Saturday, May 23, 2020

A few pics of the modular

Here's where we are, with the new case.  Apologies for the weird angles; it's in a tight space and I was trying to maneuver it so it would not be backlit by a window:

Three vertical rows and two rows set at a 45-degree angle, plus a pseudi-CP row.   Approximately 105 units of MU.

Modular, top portion
It's a mixed-format modular, with MU, MOTM, and a few Modern-A.  

Modular, bottom rows
The angled rows -- mostly still room for improvement.  I just got the mounting rail for the bottom row, and the filler panels, installed this week.  The empty space above is the CP row; I haven't made a filler panel for it yet.
Current lineup:

  • Top row:
  1. Synthesis Technology MOTM-650 four-channel MIDI-to-CV interface
  2. Synth Tech MOTM-820 voltage controlled lag processor, built from a kit by me
  3. Synthetic Sound Labs 1130 Ian Fritz voltage controlled ultrasonic oscillator
  4. Synth Tech E350 Morphing Terrarium wavetable oscillator, reformatted to MU by Low-Gain Electronics
  5. Synth Tech E340 Cloud Generator, reformatted to MU by Low-Gain Electronics
  6. SSL 1900 mini oscilloscope, a Dave Jones Design O'Tool reformatted to MU by SSL
  7. SSL 1310 voltage controlled digital delay
  8. Synth Tech MOTM-510 WaveWarper waveform math processor, built from a kit by me
  9. Corsynth C105 Lo-Fi Machine voltage controlled noise generator and downsampler
  10. Q130 clipper / rectifier
  11. Encore Electronics frequency shifter
  12. Catgirl Synth CGS57 voltage controlled switched-capacitor filter/oscillator, with panel by Bridechamber; built from a kit and modifications by me
  13. Cynthia StereOSpace stereo field manipulator
  • Second row:
  1. (3) Synth Tech MOTM-310 micro VCO, built from kits by someone else (I don't know who)
  2. Q141 oscillator aid, has behind-the-panel wiring to the adjacent Q016
  3. (2) Q016 VCO
  4. Q161 oscillator mixer, has behind-the-panel wiring to the adjacent Q016
  5. Synth Tech MOTM-890 5-channel micro mixer, built from a kit by me
  6. STG Soundlabs Post Lawsuit 4075-style VCF
  7. STG Soundlabs Sea Devils VCF
  8. Rob Hordijk Design voltage controlled phase shifter / filter
  9. SSL 1021 Nyle Steiner VCF
  10. Synth Tech MOTM-440 discrete OTA VCF, built from a kit by me
  11. Synth Tech MOTM-410, triple resonant filter; built from a kit and modifications by me
  12. Cynthia Steiner Synthacon filter, with Modcan-A panel reformatted to 1/4" jacks by me
  13. Q107 multimode VCF
  • Third row:
  1. Free State FX Macro Digital Oscillator -- a Mutable Instruments Braids reformatted to MU by FSFX
  2. Synth Tech MOTM-101 noise generator / sample & hold, built from a kit by me
  3. SSL 1250 quad LFO
  4. Synth Tech MOTM-120 voltage controlled LFO, built from. a kit by me
  5. Encore Electronics universal event generator
  6. Q108 dual VCA
  7. (2) Synthesizers, com ADSR envelope generators
  8. Q179 Envelope++ complex envelope generator
  9. Synth Tech MOTM-190 dual VCA / ring modulator, built from a kit by me
  10. Synth ech MOTM-890 5-channel micro mixer, built from a kit by me
  11. Q108 dual VCA
  • CP row:
  1. Dual 4-way / single 8-way passive multiple, built by me
  2. Gate / trigger generator, built by me
  • Fourth row (slanted):
  1. Oakley Sound Systems EFG envelope follower / gate generator, built by Krisp1
  2. STG Soundlabs integer divider
  3. Q128 dual voltage controlled switch
  4. Q119 3-row X 8-step analog sequencer
  5. Q123 Standards control voltage generator
  6. Q125 control voltage processor
  7. Corsynth C107 dual VCA / mixer
  • Fifth row (slanted):
  1. Q155 Curver non-linear amplifier
  • Not currently installed:
  1. STG Soundlabs Mankato VCF (the SSM 2164 IC has failed)
  2. Ken Stone / Cynthia Super Psycho LFO (circuit board is de-laminating)
  3. Second Q128 dual VC switch (has a short somewhere between +15V and ground)
  4. Several kits in various stages of construction

Saturday, March 24, 2018


There have been several institutions which have been important in the development of electronic music in the 20th century.  Here are brief descriptions of a few of them.

Bell Telephone Laboratories

Bell Labs, as it was usually known, was established in 1925, as several pieces of the corporate amalgamation known as the Bell System decided to consolidate their research and development efforts.  The Labs, created as a joint entity between AT&T and its captive manufacturing company, Western Electric, set up shop in a building in lower Manhattan in New York City.  As the labs grew, it began expanding into New Jersey (where land was cheap at the time), and then eventually to a handful of locations around the eastern and central United States, including notably the Chicago area.

Bell Labs was charged by its owners to perform research and development related to telephony and telephone switching systems, transmission systems, and end-user devices.  But prior to 1984, with AT&T enjoying a monopoly on telephone service through most of the USA and its profits being more or less guaranteed by the federal government, funding was available to branch off into basic research in areas only peripherally related to telephony.  Eventually this led to several fundamental scientific and engineering advances, including the invention of the transistor, pioneering work in satellite communications, the development of the C programming language and the Unix operating system, and the discovery of the cosmic microwave background radiation (a key discovery in proving the Big Bang theory of the creation of the universe).

Musically related, research into finding more efficient ways to transmit the human voice led to the development of the vocoder and voder in the 1930s.  After WWII, the Labs engaged in some of the first experiments in digital sound processing, leading to pioneering work in computer music by Max Mathews, and later Hal Alles and Laurie Spiegel.  Mathews developed the MUSIC series of music-generating computer programs, from which spun off Csound and CMIX, as well as a host of interface devices allowing a performer to interact with the software in real time.  In the mid-1970s, Alles, with input from Spiegel, developed the Bell Labs Digital Synthesizer aka the Alles Machine, one of the first digital devices designed specifically to produce music.  The Alles Machine combined concepts in frequency modulation and additive synthesis; it directly influenced the design of the Crumar GDS and the Synergy digital sequencer of the late 1970s, and indirectly contributed concepts to the Yamaha DX7.

Funding for basic research at the Labs dried up after the court-ordered breakup of AT&T in 1984.  Owned by Lucent Technologies after the breakup, the Labs wound down activities not directly related to telecommunications, and began divesting itself of some of its research facilities.  Today, what remains of Bell Labs is owned by Nokia; it remains headquartered in its Murray Hill, NJ location where it has been since 1966.  A few other locations in New Jersey are still open and a few former Labs facilities have been sold intact to other companies.  The rest have been closed and the properties sold.  The original Manhattan location has been redeveloped into an arts community and is now a National Historic Landmark.

Columbia-Princeton Electronic Music Center

Composer and Columbia University professor Vladmir Ussachevsky became interested in tape studio techniques in the early 1950s, after the university's music department acquired one of the first Ampex tape recorders.  In 1957, he and Milton Babbit, a cohort at Princeton University, applied for a Rockefeller Foundation grant to establish an electronic music studio.  Babbit was aware of the RCA Mark II synthesizer, and he convinced RCA to loan it out to Columbia.  Starting in 1958, the duo began composing on the Mark II and opened the Columbia-Princeton Electronic Music Center, opening it to other composers such as Edgard Varese and  Charles Wuorinen.  The Center's focus, as driven by Ussachevsky, was always on "serious music" and modern classical composition.

By 1970, the Mark II was considered obsolete, and the Center turned to computer music.  Led by composer Charles Dodge, the Center began using the University's IBM 360 computer to realize digital compositions using various software packages.  All-night computer runs were necessary to produce a few minutes of music.  To hear the music, the data was written to digital tape and transferred to another computer which was equipped to a digital-to-analog converter, whose output was recorded on analog tape.  All of the conversion equipment was built by Columbia engineers.  Dodge released several albums of music that he produced this way, and the Center also saw work from other composers such as Alice Shields and Mario Davidosky.  

But by 1985, Ussachevsky was in poor health and Babbit's interests had turned away from electronic music.  Princeton ended its association with the Center, and the facilities fell into disuse.  Brad Garton, the current director, reorganized the Center in 1995, bringing in new equipment and new composers, and renaming it the Columbia Computer Music Center.  Today, the Center focuses mainly on teaching.  The RCA Mark II is still there, but is said to be in poor repair.

San Francisco Tape Music Center

A group of influential West Coast experimental musicians, including Morton Subotnick, Terry Riley and Pauline Oliveros, formed the San Francisco Tape Music Center collective in 1962.  As the name suggests, the original focus was on tape manipulation; the collective had little funding and no equipment other than that individually owned by the members.  Using facilities provided by radio station KPFA, they presented live performances of mostly pieces played on conventional instruments combined with manipulated tape.  However, around 1964, Donald Buchla joined forces with the Center and began bringing in components and prototypes for his initial modular synthesizers, for the other members to try out and critique.  With their feedback, Buchla gradually assembled the pieces of what became the first Buchla 100 series modular synth.  The completed synth was premiered by the Center in 1966, with Oliveros, Subotnick, Ramon Sender, and Buchla himself performing.

The Center did not last long after this.  Subotnick tried to fix the Center's perpetually short funding situation by obtaining a grant from Mills College (where he was a professor) in 1967.  But a condition of the grant was that the center come under Mills' management.  This proved stultifying, so much that over the next two years, all of the original members (including Subotnick himself) departed, taking their equipment with them.  By 1969, neither any of the original members nor any equipment remained.  But the Center's place in the history of electronic music is secured by its role as the crucible of the Buchla modular synths, as well as advancing the careers particularly of Subotnick, Oliveros, and Terry Riley.  Subotnick employed the Buchla modular synth to record the canonical electronic music album Silver Apples of the Moon in 1967.  

BBC Radiophonic Workshop

The British Broadcasting Corporation created the BBC Radiophonic Workshop in 1958, as a studio to create electronic theme and background music, and sound effects, for BBC radio and television programming.  BBC studio musicians Daphne Oram and Desmond Briscoe had begun using tape studio techniques to produce some music for BBC dramas, and they convinced the network to consolidate all of its electronic audio production into one facility, the Workshop.  Over the next four decades, the Workshop would produce music and effects for countless BBC shows, as well as some non-commercial album releases, and serve as an incubator for musicians and engineers ranging from Delia Derbyshire to Mark Ayers.

Of all of the multitudes of music productions that the Workshop engaged in, it is probably still known best for one of its earliest efforts -- the original theme to the Doctor Who sci-fi show, produced in 1963.  Composer Ron Granier wrote out a score and brought it to Derbyshire to execute.  Using the typical tools of a tape studio -- a few tape machines, some audio test equipment, and a collection of found objects that were hit, bowed, shaken, twanged, dropped, or coerced to make noise by any means handy -- Derbyshire assembled the theme, using three separate reels of tape, each containing hundreds of splices, and hand-synced together to produce the master tape.  Granier, on first hearing the results of his score, famously said, "Did I write that?"  The theme, and other music and effects produced for the show, helped make Doctor Who a hit that is now running (with some breaks) into its fifth decade of production.  Although the theme has been re-made numerous times for subsequent seasons, some long-time fans still swear that Derbyshire's original is the best, and to this day the show still uses some of the original sound effects, including the Tardis "engine" sound created by Brian Hodgson.  Here you can hear the original theme, all two minutes and twenty seconds of it, along with an early version of the opening video sequence:

Near the end of the 1960s, the studio began to introduce synthesizers.  EMS founder Peter Zinovieff was an acquaintance of several of the Workshop musicians, and the Workshop became an unofficial beta test site for EMS gear, in the same manner that the San Francisco Tape Music Center had been for Buchla.  This caused a split between the older and younger musicians, the former of which had been trained on the tape studio techniques (which were closer to what we would think of as sampling today), and the late-1960s analog synths did not suit them.  A number of them, including Derbyshire, left the Workshop between 1968 and 1973.  However, the younger members carried on and finally managed to pry some money out of the BBC for equipment investments.  Zinovieff twisted the Workshop's arm to buy one of the massive Synthi-100 synth-in-a-desk units, and later on Hodgson (who had returned to become the Workshop director after several years away) persuaded the powers that be to buy one of the first Fairlight CMI units -- which, in a way, brought back some of the old tape studio techniques.

The Workshop continued its good work up into the 1990s, when the BBC went onto a "full cost accounting" basis, and began comparing the costs of the Workshop to the costs of using outside studios and contractors, a comparison on which the Workshop usually came up short.  Subsequently, the BBC began layoffs and moving work out of the Workshop.  As synthesizers had become less expensive, an institutional studio no longer had an equipment advantage over smaller outside studios and individual musicians.  One of the last jobs given to the Workshop, for which it had unique expertise, was cleaning up the audio on old programming -- removing pops, crackles, noise, and bad-splice burbles.

On April 1, 1998, forty years to the day after its founding, the BBC Radiophonic Workshop closed.  Mark Ayers set about archiving all of the Workshop's tapes and produced material, a task at which he continues today.  


This Paris institute for electronic arts stems from an initiative created by French President Georges Pompidou in 1970.  Pompidou asked modern classical composer Pierre Boulez to began assembling a place where French composers would have studio space and equipment to work in composition and recording of electronic music.  A main focus of the center would be to pair composers (who would not necessarily be knowledgeable of electronics or computer programming) with engineers and technicians who could help realize the composers' ideas.  The center would be named IRCAM, which is an acronym for the French Institut de Recherche et Coordination Acoustique/Musiquewhich conveniently translates roughly to the English "Institute for Research Coordination into Acoustics and Music".

It took Boulez several years to raise sufficient funding to acquire space and equipment.  The center finally opened in 1977, and straight away focused on computers and digital synthesis, as well as modern classical composition in general.  In the 1980s, Miller Puckette created the first versions of what became Max/MSP at IRCAM, and the center maintains an extensive library of music software which is available for download to registered users.  The center has also expanded out into aspects of signal processing for industrial and scientific uses.

Friday, March 9, 2018

Review: SSL 1900 O'Tool

Always wanted an oscilloscope integrated into your modular?  Euro modular users have the Doug Jones Design O'Tool, a handy scope with a little color LCD display mounted in a module.  Fortunately for us 5U guys, Doug Slocum took it upon himself to reformat some into MU format, and the result is the Synthetic Sounds Labs Model 1900 O'Tool.  Since the days of Keith Emerson, modular users have wanted to find a way to mount an oscilloscope and be able to conveniently route signals to it.  Problems with this have always included the size and weight of traditional scopes, their incompatibility with the panel formats and mounting methods that modulars use, and signal compatibility issues.  (Who has room for a Tektronix 464 in their case?  Or the $$$ for a Tek MDO3000?  Me neither.)

The O'Tool solves these problem neatly, and provides many more capabilities than your average Ebay-special analog Tektronix.  The O'Tool consists of a digital signal processing system coupled to a color LCD screen, packaged in a modular synth panel format.  It is powered from conventional +/- 15V power, and easily accepts the usual modular synth signal levels and types.  No heavy CRT, no high voltages, and no four-figure price tag.  Available functions consist of scope screens, voltage measurement, frequency measurement, signal level metering, and spectrum analysis.

This version of the O'Tool is physically packaged as a 1U wide Dotcom/MU format module.  When I received it, I was a bit concerned at first because the screen is pretty small, and my eyesight is not what it used to be.  However, the contrast and resolution are excellent, and I've had no trouble reading the screen.  The screen does take up as much of the width as could fit without structurally compromising the panel (which would make it difficult to package this in an MOTM-format module).  There are six input jacks, a pair for each of the input channels, and a pair for an external trigger signal for the scope modes.  Each pair is simply wired together; this allows them to be used to "patch through" a signal that needs to go somewhere else, so you can conveniently insert the O'Tool into a patch without needing a mult.

Underneath the screen is a row of four small pushbuttons.  The leftmost one selects the operating mode and screen to be displayed.  Pressing the mode button repeatedly cycles through the screens.  The other three buttons are "soft keys" whose functions vary depending on the selected screen.  Each screen has a small legend at the bottom showing what the soft buttons do in that screen.  The available screens are:
  1. Single channel voltage/time scope, displays channel 1 only
  2. Dual-channel voltage/time scope, with the two channel signals overlaid.  Channel 1 is displayed in red, and channel 2 in green.
  3. Dual-channel voltage/time scope, split screen.  Channel 1 is displayed in the top half, and channel 2 in the bottom half.
  4. Bar-graph averaging voltage display, described further below.
  5. VU/peak level meter
  6. Spectrum analyzer
  7. X-Y oscilloscope
  8. Frequency counter
  9. Digital voltmeter

Scope Mode Screens

In the first three screens, the three buttons allow the user to select the time per horizontal division, the displayed voltage range, and the trigger source and mode.  Pressing each button cycles through the available values (which can be a bit tedious in the case of the time/div setting since there are many possible values).  The screen is underlaid with a division grid, shown in dark blue, which appears behind the signal traces.  The available time per division settings range from 100 microseconds per division to 5 seconds per division.  There are six horizontal divisions across the screen, so at the maximum setting, the time for one screen sweep is 30 seconds.  The voltage range differs from oscilloscope convention, and from the time range, in that it applies to the entire vertical span instead of per grid division.  Available ranges are

  • Plus/minus 5V DC
  • Plus/minus 10V DC
  • Plus/minus 10V AC (DC signals/offsets are filtered out)
  • 0-5V DC
  • 0-10V AC

Here are some screen shots of the three scope mode screens.  (All of the photos from here through the end of this post were photographed from the actual screen.  I cropped the shots, and added some contrast enhancement in order to get rid of room light reflecting off of the screen; otherwise, the photos are unretouched.  The somewhat fuzzy look is caused by magnification of the photos, and the fact that I had to use the camera's digital zoom because I don't have a proper macro lens.  Bear in mind that these photos are larger than the actual screen.  All of the waveforms are from a Q106 VCO.)

This is the single-channel mode, showing a sine wave:

The dual-channel stacked mode, showing two waveforms from the same VCO.  Channel 1 is shown in red and channel 2 is in green.  Here, channel 1 (the sine wave) is chosen as the trigger signal.

The dual-channel layered mode, with the same two waveforms.

The same screen, but with channel 2 (the sawtooth wave) chosen as the the trigger channel  

The trigger can be set to trigger on either of the two input channels, or on the signal connected to the external trigger input jacks.  It can also be set to no-trigger mode, in which the scope free runs.

Triggers and Triggering Modes

The concept of triggering, for a scope in general, can be a bit difficult to understand at first.  The reason that scopes have triggered modes is to make the waveform "stand still" on the display.  Considering what would happen if the scope was free running; that is, if it scanned continuously.  Unless the waveform you are trying to display happens to be divisible by the scan rate, the wave won't be stationary on the screen; it will begin in a different place in its cycle on each scan, resulting in a display that jumps around.

To solve this problem, a scope has some sort of detection of a certain part or feature and then generates a trigger signal, not unlike the trigger signals that we use in our synths.  The trigger causes one horizontal scan to happen; after that scan is completed, the scope waits until it sees the trigger again, and then it does another scan and updates the display, etc.  By doing this, the scan always starts at a chosen point in the signal cycle, so that the displayed waveform remains stationary and you can actually look at it. 

The O'Tool can use either input channel as the source to the trigger detector, or it can use the signal at the "Trigger" input  There are five trigger modes:

  • Trigger 1.  Uses channel 1 as the trigger source.  If the ±5V or one of the ±10V ranges are selected, the trigger is generated when the signal crosses the horizontal axis in the positive-going direction.  If the 0-5V or 0-10V range is selected, the trigger is generated when the signal crosses 1.25V in the positive-going direction.
  • Trigger 2.  Same as trigger 1 except that it uses channel 2 as the trigger source.
  • Ext 0V uses the external trigger input as the trigger source.  The trigger is generated when the signal crosses the horizontal axis in the positive-going direction.
  • Ext 1V is the same except that the tigger is generated   when the signal crosses 1.25V in the positive-going direction.
  • No Trigger is a free-running mode; the scan runs all of the time, unsynchronized to the input signals.  

The trigger selection allows you to select either channel to be fed to the trigger generator.  You can even do this in the single-channel mode; you can display channel 1 and trigger off of channel 2.  The display may look different depending on which channel you trigger from.  Consider the screen shots of the two stacked-mode screens above.  In the top one, the trigger is on channel 1, so it triggers when the sine wave crosses the X axis going up.  The nature of the Q106 VCO (as with most sawtooth-core VCOs) is that the positive peak of the sine wave is where the positive peak of the sawtooth wave is.  So the top half starts with the sine wave heading up from zero towards its peak, while the sawtooth display starts with the last 90 degrees of its cycle.  In the second photo, we switch the trigger to channel 2. Now we are triggering on the positive-going zero crossing of the sawtooth, which is pretty much instantaneous.  So we see the display start with both of the waveforms descending from their peaks.  

Level Displays

The bar graph display is interesting but kind of hard to describe.  Basically, what it does is show how much time -- what percentage of the cycle -- a signal spends at a given voltage level.  The more the signal is at that a given level, the brighter the bar will be at that level.  In the shot below, channel 1 is a square wave and channel 2 is a sawtooth.  The square wave, of course, alternates sharply between the positive and negative peaks; hence the two discrete bars.  The sawtooth falls linearly and so all of the voltage steps get the same saturation, resulting in a spread of evenly lit bars.  (Not sure why the top one is a bit dimmer; may have to investigate how the sawtooth waveform is looking coming out of that VCO.)  The display range can be adjusted, and "fast" or "slow" averaging can be selected.

The VU and peak level meters do what you expect them to: display the average and peak voltage level of an alternating signal.  The display shows VU and peak levels for both of the input channels; the VU displays are grouped on the left, and the peak displays on the right. The VU indicators appear to be a true RMS measurement, as they display identically to the peak levels when a sine wave is input.  I cannot say, however, that the ballistics of a true VU meter are emulated properly; I don't have any means to measure it.  There are three selectable scale modes, which effect what reference level is used for the meters, and how the scale on the peak meters is displayed.

Like many such meters, the display uses color bars to display different regions of the measurement levels.  The blue horizontal line indicates the reference signal level (the level that is considered a "100%" signal) for whatever scale mode is in use.  Levels below and at the line are displayed using green bars.  Above the line, on the peak side, the first three steps are displayed using yellow bars, and levels above that are displayed with red bars.  On the VU side, all levels above the line are displayed using red bars.

This screen has three modes, which effect where the "100%" line is, and how the peak display is scaled.  The modes are:
  • +4dBu: In this mode, the VU scale conforms to the standard recording industry definition, in which zero VU = +4 decibel volts RMS, or dBu.  This in turn is defined as 1.228 volts RMS.  (It's defined at 1000 Hz, but that is not supposed to matter across most of the audio range.  I'll have more to say about this further down.)  The peak scale displays dBu and the blue line will pass through +4 on that scale.  (It always passes through zero on the VU scale.)  Red bars on the peak scale start at +8 dVu.
  • +2.5V: In this mode, zero on the VU scale corresponds to 2.5V RMS.  The peak scale will be re-scaled to show voltages up to 10 volts, and the blue line will pass through the 2.5V mark.  Red bars on the peak scale start between the 3.5V and 5V marks.
  • +5V: In this mode, zero on the VU scale corresponds to 5V RMS.  The peak scale will be re-scaled to show voltages up to 10 volts, and the blue line will pass through the 5V mark.  Red bars on the peak scale start between the 7V mark and the 10V mark.
An issue with the VU/peak display is that it does some preliminary high-pass filtering before it processes the signals for display.  This is common for VU meters; it prevents a DC offset in the signal from creating a false high reading.  However, it prevents the meters from working properly with low-frequency signals.  If you want to look at levels from an LFO, use the bar graph display, or one of the scope screens.

X-Y Display

The X-Y display emulates a feature of many of the old analog scopes, in which the X-axis, which is normally controlled by the scope's time base, can instead be driven by an external signal, producing two-dimensional patterns on the scope screen.  In this implementation, channel 1 drives the X axis and channel 2 drives the Y axis.

The old analog scopes depended on the persistence of the display phosphor for the user to be able to perceive the drawn figures.  The O'Tool attempts to emulate that with a setting that defines the "persistence" of each dot drawn; the dot is removed from the display after the equivalent of what would be that amount of time has passed, which determines how long each part of the figure remains on the display (which is, of course, also a function of the frequencies of the two waveforms driving the display).  To my eye, it doesn't work all that well; the continuously redrawn form is hard to perceive at faster settings, and it quickly fills the entire screen at slower settings.  The photo below was taken at a 1/15 second exposure and captures more of the drawn figure (which is made from a triangle wave driving the X axis and a sine wave on the Y axis) than was visible to the eye in real time.

Spectrum Analyzer

The spectrum analyzer surprised me with how well it works.  The update rate is pretty fast, and it seems to not have much of a problem with quantizing noise.  It has two display modes, "linear" and "log".  In the linear mode, there are four frequency ranges available, with a choice for the upper end of 20, 10, 5, or 2.5 KHz.  Vertical scaling is relative, but you can choose from 1x up to 4x.  If, in one of the higher vertical magnifications, one of the peaks exceeds the vertical range, the peak displays a red top, as you can see in the shots below.

This one is with a square wave on channel 1 (top) and a sawtooth on channel 2 (bottom.)  On the square wave, you can see the odd-harmonics pattern typical of square waves. 

This one is with a 25% pulse wave on channel 1, and a triangle on channel 2.  Notice how little harmonic content the triangle has. 

I have found the log mode to not be as useful in general, because it groups all of the frequencies into octaves and displays one bar per octave.  Depending on the range setting, it displays between 5 and 7 octaves.  Here's an example; unfortunately, I forgot to write down what waveforms I was using for this shot.

Frequency Counter

The frequency counter is straightforward and works well.  You can select channel 1 only, channel 2 only, or both.  There are three elements on the display.  At the top is the frequency, in Hz, for each channel.  Not having a calibrated frequency source, I can't really speak to whether these are actually precise to two decimal places.  In the middle, it displays the closest equal-tempered note for the frequency of each channel, and how far away in cents it is from the ideal equal-tempered value.  The bottom portion shows this deviation graphically.

For the note display, you can select concert A to be either be 440 Hz (the usual standard) or 432 Hz.  There is a lot of nonsense surrounding 432 Hz tuning; there's nothing special or magical about it.  Prior to the 20th century, orchestras were all over the map as to what standard they tuned to; Bach, Beethoven and Haydn are thought to have used an A of about 422 Hz.  Nonetheless, if you want to try something different, and you're using the O'Tool to tune instruments, you can give 432 Hz a try.  Note that some polysynths may not be capable of being tuned this far off of 440 Hz.


\The last display is a simple voltmeter, displaying the voltage present on each channel.  Only DC voltages can be displayed.  Keep in mind that the O'Tool is (in this case) being powered from a 15V supply; it most likely cannot display voltages exceeding the supply rails, and trying to do so could potentially damage it.  (I haven't tried.)  So don't use it to check the supply voltages on your Roland System 700.


The O'Tool is a useful thing to have in your setup.   And it looks cool.

Monday, February 19, 2018

Review: Q119 Analog Sequencer

The Q119 from Synthesizers,com is a 24-step analog sequencer. If you haven't used an analog sequencer before and don't know what its purpose is, it's a device that stores a set of control voltage values, and sends them to an output one after the other, under the control of a clock signal. As is the case with many analog sequencers, the “storage” for the control voltages consists of a set of knobs, each of which selects a control voltage within a given range. If you've listened to early Tangerine Dream or any other “Berlin school” electronic music, you've doubtless heard note sequences produced by an analog sequencer connected to the control input of a VCO. Repeating control voltage patterns have a huge variety of other uses, such as controlling filters, switching between different signals via connections to VCAs, and even using the output as an audio signal when the clock rate is high enough.

Like all products, the Q119 is formatted in the MU (Dotcom) format, which means it uses 1/4” jacks for all signal connections, and the standard Dotcom six-pin MTA-100 connector for power. (It does draw from the +5V power; the power supply must supply that voltage in order for the Q119 to function.) At a width of 8U, it is one of the physically largest modules that offers. The panel is divided into three basic sections: The section on the left has the clock controls and the various option switches that change the way the sequencer works. The middle and largest section consists of the 24 step controls, each having a control voltage tuning knob and an LED indicator. The section on the right is the output section, with the row outputs, and the master outputs with their offset and lag controls. Q119 analog sequencer, with a single-width Q128 A-B switch shown next to it for size comparison.

Clock Rate, Start/Stop, and Cycle Controls

Cycle option switches at the top,
clock controls at center,
start/run/stop controls at bottom
In the clock section, the most prominent controls are the oscillator frequency (RATE) knob and the GATE WIDTH knob. The RATE knob and the adjacent RANGE switch control the rate of the internal clock. With the knob full CCW and the RANGE switch on LOW, the slowest available rate is about 3 Hz, which to me is not slow enough. If you want slower, you have to use an external clock, The fastest available rate, with the RANGE switch on HIGH, is about 320 Hz. To the left of this knob is the external clock input and the SOURCE switch. As you might guess, when the SOURCE switch is in EXTERNAL, the internal clock is disconnected and the sequencer is driven by a clock signal received at the external clock input. This input should be a pulse wave (although the sequencer will square it up if it isn't), and the sequencer advances on the leading edge.

When the internal clock is being used, the GATE WIDTH control determines the “on” time of the gate outputs, as a duty cycle percentage (which means that as the frequency gets faster, the gate on time gets shorter). Unfortunately, the one on my Q119 does not work (I bought this unit used); it produces gates that are about 1 ms wide regardless of what I set the knob at. Fortunately, when an external clock is used, the gate on time follows the pulse width of the external clock; the GATE WIDTH control is ignored. This means that if you are driving the Q119 with a VCO that has pulse width modulation, you can change the gate “on” time by adjusting the VCO's pulse width, or better yet, make the gate “on” time voltage controlled by feeding a control voltage to the VCO's pulse width input.

The start/stop controls at the bottom of the clock section consist of four pushbuttons and three associated input jacks (one for each button except SET END). The START button, when pressed, causes the sequencer to start; it then runs continuously (unless the the SINGLE / CONTINUOUS switch is in the SINGLE position), until the STOP button is pressed. The GO button causes the sequencer to run as long as the button is held; when the button is released, it stops. The jacks under the START and STOP buttons accept trigger signals; receiving a signal on one of these jacks has exactly the same effect as pushing the associated button. The jack under the GO button accepts a gate input; the sequencer will run as long as the gate signal is high.  The SET END button, we'll cover in a minute.

How fast will it run?

With an external clock, I tested mine to see how fast it would run, and it made it up to 920 Hz; faster than that, and the sequencer freezes. ('s documentation only says that it will run “up to” 1 Khz.) This means that you can, in effect, use the Q119 as a sort of function generator at low audio rates; at this speed, a full 24-step sequence will cycle at about 38 Hz, and faster if you make the sequence shorter. There is no limit on the slowest rate; you can unplug the cord from the external clock jack, and the sequencer will simply wait until you plug it back in. When the sequencer is stopped, pressing the MANUAL STEP button next to the RATE knob causes the sequencer to advance one step. This is normally used to tune steps when setting up a sequence, but it can be used to “clock” the sequencer manually.

Cycle options

The four switches across the top select various options for the sequencer's operation. The MODE switch, I'll cover in the next section where we go over the step controls. The voltage range OUTPUTS switch sets the minimum and maximum range of the step tuning knobs. When the switch is in the -5 / +5 mode, turning a step knob full CCW causes tha step to output -5V, and full CW outputs +5V; the 12 o'clock position outputs 0V. When the switch is in the 0 / +5 mode, full CCW on the step knob outputs 0V. (The 12 o'clock position doesn't output 2.5V; I'll say more about this later.)

When the CYCLE switch is in the SINGLE position, the sequencer always stops on the last step in the sequence. To make it run again, a START operation has to be performed again. In the CONTINUOUS position, as you might expect, the sequencer runs in a continuous loop until you stop it. (Note that when the “hidden” random mode is selected, this switch is ignored; the sequencer always runs continuously until stopped.). The SEQUENCE switch, when in the UP/DOWN position, causes the sequencer to reverse direction when it reaches the last step in the sequence, and again when it gets back to step 1. If the configured length of the sequence is 6 steps, then after step 6 the next steps will be 5, 4, and so on, back to 1. At that point it will again change direction and count through 2, 3, etc. When the up/down mode is selected, and the CYCLE switch is in the SINGLE position, the sequencer stops when it returns to step 1.

The SET END button serves two purposes. Its primary function is to allow you to set the desired length of a sequence. This is done by pressing the SET END button once and releasing it; the LED for either step 1 or the current end step will begin to flash rapidly. Repeatedly press the SET END button to advance the end step (you have to do it quickly); when it reaches the step you want, stop pressing the button. After a second or two, the flashing will stop, and then that step will be the final step in the sequence. This is effective for all sequence modes -- up, up/down, and random. Note that when you switch the sequencer to 3x8 mode, it will automatically set step 8 as the end step. When you switch back to 1x24 mode, step 8 will remain the end step, and you will have to use SET END to reset it to a longer sequence if you want. (Or cycle the power.)

The SET END button is used with the MANUAL STEP button to select two "hidden" modes of the sequencer. The normal start mode is the "reset" mode; in this mode, any time the sequencer starts, it first resets to step 1. Pressing MANUAL STEP while pressing and holding SET END selects the "continue" mode. In this mode, when the sequencer starts, it resumes with the step after the one it stopped on. Doing the opposite of that – pressing SET END while pressing and holding MANUAL STEP -- sets the cycle mode to the random mode. In this mode, each time the sequencer advances, it selects a step at random. Although I haven't attempted to do an analysis of the distribution, it seems to be pretty uniform. One thing to note is that the code presents the same step from being selected twice in a row. This is a nice feature when generating random notes; in a random-note sequence, it tends to be jarring to the listener to hear the same note sound twice. The CYCLE and SEQUENCE switches have no effect when the random mode is engaged; the sequencer runs continuously until stopped. Either of these hidden modes may be disengaged by repeating the button sequence for that mode, or by cycling the power. 

Step Controls

The heart of the Q119 is in the 24 step blocks, which are organized in three rows of 8 steps each. Each step block consists of a single knob, which is used to select the output voltage for that step, and a red LED that indicates when the block is active. To improve finger room for the knobs, the odd-numbered steps have the knob on top and the LED on bottom, while the even-numbered steps are the reverse. This results in a rather amusing pattern of lights moving in a zig-zag when the sequencer is running, which some performers object to, but I think it actually improves recognition of which step is active. The LEDs also function with the SET END button in selecting which step is to be the last step in the sequence. Changing the setting of a knob will be reflected immediately in the output if the sequencer is on that step (the step's LED is lit), whether running or stopped.

Q119 step controls and LEDs, with row outputs on the right.

The organization of the step blocks into three rows is not merely a visual presentation. The Q119 has two operating modes, known as “1x24” and “3x8”, and selected by the MODE switch. In the 1x24 mode, the sequencer drives a single sequence of up to 24 steps long, using the three rows in series. When the sequence runs, it will proceed across the top row until it reaches step 8, then resume on the second row at step 9, going to 16 and then jumping to the third row at step 17. At step 24, it jumps back to the first row and step 1. In the 3x8 mode, the sequencer drives the three rows in parallel, producing three sets of control voltages at the three BANK outputs. The first step is steps 1/9/17, then it proceeds to 2/10/18, and so on, up to 8/16/24, at which point it returns to 1/9/17. The LEDs for the proper steps in each row will light simultaneously, as opposed to the 1x24 mode, in which only one LED is lit at a time. (In either mode, the SET END button can be used to make the sequence shorter than the maximum, if desired.)

Control voltages

The control voltage knobs are not linear with respect to output voltage. With the OUTPUTS switch in the -5/+5 position, one might expect that the zero position (12 o'clock) is 0 volts, and each major hash mark is a difference of one volt. The first statement is true, but the second is not. From 0 to +1 on the indexing is a difference of about 0.6V. The steps get larger moving further away from the zero position, finally reaching plus or minus 5V at the +5 and -5 positions respectively. With the OUTPUTS switch in the 0/+5 position, something similar happens: the full CCW position (-5 in the indexing) is 0V; -4 is about 0.3V, -3 is about 0.7V, and so on. In both modes, the steps get larger as you move farther away from 0V. This is something of a benefit if you can use the ADD offset control (further down) so that you can keep most of the steps near the 0V position, which makes it easier to make fine adjustments. However, it is confusing if you expect to be able to look at the indexing and dial up a desired voltage; that isn't straightforward. If you need a specific voltage, it is best to check it with a voltmeter. If you are running the output into a VCO and trying to tune notes, it is usually better to either let the sequence run and tune it by ear, or if that doesn't work for you, single-step the sequencer with the MANUAL STEP button and check each note against a tuner. 
Output section, with row (bank)
outputs on the left, and the master
outputs on the right.


The output section contains the master outputs, a set of row outputs for each row (labeled BANK 1/2/3), a knob for adding lag (portamento), and a knob and jack for adding an offset voltage to the master output. The master output is usually used when the sequencer is operating in the 1x24 configuration. The master OUTPUT jack outputs the voltage from the currently active step. The GATE jack outputs a gate which rises when the sequencer advances to the next step, and falls some time after, as determined by the GATE WIDTH knob in the control section (or the pulse width of the external clock, if an external clock is being used). The LED next to the GATE jack lights when the gate is active. If the MODE switch is in the 3x8 mode, the master OUTPUT jack will have the sum of the active steps from each row. This isn't usually what you want, but it does have creative possibilities. Note that the OUTPUT jack is active all of the time, including when the sequencer is stopped. The GATE output remains low when the sequencer is stopped.

The row output jacks are active when the corresponding row is active. When the sequencer is in the 3x8 configuration, the top-row OUTPUT jack outputs the voltage selected from the currently active step in that row, and the other two row OUTPUT jacks perform the same function for their rows. All of the GATE jacks pulse together in this mode. In the 1x24 mode, the row output jacks are only active for the row that contains the currently active step. When the current step is not in that row, the OUTPUT jack outputs the minimum voltage (0V or -5V depending on the OUTPUTS switch setting), and the GATE jack remains low.

Master output modifiers

The GLIDE and ADD knobs only effect the control voltage master output. The GLIDE is a conventional lag processor that acts on the control voltage output. The ADD knob adds an offset voltage to whatever voltage is present at the master output; this has a number of obvious uses, such as transposing sequenced notes, or bringing them in tune with another instrument. If a cable is plugged into the ADD INPUT jack, that is also added to the master output.  To sum it up, the voltage at the master output consists of:
  •  The current step control voltage (or the sum of the three steps, in the 3x8 mode)
  •  The ADD knob voltage
  •  The signal present at the ADD INPUT jack

Interaction with another sequencer

The DONE OUTPUT jack sends a trigger signal at the time that the sequencer advances from the last step back to step 1 (or would have, except for the CYCLE switch being in the ONCE position). This allows you to operate two (or more!) Q119s in a round-robin fashion, by setting their cycle switches to ONCE, and then patching the DONE output of one into the START input of the next. When the first one finishes, it will start the second one, etc. By careful adding of the outputs, you can create sequences of 48 or more steps. (You could take the master OUTPUT jack of one Q119 to the ADD INPUT of the next one to combine the control voltages, but you'd need some external module to combine the gates.)

Interaction with other modules

Some performers who use an analog sequencer to produce note sequences find it easier to set up the sequencer when they can run the outputs through a quantizer. offers a quantizer, the Q171, which has features designed to make it complementary to its sequencers. In particular, it has three quantization channels, so that you can quantize all three rows when using the 3x8 mode, and it has gate inputs to force quantization to only occur on the note gates, which can help avoid the “dithering” problem (where the quantizer jumps back and forth between adjacent notes). However, other quantizers could certainly be used. 

Output selector switches, such as the Q962, have potential uses with the Q119.  The DONE OUTPUT can possibly be used to cycle between different bus selections or outputs, for various purposes.


It seems a bit unfair to describe the Q119 as an “entry level” sequencer, since it is a quite capable module. It is not as full featured as, say, the Moon Modular 569, the GRP R24, or's own Q960. Then again, it also costs a lot less than those others; the direct-sale price of $560 USD is a bargain in the world of analog sequencers, which generally tend to be expensive. (Moon's direct-sale export price, excluding VAT, for the 569 is E1258.77, which at the exchange write on this date, 7 Feb 2018, works out to $1545.41 USD.) The main thing that those sequencers have that the Q119 lacks is flexibility; they typically have features like individual gate outputs for each step and reset trigger inputs. Then again, they sometimes require either additional aid modules or fancy patching to perform functions that the Q119 has built in. So yes, the Q119 is a good choice for someone who has no experience with analog sequencing and wants to get practice with it, but it's a module that will continue to be useful in your case even after you purchase one of the higher-end sequencers.

Demonstration videos

This first video is a basic demonstration of the Q119's different cycle modes.  The 1x24 and 3x8 modes are demonstrated at different speeds, with up, up/down and random sequencing, and the single and continuous cycle options.  The use of the SET END button is also demonstrated.

This second video illustrates using the Q119 in the 1x24 mode, with a sequence length of 14 steps, to generate an approximation of a familiar Synergy sequence (the one from which this blog takes its name). Driven by a pulse wave from a Q106 VCO in LFO mode, it is modulating another Q106, whose triangle output is going into an MOTM-440 OTA filter. Envelope is from a Q170 Envelope++, and it is controlling a Q109? VCA. Note that this actual patch is only an approximation of the original, for demonstration purposes.  Please excuse the rough tuning; I don't have a quantizer and I didn't spend a lot of time on tuning the notes. Nonetheless, if you listen to much Synergy, you should recognize it.  I use an external clock and gradually speed up the sequence, in the same manner as the original.  Just before the end, I take it up to a faster speed than Larry Fast's old Moog 960 was capable of, just to show off the Q119 a bit.

You will notice something at the start of the video: there seems to be a "skip" at the very start of sequence, between the first and second notes.  This is due to the fact that I'm using an external clock in this video.  (When I reach to something above the top of the picture, I'm reaching for the requency control of the Q106 that is serving as the clock source.)  The Q119 syncs its own clock when it is instructed to start, but it has no way of making an external clock sync to it.  So when I start the sequencer, it starts at some random point in the external clock's cycle.  If this is part way through the cycle, then the first step will be short, time-wise, and that is what you hear here: the first step occurs on the START button press, and then the next step occurs on the next clock transition, but I hit START at some point in the middle of the clock cycle, so the interval between the first step and the second step was short.  If I had wanted that interval to be precise, I could have watched the LED on the Q106 and pressed START at the start of the cycle.  Or I could have fed an external trigger source to the Q119's START jack, and to the Q106's hard sync input.  

This third video illustrates using the sequencer in 3x8 mode. What is happening here is that the top row is being used to modulate a Q106, whose sawtooth wave is going into an SSL 1310 digital delay that is being modulated by an LFO. (There is no filter in the patch.) The bottom row is being used to generate a gate signal – turning the knob up causes the gate to be “on” on that step, and turning the knob down causes it to be “off”, so that that step does not sound. As the sequence plays, I play with the bottom row to make different notes in the sequence sound.

Sunday, November 1, 2015

Review: SSL 1250 Quad LFO







SSL is at  They sell both direct and through dealers. 

Thursday, August 27, 2015

Analog computers and synths









Philbrick K2-P op amp


Philbrick K3 analog computer modules.  From the Philbrick Archive.


ARP 2500 model 1947 voltage controlled filter






Sunday, October 19, 2014

Fetishizing the Moog modulars





Moog 904B.  Photo courtesy of David Brown at


Moog 905.  Photo courtesy of David Brown at



MOS-LAB 921B VCO.  Photo courtesy of



