Something New from Doc Sketchy

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Dr. Sketch-n-Etch
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Re: Something New from Doc Sketchy

Post by Dr. Sketch-n-Etch » Sun Oct 04, 2020 7:31 pm

Well, in spite of all that I said the other day, I actually figured out 95% of the logic for the quantizer last night. Without getting into specifics, I will just mention that the key to it all is this amazing device known as the "tri-state CMOS buffer with enable" -- the SN74HCT125 has four of these little beauties, each independently enabled and disabled, and this thing will allow me to do this logic with a minimum of fuss (except that I need 8 of them to provide the 31 buffers I figure I'll need). So, the ADC generating binary code will feed a 4-to-16 decoder. The output of that will go to six different buses, enabled and disabled by virtue of the buffers, and those will feed a 16-to-4 encoder to generate the final chromatic steps into the DAC.

I think.

I'll also need some kind of digital switch to generate the four different reference voltages I'll need for the six different scales, and I believe I can use one more of those quad enabled buffers for this, sending a buffered CMOS power supply voltage into four different divider networks.
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Re: Something New from Doc Sketchy

Post by Dr. Sketch-n-Etch » Tue Oct 13, 2020 12:22 pm

UPDATE -- I have laid out the logic board for selecting all the scales, and now have only to create a new layout for the octave and chromatic quantizer circuits, which will be very similar to the existing quantizer layout. I should be done with this new quantizer project very soon (but I need to make a Digikey order).
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Re: Something New from Doc Sketchy

Post by Thorsday » Tue Oct 13, 2020 9:02 pm

I don't have a Quantizer in my system, however, thinking I can get by without one simply because it is built into the Moon 569 is a self imposed limitation that I am imagining being freed from... I have more voices and want to try different patching methods... So tempting...

Your quantizer looks to be another outstanding addition to the format, Doc...

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Re: Something New from Doc Sketchy

Post by kdjupdal » Wed Oct 14, 2020 1:53 am

I am guessing that you treat natural minor as the same scale as the major. But how would one change the root of the scale, so that it is not always in C? Also, did you consider the pentatonic scale?
Dr. Sketch-n-Etch wrote:
Sun Sep 27, 2020 2:01 pm
So, I did it and it worked. I now have the final layout all ready to rock, if anybody wants a board. $25 + shipping, or $75 built and tested, or $125 panelized.

Also, I'm working on dodecatonic (chromatic), octatonic, heptatonic (diatonic), and hexatonic (whole-tone) versions of the quantizer. For these, I'm separating the quantizer into a 3-bit octave quantizer, and a 4-bit chromatic quantizer. The octave quantizer will give 8 octaves in 1-V steps, and the chromatic quantizer will break each octave into 12, 8, 7 or 6 equal steps. This is relatively easily accomplished simply by manipulating the reference voltage levels to set the voltage where the 15 to 16 transition would occur (1.333V for chromatic, 2.000V for octatonic, 2.286V for diatonic, 2.667 for whole-tone). Then, if the octave quantizer output is subtracted from the incoming voltage, I'll always get a control voltage to the chromatic quantizer which is a 0-to-1-V ramp. Each of the four versions will use the same R-2R ladder which generates chromatic steps of 83.333mV. Once the proper number of notes-per-octave is achieved, the logic to the ladder will be altered to give various scales (whole-tone for the 6-step; major, ascending melodic minor, and harmonic minor for the 7-step, diminished for the 8-step, each selected by a rotary switch which drives various logic and analog switching chips).

For example, the heptatonic quantizer will generate the first 7 binary numbers in the 0-to-1-V ramp, and these have to be altered to other numbers with digital logic to achieve a major scale:

0 = 0000 --> logic --> 0 = 0000
1 = 0001 --> logic --> 2 = 0010
2 = 0010 --> logic --> 4 = 0100
3 = 0011 --> logic --> 5 = 0101
4 = 0100 --> logic --> 7 = 0111
5 = 0101 --> logic --> 9 = 1001
6 = 0110 --> logic --> 11 = 1011
7 = 0111 --> logic --> 12 = 1100

This system should never reach state 7, but if it does, then it will briefly generate an octave, before the octave quantizer jumps 1V and simultaneously resets this system back to state 0 via the voltage subtractor. Since there is the possibility of slight voltage mismatch between the two quantizers, the logic for generating an octave at step 7 should be in place since the octave transition may occur after the chromatic quantizer has already reached state 7. If this happens, the transition should be seamless, although the slew rates of the opamps may create a situation where the output jumps one octave for a few microseconds. Clever use of a small capacitor somewhere should prevent this, though.

I expect to have this design done later this coming week. I just hope the logic doesn't turn out to be too excessive. Of course, to get a melodic minor from a major, one only has to change the 2 --> 4 transition to a 2 --> 3 transition, so this is just one tiny additional logic element. This will give me a chance to dust off the ol' Karnaugh maps an' shit. Of course, it really doesn't matter how complex the logic is, since I'm doing all of this for fun anyway.

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Re: Something New from Doc Sketchy

Post by Dr. Sketch-n-Etch » Wed Oct 14, 2020 2:45 pm

kdjupdal wrote:
Wed Oct 14, 2020 1:53 am
I am guessing that you treat natural minor as the same scale as the major. But how would one change the root of the scale, so that it is not always in C? Also, did you consider the pentatonic scale?
Natural minor = Aeolian mode = scale from the VI degree of major, so yes.

To change the key, you'd have to sum the output of the quantizer with a fixed voltage, or simply adjust the frequency pot of the VCO you are controlling. I think I'll add this key-selection feature to the quantizer with a 12-position rotary switch (1P12T). Of course, the absolute pitch will still be controlled at the VCO, but at least the relative pitch could be selected at the quantizer.
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Re:

Post by Dr. Sketch-n-Etch » Mon Oct 26, 2020 12:48 am

Today, 25 October 2020, is Jon Anderson's 76th birthday. Jon Anderson is one of my all-time musical heroes.

Happy Birthday, Jon Anderson!!! :band:

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Re: Something New from Doc Sketchy

Post by Rex Coil 7 » Mon Oct 26, 2020 12:52 am

Dr. Sketch-n-Etch wrote:
Mon Oct 26, 2020 12:48 am
Today, 25 October 2020, is Jon Anderson's 76th birthday. Jon Anderson is one of my all-time musical heroes.

Happy Birthday, Jon Anderson!!! :band:

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what? :despair: he looks like he lives in a tree.

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Re: Something New from Doc Sketchy

Post by Moog$FooL$ » Mon Oct 26, 2020 6:24 pm

perhaps it's something to do with that big red butt-plug of his?? yeah that's prolly it!! :metasonix: :metasonix: :metasonix: :? :despair:
i use to drink & smoke.
that fat cat had to go..... wasn't even mine.

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Re: Something New from Doc Sketchy

Post by Dr. Sketch-n-Etch » Mon Oct 26, 2020 6:30 pm

Moog$FooL$ wrote:
Mon Oct 26, 2020 6:24 pm
perhaps it's something to do with that big red butt-plug of his?? yeah that's prolly it!! :metasonix: :metasonix: :metasonix: :? :despair:
Sounds like somebody's jealous...
A dewdrop can exalt us like the music of the sun.

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Re: Something New from Doc Sketchy

Post by devinw1 » Mon Oct 26, 2020 6:39 pm

I absolutely LOVE old Yes. Close to The Edge, Fragile. So good top to bottom.

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Re: Something New from Doc Sketchy

Post by KSS » Tue Oct 27, 2020 8:28 am

Dr. Sketch-n-Etch wrote:
Mon Oct 26, 2020 6:30 pm
Moog$FooL$ wrote:
Mon Oct 26, 2020 6:24 pm
perhaps it's something to do with that big red butt-plug of his?? yeah that's prolly it!! :metasonix: :metasonix: :metasonix: :? :despair:
Sounds like somebody's jealous...
And 99.9% of everyone who read that post saw only an acorn chair finial..

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Re: Something New from Doc Sketchy

Post by Dr. Sketch-n-Etch » Tue Oct 27, 2020 7:22 pm

KSS wrote:
Tue Oct 27, 2020 8:28 am
Dr. Sketch-n-Etch wrote:
Mon Oct 26, 2020 6:30 pm
Moog$FooL$ wrote:
Mon Oct 26, 2020 6:24 pm
perhaps it's something to do with that big red butt-plug of his?? yeah that's prolly it!! :metasonix: :metasonix: :metasonix: :? :despair:
Sounds like somebody's jealous...
And 99.9% of everyone who read that post saw only an acorn chair finial..
Well, obviously, Moog$Fool$ doesn't belong to the 99.9% ("Buttplugs... buttplugs EVERYWHERE" -- Moog$Fool$, 2020)
A dewdrop can exalt us like the music of the sun.

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Re: Something New from Doc Sketchy

Post by Dr. Sketch-n-Etch » Sun Nov 08, 2020 1:52 pm

I just wanted to announce that I have developed a new version of the Frequency Shifter, which I'm calling FS Lite. It is a very stripped down version, as it has no onboard VCO at all. You have to plug an external VCO into it to get shifting of another audio source. Instead, this unit has two Phase Displacement Networks (PDN). Whereas the first PDN is 12 stages, and generates quadrature for any audio signal between 15 Hz and 15 kHz (3 orders of magnitude), the second PDN is 16 stages, and generates quadrature between 1 Hz and 10000 Hz (4 orders of magnitude). If an external VCO (most likely a sine wave) is fed to this PDN, it will output the sine and cosine waves required to drive the shifter. The larger range ensures that the shifting will be accurate well down into the LFO range for phasing purposes. In fact, this second PDN will give accurate quadrature (within 1 degree of 90) down to about 0.8 Hz, which is about 1.25 seconds. I could go a bit lower, but really this is slow enough for phasing. The other cool thing about this unit is that you can drive it with any audio source, not just a sine wave. If you've ever wondered how it would sound to frequency-shift Messiaen with Bach, then this unit will answer that question.

I haven't built this yet -- I've just laid it out, but I have to order all the crazy resistor values for the new PDN (32 different 1% values) from Digikey. I'm 98.6% sure that it will work as intended. The panel will only have four pots, 1 switch, and 8 or 9 jacks, so could be built in 1U pretty easily. In fact, if I leave off a certain feature that is probably of very limited interest to most wigglers, then it will have 4 pots and 7 jacks. It will also pair very nicely with a dual VC XFader for crossfading both SUM and DIFFERENCE, and WET and DRY.

This new unit will be much less expensive, and much easier to build, than the current unit. I will probably have a unit to demonstrate in less than a week, and will of course be making one of my trademark videos. Stay tuned!
FSLite Guide Pic.png
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Re: Something New from Doc Sketchy

Post by BugBrand » Sun Nov 08, 2020 3:44 pm

Interesting as always, Dave!

I played with Quadnet a few months back, after your suggestion - I'd been trying to move forwards a FShift expander for my Quadrature VCO, so was very interested to check & try the software. Unfortunately I didn't find good results in tests initially & that put the project into the doldrums again.. been saying to myself to revisit for the last week, so maybe this'll give me the extra push.

You say you've not tested this yet - but maybe run it on multisim? That's very interesting suggesting a PDN so you can use any vco driver input, though the freq-range only going to 1Hz is quite a limitation, I'd say - low rate modulation (with feedback) was always an interesting sonic area when I was building FShifts 8 or so years ago.

Given I was looking to try to get the audio range wider than 15Hz-15kHz, I was wondering how to get the low freq PDN stages. I was curious about using lowish value resistors (like trying to keep sub 100k) for noise, plus found that the largest poly caps I had were spec'd at 3u3 but actually tended to test a fair bit lower - I'd thought this might have been adversely affecting the LF response because the phase relation certainly didn't seem to work right in the low regions.

Great developments!

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Re: Something New from Doc Sketchy

Post by Th°ne » Sun Nov 08, 2020 4:27 pm

Dr. Sketch-n-Etch wrote:
Sun Nov 08, 2020 1:52 pm
I just wanted to announce that I have developed a new version of the Frequency Shifter, which I'm calling FS Lite...
Fantastic !
:party: :tu:

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Re: Something New from Doc Sketchy

Post by bentoncbainbridge » Mon Nov 09, 2020 2:08 am

this sounds lovely, especially as a 1U!

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Re: Something New from Doc Sketchy

Post by Leverkusen » Tue Nov 10, 2020 8:48 am

Dr. Sketch-n-Etch wrote:
Sat Aug 08, 2020 3:57 pm
Leverkusen wrote:
Sat Aug 08, 2020 9:09 am
Dr. Sketch-n-Etch wrote:
Fri Aug 07, 2020 5:28 pm
Hey Team, I'm thinking about a modification to the Frequency Shifter module. This new one would not have an onboard oscillator on it, but would instead be driven from an external VCO. This would lower the cost of the shifter significantly.

Is there any interest in this new concept? I'll try to throw a prototype together this weekend for demonstration purposes.
I would be interested in the new concept and might finally order one in 5U. Could it be also smaller then - more like a classic ring modulator, just expanded? Two inputs, three outputs plus a feedback and a mix knob?
What would the three outputs be? SUM, MIX and DIFF? In fact, I never use the SUM and DIFF outputs. I always just use the MIX output, often hard-panned to either SUM or DIFF. Eliminating those two outputs, along with all the other changes, would really tighten things up -- this new concept could actually be 1U. Also, the unit should have a WET/DRY control, although an outboard crossfader would also work.
Hey, so great to see this eventually materialize - it is probably too late now but the benefits of dedicated SUM and DIFF outputs would be that they could get processed seperately with in the system. TIhniking of different delays/reverb/folding, VC crossfade or just parallel voices with seperateley gated VCA's - imagening a clangourous cannon or what ever weirdness would emerge from shifting Messiaen with Bach in all possible directions... :goo:

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Re: Something New from Doc Sketchy

Post by lmgrovllum » Wed Nov 11, 2020 5:58 pm

Love the new FS Lite idea. Looking forward to demos and building!

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Re: Something New from Doc Sketchy

Post by devinw1 » Wed Nov 11, 2020 6:35 pm

Dr. Sketch-n-Etch wrote:
Sun Nov 08, 2020 1:52 pm
I'm 98.6% sure that it will work as intended.

LOL! I love your confidence levels!


This sounds like a cool idea. Looking forward to the video as usual! :tu:

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Re: Something New from Doc Sketchy

Post by Dr. Sketch-n-Etch » Wed Nov 11, 2020 8:01 pm

First, to address Leverkusen, there are already dedicated SUM and DIFFERENCE outputs on the panel, as well as a MIX OUT output which is the (manually) crossfaded blend of the two.

Second, to address Bugbrand, in my experience, the QuadNet program gives very accurate results, which I always simulate both in Excel and in Multisim. The mathematical approximation in Electronotes (from Weaver's paper) isn't too bad either, but tends to lose phase accuracy at the extremes, especially when the number of stages in increased. This isn't good if you want to go very low. One problem with the QuadNet program is that it doesn't allow frequencies below 1 Hz, but this is a minor inconvenience.

I could shift the 1 to 10000 Hz down by a certain amount simply by increasing all the capacitors by a certain ratio -- for example, instead of 102, 103, 104 and 105, I could use 332, 333, 334 and 335. I don't want to buy too many different values in bulk, though. Also, above 105, film capacitors start to get too physically large for my layout. I didn't have very interesting results with my existing FS when the VCO frequency was too low -- the phasing was barely noticeable -- so I believe that 1 Hz or thereabouts is probably low enough. I guess I'll find out. In any case, the phase displacement goes a fair bit lower than that anyway for the QuadNet solution.

Finally, to devinw1, I'm confident because I believe that the design is solid. That's all. I just hope I'm not hoist by my own petard. We shall see soon enough, although I won't be building this for another week or so because I'm up to my eyeballs in midterm exams and other school work.
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Re: Something New from Doc Sketchy

Post by Dr. Sketch-n-Etch » Wed Nov 18, 2020 1:45 am

So, a brief update:

1) I haven't advanced the FS-Lite project any further because I've been spending all of my time marking midterm exams for my thermogodammits class. However, someone has ordered (and paid for) two of them, stuffed and tested, so I now have a really good excuse to actually build them.

2) I've spent what little spare time I do have working on an update of one of my older projects mentioned on this thread. A Vancouver-based wiggler asked if I could build him an interpolating scanner, and after some discussion, what we agreed upon was a module that would convert a quad (linear) VCA (like the Intellijel Quad VCA, or two uVCAs) into an interpolating scanner, but with control over the width and placement of the channel entrances. So, I have come up with a pretty nice design for that. I'll hopefully be posting something more concrete here in the next week or so. However, I have a couple big orders to get off of my to-do list first, and those midterms still aren't completely marked.
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Re: Something New from Doc Sketchy

Post by KSS » Wed Nov 18, 2020 1:49 am

Sounds busy! In a -mostly- good way. :tu:

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Re: Something New from Doc Sketchy

Post by maltemark » Wed Nov 18, 2020 11:19 am

Interpolating scanners, can't go wrong with those
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Re: Something New from Doc Sketchy

Post by kdjupdal » Wed Nov 18, 2020 11:25 am

I am interested! Waiting for the demonstration of Messiaen + Bach.
But I'm also interested in your full frequency shifter. Would it be possible to make a full version with additional input for external oscillator? If not I'll have to order both versions.

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Re: Re:

Post by onthebandwagon » Wed Nov 18, 2020 11:27 am

Dr. Sketch-n-Etch wrote:
Mon Oct 26, 2020 12:48 am
Today, 25 October 2020, is Jon Anderson's 76th birthday. Jon Anderson is one of my all-time musical heroes.

Happy Birthday, Jon Anderson!!! :band:

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