simplified smoothness on tremulus lune?

[caress]

i'm wondering if it's possible to switch out the smoothness pot on the tremulus lune with an on-on-on spdt: mid position - half tri/half square, up position - tri, down position - square. 
...or even an on-on spdt or dpdt with up - tri, down - square.

http://commonsound.org/tremulus/tremulusscheme.pdf - it might take a hot second to load...

at first guess i would think to send the points that are connected to the outside lugs of the smooth pot to the middle lug of the switch, then send pin 3 from the 4558 to each of the outside lugs on the switch, one via a 500k (or similar) resistor, the other via a bare connection (or 10 ohm or similar).  this way you get full resistance with one throw, no resistance with the other.  square and triangle.  yes, no?

[caress]

any takers?

[KMS]

I don't think that will work.  Note that the name of each control is not really appropriate except for maybe speed and fine which should be rate and fine.

The control called "spacing" would also need to be integrated into your idea if want to have on demand preset wave control.

A better set of names for spacing and smooth would be growth and decay because that is actually what is occurring. Whether the spacing is the considered growth or decay and smooth visa verse is arbitrary because it depends on what your measuring....the resistance...or the output signal.  Makes no difference because one control changes the rate of the climb up to top resistance while the other controls the rate of decent down from top resistance and each is not on the same curve unless you max one out and leave the other off....which it would have been nice if they were a little closer than that.  The speed controls the overall rate of both the smooth and spacing without changing the ratio of smooth:spacing and the depth controls the limit of top resistance...that's how it makes forms from sin to variations of tri but you won't get all of those variations unless you also include the sawtooth mod....without the sawtooth mod it will only give you variations of sin from pure sine to almost half tri and almost full tri and no square at all.  I don't think it does square even with the sawtooth mod but I have not played with my sawtooth mod enough to be sure (primarily because the sawtooth mod is very distracting sounding and even though it is a cool thing to have I can find no musical use for it).  I say all this based on my listening experience and the visual aid of the on-board LED.  I have no idea what the mathematical design of the controls are, but I do know what I hear.  The internal LED has an intrinsic growth and decay of it's own and no matter what you do, full square wave or a perfect triangle are not possible using the optical device....but perfect sin wave is.

The idea of limiting the wave forms to 3 or 4 forms would be kind of defeating the whole concept of the vast control you get using the two pots....but it would allow you to quickly find those very common wave forms with out having to play by ear with the controls.  What would be real nice is to switch in and out of the pots over too your switching idea with a multi position rotary switch.

[caress]

hmm.  i am including the spacing pot, speed, depth, and a switch for the saw shapes.  that's strange that you say you can't get a square shape....i made a trem lune a while back and the squarewave is great.  it goes from no signal to full like a good square should.  the sawtooth mod adds some interesting shapes as well, but you can get the square without it.  i love a ton of knobs but i'm building for a friend who is interested in more straightforward controls.

[KMS]

I say square......0 to limit with no time laps then stay at limit with no variation for time laps then limit to 0 with no time laps...........that is square.....or the complete opposite would also be square. The LED part of the LED/LDR is not capable of such performance and no matter what I do to the controls the 0 point and the limit never remain at 0 or limit without variation for a time laps.........thus it is a sin wave set up that can be adjusted to come close to a square wave.......you get a variety of exponential curves out it not sharp corners....it could be that mathematically the circuit will show on a scope sharp corners (I don't know) if that is the case then the performace of operation is still limited by  the LED/LDR which will not allow the audio signal to pass through with sharp corners.......look at the data sheet on the LED/LDR....it is impossible to have a sharp corner wave form via the audio signal.

Well if you friend does not like all the controls be sure to include sin....because for music sin is the main function standard of the norm for tremolo.

[caress]

i feel what you're saying...in theory, though. 
my led blinks on/off with no visible fading in or out. 
my signal is completely gone, then completely there. 
i scoped it and also recorded it and i see off/on with sharp corners...
(not trying to get into a contest of who's right/wrong...enough of that goes on here and in real life  )

to me, that's a square wave...all the rest is just semantics.  i really enjoy the little inconsistencies of leds; they throw a tiny bit of randomness in.  just a tiny bit...

[KMS]

I don't know everything that's for sure but it would appear we are talking about two completely different devices or devices with significantly different parts or conceptual difference in oppinion due to my attitude about how close to square I can say "OK that's square".

Mine from the tonepad layout will not do the square wave. It is my understanding that the tonepad circuit is the same as commonsound and the only substitution I made was to use a CLM6000 which the data sheet for the CLM6000 does not have a significant difference from the VTL5C2 as I remember checking both sheets....for which both data sheets have specs that will cause slight fading no matter what. All the LEDs I have worked with take time to go from no light to full brightness......no mater what power you apply. The same is true for the LDR.....it has a slight delay in the change of resistance.   Together the LED/LDR cannot make a (scientifically perfect) square wave FX. The data sheets have the curve shown....and it is not square.  I don't think your wrong..... I can only conclude that you have an exceptional LED/LDR that does not fit the data sheets and/or your concept of "square wave" is less strict than mine.

I was really hoping mine would do the perfect square wave so I could play that cool sounding part for Pink Floyd's "Money"  but it will not make the perfect square wave sound.....you know....completely on....then completely off...real fast.  My Lune will come close to making that sound.....but not completely square.  Keep in mind I am a perfectionist....and when I say square......I mean perfectly square.  I do not settle for "that's close enough". Which brings me to the concept of the fact that there are FX that can do this better than the Lune....what did Pink Floyd use?....it was not a Lune...because whatever they had did produce a perfect square wave sound.

So build another just like you have now and add the switches and your friend "should" be real happy because "most" folks are easier to satisfy than me.

Cheers.

[caress]

he is quite picky, although i think he would be easier to satisfy than you!   

i think my concept of squareness is just a bit less strict, seeing as how i rolled my own LED/LDR...nothing exceptional there!

maybe build one using a 555 based oscillator?  or perhaps the kay tremolo?  i read that one is very choppy...

oh and btw for anyone reading this regarding the original post, i simply used two 500k trimpots and switched between the two for the switchable square(ish!) / triangle.  still have a little bit of debugging, as the LFO is not working perfectly, but that's how it goes...

[KMS]

Rolled your on LED/LDR?.......it could be much better than any CLM6000.  Since I made my trem I have done a few other optical projects and started making my own LED/LDR (because it cost less than CLM6000 and that's all my supplier has) and found that by cherry picking a couple packs of LDRs and using the really bright blue LED I can get a better response and a lower dark resistance (40ohm) and still keep the light resistance over 2M.  I have noticed that LDRs with low light resistance also have a lower dark resistance too which makes the cherry picking kind of "slim pickins".

I don't have anyway to measure the change for the LED/LDR reaction rate but if I make some sockets and set up several LED/LDRs I could set the trem on fast and as square as possible then play and record on my Cakewalk software and then zoom in on the wave for each LED/LDR attempt and determine if the is a advantage concerning factory vs roll-your-own.
 
I had not considered tearing into my lune to replace the CLM6000 with a premium roll-my-own LED/LDR but due to our discussion I might give it try.  Like I said.......my lune comes real close to the square wave now.

You might have just helped me finally get what I want out my trem........and I should have thought of it a long time ago.....thanks.

[caress]

haha     and i thought this was going OT!  that's great to learn that the premade vactrols are not so hot compared to rolling your own...especially when LEDs and photcells are so damn cheap.  well...i was having some major problems with my lune...i had to make 3 full LFO circuits before one worked really well.  i think i made the same stupid mistake on the first two and couldn't figure what it was.     the last one i got working pretty nicely, though.  just a few more tweaks...

and if anyone wants to add a square/tri switch instead of a waveform pot, you need a dpdt wired like this:
send the 2 points connecting to the outside lugs of the smoothness pot instead to the middle two lugs on the dpdt.  send one throw to the outside lugs of one small value trim (i used 500ohm), the other throw to the outside lugs of a larger trim (i used 1M) then send the middle from each trim to pin 3 on the 4558.  you could probably even omit the small value trim, but i decided to leave it...

glad to hear that our discussion has inspired you.  cheers