Sampler guts

One nice thing I did during the otherwise mostly unmemorable previous year of 2023 was to perform further needed repairs and general maintenance on my ancient and beloved SCI Prophet 2000 sampling keyboard, serial # 00064, as it nears the end of its fourth decade in operation. Over the years I have replaced voltage regulators and other power supply components, along with countless electrolytic and tantalum capacitors that had either already failed or were likely to do so given their age. I have had to replace a dead Curtis chip on an occasion. I have also replaced the brittle grey ribbon cable that served as the wiring harness connecting the digital and analog circuit boards with sturdier, flexible wires connected individually from terminal to terminal, since the original solder joints had begun to crack. So far this has worked astonishingly well, although early on I had to go back over and track down a couple of loose connections.

 

 

This time I discovered I had to replace the little coupling capacitor between the VCF and VCA portions of the Curtis Electromusic 3379 chip for Voice 1. Each one of the eight voices of this 12-bit sampler uses a single CEM3379 for the analog signal processing of that voice channel. A quirk of that chip's design, allowing for maximum design flexibility, is that all the functions on the chip - voltage controlled filter, voltage controlled amplifier and voltage controlled panpot - are available independently with separate inputs and outputs for each function. On the analog board of the Prophet 2000 the VCF outputs are wired directly into the input pins of their corresponding VCAs through small capacitors that "AC-couple" the filter to the input of the VCA. Basically, this means that any direct current (DC) bias present in the output of the filters will not be sent through to the amplifier inputs. A failed capacitor at this location results in a noticeable loss of signal level and perceived fullness for that voice channel compared to others that are working normally.

 

 

After removing the part I suspected, it was immediately obvious that it was indeed a bad capacitor, confirmed by electrical testing. Wary of introducing subtle differences between the sonics of the voice channels, I decided it would be best to replace all 8 coupling capacitors with identical parts at the same time rather than just replace the faulty cap in Voice 1. After all, the remaining 7 were just as ancient and likely to fail before too much longer! I also replaced the remaining electrolytic caps associated with the analog voice channels which, as it turns out, form part of the filter CV bias and scaling circuits. So now the venerable Prophet has a new lease on life in the filter / VCA section and is sounding crisper and punchier than ever!!

 

 

 

As always, there is still room for improvement: I have yet to definitively diagnose and fix a random, very occasional sample playback and / or CV triggering glitch that occurs with certain envelope settings and (usually) many voices being triggered at once. The fact that it seems to happen with some envelope settings and does not appear to be associated with any one voice channel suggests that it might be a bad component in the control voltage (CV) sample-and-hold section, such as the LF356 op-amp at the output of the CV DAC that feeds the demultiplexing circuitry, or an associated component on that part of the board. Alternatively it could be a diode, a data latch or some other part associated with an individual voice channel that only acts up intermittently. The strange thing is that certain patches and settings don't seem to be affected by this glitch at all, whereas with others the error starts to crop up almost immediately. Fortunately the technical manual for this remarkable instrument is extensive and incredibly informative, so with a bit of luck and tenacity I think I'll eventually be able to figure it out!

(PS - sorry for my awful pictures. I promise I'll get a decent camera someday!)

It's about time again

Admittedly, however, this could be a somewhat willfully obtuse reading of Barbour's timeless physics, and not consistent with his intended meaning. Perhaps a fairer appraisal would conclude that Platonia IS the real universe, and all of the experiences and perceptual events that we take to be "real" (and are thus rendered temporally) are actually composed of phenomenological "granules"; spatio-temporal aggregates of timeless physical states, like individual volumes in a series, centered around some locus of nervous activity. But it could only be the perceived continuity of the headspace resulting from particular configurations of matter undergirding any notion of a relation, analogous to the idea of a series, between the multitude of unique yet atemporal configurational possibilities. At least that seems to me to be a necessary consequence of this variety of timeless physics.  

Given how (relatively) little is definitively understood about the role and nature of consciousness, there is no obvious reason to immediately reject such a notion, but there is neither an obvious reason to favor it other than its utility in supporting the hypothesis. 

Several important questions remain: whether we have access to the tools required to adequately understand the nature of matter, which, as the presumed basis of the phenomenon in question, must be thought of as essentially valueless, both existing and acting independently of our peculiar perspective. But it is precisely that "peculiar" perspective, if we accept that physics is fundamentally an empirical pursit, that has itself formed the basis of our understanding and description of what we take to be the material universe. Moreover, we lack an adequate description of the phenomenon of consciousness as a material process, leaving us at a loss to explain why or how this type of scenario might even emerge - and for what reason the material universe would go to such great lengths to conceal, deceive or otherwise baffle its (apparently) sole consciously aware inhabitants as to the reality of their true condition.     

On the level of theory these questions have tended to hinge in no small way on what is assumed to be real, and how that notion of reality is to be defined. In what sense can anyone confidently declare they have thoroughly resolved this "timeless" paradox? On the one hand, we take for granted the reality of everyday occurances, what we might call "events", playing out in their various expected and often unexpected ways in the theater of the world. But we also know that beneath all of this there is a deeper reality, that of the material substrate of which the universe actually consists, as described by physics. But despite this being the reality that is typically taken to be more fundamental in an important way, nobody actually lives in such a reality. In fact, the only reality you or I or anyone else can reasonably claim to know is the world of experience, which consists not only of perceptible objects and events but an entire range of sensorial and phenomenological flora, the full reality of which a mere description of the material universe at any point will not suffice to render.

To be fair, this is a paradox afflicting practically the whole of physical theory, not just that of Julian Barbour, so it should be noted that in this respect his fares no better or worse than other physical theories, including those that may also accept the reality of time.

31 staples

So as I was discharged from the hospital last week, I thought it might be a good opportunity to put in a few words finally about the state of my health. 

Now before anyone jumps to any apparently obvious conclusion, it could be said that it actually isn't as bad as it might otherwise seem. Of course, it's conceivable that anything could have turned out slightly or even significantly worse than it actually did, so the point may be trivial. But this possibility aside, by all appearances I am beginning to make some significant progress past the horrendous ordeal that began the very early hours of Friday the 16th of February, a little over two weeks ago now. With even greater accuracy it might be said that the ordeal began over 20 years ago, and has been ranging in intensity of unpleasantness from total remission to unrelenting agony and most everything in between during that time. The last few weeks have unfortunately been largely defined by the agonizing species. What started as intractable gastrointestinal distress in the middle of the night concluded with a major surgery the following week to remove 6 (six!) small bowel adhesions which, over time, had effectively narrowed certain sections of my intestines, making it difficult or impossible to pass food through them. Adhesions of this kind are unfortunately an all-too-common complication that can ensue from the type of bowel surgery I had nearly six years ago, during which my entire colon was removed. This became necessary due to the presence of a longstanding chronic disease called Ulcerative Colitis, which some of you may have heard of. It's far from uncommon, and along with the closely related Crohn's disease it affects a significant number of people from many walks of life all over the world. In the more severe cases, such as mine, the only way to effectively "cure" the disease is to surgically remove the inflamed and damaged tissue, leaving behind the remaining healthy parts to assume all digestive function. This might be done for more than one reason in fact: for me, the risk was not only the ongoing manifestation of dangerous and debilitating colitis symptoms, but left untreated this condition entails an enormously high risk of developing colon cancer as well, which can be quite fatal. So the only real choice, if you can even call it that, was to have whole damn thing chopped out. That was in May of 2018. My life has not been the same since, to put it mildly. 

Now, in reality, no one's life is ever the same since anything, if you catch my meaning, but again, we will put this aside for the time as it merely illustrates the magnitude of difference here. Little did I know that my life was about to get even different-er all over again, with the length of my new scar far exceeding that of the original incision to remove the offending organ in the first place. It's quite long indeed; in fact it may even approach the size of some C-sections, but turned the other way 90 degrees, straight up and down. Actually the wound itself is healing up very nicely, and the amount of pain from it has often been overshadowed by ghastly gastrointestinal discomfort as my poor innards begin to "wake up" from being totally shut down by the blockage and the surgery both (the medical term for this is an "ileus"). At first it was pretty excruciating. But after a few days of taking stool softeners and simethicone along with my regimen of heavy pain meds, my guts began to move freely at last and I began to expel vast quantities of formerly trapped gas and so on, and I began to feel much more comfortable. This will probably sound familiar to many people who have had a major abdominal surgery of one kind or another. It will likely be up to another week or two until my digestive function returns to something comparable with what I'm used to. 

At the same time I am dealing with a lot of muscular fatigue and bruising due to the disruption of the abdominal wall and the attendant alteration in muscle usage across the midsection. There is also a lot of ugly skin stretching and discoloration in connection with the staples (yes, there are 31 of them, scheduled in theory to be removed tomorrow). I'll try to keep readers posted on my recovery. In the mean time, it can be a lot of effort just to get through the day, which is practically the extent of my capability at this point. Other things will again become possible in due course. 

Thank you for your patience.