Tuesday, December 30, 2008
Saturday, December 20, 2008
Now, in the original MIDI standard, the manufacturer was defined as one byte long. Allowing for the fact that the high bit in any data byte in any MIDI message must be 0 (in order to distinguish it from a command byte, which always has a high bit of 1), that leaves a usable range of numbers of 00-7F hexadecimal, or 0-127 decimal. Long ago, in the original 1983 standard, the MIDI principals (which at the time were Sequential Circuits and Roland) decided to divide the manufacturer IDs into four groups, to be assigned to manufacturers on a geographic basis:
- 01 to 1F for American manufacturers (00 was reserved, which I'll get to in a bit)
- 20 to 3F for European manufacturers
- 40 to 5F for Japanese manufacturers
- 60 to 7F were reserved for future use (Some of these have since been assigned for certain special purposes, such as the MIDI Sample Dump Standard)
In the original specification, published by Sequential in the January 1984 version of "The Complete SCI MIDI", these manufacturers were assigned:
02 Big Briar
04 Moog Music
05 Passport Designs
20 Bon Tempi
Sequential received ID #01 as befitting its status as co-originator of the MIDI standard, along with Roland, which was given the "first" number in the Japanese group. (I don't know why Kawai was given 40; it may have been the case that 20 and 40 were reserved at first, as 00 was, and then un-reserved and assigned later.)
A few things to note from that list. Both Moog Music and Big Briar are assigned IDs. At the time this list was issued, in 1984, Moog Music was the original New York company, owned at the time by Norlin (I think; it was about this time that Norlin broke up), while Big Briar was Bob Moog's company in North Carolina (he had been gone from Moog Music for a number of years at this point). As most of you know, the Moog Music that exists now is actually Big Briar renamed; the original Moog Music has long since folded. So I got curious as to which ID Moog is using now. Turns out the current production Voyager uses 04, the original Moog Music ID, and presumably 02 is no longer in use. The MMA's rules today state that a manufacturer must renew their ID each year, or it can be reassigned (much like Internet domain names). However, I doubt that the MMA will reassign 02, even if Moog is no longer renewing it.
Some of you may be wondering now who those other companies in the American and European groups are. Other than Moog/Big Briar and Lexicon, they are all gone from the music industry now. Sequential you know about, the creator of the mighty Prophet-5 and the co-inventor of MIDI. Oberheim is another familiar name to synth perfomers. Octave/Plateau had an interesting run in the '80s; they created what was probably the first rackmount synth, the Voyetra-8, with a remote keyboard that connected to it via a (non-MIDI) control bus. A couple of years later, they introduced the first computer-based sequencer software, which was also called Voyetra, and at that time they changed the company name to Voyetra. This was a very popular package from 1986 up until about 1992, when competition overcame it.
Passport Designs was also a music software company, coinciding with the MIDI era. Like Voyetra, they marketed a sequencer package, called Trax, that was popular in the early days of computer sequencing. They are probably best known for Alchemy, a sample librarian marketed in the 1990s. They were bought out and the existing product line discontinued in 1998. SIEL was an Italian synth manufacturer of some note, one of the two most successful of the 1980s European manufacturers (along with Crumar). They were bought out by Roland in 1987. Bon Tempi was a European maker of combo organs and string machines. They are still in business, but no longer manufacture any keyboard instruments other than some toys. It's curious that they were one of the first to get a manufacturer ID, since I don't think they ever marketed a product that used MIDI.
Despite the demise of these companies, the field of products that use MIDI has expanded dramatically since that 1984 specification. At the time, it was anticipated that only a few dozen manufacturers would ever request or need IDs. But a funny thing happened on the way to the 21st century: the MIDI-using synth field grew dramatically with the advent of soft synths and plug-ins, plus there was an unanticipated explosion in the number of non-synthesizer applications of MIDI. It's common now to find the protocol in use controlling not only studio effects and pipe organs, but also totally non-musical applications such as video editors and light show controllers. By 1990, the pool of available IDs was running out. So the MMA created an "escape hatch": They redefined the manufacturer ID standard to state that an ID byte of 00 indicates that the following two bytes constitute an extended ID field. This opened up another 16,384 ID numbers. They retained the convention of the geographical groupings: the numbers from 00 00 00 to 00 1F 7F are the American group, the 00 20 00 to 00 3F 7F group is the European group, and the 00 40 00 to 00 5F 7F group is the Japanese group. The group from 00 60 00 to 00 7F 7F is apparently going to be a new Asian (China/Russia/Korea/India et al) group, but I don't think any of those have been assigned yet.
There's a list on the MMA's Web site of the most recently assigned IDs (not updated in about a year, unfortunately), and there are some interesting names that pop up. I wonder why National Semiconductor and U.S. Robotics need MIDI IDs? Nvidia (manufacturer of computer video cards) appears, as does supercomputer maker Silicon Graphics (I didn't realize they were still in business). Some old-school names in the professional audio business appear: Electro-Voice, Shure, Otari. Is someone designing MIDI-controlled microphones and loudspeakers? ID 00 01 51 is assigned to Research in Motion, the Blackberry maker. Can you remotely control your Blackberry via MIDI? If so, why? There's a few sad notes too: among the IDs marked "relinquished" is 00 20 50, which belonged to Hartmann GmbH, maker of the brilliant but ill-fated Neuron.
Anyway, what prompted all this was this posting on Matrixsynth, which points out that Dave Smith Instruments is using ID 01, which was Sequential's. Nice to know that the MMA hasn't forgotten their roots. If anyone should be entitled to use Sequential's number, Dave Smith is the guy.
Monday, December 15, 2008
Procuring the 650 will allow me to dedicate the JKJ Electronics (RIP) CV-5 to the EML 101. For the past several years, the CV-5 has done double duty, interfacing to both the 101 and the modular. This has been a pain because the EML uses 1.2V/octave scaling, so every time I move it from one to the other, I have to re-scale it. There are, however, a lot of convenient features about the CV-5, which I'm going to have to work a bit to get the 650 to do the same things. One thing I appreciate about the CV-5 is that it contains a built-in MIDI-controlled panner; you plug in a mono audio signal, and it produces a stereo out. The panning is contolled by the MIDI Pan continuous controller, and it's internal to the interface. This is nice for automating panning during mixing; I do a lot of virtual-mix techniques, and to make that work you need the mixdown to be absoultely as automated as possible.
Other handy features of the CV-5: It processes pitch bend messages and adds or subtracts pitch bend from the pitch CV output, and you can set the bend range via MIDI. It also has a built-in LFO which can be added to several of the CV outputs, and the LFO can be sync'ed to MIDI clock. (It also has the ability to convert MIDI clock to DIN sync, but I don't use that.) A built-in portamento can also be programmed via MIDI and added to the pitch CV output, and there are several choices for note priority, velocity and aftertouch routing, and gate/trigger modes. (This includes S-trigger output, which is another thing I don't use since I'm not driving a Moog with it.)
Those are the sorts of things I've been looking for in a replacement for the CV-5, and the 650 fills the bill. Plus, it is of course built in the MOTM form factor, which the CV-5 is not. And, the 650 has lots of additional goodies, including built-in sequencing, microtuning tables (which work by offsetting the pitch CV output depending on what note is played), and the ability to update the firmware via MIDI. One little glitch is that there is an updater program for Windows and Mac OS9, but not OSX. I'm going to ask Paul S. if he's willing to document the updater protocol; if so, I'll write an OSX updater program and give it away to other 650 owners under GPL-type terms.
Saturday, December 6, 2008
Wednesday, November 26, 2008
Sunday, November 16, 2008
The wall wart power supply gets pretty warm. It's rated 1A so, with the new regulator (which probably dissipates more current than the old one), it's running right on the edge. Wall warts rated higher than 1A are kind of hard to find. I might replace it with a 1.5A open-frame linear.
Friday, November 14, 2008
Friday, October 31, 2008
The Moog Archives seems to have resolved the dilemma. It now appears that the Eboard folks do in fact own production #1001. Audities also owns a unit #1001 -- but it's not a production unit; it's a prototype Model C! (All of the vintage production Minis are Model D, except for the handful known as the "Welsh Minis".) The Audities photo that I reproduced in the March post is not this synth. Here is that synth:
Note a few things about it. The big thing is the pitch and mod wheels -- they are completely different from anything that ever appeared on a production Mini. In fact, I'm not sure that they are wheels at all; they may be sliders. Second, note the A-440 oscillator switch; it's a plain toggle switch rather than the typical rocker, and it's a bit to the right of where the production Mini has it. Third, the pilot light: It's higher up on the panel than the production article.
(The thing sitting on the panel that covers the keyboard keys' hinge mechanisms appears to be a ribbon controller of some sort. My guess is that it was added later.)
I had speculated in the March post that Moog may have assigned serial numbers to prototypes and then later re-used those numbers for production units. And sure enough, it appears that that's what happened here. Another clue to the Eboard one is the white-background logo plate, whose legitimacy I had questioned back in March. The Moog Archives now says it's legit; it's the earliest version of the R. A. Moog logo. Unfortunately, we don't have the Audities one to compare to; if it ever had a logo plate, it appears that it was removed when the ribbon controller was installed.
I think we can conclude that the Eboard Museum legitimately has the first production Minimoog. The Audities Foundation has a prototype.
Saturday, October 18, 2008
Wednesday, October 15, 2008
So let's start by getting a couple of things on the board out front. The VCO, VCF, and VCA circuits are nearly identical. "How can you say that", you might ask, "when the 106 uses those 80017A's that keep failing, and the 60 doesn't?" Consider: The 60 uses a VCF filter circuit based on the IR3109 quad OTA. It uses a BA662 VCA to control the resonance. A second BA662 serves as the voice's VCA proper. As for the 106? The notorious 80017A is really just an encapsulation of three ICs and some resistors. The IC's? An IR3109 and a pair of BA662s! It's the same circuit, just in a smaller package. A lot of people don't realize that when you look at an ordinary IC, most of what you see is packaging; the actual integrated circuit is a tiny bit of silica embedded in the plastic. Roland bought a bunch of unpackaged 3109s and 662s and had someone encapsulate them, and voila, the 80017A was born. Similarly, the Juno-60's DCO circuit: the counter IC that times the DCO, the reset transistor, and the wave shaping circuitry are encapsulated into the much-less-infamous (because it seldom fails) MC5534 in the Juno-106. The voice circuits are, for all practical purposes, the same.
So assuming that there is a difference in sound (and I've heard enough reliable witnesses say there is), where could it be coming from? Let's take a look at the rest of the audio processing: the portion that follows the summing amp, which combines the six individual voice signals into a single mono signal. A lot of Juno players don't realize that there is not a highpass filter per voice; Roland cleverly placed the HPF switch on the panel to suggest that the HPF precedes the VCF, but it isn't so. There is only one HPF circuit for the whole synth, and it works on the summed mono output of the voice circuits. Following the HPF is a seventh VCA, which is tied to the VCA level control on the panel (that bit looks like a kluge; maybe I'll write about it later), and then the chorus circuit, which takes the mono input and produces a stereo output. There's a bit more stuff for the master volume control and the various outputs, but all of that is bog-standard IC amp and buffer circuits.
The chorus circuit on the two synths looks the same; there may have been minor improvements that have eluded my quick scan of the circuits, but they both use the same bucket brigade ICs, the same control circuits, and the same gain make-up circuits (there is no noise reduction, which anyone who has heard either synth on headphones has already realized). However, I found some differences in the HPF circuits. First of all, on both synths, the HPF is not a voltage-controlled filter. It's basically a set of four passive RC filters. The panel or recalled setting controls an 1-to-4 analog demux which routes the signal through one of the four.
The one on the Juno-60 is pretty straightforward. Here's the portion of the schematic:
The four outputs of the analog demux are on the right (the two inputs from the control CPU are on the bottom, and the mono signal enters at the top left at pin 3). The pins are labeled as to the corresponding position of the HPF switch on the panel. As you can see, going up from output 1 to output 3, the signal gets routed through progressively smaller-valued capacitors; the smaller the cap, the higher the cutoff frequency. The output for position 0 has no cap; it's just a straight wire, so position 0 of the HPF is actually no filter at all. It's straight through.
As you can see, it's more complex. First things: I am pretty sure that the CPU is sending the two input signals, A and B, inverted. Therefore, the pin labeled "Y0" corresponds to position 3 of the HPF switch, "Y1" is position 2, etc. The opposite interpretation doesn't make sense when you look at the circuit.
Now note the first difference: The straight-wire output corresopnds not to position 0, but to position 1. The circuits for positions 2 and 3 look pretty similar to the ones on the Juno-60. But what's all that business connected to the position 0 output, around IC4b? Well, it sort of looks like a Sallen-Key filter, as used on the Yamaha GX1. What's it doing? Note C8, the 0.01 uF cap shunted to ground. That's a lowpass filter! This part of the circuit is acting like a bass boost. (C6, I think, is just there to keep IC4b from self-oscillating.)
Second difference: Note IC4a. In both the 60 and the 106, the "seventh" VCA that I mentioned earlier immediately follows this HPF circuit. Although the VCA is an oddball part ("uPC1252"; the only data sheet I've found is in Japanese, but some Googling reveals that it was manufacturered specifically for dbx), it doubtless is based on an OTA circuit, and like all OTA circuits, it loads the input some, particularly as the gain is decreased. The Juno106 uses IC4A to buffer the input to that VCA. The Juno-60 doesn't have that buffer; it couples almost directly, only separated by a DC-blocking capacitor. That means that the 1252 VCA is loading down the outputs of the passive filters on the 60, which introduces high-frequency rolloff. So the HPF actually acts a bit more like a fairly wide bandpass filter, particularly as the VCA level control on the panel is turned down and the input impedence of the 1252 decreases. That doesn't happen on the 106 because the buffer amp provides a constant high input impedence for the HPF output.
Third difference: The analog mux used is a different part. The Juno-60 uses a 14051; the 106 uses a 4052. They work basically the same way, but possibly the properties of the analog portions of the two circuits are different. I need to look into that some more.
To me, the biggest difference is in the configuration of the filters, with the 106 providing one "high pass" position which is actually low pass. And, the loading of the filter circuit on the 60 is probably significant; circuits with some rolloff above 8KHz or so are often perceived as "warmer" by listeners. Maybe I'll have to get a 60 so I can compare them myself.
Tuesday, October 14, 2008
About the organ: It's an A100, one of the spinet styles that Hammond produced mainly for the home market. Despite that, it's a full-up tonewheel organ, with exactly the same layout, sound generation, and controls as the venerable B3. In fact, if you are looking for that B3 sound but find the price tag daunting, you can pick up an A100 and get that exact same sound for $500-1000 less. I don't know why it is that the A100 should sell for that much less than the B3 when they both use the same components. The only difference is that the A100 contains a built-in power amp (two, actually) and speakers, so you don't have to have an external tone cabinet to play it. (Despite that, it does have a socket for connecting a Hammond tone cabinet, or with the proper adaptor, a Leslie.)
The A100 weighs about 350 lbs., and this one has a magnetic attraction for my toes. I actually dropped it on my toes once! So, of course, as we were moving it in, my shoe got stuck in a gap in the floor between the hallway and the room, and it nearly ended up on my toes again. But I eventually got myself unstuck, and now here it resides in all its glory:
Once it was in place, the first step, after a good vacuuming, was to unlock the generator's locking bolts. The generator, and all of the rest of the rotating mechanism, is suspended by a set of springs for mechanical isolation while in use. For transport, it has to be locked down to avoid damage. Here is one of the locking bolts, protrouding from the underside of the generator shelf:
Next step: oiling the generator and motor/scanner assembly. The generator has two funnels on top of it. To oil, fill each one of these funnels with Hammond oil once, and then let it drain. The oil runs into a resevoir and from there to a bunch of little cotton threads which convey it, via capillary action, to the many bearings inside the generator. I don't have a good shot of the funnels (there will be a video of this part up next week), but here is the front of the generator:
The motor/scanner assembly has a little pot on top of the motor which contains a cotton pad. To oil, squirt oil on the pad just to the point of saturation. More will not do any good; it will just wind up all over the place and possibly crud up the contacts of the scanner. Here's a shot; the motor is the square box, with the oil pot on top of it. The scanner is to the left:
Note that this is the run motor. The start motor is at the other end of the generator; it doesn't require regular oiling. However, while I was in there, I put a bit of oil on the mechanism that couples the start motor to the generator shaft. This particular organ has always had a bit of trouble with the start motor not engaging the shaft, and some oil seems to help.
Now, since the organ hasn't been started for a while, I'm going to wait a few days for the oil to propagate through the mechanism. As it happens, I had to go out of town for a few days on business anyway.
The next step was to reinstall the tubes, which I had removed and packed away before the organ was moved from the old house. This organ has a bunch of tubes carrying the Hammond brand. Now, Hammond didn't actually make its own tubes. I'm not sure who made them. They are all noted "Made in Holland". Here's a 6Y5 full-wave rectifier tube, from the reverb power amp:
And a 12AX7 from the preamp:
So when I get back, it will be ready to attempt to start. Before I do that, since it hasn't been on for a while and the filter capacitors are likely completely discharged, I need to come up with a way to limit the power inrush the first time it's turned on. I think I know where I can borrow a variac, but if I can't find one, the backup plan is to plug together all of the long extension cords I bought while were were building the house, about 200' worth, and plug the organ into that. That much wire should do a fairly decent job of limiting the inrush. I'll turn on the run switch for a few seconds, without trying to start it (I'll bet it won't start with that much voltage drop). Then I'll get rid of all the extension cord and attempt to start it.
A few glam shots: Some of the drawbars.
The start and run switches. Older Hammond tonewheel organs have a run motor (the one in the photo above) which is an old-style synchronous motor. It does a fine job of regulating speed once it's started, but it does not have enough torque to start by itself. So there is a second, compound motor which does the starting. It's sort of like starting a car: You switch on and hold the start switch (it's spring loaded) for about six seconds, while the start motor cranks it up. Turn on the run motor, wait a second or two for things to stabilize, then let the start switch go.
Something that a lot of Hammond players don't know about: This is the patch panel that alters the fixed presets (the reverse keys that don't correspond to a set of drawbars). You change them by moving the wires from one terminal to another. Hammond put a paper sticker on the back of the generator compartment cover that explained how. I was surprised to find this still intact when I first took the back off of mine, and I preserved it. I'll summarize it in a post next week. Note the little white cloth sack hanging from the far edge; it contains spare terminal screws. I've got some special plans for this panel, which I will explain in a future post.