my trip reviving Wayne's CTP patent is taking twists and turns ... with a first solid landing
I'll just mention in passing that the lattice in Wayne's 1956 (applied for) patent
is also known as a Norgaard filter ... and much studied previous to that time
I'm trying to figure out if we can get an LC equivalent to do same job for us
as it, is the RC version yields -10db of loss roughly ...
an LC equivalent would take away much less (depending on internal resistance of inductors)
it's not crucial at this point, but worth exploring nonetheless later on
---
well, some good new, some bad and more great news ...
I just finished boxing up two CTP-jFET "mini" boards ...
one running with a 200mS period, the other at 600mS // ie., 5Hz and 1.66Hz
they are working, haven't pumped any audio yet
but they scope fine ...
that's the good news
I will say this, other than being the most boring and archaic looking pedal
(I mean, no controls ... and all)
I know it will sound insanely magical as per my previous tests
but, I must also concede that these jFET emulators are the most impossible builds I've ever dealt with
just getting the oscillators to start can be a b*tch ...!
(the opto switching was disabled for various reasons)
I realize now that to do the startup function right I would need to use selectable voltages fed thru analogue-gates (CD4066)
again, that's just too much work just to get a start function on an oscillator ... plain sillyness
at the moment, the strategy seems to hold the start switch, then release and hit it again in two quick successions
it's guess work ...the electronic equivalent of rubbing two sticks
then, the matching jFET's to such a high degree, the bias tuning that is finicky beyond ^%$# ...
to get the lobes just right requires tireless micro tweaking of the bias
etc etc // almost insane ...
so, jFET's - tho they work - are not the way to take unless you're willing to deal with extreme aggravation
I knew this before hand, just didn't know how much
so all this to say that I will not be releasing any jFET version for mass consumption ...
that's the bad news
it can be made to work, I have a working 2-channel unit that will exemplify its behavior ...
filed under extreme challenge //
so, moving on then ...
---
luckily, I came across another patent of Wayne's a few days ago
which clearly shows how a PWM/pic hookup would work for us ...
https://www.google.us/patents/US3516318
duh, it's all there ...
a BJT ring oscillator running at 16vdc
driving opto-couplers // etc ...
(and notice how the intention of the text is way clearer than the first Baldwin-CTP patent ...)
anyway, I think it's pretty obvious how a PIC would interface with all this
it's almost trivial ...
which means the time for the masses to partake might be around the corner ...
and all this electronic analogue craziness you've been exposed to here will all go away
that's more great news ...!
so, I've contacted Tom at Electric Druid
to ask if a 3-phase TTLFO would be possible
he's busy in the middle of other projects and says he will give it look
(fingers are crossed)
any other codesters out there are most welcome to chime in if they want ...
I can provide more details if it isn't already obvious
otherwise, there are tons of electric motor driver IC's
just not sure if any will go as slow as we need
I'll wait for Tom to get back to me on this ...
---
a quick recap,
had I seen this newer patent three months ago
I would not have gone on this design foray ...
glad I didn't tho // I enjoyed coming up with the 3-phase differential oscillator based on the Gilbert gm-R cell
I will build the speed-contollable OTA version now that I know how good
one channel can sound ... (as a typical Chorus pedal does in function)
for now this 2-channel jFET-MINI unit is gonna get further tested and then used in the studio as a novelty device
next on the agenda is the Tap-Tempo version ...
~jcm