The FM Tube Modulator Jimi Loved

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Re: The FM Tube Modulator Jimi Loved

Post by Eb7+9 » Sun Jan 03, 2016 7:25 pm

Xplorer wrote:
... if it's as easy as building a fuzz, why not ? :lol:

seriously, maybe one day because it's worth it. for now, i don't even know how to match the jfets and i may not have the right Tools for this.
thanks for the idea and for the offer.
to make things easier I'm going to draw out a jFET "test" jig/pcb ...

with on-board trimmers, device socket.
and test lead attachment points that will go to a pair of 9 volt batteries, and three DMM's

the DMM's can be cheap/basic utility units ... obtained for $5~$15 on eBay
as long as they performs basic V/mA functions supreme level of accuracy is not paramount here

of highest importance is keeping a constant test setup
if the meters stay where they are in the test jig for the duration of the test,
as opposed to wrapping up the test half way and coming back with different meter ordering,
then one can infer relativity of values ...
and therefore, end up with number pairs that are good enough for matching purposes

the method is going to be very "simple" // beginner friendly ...
and very quick ... not requiring interpolation like I did in my full-blown "characterization" testing

those interested in trying this out might want to try their luck to save some dough by going on eBay ...
or forking out, say $50us on a 100x lot of bone-fide 2n5457 jFET's from Steve at smallbear.com ...
and see how the dice fall before attempting to build anything

at some point I'm going to have to say something about the PSU circuit, and also capacitors ...

~jcm
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Re: The FM Tube Modulator Jimi Loved

Post by Xplorer » Sun Jan 03, 2016 8:14 pm

:toast: :thumbsup:
Thank you !!

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Re: The FM Tube Modulator Jimi Loved

Post by Eb7+9 » Sun Jan 03, 2016 11:37 pm

my pleasure Adrien ...

I plan on doing a revision of the 4-channel jFET emulator (board #2b), and also a "mini" one channel job (board #3)
as well as a jFET test jig (board #4) ... that's three more boards, and my minimum order cost ranges between $25 and $35

and, will have to get more IC's and I'd like to get a (new) batch of 100 jFET's from smallbear
and document the second matching approach that will described herein shortly ...
this will give me an idea of the odds involved ...

(DONE! ... on their way)

---

btw, those curious about my work might want to check out the tube amp book :
"Inside Fender and Marshall Tube Amps" ...

http://www.lynx.bc.ca/~jc/ifmta.html

proceeds help fund research like this ...

---

also, ... there's an opportunity to crowfund this thing into being
if enough peeps feel this is a worthwhile thing to have made it can be made to happen

just a thought, ... for later down the road

discussion/pm's most welcome ...
~jcm
Last edited by Eb7+9 on Sat Jan 09, 2016 6:43 pm, edited 2 times in total.
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Re: The FM Tube Modulator Jimi Loved

Post by Xplorer » Mon Jan 04, 2016 12:13 am

crowdfunding ? to launch a commercial version first ? but it won't prevent diyers to jump on it anyway, i don't know if there will be so many like for some fuzz projects for example.

seriously, you really deserve some donations, with everything you bring to peoples.
my bank account is in danger so my paypal is at zero but i'm working hard on 3d field to make something endly happen.

but the day i can afford a new project like this, even if it isn't super expensive, then i'll can afford to give you something cause you deserve it for sure.
maybe .. if somebody knows some potential clients for some 3d architecture viz ... ? it could happen sooner !

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Re: The FM Tube Modulator Jimi Loved

Post by Tek465b » Mon Jan 04, 2016 8:53 am

I agree.
First you need to keep the schematic private, i know it suck but its best not to share it public.
When the final version is ready, am looking to buy it from you(if possible as a kit, since am short in cash me too).
All that work deserve some $ income. I will check how little $ i have and maby ill do a donation to you this month. its not going to be a big ammount, something like 10-20$ but at least its 10-20$ more. If i can do something else let me know.

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Re: The FM Tube Modulator Jimi Loved

Post by Eb7+9 » Tue Jan 05, 2016 5:47 am

sorry - didn't mean to put anybody on the spot

as luck would have it I had two orders come in last night
and the money went straight back to smallbear in NY

so now, I have a lot of 100 2n5457's and select film caps coming in shortly;
I also drew and ordered a new jFET tester board, that I will sell as a complete "parts" kit, with instructions, etc .

// thx for the suggestions ...
~jcm
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Re: The FM Tube Modulator Jimi Loved

Post by daveweyer » Tue Jan 05, 2016 8:26 pm

First off, what kind of crowd funding amounts are you looking at?
Secondly, I am glad to hear the results of these tests; I think the unit you built has certainly proved the point, and I am heartened to see proofs of performance which were hallmarks of the first implementations of this circuit, namely the signal to noise ratio, the headroom, and the low distortion characteristics. As you correctly point out, no circuits of the day used anything like this implementation, and none of them could match the performance of this particular arrangement.
I have found, through the years of experimenting with it, that there are definite advantages to using the LC bandpass networks on the oscillator outputs, at least with respect to the hard-to-define "bubbling sound" that the full bandwidth AM modulations produce in the combined output signal. That said, there are no rules for this, whatever pleases the ear the most with a particular instrument should probably lead. One of the important relationships is the operating level of the four outputs. Varying this relationship created wide differences in sound, and this goes along with the LC filters as well. Ultimately you may desire to use a buffer on your oscillator outputs, to boost the gain, and to provide mixing capabilities for the four modulated signals.
I think the few who are following this thread may have come to understand why Jimi went nuts when he heard it, especially when he saw that it could be plugged in to the speaker cabinet jack or amp output, and fed directly to another speaker cabinet--and switched in and out with a little relay which was attached to the modified unit. We even experimented with a guitar switch using phantom power for switching in and out.
As I mentioned, the unit likes the distorted sound of the amp output, but really doesn't like to distort itself. It is a weird sound which I never could figure out how to tame.
Anyway, it's all off to a good start!

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Re: The FM Tube Modulator Jimi Loved

Post by Eb7+9 » Thu Jan 07, 2016 2:52 am

as far as crowdfunding goes, I have no experience at this ...
but, if I get the gist ... 100 people pay $X each to get a pedal made (shipping costs, xtrs, blah blah)
a limited run ...

just getting the mask done, and prototypes of populated PCB's plus fab proof, maybe $2500CDN
then, cost per populated board ... assembly time ... matching transistors, ... time
needs to be all rounded up and figured so that whoever does it (me) don't run short
on the plus side, a 100 folks here on the forum get a custom/original pedal design
maybe even get to choose the look, ideas for ergonomics ... a forum thing
just an idea // ...

as Tek suggested, I'll probably put out a kit either way ...
the crwodfunding is not my thing, but I know it appeals to some
if someone here on the forum wants to organize that and muster up interest, fine
again, no rush ... in time, if peeps become interested in this // talk to me

---

as far as th design goes ... I think this is a good first step also
I get what you're saying about the bandpass filters

you know, right now I've shown the circuit topology doing its thing on jFET's
and I can either mix them ll together without tanks, like I did in the video

or have seperate outputs for each oscillator/modulator ckt ...
at that point one could send the signal thru an EQ circuit and separate amplifier
many, many possibilities as you pointed out

I think simply building a basic modulator circuit (either x1 or x4 Osc's) is the way to go for now
the TANK's simply killed the signal too much ...

I need to investigate that further actually
maybe you could do me a favor and measure the DC resistance of the inductors in your unit
and also the parallel cap values // just to double check ...

as you suggested before, I may want to consider bringing an "active" Band-Pass solution to the problem
right now, I'm really digging the passive output mixer

so quiet ...

I'm just sending out the artwork for a single channel CTP-mini board
I installed a slowed-down CMOS LED driver to kill the oscillator
and to start it again, ... without making a "popping" noise at the output

all intermediary steps I need to take before I get to the big x4 with the no-pop on/off feature

... luv hearing about you and Jimi // musta be a very fun time indeed
~jcm
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Re: The FM Tube Modulator Jimi Loved

Post by Xplorer » Thu Jan 07, 2016 12:08 pm

it could be a fun idea. if 100 peoples participate for a crowdfunding, with costs getting down thanks to this, i'm in.
and ideas could pop up, that would be a nice forum project.

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Re: The FM Tube Modulator Jimi Loved

Post by Eb7+9 » Fri Jan 08, 2016 1:59 pm

btw, I just wanted to mention Wayne's other patents ...
at least one, anyway

the one about his chorus "system"

https://docs.google.com/viewer?url=pate ... 147333.pdf

looking at Fig. 1 in particular, where the four channels are grouped in two pairs
I'm wondering if that's not what I should be building

right now, I'm gonna do a single channel "mini" job just to check out the switching features and new PSU
and I am also considering how to implement the TANK circuitry and maintain strong output signal levels

... maybe two-channel gizmo's is the way to go

of course, now you're looking at a main guitar amp // and two side amps, or a PA, just for the chorus

might be very cool in the studio ...
~jcm
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Re: The FM Tube Modulator Jimi Loved

Post by daveweyer » Sat Jan 09, 2016 4:41 pm

J.C. something to keep in mind about Wayne's inventions, and it's pretty important from at least a conceptual perspective, these devices were made to augment an organ system where the frequencies developed were all in sync, as was the case with the original Baldwin designs, designs that carried through right up until Jerome Markowitz over at Allen Organ company bought the rights to a form of digital sampling from Rockwell, right after the Apollo mission.
It was also the case that Markowitz had earlier patents on an organ system which used individual oscillators for every note in a particular rank of organ tone generators, an option which made the need for tone modulators irrelevant.
These systems became more and more a system of analog parallel processing, whereby smaller and smaller sections of generators were routed through individual channels so that loudspeakers never had to process more than one phase or one set of octaves, thus lending even more of a pipe organ-like quality to the overall perceived sound, pipe organs being the ultimate in parallel processing, one pipe equals one speaker, one sound generator and one tone.
In the '60s I took the concept to its logical conclusion by building a system where each oscillator had an amplifier and a speaker of its own, meaning there was no possibility of any kind of intermodulation except in the air which carried the vibrations to the ear. I got funding from some doctors in Long Beach to build this contraption in my house, (300) 6x9 speakers, 300 small amps, and a bunch of speaker cabinets to house everything. At the time I thought it would be the ultimate electronic replacement for a pipe organ, but digital technologies made it too cost ineffective to be of any significance other than as an historic artifact.
All this comes back to Wayne's idea of splitting up the bands or shifts and feeding them to separate speaker systems.
I certainly could have beaten him to the patent office with that idea, since I had already been doing the same thing for years, with whatever technology was available to me (as a teenage kid, and that meant quite a few restrictions about what I could be trusted with).

So to your thoughts about splitting things up; intuitive, logical, and probably inevitable, even as the number of speaker and amp systems grow to outrageous proportions. And yes, it adds a new dimension every iteration.
I had a film company come to my house to listen to a multi-channel system which recorded every instrument an a band on a separate channel, and than blended them acoustically, sharing nothing but the power line coming into the studio. They were so blown away by the dimensionality of it that they brought in some expensive mics and tried to record it, the obvious result being that they were back to sharing again and faced all those limitations.

Again I return to the filters. When you reduce the frequency of a 10KHZ tone by 10 HZ and play the two derivatives together, you get a very slight, and quite pleasant beating. If you take a 100HZ tone and reduce its frequency by 10HZ and play the two derivatives together, you have two separate notes playing, and not a pleasant beating.
If chorus is what you seek, then keeping the 100HZ frequency out of the LFO which produces a 10HZ deviation is rather imperative--that is the reason for the band division in Wayne's circuit. If you want to create chaos or weirdness (like I always have) then trying to run a 100HZ tone against a 10% deviation is a wonderful idea.

I offer all this because I see the same temptations I had when I first discovered all these possibilities back in the "old fashioned" days of resistors and capacitors, the ancient equivalent of ten year old kids developing games and applications in modular programming languages on their laptops.

I've experimented endlessly with these modulators for guitar, changing frequencies, bandwidths, relative levels, and regeneration, generally always coming back to a rather practical application which most players will find pleasing and useful in normative guitar playing Zeitgeist. As for my own studio, well anything goes.
I have never found a "regular" guitar player who would budge past two amps and speakers, even though I have recorded them with multiples of amps, processors and speakers.

To demonstrate the expansive mental allure of multi-channel processing for guitar I invented a system in the '60s to divide the guitar up into six pickups and amplifiers, then take the process a step further by enlisting the help of Robert Hovland at Vox, to use the computer labs to run simulations for filters sufficient to divide each string up into its individual notes, and also process them separately. This involved making an envelope generator for each available note to control attack, and a trigger system. All these notes were then fed into the 300 channel amplifier/speaker system which was sitting at my house on Mt. Washington, near LA.
I can provide Xplorer with a clip of a guitar played through this monstrosity if you think you would enjoy hearing it.
(hint, it sounds nothing like a guitar as you know it)

I guess the point of all this is that Wayne had his original (musical) reasons for doing what he did, and they were solid, from an organ perspective and from a practical perspective. The expansions of this idea were intuitive, logical, and reasonable, but they never found traction in the field save for a few custom large scale installations. Having taken these concepts to absurd extremes myself, I can certainly see why. The advent of digital sampled instruments in 1971 by Allen Organ Company, obviated all the need for parallel processed analog modulators, mechanical dopplars such as the Leslie, and Jerome's own "Gyrophonic System" patented in 1937.

The guitar player, with his love of tubes and analog devices has surely kept the ancient art alive. Without him I doubt there would be a tube on earth except in museums. And I'd bet JC would have to become a game programmer.

I hope I didn't bore you all with this, I think I had a point when I started writing.

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Re: The FM Tube Modulator Jimi Loved

Post by Eb7+9 » Tue Jan 12, 2016 1:59 am

pretty crazy Dave ...!!

:shock:

the best tech story I've read in a long time

I can't believe we haven't heard about this before
300 amps ... 300 tube amps

wow //

well, you know ... this really puts things into perspective
chiefly, you describe the purpose of the TANK circuits in the bigger picture

seeing that guitar strings are NOT vibrating synchronously
I can see why the CHORUS circuits that we know nowadays (simple in comparison) work so effectively on stringed instruments
and why my first CTP pseudo-clone sounds good on Gtr, running flat across the band ...

at least, I feel very satisfied with the effect it produces ...
I have not tried it on Bass or my Moog ... but am sure it will sound impressive

now, I completely agree with you that too many independent channels would sound way chaotic
and trying to fit all that "spatiality" thru microphones // ... quite difficult, or even futile

OTOH, from the clips I created by running audio thru a TINA-TI simulation of the OTA version of the CTP pseudo-clone
and from my experience playing and recording with stereo phase/vibrato circuits
I have the feeling that it might be OK to have a similar phase-anti-phase R/L version of the CTP happening

something that falls out of the OTA approach as I mentioned // so, to be explored later on ...

as far as recording purposes go, I was thinking that going just one step further than this might prove useful ...
that is, running the output of one CTP (1hz) panned hard R, say, and another CTP channel (2hz) panned hard L
and DRY down the middle ... something I mean to try in the studio

or, maybe this idea will only fly well with two stereo versions...
certainly, that's almost as far as I'm willing to take things

as far as a performance rig goes I still intend to try a three-amp setup, or one (main) amp and a PA
and have one amp (or PA channel) running one CTP and another amp (or other PA channel) running a x2 speed CTP
besides the main amp ... I can see an old Marshall, and PA working well together here ...

I agree that having more channels than that is either unnecessary, due to the asynchronous nature of gtr strings,
or it will sound just too chaotic // not what I'm into myself ...

I just want a better sounding Chorus circuit ... and, mainly do away with the hiss we always get from BBD chips

I'm keenly aware of the need to keep this practical
and this info helps dispel the questions and doubts I was having regarding the use of the TANK circuits

now, I have no problem exploring a full clone of the CTP, but to be honest,
from what you're saying the full-meal-deal applies more to a synchronous organ signal

I think it would be wise to respect what chorus circuits became
and to not deviate from that // at least as far as Gtr/Bass/Synth sound production goes ...

so, the question becomes ... why build something that sounds still somewhat like an ordinary Chorus pedal ?

well, first of all, the headroom //
this results in extreme reduction of hiss when used in a large signal context
and without going thru companding IC's etc ...

so it can be used in FX loops and at the output of preamps, instead of in front of the amp
which ordinary Chorus pedals cannot do by the headroom restrictions of the BBD chips
(very much like comparing optical phasors to jFET based ones, not that low-headroom ckts are categorically bad or anything)

second, to my ears it sounds better and has a more natural character than any chorus pedal I've played ...

so, I'm sold just on what I've experienced so far ...
two amps, like I showed in that last clip, certainly produces a fine effect quality ...

---

next, I want to check out the three amp (or one amp and stereo PA) version to see what that does
that's where a couple of "mini's" will come into play (my next builds)

thanks much Dave ... appreciate your invaluable historical input and explanations !!

more shortly on my progress ...
~jcm
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Re: The FM Tube Modulator Jimi Loved

Post by daveweyer » Tue Jan 12, 2016 1:25 pm

It's easy to see why engineers moved to multiplexing, after all, 300 little two-transistor amps and an associated speaker for each one just sitting there doing nothing but drawing power until it was their turn to play a note represented a huge waste of resources.
But as you point out, the interest for the ear drives men to do some very impractical things, and logically there is every reason to split things up to find out if negative shifts on one side and positive shifts on the other side (or any other permutation of channels, shifts, band limitations, recombinations, and variations) make the overall sound so compelling that the extra equipment involved becomes worth it.

You have also found out that the headroom and signal to noise ratio of this implementation surpassed anything built in those days, and maybe even these days. I can tell you that if it we're me undertaking this development, I would try every possible combination, just to hear it.

What you can convince a guitar player to do or buy to have these sounds remains one serious compromise to the final implementation of a product, especially since most guitar players except for Neil Young don't have shit to spend on their equipment.

I can sure attest that this has been fun so far though. I look forward to the next chapter!

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Re: The FM Tube Modulator Jimi Loved

Post by Eb7+9 » Sun Jan 24, 2016 10:25 pm

Thanks for the observations Dave,

I just finished testing my CTP-Mini board ...
it's a single modulator version of my previous build, minus the resonant TANK circuit at the output

this time I decided to use single Panasonic ECQ cap values that are "roughly" close to Wayne's values, those that are directly available from Smallbear electronics' stock, just to see if I could get blind-DIY friendly here

ie., not having to measure each one, sum them, measure the sum, etc ...

I also decided to build a PSU circuit that would operate from a 16vac/300mA wall-wart
and give me three clean DC voltages ... +/-9 volt and well above 20 volts for the modulator section

I also added a CMOS inverter chip, operating gates in slow-ramp mode ...
and two opto-couplers (NSL32-SR3) for optically "shorting" key node pairs

this way I can start/stop the modulator without incurring a loud "pop" at the output ...

---

first, the good news ...

the PSU circuit woks fine ... yielding +/- 9.3 volts for the op-amps and 22.0 vdc for the modulator
the CMOS-opto start/stop ckt does what its supposed to as well ... no "pop"

the Chorusing quality is very good, and the S/N is outstanding (again) ...
even in this basic one-oscillator structure the effect quality is lush and musical

---

second, the not-so-great news ... (no panic, I'm still in the proto phase ..)

I scoped the circuit while sending a 2kHz 10v pk-pk sine wave at the input ...
that's a pretty large signal ...

I could not detect any clipping at the output ... (good news again)

but, I found the "A" output to be about 1volt pk-pk while the "B" output was about 4volt pk-pk
so, this is a major discrepancy as they should be much closer in amplitude ...

while the SPICE simulations of the previous Wayne lattice values gave me about 0.3db variation
between these outputs, by using non-exact (Smallbear stock) values I found the deviation to be too large
SPICE simulations also confirmed the bench results I was seeing ...
(just needed to double check what would happen in reality)

the result was a bumpy sounding effect, with every three cycles coming out quite stronger

so, this suggests sticking "closely" with the Wayne values ... it's still cool as an effect tho
but not as good maybe as when all three cycles put out the same amount of signal

(why the matching of jFET's in the first place)

all this then requires careful measuring of caps and jFET's prior to circuit insertion
so, it's unfortunately not at all blind-DIY friendly in the end

---

this experiment was useful ...

it confirms that Wayne's lattice network values need to be closely maintained

originally I had a problem with Wayne's R/C approach as it produces significant losses (ie., signal attenuation)
which, to be clear, lies in contradistinction to using an L/C approach (as per Darlington's original paper)

indeed, I would very much like to figure out how to get an equivalent L/C lattice working
as described in Darlington's paper, and also here:

http://www.highfrequencyelectronics.com ... Itemid=189

maybe one day, if I can get my Filter Theory chops back ...

at the same time, I'm curious to know where Wayne got his idea to simulate Darlington's idea using an R/C lattice

for those interested, this could be a good lead in ...

[url]http://www.dtic.mil/dtic/tr/fulltext/u2/769585.pdf[url]

if anybody finds anything further relevant, please post ...

---

anyway, the single-channel "mini" still produces a great sound when running thru a second amp
awesome for live performance

the noise specs are really good, even operating in free air (unshielded) ...

but there's no speed control ...
still, to be honest, I didn't feel like I was really missing the option while playing

---

obviously, I'll be swapping in Wayne's cap values to make the lattice network operate as it did before in the 4-banger

~jcm
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Re: The FM Tube Modulator Jimi Loved

Post by Eb7+9 » Fri Feb 05, 2016 10:28 am

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
Attachments
frontCTP2jcm2015.jpg
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fastCTP2jcm2015.jpg
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slowCTP2jcm2015.jpg
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modern VT circuit analysis and modeling: https://viva-analog.com/product/ifmta-book-pdf/

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