systech phase shifter schematic even/odd cycling trimmer

[markphaser]

The systech phase shifter schematic has 2 trimmers a feedback rheostat trimmer and a "even/odd cycling trimmer"

Do u guys know what this "even/odd cycling trimmer" does to the LFO or FETs to the phase filters section?

[R.G.]

It unsolders one JFET on the odd cycles, and puts it back in on the even cycles.

The trimmers make the JFETs bigger or smaller as you turn the knobs.

[$uperpuma]

[Sir H C]

It unsolders one JFET on the odd cycles, and puts it back in on the even cycles.

Hence the need for the rheostat.

[R.G.]

Hence the need for the rheostat.

Correct. That adjusts power factor and prevents overheating.

[markphaser]

R.G i don't know if me and u are looking at the same schematic or even talking about the same schematic
please don't change the subject so other people that wish to contribute are not confused

[StephenGiles]

Where is this schematic (I hate that word!!!)

[R.G.]

R.G i don't know if me and u are looking at the same schematic or even talking about the same schematic

I'm pretty sure we are. To which schematic were you referring? Isn't this the one with the flux capacitor in the lower left hand corner?

[StephenGiles]

As it's Friday I shall gripe - in the UK we call them circuit diagrams - is this yet another example of USAianism that we are stick with???

[R.G.]

As it's Friday I shall gripe - in the UK we call them circuit diagrams - is this yet another example of USAianism that we are stick with???

Sadly, yes, its a bit of Am-english (as we xeophobically call it on this side of the pond) that we are *all* stick with. 

You see, the thing is that we USA'uns only got second choice on all the good words. You guys got "bonnet" and we have to use "hood". You got "windscreen" and we have to make do with "windshield". You get petrol when you fill up your cars, we have to get gas. When we're in a hotel, we have to be asked for a "wake-up call". You guys get to ask to be "knocked up".

As you can see, it's plenty enough to give us derivative-English users an inferiority complex. 

So we make out where we can. If it's any consolation, it started out as "schematic circuit diagram" and because we're always in a rush, we shortened it down to "schematic diagram" then finally to "schematic", the "circuit diagram" being implied. No time to say all those extra words.

Oops! Look at the time! I gotta go - time's a-wastin'.

[stm]

Stephen, I dig your comment about Fridays... Still 6 more hours at work until I can go home to play with my new BB&E.

R.G., where do you source your flux capacitors?  The clerk at Rat Shack told me they didn't carry them anymore due to the enforcement of the new RoHS policies--too much CdS (cadmium sulphide) inside.  Nevertheless, this guy told me that I could replace the flux cap with a non-polar 10uF cap (after all they are both capacitors!), however I am a bit reluctant about this, since the flux capacitor I need to replace is labeled as 10MF / 1GV.  The clerk says that the difference between the "u" or micro and "M" prefixes is not relevant as they both represent the letter "m", and the fact that the former is in the greek alphabet is irrelevant.

What should I do?

---------------------

P.D.  I almost forgot, regarding the original question, I suggest doing the following:

a. Posting a link to the electrical *drawing* or *sketch* of the phaser to see what's this ODD/EVEN thing is about in that particular circuit..

b. Take a look at John Hollis' Ultra Flanger, drawing/sketch here: http://www.hollis.co.uk/john/ultraflanger3.jpg

As you will see on the upper-left corner, the ODD/EVEN thing has to do with applying feedback in-phase or out-of-phase (wet signal with direct or inverted polarity).  The trimpots there are to establish the maximum possible feedback in each case without entering into self oscillation.

[StephenGiles]

RG, what you say is interesting! In the nineteenth century, ladies wore "bonnets" on their heads, and we sometimes use the expression "look under the bonnet" to mean investigate something in detail - I'm an accountant so it crops up from time to time, and there's another - "crops up" who knows where that came from, crops being things that grow, usually on a farm which you probably call a ranch and our friends in Argentina call an estancia! Probably a connection there somewhere. And then there was a sailor called Chris Bonnet.............

[R.G.]

"Bonnet" is still rural USA usage for a woman's headgear, usually only a homespun, simple thing. Much of USA rural usage came direction from poor Scots immigrants who settled in the USA Appalachain mountains and still use terms which are directly derived from the Scots' use of English. How's that for confusing? In any case, My mother possessed and wore bonnets, which were different from hats.

As much as it's tempting to think that "bonnet" was originally another term for "skirt", I think the term "have a look under the bonnet" comes from early 20th century usage on automobiles needing a lot of repair work after the covering over the engine was already called a bonnet. British (as opposed to "English") autos are famous here for needing mechanical work. The conventional wisdom is that you need a live-in mechanic if you own a British car, but I'm sure that is no longer true since the dual side-draft carburetor is no longer used.

We did once use "boot" for the rear luggage compartment in a car, but it's been "trunk" for as long as I've been alive.

Hmmm...

There once was a sailor named Bonnet,
Who penned a slacious faux-sonnet.
The subject, a lady,
An reputedly shady,
(You fill in the blanks here) on it.

where do you source your flux capacitors?

The clerk is correct. You can insert almost any 10uF cap in the place of a genuine flux capacitor and get exactly the same operation as the original.

[Sir H C]

Just don't get into the "fanny pack" debate.   

[$uperpuma]

anyone have a charge pump circuit for 1.21 JigaWatts?

[Mark Hammer]

The systech phase shifter schematic has 2 trimmers a feedback rheostat trimmer and a "even/odd cycling trimmer"
Do u guys know what this "even/odd cycling trimmer" does to the LFO or FETs to the phase filters section?

I understand the temptation to be silly and frivolous guys, but lets be serious for a moment.

To respond to the questions....

The feedback rheostat trimmer does nothing to the FETs or LFO.  If there is too much feedback, a circuit will break into oscillation.  So, many circuits using feedback will include a trimmer rheostat to set the maximum feedback possible without oscillation.  This is true of many phasers, flangers, and analog delay lines.  This is set by turning the feedback or regeneration or resonance control (whatever it is called on that pedal) to maximum, and setting the trimpot to the lowest resistance.  This will produce oscillation, or what some call "runaway feedback".  The trimpot is then gradually increased in resistance until the oscillation stops.

I do not know the Systech circuit, but what I will say is that the exact same amount of negative or positive feedback from the last stage will produce outputs of different volume levels, because one will produce notches and the other will add peaks.  I am guessing here that the even-odd cycling trim might be something that adjusts the relative levels of negative-vs-positive feedback output levels to get something approximately equal level.  Keep in mind that is just a guess and not based on a schematic or a detailed picture of the pedal.

[markphaser]

Thanks Mark Hammer for being serious

I understand the feedback trimmer

The phase filters have FETS or LDR's and sometimes u see a trimmer thats inbetween the LFO output and the FET's or LDR's
but the trimmer is connected to the FET so make it unbalanced or balanced it changes the cyclicing from being even cycles to
odd cycles

even cycles: i mean u hear the swirl evenly everytime  1,2,3,4   swirl,swirl,swirl,swirl
odd cycles: i mean u hear the swirl   1,nothing,3,nothing  swirl,nothing,swirl,nothing

DOD Phasor 201 schematic has a trimmer connected to the FET
MXR phase 90 and 180 has a trimmer connected to the FET to change the bias of it ?
EH bad stone has 2 trimmers after the LFO outputs inbetween connected to the FETS
it changes the cyclicing swirl interfacing the LFO to the FET biasing or something

They call it a Bias trimmer on some schematics. The bias trimmer is connected to the Gate and source of the FET in the phase filters

[Joe Viau]

Could someone post a link to the schematic / circuit diagram for the Systech phaser?

[markphaser]

Sorry Toneman i don't have the schematic in a PDF file or converted from a scanner

Whats the difference between a JFET,Mosfet,FET-based phasers?

[Mark Hammer]

Whats the difference between a JFET,Mosfet,FET-based phasers?

That's a VERY big question markphaser.  You need to look through the archives.  I'm certain there is discussion about it there that doesn't need to be typed all over again.

The even/odd cycles description you give is interesting and very unusual.  Although it may exist, I have never heard of such a thing or heard it in action.