting come about when the circuit behaviour is modified over time, in the case of an all-pass filter the phase shift produce by the filter changes over time.  When the phase shift is varied over time you get a perceived pitch shift.

> Does a phase shift oscillator LFO pitch shifts the notches?

It is important to realize that it doesn't matter how an LFO works internally, all LFO which produce the same output will sound the same.  A phase shift oscillator is just one method of  producing a sinewave output.  (Note:  Most phase shift oscillators do not produce pure sine waves the output is slightly distorted.)

> The DC offset changes the "positions" of the notches also but whats the main difference please?

The LFO determines how fast the notches change in time and the*span* of frequencies the notches are moved over.
The DC offset determines the what frequency the notches move around.  See above post:

"> Manual Parameter

> If the LFO "sweeps" the Notches up and down the DC offset "shifts" the notches up and down also but whats different?

There's two cases here.  The first is where the LFO is complete...."

[markphaser]

Thanks so much George Giblet for answering my questions

"Most phase shift oscillators do not produce pure sine waves the output is slightly distorted"

Like crossover distortion?

What does this distortion do to the notches does it vary them differently?

I thought a LFO varyed the notches only in amplitude up and down
Because if the LFO is outputing a Triangle waveform i thought it just used the triangle waveform to ramp up and down
the amplitude of the notches only.

How does a LFO vary the notches in Time?

How do u set the LFO to move the notches in Time?
Is there a way to set the LFO to move the notches more or less in time?

In phase shift Vibrato pedals the LFO moves the notches in time but how much in Time? is there a setting
inside the LFO circuit to vary the "LFO time" so the notches "Shift" in time differently?


Thanks alot George Giblet for all these

[markphaser]

would changing the LFO "time period" change the notch shift? or moving the notches in time

For a phase shift vibrato pedal it shifts the notches the LFO "time period" is what sets the "Shift points"?

[markphaser]

The LFO circuit does have a "time period" which shifts the notches left to right i think

[markphaser]

the notches result from mixing the phase shifted and input
signals. If you remove the input signal from the mixing node to get the vibrato
effect there are no notches.

If there is no dry/clean signal mixed with the phase shift signal is there notches or no notches?

Because when i hear a vibrato pedal like a univibe on vibrato mode i hear the notches moving in and out of time/frequency
so the LFO is moving the notches back and forth?

When mixing the Dry+phase shifted notches= notches

When no dry at all just the phase shifted notches= notches

Whats the difference?

[DiyFreaque]

If there is no dry/clean signal mixed with the phase shift signal is there notches or no notches?

You answered your own question with the previous paragraph:

the notches result from mixing the phase shifted and input
signals. If you remove the input signal from the mixing node to get the vibrato
effect there are no notches.


Because when i hear a vibrato pedal like a univibe on vibrato mode i hear the notches moving in and out of time/frequency
so the LFO is moving the notches back and forth?

OK, so you've established that mixing dry with wet produces notches. It's been pointed out that the phase shifter shifts the phase of the input signal, depending on the frequency of the signal, etc.  It's also been pointed out that this phase shifted signal, which  is the wet signal, gives the effect of shifting the frequency up and down.  The LFO's sole job is to shift the phase of this signal up and down and up and down.  If the LFO stops, the phase shift freezes at that point.  If the LFO starts again, it shifts the phase up and down and up and down.

The LFO output is a voltage that rises and falls.  When the voltage rises and falls, the phase shift rises and falls.  If the voltage stops at 2V, you have the amount of phase shift on the wet signal that the LFO provides at 2 volts.  if the voltage stops at 3V, you have the amount of phase shift the LFO would provide at 3V.  Look at it this way, you decide you don't want an LFO.  You just put in a pot that you can adjust the voltage that determines how much phase shift is in the signal.  You turn the pot to 1V, and get X amount of shift.  You turn the pot to 2V, and get Y amount of shift.  You get a wild idea and start turning the pot up and down and up and down.  Your hand and the pot have now formed an LFO.  That's the function of the LFO.  It just puts out rising and falling voltage, it doesn't matter if it's a phase shift LFO, an integrator and schmitt trigger, or a photocell tracking how much light shines on it from the sun.  All it wants to do is shift the phase of the wet signal.

Do not confuse the phase shift of the wet signal with notches.  You said yourself that notches are only created when mixing dry and wet signal together.  This is true.  So, you only have notches when you mix the dry and wet signal together.  When you do this, you hear the classic 'phase shifter' sound.  'Phase Shifter' is just an easy term for what it really is.  To make it more clear, they could have called it "A Device That Takes Your Signal, Sends It Down Two Paths, Shifts the Phase of the Signal On One Path, And Mixes It Back With The Original Signal to Form Notches'.  But, this was just too wordy, and most people don't care anyway - they just like the sound.

On your Univibe, they should have just called the switch 'The Control That Doesn't Let The Phase Shifted Signal Mix Back With The Original Signal, But Instead Only Puts Out The Phase Shifted Signal So It Has A Vibrato On It'.  But, they ran out of room on the box, so they just gave it a short little name hoping no one would notice.

So:

When mixing the Dry+phase shifted notches= notches


Is correct.  And


When no dry at all just the phase shifted notches= notches


Is incorrect.  Because, when no dry at all means to me that you have not mixed the phase shifted signal with the dry signal.  Your first paragraph already nulled this.  It means nothing.  Notches do not shift phase.  A notch is created when a phase shifted signal is mixed with the dry signal.

Whats the difference?

Breadboard the simplest phase shifter you can find.  Then you will know.  Breadboard everything you've asked about, whether it be phase shifters or flangers or fuzz boxes or whatever.  The knowledge you glean will help someone else.  And, it's fun.  Use your computer to go to Jameco, order parts and one of their good breadboards.  Go to Aron's shop, go to Small Bear, go to Mouser, buy parts lots of parts parts to fill bins and bins and bins.  Buy wire.  Get a good power supply.  Go grab schematics of all the things you want to try out, print them.  Put them in a file.  Sleep with them under your pillow, whatever it takes to motivate you to do something.

Then, turn your computer off.

I've read all of your posts on this board, and a lot other boards you frequent, as much as could I allot time for anyway.  Friendly advice - you spend waaayyy too much time on the computer asking and not enough doing.  The proof in that is the number of questions asked divided by the time frame the questions were posed.  Turn off the computer, go outside.  Breath air.  Look at the clouds.  Listen to the birds.  And, above all, plot your next move, which is to build something that you can call your own.

Asking is good, but doing is good, too.  Between the two, I'd say doing nudges out asking when all is said and done.  When you have a problem, try to solve it on your own first.  If you can't solve it, don't feel bad about it, turn your computer on and ask someone here.  At least this time you'll be asking something more constructive and less theoretical.  You'll find yourself doing that less and less and feeling better and better about yourself and even helping people.  I'm not saying this to be a prick, I think you've got it in you to build a monster.  You've just got to do it.  Otherwise, why bother asking?

Cheerio,
Scott

[markphaser]

Thanks DiyFreaque for the help

'The Control That Doesn't Let The Phase Shifted Signal Mix Back With The Original Signal, But Instead Only Puts Out The Phase Shifted Signal So It Has A Vibrato On It'

If the output if just the Wet signal and No dry signal being mix if it's not notches what are they ? because when i just hear the wet signal with out the dry being mixed i hear the vibrato is are they notches or ? what sorry i don't got the name for it so i called them notches but the phase filter produces a wet signal so the output is a vibrato so the LFO must be shifting something.

Yes i know the phase filter is changing the phase of the frequencys and the LFO is shifting up and down but with a vibrato wet signal the LFO seems to be shifting left to right instead of up and down

THanks for the help to clear me up on this

[George Giblet]

> Yes i know the phase filter is changing the phase of the frequencys and the LFO is shifting up and down but with a vibrato wet signal the LFO seems to be shifting left to right instead of up and down

With the vibrato (ie. Dry path removed) there are no notches at all. The frequency response of the all-pass filter chain is flat.   What you hearing is entirely due to pitchshift.  The pitch shifting arises because the phase (of the all-pass filters) is being modulate over time by the LFO.

[markphaser]

Thanks George Giblet

The pitch shifting arises because the phase (of the all-pass filters) is being modulate over time by the LFO.

Can u please explain to me about how the LFO modulates over in time?

Does the LFO "time period" affect the pitch shifting?

[markphaser]

 How do i adjust the "time period" of a LFO?

What does the "time period" of a LFO do to the notches or controlling element?

Does the LFO "time period" change the LDR or Lamp or FET ?

[markphaser]

How do i change the "Frequency" of the LFO?

what sets the Frequency of a LFO?

[markphaser]

I need help with these questions can someone explain or give some feedback to me

[DiyFreaque]

http://www.elixant.com/~stompbox/smfforum/index.php?topic=40557.0

[markphaser]

DiyFreaque can u help me with my questions ?

[George Giblet]

markphaser, there's a couple of things you need to get straight.

An LFO is just an oscillator, very roughly categorized as an oscillator with a frequency less than 15Hz or so.  It is an oscillator in it's own right regardless of what it is connected to eg. part of phaser, LED flasher.  As already mentioned, an LFO can produce different waveforms but that doesn't change the fact it is just an oscillator.  In most cases different types of circuits are required for different waveforms.  For any given waveform there is more than one type of circuit that will do the job.

The frequency of the LFO is a matter of choice when designing the oscillator, and to a large extent so is the range of frequency adjustment from the speed pot - some types of oscillators don't allow arbitrary adjustment ranges with a single gang pot.


>  Does the LFO "time period" change the LDR or Lamp or FET ?

The second thing the realize is the LFO output is used to control something else.   In a phase the thing that is controlled is the all-pass filter frequency characteristics.   For example the frequency response  of the all pass filter is tunable (adjustable) using a resistor and capacitor components which are part of the filter.   The resistor is fixed.  In a phase the resistor is replaced with an adjustable resistance.   The adjustable resistance is an LDR or JFET.   The LFO voltage controls the LDR or JFET, that changes the resistance which then changes the all-pass filter frequency response.  So in effect as the LFO output voltage changes over time the all-pass filter behaviour changes with it - this type of thing is call a swept filter.

What you need to do is read up on oscillators, all-pass filters, and voltage controlled resistances (like a JFET).  You have to undertsand each one of these in isolation fairly well before you can grasp the whole picture of how these all work togther to form the basic behaviour of a phaser - as a bonus you will be able understand other things like flangers, chorus, tremollo.

[Sir H C]

What you need to do is read up on oscillators, all-pass filters, and voltage controlled resistances (like a JFET).  You have to undertsand each one of these in isolation fairly well before you can grasp the whole picture of how these all work togther to form the basic behaviour of a phaser - as a bonus you will be able understand other things like flangers, chorus, tremollo.

Good luck.  He doesn't like to read.

[DiyFreaque]

Markphaser,

I can't really add anything to what has already been laid out - the questions you've posed have been answered already in this thread (and others).  I linked to the breadboard thread hoping you'd be inspired to get a known good working phase shifter schematic, breadboard it, get it working and let the lightbulb appear over your head once you probed around and also listened to it.

Good luck with your quest(s),
Scott