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Muied Lumens
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 Posted: Thu Feb 21, 2013 6:17 pm Post subject:
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Thanks for reading, and good idea on the diodes!
| umschmitt wrote: |
* those no-input devices behave quite differently when feedback is delayed (na really ?). It may not matter for drones but some (rather violent) blips & squeaks need immediate feedback, as far as I understood the process. |
Yeah anything that goes into the loop will make it sound and behave differently, and you don't need the delay and limiter unless there is a mic involved. Strictly speaking, you could do with just the limiter, or if you like taking the risk, just the delay. Or you could put the speakers and mic in a different room and see what happens. 
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State Machine
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| Posted: Thu Feb 21, 2013 6:21 pm Post subject:
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Rob
The article on feedback is very informative and well written. It is certainly a great launch pad for learning to use feedback as a performance technique. I think now between yourself and Dale, I can overcome my fear of annihilating my speaker system  I will take the advice of starting with single feedback loop, massage that a while and record fro those serendipitous moments, then increase the patches in complexity by adding more feedback paths as I get more comfortable at each preceding step.
One of my mixers that I shall use has 4 buses and thus will act as a 4 x 4 matrix mixer. I can then INSERT an FX unit ( a delay for example) into each FB path if I choose to. This will allow for great flexibility.
As for doing a DIY matrix mixer, check out this one by Ken Stone. It is a 5 x 5 matrix mixer that can operate in either bipolar or unipolar modes.
Simple to build and easy to obtain parts.
http://www.cgs.synth.net/modules/cgs33_matrix_mixer.html
Bill |
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Muied Lumens
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| Posted: Fri Feb 22, 2013 8:04 am Post subject:
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Thank you kindly Bill. 
That mixer is exactly what I had in mind actually. Ideally it would have a short variable delay on each channel, 50 ms max. You could then combine phase reversed channels to create filters and other effects, at least in theory.
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| Posted: Fri Feb 22, 2013 9:50 am Post subject:
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Since I usually run my signals through my laptop as the last stage before speakers or the Internet stream, with Ableton Live as the final tool, I always place a compressor / limiter into Live's output to good effect. Even with a limiter, I recommend starting with all the faders down so you know what will happen on power up, which is to say, nothing.
I have noticed the snake that lives next to my workspace paying keen attention when I use speakers, although that may be due to the fact that I moved next to him and added some lights in that end of the room about the same time that I started playing zero-input mixer. He doesn't seem agitated.
At electro-music 2012 John Driscoll and I discussed non-linear transitions in the feedback path; Rob's article mentions them as well. Those are the really cool spots, for example where regenerative feedback becomes degenerative or vice versa, because some active filter or effect is crossing a threshold. Finding those spots and milking out the sounds is one of the fun aspects of this thing.
Take a look at this article from spring 2009 when you get time.
| Quote: | While exploring transistor behavior, the team found evidence that a widely accepted model explaining errors caused by electronic “noise” in the switches does not fit the facts. A transistor must be made from highly purified materials to function; defects in these materials, like rocks in a stream, can divert the flow of electricity and cause the device to malfunction. This, in turn, makes it appear to fluctuate erratically between “on” and “off” states. For decades, the engineering community has largely accepted a theoretical model that identifies these defects and helps guide designers’ efforts to mitigate them.
Those days are ending, says NIST’s Jason Campbell, who has studied the fluctuations between on-off states in progressively smaller transistors. The theory, known as the elastic tunneling model, predicts that as transistors shrink, the fluctuations should correspondingly increase in frequency.
However, Campbell’s group at NIST has shown that even in nanometer-sized transistors, the fluctuation frequency remains the same. “This implies that the theory explaining the effect must be wrong,” Campbell said. “The model was a good working theory when transistors were large, but our observations clearly indicate that it’s incorrect at the smaller nanoscale regimes where industry is headed.”
The findings have particular implications for the low-power transistors currently in demand in the latest high-tech consumer technology, such as laptop computers. Low-power transistors are coveted because using them on chips would allow devices to run longer on less power—think cell phones that can run for a week on a single charge or pacemakers that operate for a decade without changing the battery. But Campbell says that the fluctuations his group observed grow even more pronounced as the power decreased. “This is a real bottleneck in our development of transistors for low-power applications,” he says. “We have to understand the problem before we can fix it—and troublingly, we don’t know what’s actually happening.” |
I am interested in quantum mechanics for an assortment of reasons. I am very interested to see that the primary model for transistor noise all these years has been incorrect. Zero-input mixer is driven at its core by this phenomenon, although I guess all solid-state oscillation is.
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State Machine
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State Machine
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| Posted: Fri Feb 22, 2013 6:17 pm Post subject:
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| Quote: | | Since I usually run my signals through my laptop as the last stage before speakers or the Internet stream, with Ableton Live as the final tool, I always place a compressor / limiter into Live's output to good effect. Even with a limiter, I recommend starting with all the faders down so you know what will happen on power up, which is to say, nothing. |
This is probably the best solution for me as well Dale as I also want to utilize a laptop in my setup. I like this idea and will also use a software limiter on the channel where I bring in the mixer.
| Quote: | | I am interested in quantum mechanics for an assortment of reasons. I am very interested to see that the primary model for transistor noise all these years has been incorrect. Zero-input mixer is driven at its core by this phenomenon, although I guess all solid-state oscillation is |
After reading books about quantum computing, and they were fairly intense reads with some of the material going right over my head, it seems that all known physics goes out the window and things start to behave in very strange & different ways ! I would think that as transistors approach quantum dimensions, they would start to deviate from their expected behavior as well.
Zero Input mixing, the core of this is the violation of Barkhausens stability criterion by which we have an amplifier that has a gain of greater than 1 around the feedback loop and with zero phase shift between the output and input signal thus positive feedback.
Thus to sustain oscillation:
The loop gain around the amplifier is equal to unity (or greater)
The phase shift around the loop is zero or an integer multiple of 2pi radians (360 degrees)
Oh this is great stuff !!!!
Bill |
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Blue Hell
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| Posted: Fri Feb 22, 2013 6:43 pm Post subject:
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| State Machine wrote: | | You can create variable delays from 30 to 350 milliseconds[...] |
I may be missing the point .. but would have expected delay times from say 50 µs to 50 ms (or it's 'inverse' 20 kHz down to 20 Hz) to be most useful.
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Acoustic Interloper
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| Posted: Fri Feb 22, 2013 7:16 pm Post subject:
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| State Machine wrote: | | After reading books about quantum computing, and they were fairly intense reads with some of the material going right over my head, it seems that all known physics goes out the window and things start to behave in very strange & different ways ! I would think that as transistors approach quantum dimensions, they would start to deviate from their expected behavior as well. |
Here is my light reading for the upcoming summer, staring me in the face from atop a pile of books right now. Humans as quantum amplifiers. It wouldn't surprise me. People are strange.
Here's another light read.
| Quote: | Can the rate of decohrence be slowed down? Astonishing new evidence
says that the answer is almost surely "Yes". Chlorop
hyll is the molecule in
plants that carries out photosynthesis. Photons hit a receptor site and
migrate to a reaction center. Recent experimental work has demonstrated
that the quantum coherent state of chlorophyll during this process lasts
1000 femtosecon
ds, or a nanosecond, or even longer! So decohrence can
be slowed down, and the coherent state is thought to sharply increase the
efficiency of energy extraction by the plant from the photon. More, the
chlorophyll molecule is surrounded by an "antenna" prot
ein which is
thought to suppress decohrence, or possible enable recoherence. This
hypothesis can be tested using mutant antenna proteins.
The long time scale coherence at ambient temperature of a quantum
coherent state is important because until recently,
most physicists would
have believed that at room temperature, decoherence would rapidly
destroy all quantum coherence. This suggests that long lived coherence
may be biologically useful, selected for, and tuned for sundry functions.
What about the convers
e? What is now known about conversion from a
decohered, classical (for all practical purposes) state to regain the
quantum coherent state? There are, at present, two bodies of work.
First, mathematician Shor proved a quantum error correction theorem for
qu
antum computers. This work has been expanded upon. Briefly, if
quantum degrees of freedom in a quantum computer are decohring due to
loss of phase information from the computer (the system), to its
environment, then Shor showed that if information is added
to the system
from the outside, the decohering degrees of freedom could be made to
recohere again. This clearly says that recoherence is possible.
Second, physicist Hans Briegel, University of Innsbruck, Austria, has
published two papers showing that a qu
antum coherent "entangled"
system can decohere to classicity than recohere to quantum entangled
coherence.
I am not a physicist or mathematician. But based on the above, I will
assume that the quantum coherent to classical conversion can happen
acausally by decoherence, and recoherence can also be attained.
This immediately raises four huge sets of questions.
First, what determines
the ratio of quantum to classical processes in the universe? Second,
can a
sustained, partially decohrent "Poised Realm" be attained and
maintained?
Third, and critically, what laws,
if any laws exist
, describe
the behavior of a syst
em in the "Poised Realm"? I return to this in a
moment, for we really know almost nothing. But we do know one critical
thing. Fourth, how can one expermentally achieve and study a possible
sustained partially decohrent "poised realm" physically?
I will ju
mp to the third question:
If
a Poised Realm exists and persists
between quantum and classical, partially decoherent, in a system in its
environment, what laws if any apply to its behavior? At this stage the only
thing that seems certain is this:
The quantu
m system is losing phase
information to its environment, therefore the Schrodinger equation for
the system cannot be propagated "unitarily.
"Unitarily" means that the
Schrodinger wave propagates in such a way that the square of the
amplitudes of all the po
ssibilities, interpreted as probabilities, sum to 1.0.
This is
the only way
physicists know how to compute the forward time (or
reversed time) behavior of the Schrodinger equation describing the
behavior of a quantum system. But this cannot be done for the
system
alone if phase information is being lost from the system to the
environment. Thus, at present, we have no idea if the behavior of a system
in the Poised Realm is lawful or not, or what that or those laws may be.
Thus, if a maintained Poised Realm c
an be created, it seems to be a realm
of very new physics.
One possibility to bear in mind is a contrast. We are used, since Newton, to
ordinary differential equations and partial differential equations in
physics. In areas of computer science we grow
used to "agent based
models", which interact to exhibit behavior, but so far we typically cannot
write down differential equations for their detailed behavior. With respect
to the Poised Realm, if a sustained Poised Realm can exist, we don't have
any idea
what happens except at the quantum and classical limits of this
Realm.
The second question asks: Can a Poised Realm state be maintained? It
would seem possible. If the quantum system is losing phase information to
its environment, Shor's theorem assures us
that addition from the outside
of information can cause decohering quantum "degrees of freedom" to
recohere. Thus it is conceivable that a balance can be struck between
decoherence and recoherence, leading to a sustained state in the Poised
Realm. Obvious
ly, at this point, how to do this "in principle" possibility is
unknown.
If the quantum to classical transition via decoherence is reversible, then
the first question looms large: What is the balance between quantum and
classical processes in the universe
and its "parts", via what means, laws, or
otherwise. One radical possibility is a kind of abiotic natural selection in
which bits of classical matter which are good at avoiding return to a
quantum state persist. If they have variants by accretion of differ
ent added
bits of classical matter there are even more resistant to return to a
quantum state, they will be abiotically "selected" ie they will persist better. |
A little something to think about as you fall asleep. The author's conjecture (a rather formidable biologist) is that aspects of consciousness may arise out of the process of decoherence / recoherence in the brain.
My interest, of course, is computer musical, and my position as a computer scientists is not to strive for autonomous algorithmic compositional agents, this being a trend in academic "music meta-creation," because classical computation is fundamentally weaker than quantum computation. If there is even a reasonable case for quantum cognition in humans, then taking humans out of the loop reduces the dimensionality of the system -- musical or otherwise -- at least until we crack practical quantum computing.
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"Just say no."
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State Machine
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| Posted: Sat Feb 23, 2013 4:57 am Post subject:
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Jan
| Quote: | | I may be missing the point .. but would have expected delay times from say 50 µs to 50 ms (or it's 'inverse' 20 kHz down to 20 Hz) to be most useful. |
You are correct. The range of delays that the PT2399 is capable of are what was quoted. For this application, only the 30 to 50 millisecond range would be technically useful but one never knows how it will behave what you start to get chirps and ticks, along with the delays, in the feedback path. It would be interesting to see what the circuit does as a trial with a single channel before committing. 
Bill |
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Muied Lumens
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| Posted: Sat Feb 23, 2013 2:06 pm Post subject:
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| State Machine wrote: | Jan
| Quote: | | I may be missing the point .. but would have expected delay times from say 50 µs to 50 ms (or it's 'inverse' 20 kHz down to 20 Hz) to be most useful. |
You are correct. The range of delays that the PT2399 is capable of are what was quoted. For this application, only the 30 to 50 millisecond range would be technically useful but one never knows how it will behave what you start to get chirps and ticks, along with the delays, in the feedback path. It would be interesting to see what the circuit does as a trial with a single channel before committing.
Bill |
Very true Bill... I have not conceptualized it properly in my mind yet, but the general idea was something that spans the audible spectrum and can "morph" between different types of effects ie filters and delay stuff, as well as being used for feedback and other things. I suspect that trying to control these effects in a predictable way wont be easy though. Which does not matter too much in general, but for now its just an idea, I think I might have to mock up something virtual first.
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State Machine
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| Posted: Sat Mar 16, 2013 7:50 pm Post subject:
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In preparation for March Equinox radio concert, the first 15 minutes of my show will be a zero input mixer performance utilizing a Eurorack MX2642A mixing board with a Korg QUAD FX in the feedback path of channels 1 & 2. Channels 3 & 4 are feed straight back to each other using two AUX 1 & 2 sends. My DIY dual digital fraktal synthesizer, also shown in the pictures below, will add additional layered sounds. A picture of the mixer setup is also shown below. Recordings to follow.
Bill
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Acoustic Interloper
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| Posted: Sun Mar 17, 2013 7:16 am Post subject:
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It looks great, Bill! I am looking forward to hearing you in action 
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