The Minimoog is a landmark classic instrument in several ways. It
was the first portable monophonic synthesizer aimed at the performing
musician. It set the path for other imitators and is the standard
against which other monophonics (and polyphonics) are measured
against. The sonority is similar to its big brother modular
synthesizers at a fraction of the price (and the headache of
patching
it). Back in the early 1970s a studio keyboardist couldn't get a
job
unless they had a Minimoog. Most onstage keyboard rigs
included a minimoog. It held the record for the
longest production product life for a keyboard instrument (1970-1981)
until the its modern replacement Moog Voyager surpassed it (2003 -
present). Although it fell out of favor during the 1980s (back
then I
turned one down for $200), today it enjoys vintage status and has
returned as a favorite once again. It does not command total
loyalty
as many cursed its inability to stay in tune. To be fair, this
is not a fault of the instrument itself as age has not been kind to
minimoogs.
Back in the early 90s I have had an arsenal of Moog synthesizers - but
never owned a minimoog. I decided it was about time I owned one
of these
classics. In shopping around (this was way before ebay) I found
this very early minimoog - it was a little more $$$ than market value
but I decided to take the plunge. Mind you this was shortly
before minimoog values started skyrocketing so my timing could not have
been better. When it arrived three things struck me. The
front badge read "RA MOOG" which was unfamiliar to me. The left
hand
controller panel was unusual. And the blasted thing would not
stay in tune for five minutes.
I've seen a few minimoogs in person, but the left hand controller panel
was unusual on my specimen. One, the mod and pitch wheels were
clear plexiglass. Instead of rocker switches for decay and glide,
this one had mini toggle switches - I later learned these were not
original as they left the factory with red momentary pushbuttons.
Small wonder that the pushbuttons were replaced. There are also
no
jacks for decay/glide footswitches. You can see the differences
in the images at the top of this page. There is a TRS jack that
is
not original but it is unwired. Also not stock is the XLR jack although it does
appear to have been installed at the factory as the black dymo label is
typical for custom work at the factory. This XLR jack was never
wired but I installed a direct box transformer on it to give it a
balanced output.
Upon receipt of this very early specimen I was dismayed to learn that
it drifted so bad that it would not stay in tune for five
minutes. My EE experience would have a challenge to correct
this. I located a service manual and proceeded to search for
sources of drift. My unit has the 3046-based oscillator board
which has a reputation of good tuning stability so I focused on the
control voltage processing circuit. Through piecemeal component
substitutions I arrived at a stable solution. This involved
replacing selected 741 opamps with modern BiFET opamps that have better
tempco and offset parameters. 741s suffer from large offset
errors that also vary with temperature. This was the best that
technology had to offer when the minimoog was designed in 1970.
Today the modern BiFET pin-for-pin replacement is much less vulnerable
to temperature variations. In addition to opamps, I redesigned
some other circuits and modified the power distribution. Not only
were the minimoog power busses wired in a "daisy chain" as opposed to
the "star" configuration, but the oscillator cards had their own power
rails that were offset from the busses at the tuning pots. My
work experience with system engineering played a part in correcting
this. No wonder the 1970s musicians cursed when their minimoogs
drifted onstage!
My modifications focused only on the control circuits as none of the
audio circuits were altered thus retaining the original sonority of the
instrument. When I finished the tuning improvements I gave it the
ultimate test - the stage. I gigged with this minimoog in clubs
in the mid-90s. To my delight, it only required tune up at the
beginning of the night and I never had to adjust it the rest of the
night.
I later learned that "RA MOOG" was Robert Moog's original company name
and was operated out of Trumansburg NY. The rear badge confirms
this. The birthplace of minimoogs was an hour from where I
lived!! It wasn't until I met Roger Luther of Moog Archives
when I learned the location of the original factory, which still
stands. Trumansburg is a quiet town with quaint little
early 20th-century storefronts, hardly where you'd expect the
blossoming of the modern
synthesizer. Bob Moog selected this location because of its close
proximity to Cornell University where he was studying for his PhD in
Engineering Physics, and his original products was not synthesizers but
theremins. Today the former factory is an italian restaurant,
which serves excellent food. Look behind the bar for a framed
blueprint of a theremin schematic, the only hint of its historical
significance.
Age is not kind to minimoogs as pots and switches fail and connector
contacts oxidize. Often a pot can be restored by repeated
sweeping between extremes, this was the case with the filter emphasis
pot on my unit. Same with switches, sweep 'em back and forth and
they're good as new. Contacts have to be restored manually and is
best left to a qualified repair tech. Minimoogs aren't hard to
work on and with the exception of the ua726 all the components are
standard and readily available.
The tuning calibration in the service manual is incorrect. There
is an OCTAVE trimpot that must be nulled while calibrating the
oscillators and the service manual neglects this. The correct
procedure is to set the oscillator range all the way to "2" as this
will null out the OCTAVE trimpot. Once the oscillators are
calibrated, then the OCTAVE trimpot can be adjusted. The complete
procedure is posted here on the Analogue Heaven archives.
The original RA Moog company of Trumansburg ran into financial trouble
and
in 1970 it was bought by an entrepreneur who moved the company to
Buffalo and renamed it "Moog-MuSonic". The predecessor MuSonic
company designed and produced the Sonic-5 to exploit the growing
popularity of synthesizers, but slow sales convinced the owner that
name recognition through acquisition of Moog's company would improve
his bottom line. The Sonix 5 ultimately became the Sonic 6 during
the Moog era. By 1974 the company was
purchased by the huge music corporate conglomerate Norlin (who also
owned Gibson guitars, Lowrey organs, Maestro effects pedals, Pearl
drums, etc) who renamed it "Moog Music". This corporate entity
continued until 1986 when Norlin dropped all the music businesses, and
Moog Music became part of EJE Electronics in Buffalo. EJE/Moog
Music's
only musical product was a guitar amplifier (Rockie amps), and its only
function in any keyboard
entity was warranty services. By the early 1990s EJE/Moog Music
was
history. Analog synthesizers were no longer desireable.
Why do Minimoogs
sound different? Which oscillator card sound better?
There is much debate over which oscillator card sounds better.
Few people realize that the oscillator card is not the main contributor
to differences in sound - the filter is.
I became aware of this on my first visit to a NAMM show. I was
invited to this NAMM show to help set up a display on many wonderful
vintage keyboards, including the first three minimoog prototypes and
production unit numero uno. The minimoogs were wired up and
making noise. The numero uno unit is very similar to my unit
except this one had the original discrete oscillator board. It
sounded very similar to mine. Another colleague had a later
minimoog set up at the Big Briar booth with the same oscillator card as
mine. I was shocked at how different it sounded.
To paraphrase Sherlock Holmes, the game is afoot! Why did two
early minimoogs with different oscillator cards sound identical while a
later unit with same oscillator card sounded radically different?
Later Roger Luther acquired an early minimoog of his own and THIS one
had the third oscillator card - the UA726 version. THAT minimoog
sounded like my unit too! Therefore I have played three RA Moog
Minimoogs each with different oscillator cards, and they sounded
EXACTLY the same.
I found minimoog schematics from the RA Moog days. My suspicion
zeroed in on the filter schematics. The filter is a configuration
of five transistor pairs. A little sidenote specified that all
the pairs had to be matched. When I referred to the newer service
manual, the sidenote revealed that only the top and bottom pairs were
to be matched. Here was the secret! Since the middle pairs
did not have matched transistors this impacted the sonority of the
filter in that the poles (formed by the RC product comprised by the
transistors and filter caps) are no longer equidistant. Therein
lies the answer - later minimoog filters did NOT have 100% matched
transistor pairs and thus this contributed to sonic differences from
one unit to another. Because the early minimoogs (RA Moog and
some early "Moog-MuSonics") had 100% matched transistor pairs in the
filter, the sonic quality was identical from one unit to another.
When I was getting the NAMM display ready I played around with the
model C prototype. This
had no PC boards at all, the circuits
were manually laid out on vector
boards. The filter sounded radically different from ANY minimoog and the resonance was
very sterile. They had traced the
circuit and I got to examine the schematic. I found that the
filter feedback was radically different in that instead of BJT
transistors in the production models, the prototype used JFETs.
The two transistor technologies yield vastly different sonics.
There were seven minimoog prototypes in all. One model A was
built
from existing modules from the modular system. Two model B
units (one was lost in a pawnshop fire years ago) used circuit boards
from the modulars but used a single control
panel. Four model Cs were built which were close to the final
production model (one of them is unaccounted for). The Audities
Foundation has the prototype model A, B, and C as well as minimoog
numero uno.
Minimoogs had three generations
of oscillator cards, each with
improvements on tuning stability. The majority of analog
synthesizer - Minimoog included - are volts-per-octave (v/oct)
oscillators. V/oct oscillators require an exponential converter
to conver linear control voltages to exponential currents. Tuning
stability is a challenge
because the transistors used in the exponential converter has a
temperature factor in the
transfer equation. As temperature changes, this changes the
scaling and the oscillators will drift and/or the scaling will change
IE pitch will not track across the keyboard. This temperature
factor must be nulled out. A
common technique is to use a "tempco" resistor that has a known
variation with temperature. The first generation is
a 100%
discrete design with no opamps and a single tempco resistor shared
among all three oscillators. This wasn't entirely
successful. These were installed in the first few hundred
minimoogs up to serial #1299, which was superceded by the "3046" design
that introduced opamps and had independent "tempco"s per
oscillator. The 3046 cards were
better but still not great.
By serial #12175 a 3rd oscillator card was installed which used the
UA726 heated transistor pair to compensate for temperature
variations. The UA726 version is the one that commands the
highest prices on the vintage market, although the RA Moog units are
quickly closing the gap. It was not uncommon for early oscillator
cards to be replaced with later ones. You can often tell a later
unit from the nine trimpot access holes on the back of the unit, on the
right. If you count less holes it either has the earlier card or
the owner upgraded to a newer card without making more access holes.
The minimoog oscillators were BEEFY. Two were usually enough to
do the job, three can be overkill (in a good way). The minimoog
oscillators were special in that fine detuning led to a pleasant
sweeping of harmonics as the oscillators "beat" against each
other. This is a trait that is rarely duplicated and is the most
appealing feature of the minimoog. Unfortunately hard sync is not
available. The keyboard is single trigger low priority, crude
compared to today but effective. The famous Moog filter is the
24dB lowpass
class and it has a wonderful resonant quality. At high resonance
it can
accent the sweeping harmonics of multiple oscillators and can
eventually break into self-oscillation, creating a sine wave at the
frequency of its cutoff. This instrument can produce some of the
fattest sounds in the industry. Even though derivative moog
products were introduced, they failed to duplicate the fat sound of the
minimoog. Only the Moog
Source and Memorymoog
came close.
If three oscillators weren't enough, Moog offered a custom unit built
to order: the Dual VCO expander. This
unit had the equivalent of two UA726 based oscillators in a 2U rack
format with independent
VC inputs and audio outputs. Minimoogs had to be modified to
supply the CV voltages to this unit. It also offered variable pulse
width
which the minimoog did not have. This is a rare unit and is not
often seen on the market.
Vintage Sound -
Why?
Why can't modern synthesizers or softsynths
duplicate the creamy fat sounds of the Minimoog?
Cloning the VCOs didn't get it, cloning the VCF didn't get it.
Some people think it's the filter, some people think it's the
oscillators.
The real reason is the Minimoog's discrete VCAs. VCA fidelity
when the Minimoog was designed in the late 1960s was pretty poor and
distortion and noise was a necessary evil. The VCAs in a Minimoog
(there are two) were not high
fidelity low distortion audio devices, in fact if you pump CD material
through a wide open Minimoog filter that program material will sound
terrible. That was the best that 1960s technology had to offer at the
time. In fact, the VCA was a simple differential amplifier right
out of an EE college textbook. As technology advanced through the
years VCAs got cleaner and quieter. Musicians noticed that the
new synths were missing a certain high frequency "sheen" that vintage
synths like the Minimoog had, especially when you open the VCF cutoff
all the way. The signal path in the Minimoog is driven a
bit hot, driving the VCAs into subtle distortion and creating that
creamy fat sound that we all
know and love. This hot signal was a design error not spotted
until they were well into production at the RA Moog works, but in their
wisdom they left it intact. Imperfections can be useful!
The same VCA distortion was responsible for that big Oberheim sound on
their early polyphonic synthesizers. VCAs contribute more to the
"vintage
sound" of synthesizers than designers care to admit. When Moog
Music set out to re-issue the Taurus I bass pedal synthesizer in their
Taurus III, they even duplicated the dirty sounding VCA in key
circuits. Taurus
enthusiasists all over the world were delighted at how close the Taurus
III sounded to the original.
Today high fidelity VCAs are readily available and they are easy to
implement
in softsynths. What they missed out is the distortion of the
classic VCA which is a direct contributor of that "vintage
sound". By the time the Oberheim OB-8 was
designed, they exploited new technology with cleaner VCAs and Tom
Oberheim lamented that "something" was lost in the sound.
Modeling dynamic distortion in softsynths is a big
challenge because the exact mathematical model is not easy to derive
and it is a
major number cruncher to implement on a microprocessor. The
challenge to modeling VCA distortion is that it varies with the
frequency spectrum (IE triangle vs ramp vs all variations of pulse
width) and how hard you drive it. Many
owners of Moog Voyagers have noticed that when you opened the filter
all the way, it was missing that Minimoog high end "sheen". I was
able to
confirm that the Minimoog VCA was the contributing factor by routing
the Voyager output to the Minimoog external input which put the Voyager
through the Minimoog VCA and - wala - instant Minimoog "sheen" on the
Voyager. The Voyager VCAs are too clean! top
Production
Variations and Modifications Sometimes a minimoog is found with different color rocker
switches. This isn't any great mystery as Moog simply ran out
of
their stock and substituted what they had on hand. I have seen
minimoogs with all black or all white rocker switches, sometimes a mix
of colored and white. Early units had
handsome stained walnut cases while later ones were painted
basswood. RA Moog and early MuSonic minimoog panels were anodized
aluminum while later ones had an overlay on top of the aluminum
base. The lettering font was different between the panels.
Early units did not have a mains
voltage selector and operated on
US110VAC only. Moog offered an optional replacement left hand
controller that replaced
the pitch wheel with the pitch ribbon found on the Polymoog, Micromoog,
Multimoog, and Liberation. Over the years there were minor
circuit differences such as input impedance to the filter's audio input
and a trimpot to calibrate the filter resonance. The last 25
minimoogs had lights under the clear mod/pitch wheels and a plaque on
its front identifying it as one of the last 25. The very last
minimoog was given to Bob Moog.
Some outfits such as Rivera Music
Services on the west coast offered
customization of minimoogs. Modifications included hard sync, a
dedicated LFO, multiple trigger for the keyboard, multiturn tuning
pots, tunable distortion, chromatic transpose of each oscillator,
modulation from filter EG, beat indicator for ease of fine tuning the
oscillators, etc. RMS had the most extensive modifications
available, but they are very rare on the market.
Sounds
I'll start this off with not-so-typical Minimoog sound...
A forum member on the Moog Music discussion website asked a good
question: what uses would there be for the LO octave setting on VCO1
and VCO2, as VCO3 in LO octave is usually for LFO? Well, I like a
good sound design challenge.
Well it turns out there is something useful.
Turn off all the VCOs, press a key, turn up the emphasis control on the
filter until it self-oscillates, then back off the control until the
oscillation stops.
Now turn on VCO1, set it to "LO" and ramp waveform, and turn it all the
way up in
the mixer. Set VCF cutoff to "0". Press a key, and you'll
hear a repetitive damped sine wave whose frequency is the filter cutoff
frequency. What is happening is that the steep vertical part of
the ramp waveform - a step edge - is disturbing the stability of the
almost oscillating filter; as it is abruptly "bumped" by the step
edge, this triggers a "ringing" that settles to nothing IE a damped
sine wave.
...So what? Change the waveform to square. Now the
repetition is double because that waveform has two step edges. Change to
other non-square pulse shapes and it sounds like a slap echo
effect. Use real slow glide and play different keys (with or
without keyboard tracking on the VCF).
Now set VCO3 to "LO", square waveform, turn off OSC 3 CONTROL, turn it
up all the way in the mixer, and use VCO3 tuning knob (whose range is
much wider with OSC 3 CONTROL turned off) to sweep VCO3 pitch while
playing different keys. Set NOISE to PINK, set MODULATION MIX to
about 7 (modulation noise is actually "RED" AKA "smoothed S&H" with
the noise switch in
"PINK" position), turn on FILTER MODULATION, turn up the mod
wheel. Experiment with different waveforms of VCO3.
Add VCO2 at "LO" and any pulse waveform with offset tuning for a real
non-repetitive effect. You can simulate hearty belches, acid
indigestion, boiling wicked witches caldron, heartbeats, bubbles in the
river of molten wax at the diabolical villain's lair, even flatulence
noises (farts)... sounds
you didn't know you could do
on a Minimoog! By the way, there was ZERO processing in those
sounds.
MIDI Retrofits
When MIDI came along, fans of the minimoog wanted their units
retrofitted to respond to MIDI. This isn't trivial as a MIDI to
CV converter must be designed. But the Minimoog did have CV and
trigger inputs on the rear panel which facilitated adaptation of these
MIDI to CV converters.
Rudi Linhard of Lintronics
offers an excellent MIDI retrofit for the minimoog, known as the
LMC. Back
then Bob Moog's company - called Big Briar then - offered Linhard's
retrofit as a modification or a kit for user installation. Big
Briar eventually was renamed Moog Music when Bob got his namesake
trademark back. I paid a visit to Big Briar and they showed me
the Lintronic retrofit (they were a small operation then, they have not
yet introduced the moogerfooger pedals or even the Voyager). It
didn't take long to sell me. I told them I had my unit with me
and they were interested in seeing it. When they spotted how old
it was, they called Bob to check it out. Bob was quite taken
aback as he hadn't seen one of his Trumansburg minimoogs in a long
time. After a little digging through my archives I uncovered a
photo of this visit.
Anyway, the Lintronic retrofit is superior to other MIDI to CV
interfaces in a couple of ways. The minimoog has CV and trigger
jacks on the rear panel that can easily interface to a MIDI to CV
interface. However this approach has two shortfalls - the CV is
NOT processed by
the glide processor, an important component of the minimoog
sound. Also the keyboard is still part of the CV circuit - since
the S&H tends to droop over time the keyboard CV will slowly drop,
resulting in flat pitch. One must periodically press a key to
restore the S&H and thus correct the flat pitch.
The LMC overcomes this by directly shoehorning into the keyboard
circuit. You get glide processing and you no longer have to press
a key to restore the keyboard S&H. It also extends the range
so you have full MIDI control of the minimoog from a 64 note
keyboard. The LMC implements many useful MIDI functions such as
MIDI sustain pedal to enable final decay (IE release), MIDI pitch
wheel, MIDI mod wheel, MIDI velocity which is assignable to filter or
VCA. MIDI velocity to filter cutoff is my favorite modulation as
it leads to funky basslines. The LMC also offers a standalone LFO
so you don't have to sacrifice the 3rd oscillator for this chore.
The LFO offers all the waveshapes of the 3rd oscillator plus
S&H. At power up the LFO rate defaults to 6hz but this can be
changed over MIDI. The interface can respond to any of the 16
MIDI channels. It evens offers some unusual stuff like
reversed keyboard tracking - as you traverse from low to high MIDI
keys, the pitch traverses in reverse from high to low (this really
messes with
your head!). All configurations can be changed over MIDI using
program change messages. Custom configurations are not
programmable but with today's sequencers you can store MIDI strings
with your sequenced songs so this is not a big deal. This is much
more than a standard MIDI to CV interface can offer. All this is
done with no modifications to the front panel, only a MIDI jack and
mini toggle switch is added to the rear
panel.
Minimoog clones
There have been some attempts to clone the minimoog. One of the
first was Stage Electronics out of Buffalo that comprised the remnants
of the original 1970s Moog Music. In the early 1990s they announced
a
reissue minimoog in the form of two rack units
- one had the sound
engine while the other was a remote controller with the panel full of
knobs and switches. The remote unit looked a lot like the Studio
Electronics SE-1 that was to appear almost ten years later. It
had MIDI and was programmable. It never got into production and
no report of any of these units has surfaced. A shame because it
certainly had promise.
Studio Electronics got their start by cannibalizing minimoog guts,
adding a MIDI retrofit, and
stuffing them into a rack format dubbed the MIDIMOOG later known as the
MIDIMINI. The difference is the MIDIMINI used SE's custom
designed oscillator card to replace the original. I have recently
heard a friend's MIDIMINI and can attest that it is a dead ringer for a
minimoog. SE also did
"racktrofits" of Prophet-5s, Oberheim two voice SEMS, Oberheim OB-8,
and Roland TR-808 all with MIDI retrofits. As minimoogs went up
in value customers became
reluctant to cannibalize their minimoogs so SE dropped the racktrofit
business and started their own successful design of rackmount analog
synthesizers. Not many MIDIMOOGs or MIDIMINIs are around but they
command a high price on the market.
The next clone attempts came from Welsh UK and from Cincinnati
Ohio. When Norlin folded in the mid-1980s, the moog trademark
lapsed in the UK by early 1990. A welsh
brit by the name of Alex Winter snatched it up through the legal
system with the intention of making reissue moog products.
Likewise in the US, the trademark was snatched by Don Martin with the
same intention. The former had better success at cloning what was
known as the "Welsh Minimoog". Because Martin owned the moog
trademark in the US, the UK company never had any distribution in the
US. Both companies announced grand plans to reissue the modulars,
the Taurus pedals, and other moog products. At the time Moog
fever was building so this wasn't a stretch of marketing.
Unfortunately cloning was easier said than done as some of the critical
components are no longer available. The Welsh Minimoog was
actually made in respectable numbers. The "Martinmoog" operation
was
less than successful.
Don Martin was a businessman, not an engineer. His cloning
efforts failed to redesign the instrument to replace obsolete component
with modern ones. The late great Kevin Lightner
had one of these clones in his shop
and I got to
examine it. The clone was an exact duplicate of original circuit
boards, but where the unavailable-at-any-price UA726 was supposed to be
present was an empty socket. The oscillators make no sound
without the UA726!!! Besides the missing UA726s, the "Donimoog"
looked good on the outside but it was a poor clone owing to horrible
construction. They simply did not
employ qualified staff to make a bonafide clone. However Don
Martin had been accepting deposits from customers wanting the new
minimoogs. As time progressed, Don couldn't make his minimoog but
he kept accepting deposits. After a couple of years customers
started getting upset. Internet boards everywhere became peppered
with posts from angry customers. Soon Don stopped answering his
phone and
did not return letters inquiring when orders would be ready. At
one point somebody visited the physical address of "Martinmoog" and
discovered that it was a storefront for MailBoxEtc.
In a classic case of trademark name confusion, angry customers found
Bob Moog at Big Briar and demanded to know when their minimoog would be
delivered. Bob had no idea of the Don Martin business. He filed a
lawsuit against Martin and petitioned the US trademark office to revert
the moog trademark back to its rightful owner - Bob Moog.
Don Martin ultimately was forced to declare bankruptcy. But Don
Martin was a crafty fraudster with no listed personal address and the
court server was forced to sit at the doors of the storefront waiting
to deliver papers. The bankruptcy court liquidated the assets and
awarded the trademark to Bob Moog, which enabled him to rename Big
Briar to Moog Music. Nothing was ever heard from Don Martin again
and the customers lost out on their deposits. Few "Donimoogs"
have
surfaced along with some model 9500 modules for modular systems, which
have been built better than the Donimoogs. An Ohio university
lent their vintage Moog modular synthesizer to Don Martin for study of
cloning operations but they never got it back and it is still missing
to this day.
The Welsh Moog? He never made more than a few minimoogs before
shutting down his operation.
By 2003, Bob had released the Voyager
Minimoog to great fanfare.
