Jörgensen Clavioline   monophonic portable tube synth keyboard with 
great electro noises

This portable tube instrument was basically the monophonic sister of the Jörgensen Tuttivox. But unlike the once very expensive Tuttivox, the Clavioline was in 1950th to 1960th a halfway common instrument that was even manufactured by multiple companies. The Clavioline could be mounted with screws and 2 metal brackets directly under the keyboard section of a piano (yes, the heavy wooden thing with strings and felt hammers inside ;-) ), because originally it was intended to be played in dance music bands by the piano player to imitate acoustic string or wind instruments e.g. when a band member was sick or the like.

But far beyond this, a Clavioline can do much more, because basically it was a predecessor of the analogue synthesizer with lovely droning hardsync tones those resemble multipulse squarewave and permit very sonorous and buzzy electro bass noises those are great for tekkno. The sound is made by a tube operated (sort of?) squarewave tone generator with a hardsynced suboscillator (octave divider) that makes a sort of subharmonic mixture (adds lower octave undertones). As well the main voice as the suboscillator can be switched to different octaves. The resulting waveform is passed through an analogue filter bank that is controlled by 10 combinable OBS tab stop switches (i.e. no continuous controls). The attack phase of the envelope can be switched between a soft (like flute) and a very percussive popping one (intended for picked strings?), but at least my specimen has no working envelope generator, i.e.. the rest of the envelope is a continuous tone and its volume curve can be only controlled manually by a knee lever (used much like a volume pedal). There is also a vibrato LFO with stepless adjustable intensity and frequency, which makes great bizarre textures when the octave is set so low that the tone frequency gets into the range of the LFO.

On the type plate stands the manufacturer "Jörgensen - Electronic" and the German address "Düsseldorf - Hüttenstr. 8". Jörgensen made different Clavioline versions over time; my amplifier is model "V/C" and the keyboard is model "M02". Both have the serial number "Y49" and the note that it was licensed from Constant Martin, Rene Seybold and Harald Bode. I don't know how rare my version is; at least I yet saw no other with exactly the same case style on the internet.

Jörgensen Düsseldorf

main features:

Jörgensen-Electronic, Type: V/C  Gerät Nr. Y49
Jörgensen- Electronic
Type: V/C, Model Nr. Y49
110/220V 80W ...
The organ jack had bare contacts with about 340V high voltage. To the right is my sound output jack with speaker mute switch.
The keyboard can be stored inside the amplifier case.
To play, it was originally mounted with its rear end under a piano using these metal rails...

but it also fits well into my Tuttivox stand.
Jörgensen-Electronic, Type: M02 Gerät Nr. Y49
Jörgensen- Electronic
Type: M02,  Model Nr. Y49 ...
The only volume control was a detachable knee lever.

It is made of lightweight (but fragile) bakelite and held by a clever screw fixture. The same lever type is also employed in the Tuttivox.
18 combinable "tab stop" switches control the sound synthesis.
2 knobs set vibrato depth and speed.

The vibrato knobs are mounted on an inserted metal panel. Likely the case frame was designed more generic since other brands Clavioline models had 22 switches and no knobs instead.
Above the "tab stop" switches are 2 strange slots those are shut with glued fabric. Other Clavioline models apparently had additional sliders here.




Although the Clavioline was invented already in 1947 (by Constant Martin in France) and there are quite many references to it on the internet, I found only one page about the Jörgensen version (on the site Clavioline.com), which shows even a different model with more tubes inside the amplifier and claims that this one was built only in 1960th. Initially my instrument had a lot of more or less rotten "explosive candy" capacitors (and a very melted one in the amp), but fortunately these were easy to replace because the hardware of the Jörgensen Clavioline is easy to maintain since it hasn't the horrible 3 dimensional component mess like my Tuttivox, but contains not more components than a good tube radio, and thus looks like a reasonable, efficient hardware design for its age. (The Tuttivox in opposite was an exceptionally crowded piece of electronics that had cost certainly a moon price and appears to me more like meant as a fragile but unaffordable electronics demonstration object than a robust instrument to play on stage.)

On my Clavioline I also had to replace the smashed bakelite light bulb fixture at the amp; because the chassis hole was too small, I initially shattered the new plastic fixture when I used force during installation; I used superglue to reassemble it and drilled the hole larger with household scissors. For safety I replaced the 2 lead mains cable with a grounded one. One of the leaf switch contacts under a key was cracked off; I replaced it with a piece of sheet steel from a 3.5 inch diskette slider. Another key had a bad solder joint and all switch contacts needed a clean with sand paper. Unfortunately my Clavioline is missing a keyboard stand because originally it was mounted with 2 smell sheet metal brackets at a piano, but at least it fits well into my Tuttivox stand.

Warning: It is crucial always to unscrew and detach the knee lever from the instrument bottom before taking the instrument out of its stand (or brackets), since the lever is of brittle bakelite and may break easily when the heavy instrument is accidentally dropped onto it.

Thanks to its combinable octave-, waveform- and filter switches, the Jörgensen Clavioline can make a lot of different timbres. The "P" switch adds a loud and usually bassy popping percussive attack phase to the timbres, which sounds between base drum and picked string depending on the actual filter settings, but beside this there is not automatic decaying envelope (or at least mine is broken). But in a 1960th movie I saw a stage pianist with 2 Clavioline models (at least there were 2 amps) of those one apparently even had an automatic mandolin ring effect (it rang quite fast and sounded too regular for a manually trilled sound). The "P" envelope is not re-triggered when keys are held down; only the pitch changes to the note of the currently highest pressed key, which can be used as a sound effect. The "V" switch is rather fake since it makes no own waveform or envelope but is only yet another low pass filter switch.  Here is a list what the switches of my specimen do, although I am not sure if this is their intended behaviour:
tab stop switch function
octave switches: (Switches "I", "II", "III" are mechanically coupled and can be theoretically only pushed in sequence.)
"I" 1 octave lower
"I"+"II" 2 octaves lower
"I"+"II"+"III" 3 octaves lower 
waveform/ envelope switches: (The suboscillator is muted unless "A" or "B" is pushed.)
"< >" sets main oscillator volume very low; only suboscillator stay loud and turns a bit duller
"A" 1 octave lower (a bit duller than octave switches, swaps main and suboscillator?)
"B" sonorous multipulse bass, activates suboscillator 2 octaves lower (with "A" main oscillator is 1 octave lower =>less harsh with more mids)
"P" percussive popping attack phase & louder
"V" makes everything duller (simple low pass filter, should have rather another number instead of the letter)
filter bank switches:  
"1" (low pass) much duller and quieter
"2" (low pass) similar but less dull
"3" (low pass) same like "2" ("2"+"3" is even duller)
"4" (low pass) similar but less dull
"5" (treble resonance) brighter
"6" (treble resonance) same like "5" ("5"+"6" adds to combinations of "1".."4" more mids, makes them more sonorous)
"7" (treble resonance) rises very high overtone (most noticeable with "9")
"8" (treble bypass) brighter (adds trebles independent from low pass filter settings, "1" or "2" and not "0" make treble louder)
"9" (high pass) thinner (removes bass)
"0" (mode change) muffles "1".."2" (most noticeable with "7".."9"), does nothing when "1".."2" unset

With no switches set, the timbre resembles a bright flute at high notes and a saxophone at lowers. On the site Clavioline.com there is a list of sound "patches" with switch combinations to simulate various acoustic instrument timbres.

Although the 10 filter "tab stops" are only on/ off  switches and no continuous (potentiometer) controls, they can be used in various creative ways for realtime sound effects. E.g. by pressing a switch with a short delay after playing a note, you can imitate a gritty pseudo- wahwah effect, and you can also do a lot of rhythmic modulation effects by holding a key down and manually switching the timbres. As you can imagine, the result sounds very blocky since these are only individual switches and no smooth filter sweeps or the like. But this gives the thing also a special sound style, with that a lot of wicked electro tekkno stuff can be created, although (like with a classic organ) the result depends much on the play skills since this is nothing programmed but only played by hand. Don't fear - the switches appear to be a durable minimalistic design; they contain simple brass leaf contacts without clicking mechanical parts (similar like key contacts), thus they are unlikely to break from repeated use despite their caps are of fragile duroplastic. My Clavioline is badly shielded and makes a lot of hum when placed next to a running (CRT based) TV set. The resulting buzz also changes with the actual filter setting. Great is also that you can set the octave so low that the bass range turns into a very buzzy purring that resembles rather a motor bike or motor hum from historical car racing videogames, and with vibrato it makes great bizarre textures when the octave is set so low that the tone frequency gets into the same frequency range. (Remember, there is a stepless vibrato amplitude and frequency control.)

But very noticeable is that the volume differs extremely among different filter settings. Possibly this was the reason that there was no volume control except the knee lever, which range this way reaches from (almost) silence to maximum volume. Annoying is that the lever needs to be pressed continuously to hear any sound, because it moves back into the silence position by its return spring. Unfortunately there are no means of pitchbend control (beside the awkward and fragile tuning knobs), although from everything I read about the age and purpose of the Clavioline (namely to imitate brass and string sounds) I had surely expected this thing to be more like a trautonium than an ordinary keyboard instrument. By the monophonic tone generator it would have been technically easy to integrate a ribbon controller, to give the thing a rather theremin- like expressivity, not least because the continuous volume control (knee lever) is already there, and its suboscillator could make it sound almost like one half of Oskar Sala's (2 note polyphonic) Mixtur Trautonium.

The instrument can be tuned with a black bakelite knob hidden in a simple hole to the left of the case bottom. A similar knob exists to the right to adjust the octave linearity, i.e. it shifts the pitch of the high keyboard octave notes against the low notes by few semitones. Generally this linearity is not really perfect and makes the octaves a little disharmonic, especially after switching the octave setting. But  this can be also used as a sound effect to make the sound "squint" in a lovely anarchic way. (These are things you really can not do on average digital keyboards, and even a mechanical Hammond organ stays always perfectly in tune within itself and never leaves the chromatic scale.) Nasty is that these holes contradict any modern CE consumer safety rules, because when you push your fingers only some cm further in, you can easily damage cable solder joints or (at the right knob) get a really unfriendly 78 volt jolt fired through your bones from the keyboard envelope trigger voltage.
This is the classic loudspeaker cloth...   ...and this a sample of the imitation leather material.   The case lid has a grey paper lining.

repair & circuit bending details

Danger: Tube electronics works with high voltage that can cause lethal electric shocks or fire. Thus don't repair or modify these unless you know what you do.

amplifier cabinet:

The Jörgensen Clavioline instrument is powered by its external tube amplifier. I read that with many such instruments the original amp got lost, but likely also a new tube power supply could be build to resurrect such incomplete specimen. There seem to be multiple amplifier versions with different tube counts inside. My specimen has the model name "V/C" and serial number "Y49"; its hardware is designed very strait forward like from an educational book and contains only 3 tubes (1x "EZ81", 2x "6V6"). 
The amplifier contains only 3 tubes although there are holes for 5. Also on the chassis front were 3 unused holes. All surplus holes are closed with glued fabric.

The organ connector jack at the amp has the following pin assignment:
  1. "+" 5.95V AC
  2. NC
  3. +237V
  4. audio in
  5. GND
  6. -102V
  7. GND
(counting right to left anticlockwise)
All voltages were measured with transformer set to 240V mains voltage, organ connected and "< >" switch off. The tube heater voltage of 5.95V (instead of normal 6.3V) is a bit low, but setting the transformer into 220V mode rises it to 6.53V, which is certainly worse for the tubes than a little undervoltage. With "< >" on, the negative high voltage becomes -92V and the positive high voltage becomes +245V. With organ disconnected, the positive high voltage becomes +281V, and the negative voltage only -74V. I shielded the high voltage pins with shrink sleeve pieces for touch protection. Although the jack looks similar, the pin assignment is different from the Jörgensen Tuttivox.
In the amp chassis was a melted capacitor. This is the chassis with new caps, a new lamp and my sound output upgrade. To the right you see the shunt resistor. For high voltage touch protection I covered the amp vent holes with nylon mesh.
My original mains cable had only 2 leads and thus no grounding. Due to the metal case and chassis of the instrument it is strictly recommended to replace it with a grounded mains cable to prevent the risk of electric shocks in case of failures.

mains voltage selector & capacitor replacement

To select the mains voltage, unscrew and pull out the fuse holder at the mains voltage selector. Then loosen the center screw, rotate the selector to the new voltage setting and screw everything back into place. With my specimen the fuse was corroded and thus got stuck and cracked apart. when I attempted to remove it. When I finally managed to lever the sheet metal fragments out of the holder, the fuse type was not readable anymore. Thus for 240V I used a slow 630 mA fuse, which works well. (The instrument consumes only 65W (measured) although it claims 80W on the model plate.) Unlike claims on the model plate, this instrument has not only a 110 and 220V AC setting, but also one for 240V, which is the actual German mains voltage. When set to 240V, the tube heater voltage of 5.95V (instead of normal 6.3V) is a bit low, but setting the transformer into 220V mode rises it to 6.53V, which is certainly worse for the tubes than a little undervoltage.

Danger: In the amplifier chassis the fuse holder is integral part of the mains voltage selector, which routes the fuse protected voltage directly to the individual mains transformer inputs. Thus to take effect at any voltage settings, the mains filter capacitor was placed in the unfused part directly across the mains lines behind the power switch. This is a dangerous design flaw which may cause the amplifier catch fire, since the employed Niwatrop capacitors are of very questionable quality and tend to melt and burn out sooner or later. It therefore would be only a matter of time when this timebomb will blow up, and thus it is strictly necessary to replace this "explosive candy" cap with a modern foil capacitor that can bear 240V mains voltage.

To avoid further trouble, replace all Niwatrop capacitors in the amplifier, and it is a good idea also to replace inside the instrument at least any Niwatrop caps those have cracks or are not perfectly smooth, shiny and dark red anymore.

add a sound output jack

Strange is that (unlike my Tuttivox) this Clavioline had no sound output jacks; likely because it was a much cheaper instrument and not designed as a really professional stage instrument, but it may also be that at its time there were anyway no real studio mixers yet, and thus it was standard to record everything through a microphone from the internal speaker. The loudspeaker is an Audax model with chassis- mounted output transformer and the very unusual speaker impedance of only 2.5 Ohm. (Normally old tube hardware tends to have rather high impedances like 16 or 32 Ohm but not anything below 5 Ohm.) I installed into given amplifier chassis holes a cinch sound output jack and a speaker mute switch, which loads the output transformer with a 3 Ohm power resistor when muted. (Tube amps need a shunt resistor with speaker disconnected to prevent high voltage damage.)

cabinet metal letter restoration

A common problem with the Jörgensen Clavioline is that the metal letters on front of the amplifier case cracked off and got lost over time. As seen on Clavioline.com, Jörgensen made these brand signs in multiple different styles, although the specimens I saw there were in even worse condition than mine.
The embossed brand signs on the amplifier case were apparently punched out of sheet copper and badly tin or zinc plated (some spots left bare). The "i" letter in my word "Clavioline" was cracked off, thus I carefully embossed a new one of thin sheet aluminium, using the given "i" as a mould.
Also the "n" and an underline piece in "Jörgensen" was gone, but its shape was still visible by glue remains underneath, thus I could imitate these missing parts with the same method and hotglued all of them into place. The result doesn't look perfect, but at least the writing is completed.

inside the main case:

The tube instrument is an efficient hardware design...

There were multiple versions of the Jörgensen Clavioline main device with different tube counts inside. My specimen has the model name "M02" and serial number "Y49". Special in this model is the gas discharge tube "STV 108/30, -OB2-", which may be a voltage regulator. The other tubes (1x "ECC81", 5x "ECC82", 1x "EF93") are standard types. Mine seems to contain more components than other brand versions shown on Clavioline.com, despite it is not even a "Concert" model.

...but contained plenty of more or less rotten Niwatrop "explosive candy" capacitors, thus I replaced most of them.

The new caps may look less pretty, but increase reliability a lot.

volume control

The knee lever pulls the sound output voltage through a capacitor against GND(?) to reduce the volume. When not pushed, the resistance is near 0 Ohm and thus the sound is very quiet. When the lever is pushed right, the wiper of the custom made potentiometer slides over its carbon trace to increase the resistance (up to about 130 kOhm with logarithmic behaviour) and thus increases the volume. The carbon trace of my specimen was worn out, which made the lever fail and thus stayed at maximum volume. To fix this, the wiper finger can be shifted after loosening a screw. Also the contact screw on the trace was loose and had to be fastened (use no excessive force here - it may crush the trace board easily).

Normally the instrument can not be played without always pushing the knee lever, because the spring loaded lever otherwise returns to zero volume position. To fix this, add a logarithmic 100 kOhm potentiometer in series to the lever pot to make the minimum volume (with unpushed lever) adjustable. To reduce the maximum volume (with lever pushed fully right), add another potentiometer parallel to [lever pot in series to min. volume pot]. For this I used an old 50 kLog potentiometer with carbon trace cut (by screwdriver) at its right end to disable its volume limiting effect when turned fully right. I mounted mine with a piece of sheet plastic and hotglue, although there are certainly more elegant solutions.

These are the added hardsync and volume controls; I equipped them with classic bakelite knobs.

tuning & octave linearity pots

There are 2 hidden knobs in case bottom holes; the left one adjusts tuning, while the right one adjusts octave linearity. It is a good idea to glue some sheet plastic behind them to prevent cable damage and electric shocks.

Initially my tuning and octave linearity potentiometers were stuck and didn't turn well because their oil was hardened. A drop of isopropanol and new machine oil at the capstan gap helps a lot here. (Do not attempt to turn with raw force; the brittle bakelite knobs may break easily.) Dismantling the pot didn't help, because the capstan is bolted and can not be pulled out for cleaning even when the back of the potentiometer is opened. The knobless "trimmer" pot next to the tuning pot seems to be another octave linearity control.

hardsync control knob

Between the tubes in the back of the instrument is a trimmer potentiometer (quite big, like a normal one) to adjust the operating point of the hardsynced suboscillator (octave divider). The suboscillator is only active during certain waveforms; when normally adjusted, all notes on the keyboard will have the same timbre. But this knob rocks way too much to keep it there, because when "misadjusted", the suboscillator will make a foldback to a lower (wrong) octave on higher note keys (was the case when I bought the instrument), and in other settings the timbre varies cyclically every n-th note (similar like a ring modulator). The resulting warm roaring overtone structures resemble a distorted heavy metal guitar or overblown saxophone or like stepping through the individual buzz timbres on the Atari POKEY sound chip (like the ascending motor hum in Atari VCS2600 car racing games), and some settings and note combinations even remind to a howling wolf. To make it available, I simply cut a small hole into the back grill and prolonged the potentiometer capstan with a plastic stick that I connected it in a semi- flexible way by pushing a piece of PVC mains cable insulation over both ends. By the (clutch- like) flexibility, the knob can be safely rotated over the limits of the potentiometer to bring the mark on the knob (mine is simply hotglued to the stick) into correct position to indicate the neutral position when facing up.

With unknown internal trimmers it is always important to verify that they won't overload other components when turned too far, but I have checked with a power meter in the mains socket that the power consumption of the instrument stays independent from its actual trimmer setting (and also the tubes don't glow abnormally), thus it is unlikely that the new control knob will damage the oscillator tubes.

key contact maintenance

The key contacts were oxidized, had bad solder joints and one was cracked off... but after removing both bakelite sides and side screws, the keyboard can be flipped up for maintenance.
The key levers are held up by a row of springs.
One of these silver plated leaf switch contacts was cracked off and missing. I replaced it with a sheet steel piece made from a 3.5'' diskette slider; the key works perfectly now.
With keyboard flipped up, the key contacts can be easily cleaned with fine sand paper. Important is to straiten bent contact wires to make the keys respond equally. Also the tab stop switches may need cleaning and adjustment, but they can be easily reached with case bottom removed.

control voltage inputs - adding a ribbon controller?

The keyboard has 2 contacts per key, made from each 2 wires touched by a grounded leaf spring contact. The first contact controls the note pitch; these contacts of all keys are wired in series with resistors in between, forming a voltage divider chain with one resistor per key. The VCO input line has -20V with no key pressed, and is pulled up to 0V at the rightmost key. The control voltage does not change by the octave switches. The VCO input measures against GND 416 kOhm with no key pressed, 260 kOhm with the highest note key pressed and 0 Ohm with the lowest note key pressed. The 2nd contact triggers the envelope and these are wired parallel at all keys. With no keys pressed, there are about 78V on this line. With keys pressed, the voltage reduces to 21.7V with "P" switched off, and to 0.6V with "P" switched on.

Although by the high voltages I would not recommend to add the ordinary touch sensor contacts known from circuit bending, it would be very worth the effort to upgrade this thing with a genuine ribbon controller, like known from a Trautonium or Ondes Martenot. To get the hands free to play with the switches, theoretically also a MIDI converter could be connected to the VCO control lines, but I doubt that the voltage per octave ratio of the control voltage input is anything standardized. Otherwise a homemade opto- mechanical loop sequencer wheel in the style of a 1950th Circle Machine would anyway fit better to the appeal of this ancient tube synthesizer, and with optional crank and flywheel it would be much more fun also.

The Clavioline was manufactures by multiple companies; beside Jörgensen there were also versions made by Selmer, Gibson and Bode, those had different case and hardware designs (e.g. vibrato switches instead of knobs).  Selmer and Gibson variants were also released as "concert" models with 4 additional waveform tab stops (e.g. for "clarinet").

On the Selmer model (seen on eBay) these 4 black switches were labelled {"SUB I p", "SUB II p", "SUB I f", "SUB II f"}. The "p" and "f" may be "piano" and "forte" (quiet and loud) while "SUB I" and "SUB 2" certainly refer to the suboscillator. Either this instrument had a second suboscillator or only 2 suboscillator (octave?) settings where each setting could play quiet or loud. Also one of the normal waveform switches was labelled "F". For vibrato it had 3 black "vibrato" and 1 "amplitude" switch; my Jörgensen model controls both stepless by potentiometers. Selmer released in 1963 also a concert model with built-in spring reverb. In Italy a concert model was released with the name "Ondiola". Similar instruments like the Clavioline (but with partly different timbres) were the Ondioline, (in Holland "Orcheline"), the Lipp Pianoline, the Jennings Univox and the Hammond Solovox. The latter was likely the world first electronic mini keyboard (invented in 1940), because although its wooden main cabinet was quite large, the keyboard itself had almost as small keys as My Music Center. More info about these instruments can be found on the site Clavioline.com. A remotely similar like the Clavioline sounding (but modern and much cheaper) analogue instrument is also my modified toy tablehooter Golden Camel 7A.

 removal of these screws voids warranty...    
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