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Through Zero Oscillators

Anything modular synth related that is not format specific.

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dB4u
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Post by dB4u »

+1 on the rubicon :tu:
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Post by orlog24 »

+2 on the Rubicon... my second one is coming soon in the mail... Very excited to use them together!
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nikmis
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Re: Through Zero Oscillators

Post by nikmis »

Agent86 wrote:
frijitz wrote:There were early synth circuits in Electronotes from Bernie and from Jan Hall. Other diy versions came from Don Tillman and Henry Wamsley. These all used different methods!
Thanks for the lead on Henry Wamsley, I found an article in EDN from 2003. (I assume this is the one? http://www.edn.com/design/test-and-meas ... requencies)

I had read Don's article some years ago (seems he still hasn't finished writing it) and I just skimmed Henry's. Some day I hope I'll actually understand what I read!
:hmm:

I'm dredging through my old brain for a connection... Years ago, I remember reading a comparison of frequency shifters that used either digital or analog oscillators and I was wondering if this is related...
I know that guy! unless its a different Henry Walmsley, electronics engineer.
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wsy
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Post by wsy »

And I knew Don Tillman (suitemate in the same dorm in undergrad at RPI). Pranked him with a ~50 uF tantalum capacitor
pretty good once. :-) (yes, I know that 50 uF is not in the standard tantalum series, but it was something _like_ that.)

I just had a brainstorm on how to make a TZFM oscillator out of a regular osc with linear inputs, plus two diodes, a TL074, and a CD4066.

Now, two questions remain:

1) can it be done from the front panel - that is, can I make a "TZFM AID" that you jack a normal osc into with just the normal
oscillator connections and then the TZFM AID does the magic needed, or does it have to connect to voltage nodes inside the
normal osc core that don't show up on the front panel?

2) To be perfectly honest, after playing with a Rubicon, especially after self-patching it and seeing how easy
it is to get itself "hung" at 0 Hz, (plus my experiments with the FM Operator) I'm starting to think that PM (Phase
Modulation) and not FM is the right-right way to go for interesting timbres. (plus PM retains pitch even with a
DC offset, which is really handy for tonal music.)

- Bill
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Dr. Sketch-n-Etch
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Post by Dr. Sketch-n-Etch »

wsy wrote:I just had a brainstorm on how to make a TZFM oscillator out of a regular osc with linear inputs, plus two diodes, a TL074, and a CD4066.

Now, two questions remain:

1) can it be done from the front panel - that is, can I make a "TZFM AID" that you jack a normal osc into with just the normal
oscillator connections and then the TZFM AID does the magic needed, or does it have to connect to voltage nodes inside the
normal osc core that don't show up on the front panel?
So, what is this idea?
2) To be perfectly honest, after playing with a Rubicon, especially after self-patching it and seeing how easy
it is to get itself "hung" at 0 Hz, (plus my experiments with the FM Operator) I'm starting to think that PM (Phase
Modulation) and not FM is the right-right way to go for interesting timbres. (plus PM retains pitch even with a
DC offset, which is really handy for tonal music.)
I'm not aware that the Rubicon "hangs" at 0 Hz. I've never seen that behaviour. Under what circumstances does that happen?

Also, AFAIK, phase modulation is only really plausible in the digital domain. I once devised a circuit that would phase modulate a triangle wave 180 degrees forwards or backwards, but the WMD module has a much larger range than that, and I believe it is digital. I couldn't see how to do it in analog beyond +/- 180 (but, then again, I'm a bear of very little brain).
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Post by adam »

that cheaty cheat way with a saw animator seems good (plus saw core vco)
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Post by wsy »

As to the Rubicon "hang" - grab a Rubicon, and patch sine out into FM in, linear. Monitor the saw output audio. Start with
very low gain in the FM input attenuator, and slowly crank it up. You'll get some good timbres, but at some point, the
Rubicon's sine out at roughly 220 degrees phase x attenuator will exactly balance the 1V-octave input, and the Rubicon
will just output a DC voltage.... hung. If the Rubicon heats up a little, and the 1V/octave currrent increases, it just moves
along the sine curve further (say to 221 degrees) and gets a slightly more negative value.

You can get it out of the hang by decreasing the FM modulation. Increasing it won't help. It's hung.

Basically, the Rubicon has found a fixed point where V(t+e) = V(t) and the region around that point in vector space
all slides "downward" into the hang; it's a "stable equilibrium" in the mechanical sense of the word, so small amounts
of noise or thermal perturbation don't knock the Rubicon out of that stable equilibrium

Mathematicially, this is "correct" - I've duplicated the result in simulation, and again in the FM Operator with external patching.
So, it's real.

I found this most annoying, because it means the Rubicon CANNOT do self-feedback FM without a second
oscillator to kick it out of these hang points.

EDIT: should be "self-feedback THRU-ZERO FM without a second oscillator.

This is another reason why the FM Operator (and the Yamaha FM synths) do feedback in PHASE, not frequency. No
such "hang" point exists with phase-based feedback; you can get a chaotic zoom but not hung at DC.

And that's why I wonder how to do an analog PM oscillator. Although, if you can create a sine lookup
circuit ( Vout(Vin) ~= sin (Vin) ) then you can cheat it fairly easily. :-)

You don't need much control authority to do really fun PM - 720 degrees is getting there, and four or five is timbral gravy.

Seriously. Grab a Rubicon, (or an FM Operator) or try it in simulation if you want.
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555x555
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Post by 555x555 »

There's at least two ways to do PM in analog. The first is the fm-aid style, which if I understand it correctly (I may not) essentially takes advantage of the fact that a saw wave with modulo addition is a phase-shifted saw.

The other way I don't really see people doing, but fm is equivalent to pm with the integral of the modulator. So to go the other way you just need to differentiate. A single pole fixed high pass filter (rc filter) is a differentiator with a fixed gain limit in the upper frequencies (which is sane) and some arbitrary scaling factor. You should be able to throw your modulator through a single-pole high pass tuned high, then an amplifier, and then onward to the fm input jack. I'm not sure if this will allow for self-modulation; thinking about the math tells me maybe, intuition tells me no.

There's maybe a third way that would take advantage of the fact that sin(c + sin(m)) = sin(c)cos(sin(m)) + cos(c)sin(sin(m)) ---but then you're stuck with producing sin(sin(m)). Maybe there's a saw-to-sine/cosine converter somewhere that uses only voltage contours? You could plug a sine signal into it and get sin(sin(m)). (As an aside, note that the carrier signal just adds a frequency shift, as with fm. Through-zero makes it possible for the frequency shift term to go to zero, which is the best way to think about it for me.)
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Post by wsy »

Then there's a fourth way to do FM. :-)

It works with both triangle and sawtooth cores. Near as I can tell, it *does* require cutting the wire to the current
accumulator inside the oscillator core, and also post-processing the output.

Maybe the hink for doing PM is to start with a saw core, use modular add to convert it to a PMed saw (like FM Aid,
but just one saw's worth) and then use a saw->sine converter.

Now to find a cheap-n-easy saw core.... any suggestions?

- Bill
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J3RK
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Post by J3RK »

Check out Ian Fritz' Saw Core.
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Post by thermionicjunky »

wsy wrote: ...Now to find a cheap-n-easy saw core....
Yeah, Ian has a couple of good ones. The old one:

http://ijfritz.byethost4.com/sy_cir2.htm

The new one:

viewtopic.php?p=581946#581946
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Post by Starspawn »

I made a stripboard of the new one, works fine but some voltage drop on the non reference voltages cause of the zeners.

Tested very well, but waiting for its panel and 5 pulser (and another bipolar input 5 pulser for XOR).

http://electro-music.com/forum/viewtopi ... 214#420214
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bonjourmyfriends
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Post by bonjourmyfriends »

Are there any Thru Zero FM DIY projects?
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Post by sduck »

The Ian Fritz Teezer, although I'm not sure where one would get a PCB for this currently. Dr. Sketch-n-etch has promised a rubicon PCB, but I don't think it's available yet.
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Post by wsy »

bonjourmyfriends wrote:Are there any Thru Zero FM DIY projects?
Yes.

You could build an FM Operator (aka FM Ogre). It's full Open Source Everything.

The only downside is I have not yet been able to figure out how to kit it and sell it and not lose significant time/money
on each unit.

But the full BOM and PCB layout and schematic and Gerbers "known to work from OshPark because we have
built some" are here:

viewtopic.php?t=134469&highlight=

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Post by drumsofd00m »

Dr. Sketch-n-Etch wrote:
drumsofd00m wrote:Just a quick note off the top of my head (I posted this before in another thread and no one corrected me, so I hop I'm still getting this right after many years): (snip)
Nearly everything said in the quoted post is wrong.
Thanks for unearthing a three year old post to point that out. As I said, I was half expecting (and hoping for) some correction. However, would you please point out *which* part wasn't wrong and *where* I can find decent & reliable info on the rest (including frequency shifting and barber pole phasing)? If it was easy to find I wouldn't have taken the time to post so much stuff that I clearly was uncertain about.
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Post by ninGiaBoom »

Dr. Sketch-n-Etch wrote:There are currently three analog options for through-zero FM:

Intellijel Rubicon (euro)
Cynthia Zeroscillator (various formats)
Fritz Teezer (5U, others?)

There are also various digital options:

Intellijel Cyclebox
Harvestman Hertz Donut
others?

It's a fairly old idea, but not one which is very easy to implement, and therefore has not seen much use. However, given the amazing sounds of which TZFM is capable, the situation is changing now.

Well, i hope it's not discontinued because I'm looking since a while to this Schippmann Omega-Phi (just give a look to schippmann's homepage, it's the first module on top, price was more or less 999€): this module seems like TZFM juicy :hyper:

:guinness:
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Post by Dogma »

ninGiaBoom wrote:
Dr. Sketch-n-Etch wrote:There are currently three analog options for through-zero FM:

Intellijel Rubicon (euro)
Cynthia Zeroscillator (various formats)
Fritz Teezer (5U, others?)

There are also various digital options:

Intellijel Cyclebox
Harvestman Hertz Donut
others?

It's a fairly old idea, but not one which is very easy to implement, and therefore has not seen much use. However, given the amazing sounds of which TZFM is capable, the situation is changing now.

Well, i hope it's not discontinued because I'm looking since a while to this Schippmann Omega-Phi (just give a look to schippmann's homepage, it's the first module on top, price was more or less 999€): this module seems like TZFM juicy :hyper:

:guinness:
Make sure you ask if its a Mki or mkii - do NOT buy a mki
http://schippmann-music.com/
look up!
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Post by ninGiaBoom »

Dogma wrote: Make sure you ask if its a Mki or mkii - do NOT buy a mki
http://schippmann-music.com/
Hi Dogma, thank you for your suggestion...may i ask you why? is it something wrong with the first version?

Cheers :guinness:
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listentoaheartbeat
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Post by listentoaheartbeat »

Dogma wrote:Make sure you ask if its a Mki or mkii - do NOT buy a mki
http://schippmann-music.com/
Overemphasizing the MK1 vs. MK2 (non-)issue harms both Schippmann and even more so the retailers.

To quote Schippman himself..
Schippmann wrote:Relating the improvements: These are a quantum leap from maybe 95% to 99.1%, I would say. Very little tolerances of 0.1% and less are now trimmed to almost zero. These correction you will hear under extreme circumstances. From view of musicality they are not to overrate, please. The sound and stability will not change.
From: viewtopic.php?p=2315279#2315279
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listentoaheartbeat
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Post by listentoaheartbeat »

Dr. Sketch-n-Etch wrote:Also, AFAIK, phase modulation is only really plausible in the digital domain. I once devised a circuit that would phase modulate a triangle wave 180 degrees forwards or backwards, but the WMD module has a much larger range than that, and I believe it is digital. I couldn't see how to do it in analog beyond +/- 180 (but, then again, I'm a bear of very little brain).
The Schippmann CS-8 Omega-Phi does analog PM (in addition to TZFM). It's not as clean as digital at very high indices, but it sounds great overall. No idea how he does it, though. Maybe there are clues in the manual, it is very comprehensive and technical:

http://www.schippmann-musik.de/download ... 202_EN.pdf
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Post by Dogma »

listentoaheartbeat wrote:
Dogma wrote:Make sure you ask if its a Mki or mkii - do NOT buy a mki
http://schippmann-music.com/
Overemphasizing the MK1 vs. MK2 (non-)issue harms both Schippmann and even more so the retailers.

To quote Schippman himself..
Schippmann wrote:Relating the improvements: These are a quantum leap from maybe 95% to 99.1%, I would say. Very little tolerances of 0.1% and less are now trimmed to almost zero. These correction you will hear under extreme circumstances. From view of musicality they are not to overrate, please. The sound and stability will not change.
From: viewtopic.php?p=2315279#2315279
Agreed but what about the customer?
its all in that thread, enough to make up ones own mind.....i personally didnt have the cash to get a Mk1 and then find out a month later while MK1's are still in stock that the VCA is totally redesigned, 15db of parasitic noise eliminated and it is now mathematically correct regarding FM....
So his site now just says "the benchmark" and hes pulled the Mkii info entirely...and im friends with retailer who has 20+ Mki's still in stock he bought from the pre-order.....
look up!
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Post by MarcelP »

I use a Doepfer A-110-4 for all my "thru zero" oscillation needs. To honest I got it particularly for the very low distortion low frequency sine output - but find the modulation side produces some pleasing and controllable harmonics...
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Post by PrimateSynthesis »

wsy wrote:And I knew Don Tillman (suitemate in the same dorm in undergrad at RPI). Pranked him with a ~50 uF tantalum capacitor
pretty good once. :-) (yes, I know that 50 uF is not in the standard tantalum series, but it was something _like_ that.)
I'm sure you know from E6 to E24, the closest value would be 47. But I want to know what the prank was :mrgreen:
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Post by wsy »

PrimateSynthesis wrote:
wsy wrote:And I knew Don Tillman (suitemate in the same dorm in undergrad at RPI). Pranked him with a ~50 uF tantalum capacitor
pretty good once. :-) (yes, I know that 50 uF is not in the standard tantalum series, but it was something _like_ that.)
I'm sure you know from E6 to E24, the closest value would be 47. But I want to know what the prank was :mrgreen:
It Was Glorious!

He was in the habit of coming back from class and immediately turning on his guitar
and playing a half-hour of whatever made it hard to concentrate on. Very intrusive.

He had a guitar amp with an exposed back (probably he took the cover off himself), and
bridged the power input just after the power switch with the 47 uF tantalum cap. This
is the US, so power is 120VAC nominal, and the tantalum was rated for 16, tops.

We carefully turned the switch _off_ and plugged the amp back in, precisely where he
left it.

He came in. Grabbed guitar. Turned on the amp. A fireball the size of a grapefruit
came out of the back and bounced off the wall. Not ball lightning but not bad, considering.
It blew the circuit breaker; we had to reset it.

He just stared.... eyes wide open. "It blew. It blew. It blew". He kept saying that for
at least five minutes. "It blew. It blew. It blew." The words ceased to have meaning.

He recovered when we showed him the remains of the capacitor wires soldered across
the power input.

Someday, I will tell you about how we de-crotched his jeans. If you're nice.

- Crash
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