[caption id="attachment_85" align="aligncenter" width="258" caption="Norm Leete with MkII Mellotron"][/caption]

In 2008  I finally went self-employed and formed NormLeete Industries repairing and restoring old electronic musical instruments as well as building bits for new ones. One of my roles in creating the controller for the M4000 was writing the software (in assembler - very Old School).  As I cannot completely escape my past I have also done some Software Consultancy.

[caption id="attachment_43" align="aligncenter" width="557" caption="Norman, Frank and Les Bradley (picture courtesy of John Bradley)"][/caption] The Chamberlin, described as "a sideboard with keys on", had many shortcomings but the Bradleys were "staggered" by the concept of a tape replay keyboard. The Chamberlin was also very difficult to produce in large numbers so the Bradleys refined and added their own innovations to the design and produced a new instrument that was named the Mellotron Mark I (The name came from MELOdy and elecTRONics but was finally spelt with two l's). By the end of 1962 financial backing was in place from some quite well known show business names such as David Nixon (TV magician) and Eric Robinson (Big Band leader, and supplier of many of the musicians who were recorded onto the tapes) and the factory in Streetly, Birmingham was opened.

The first Mellotron produced was the Mark I and was designed as a home instrument along the lines of an electronic organ. 55 were made in 1963.

The Mark I was quickly followed in 1964 by the improved Mark II. Most Mark I's were converted to Mark II spec as well. Also having two 35 note (G - F) keyboards side by side it looked very similar. About 250 were made between 1964 and 1968.

An offshoot of the Mark II was produced for the BBC that was called the FX Console. It was a modified Mark II used for adding sound effects for radio and TV programmes (including Doctor Who). About 60 were made between 1965 and 1970. There was also an offshoot of the M400 used for the same purpose.

The M300 followed the Mark II and was the only production model that used 1/4" tapes. Although Mark I and Mark II Mellotrons had already been used on quite a few albums in the late 60's this was still produced as an alternative to the home organ. About 60 were produced between 1968 and 1970.

The M300 was followed by the most well known and successful model, the  M400. By now Mellotronics had realised that the main customers for the instruments were rock bands so this was the most portable and oft-gigged version. About 2000 M400's were produced between 1970 and 1986. This includes all Novatrons and the one-off teak flavoured batch of 100 produced by EMI in the mid seventies.

[caption id="attachment_44" align="aligncenter" width="489" caption=" Inside the original Streetly Electronics factory - more Mellotron mass production (picture courtesy of John Bradley)"][/caption] A variation on the 400 was the Mark V that was basically two 400's side by side with a common capstan but only 30 were produced before disaster struck and the parent company Mellotronics went bust.

Two sad facts here, firstly Streetly who were actually producing the instruments were still financially sound and secondly, they were no longer allowed to call the instrument they produced 'Mellotrons'. The reason for this is that the registered name 'Mellotron' was accidentally lost along with the other assets of the company 'Mellotronics'. The M400 was quickly re-christened the 'Novatron' and was produced until the sad (but temporary) demise of Streetly Electronics in 1986.

Although originally designed as a 'home entertainment' keyboard by the mid sixties the Mellotron was starting to appear on contemporary rock / pop records. A few of the many users of note have included The Beatles, Yes (Rick Wakeman burnt his!), Genesis, Tangerine Dream, King Crimson, Moody Blues, Manfred Mann, Strawbs, Traffic, Led Zeppelin, Rolling Stones, Gentle Giant, Jethro Tull, Larry Fast (says he still has it), J M Jarre (recently seen on German TV with his M400 and is still touring with them), Barclay James Harvest, England, Pallas, Peter Sellers and (allegedly) Princess Margaret!

For most people the Mellotron finally faded into oblivion in the eighties, replaced by affordable solid-state samplers and sample replay keyboards. Mellotrons ended up being scrapped off or were left abandoned in squalid conditions in damp cellars and dusty storerooms.

However this is not the end of the story as the Mellotron has recently seen a revival in it's fortunes in recent years. Quite a few fashionable people are starting to rediscover it's unique sound (check out Oasis, Radiohead, Julian Cope and Node to name but a few). Sadly this has caused a considerable hike in the price of a Mellotron here in the UK so expect to pay at least 1500 pounds for an M400 (probably in dire need of repair) and about 4000 pounds for one that has been professionally restored by Streetly Electronics (restarted by John Bradley, Les Bradley's son, who know all there is to know about Mellotrons).

However the story has taken a twist that even I couldn't have forseen and that is I have been involved in the design of the next generation of instruments namely the Streetly M4000. Now available in limited numbers as the production process is still being developed. The reaction I have seen to the first fully working prototype has been extreme exitement, something you can lose sight of having worked on a project for a very long time.

I still have a Mellotron M400 after all these years and although I was tempted to sell it once during the 'dark years' I am glad that I retained my small piece of rock history.

The Mellotron is a revolutionary keyboard instrument providing pure music on triple channel pre-recorded tape. 18 different rhythms can be selected on the left-hand keyboard by means of a simply operated press button panel. On the right-hand keyboard 18 different lead instruments are available on which you can play the melody of your choice. The ingenious numbering system enables anyone with the slightest knowledge of music to play this fascinating instrument of the 60's." MEASUREMENTS: 39" High x 51" Wide x 27" Deep. WEIGHT: 350lbs. VOLTAGES: The instrument operates on all normal voltages. AMPLIFICATION: Transistorised amplifiers of special design are fitted together with full range volume controls. LOUD SPEAKERS: Two 12" heavy duty loudspeakers of high quality fitted. Output capacity 15 Watts each. Built in jacks for independent loudspeakers fitted as standard. INSTRUCTION MANUAL: A comprehensive instruction manual accompanies each instrument. GUARANTEE: Each instrument carries a 12 months guarantee. SERVICING: A service organisation is available. EXTENDED AND RENTAL TERMS NOW AVAILABLE

Only 55 were made, mostly in 1963. Most were converted to MarkII specifications when serviced.

The Mellotron - Mark II

The Mellotron M300

The 300 followed the Mark II and was the only production model that used 1/4" tapes. It had a single 52 note (A-C) keboard although it still had the left hand accompaniments. The recordings were all new (including the "melancholy" violins) and now included piano, harpsichord, celeste, clarinet, trombone vibes and several electronic organs(!). They were better recordings than before as Streetly learned which sounds worked well. The left hand included rhythms such as samba, quickstep, latin and several waltzes with more 'open' chords than before making them more versatile .A few selections allowed an instrument such as piano, organ or cello to appear on the left hand as well making all 52 notes either a single instrument or allowing a split between two instruments.

The Mellotron- M400

The range of sounds available was far wider than before coupled with the ability to order any combination from the Mellotron library or even ones recorded by the user could be put onto custom frames by the manufacturer. Mellotronics offered 8 string sounds, 5 woodwind sounds, 8 brass, 5 choirs, 3 organs, 11 'acoustic percussion instruments' and 11 'electronic percussion instruments' and a large number of sound effects.

This is because a variant of the M400 (called the 400FX) was available to special order to replace the FX console once the production of Mark II's had ended. What you ended up with was an grey or black M400 with the tone control replaced by a 'monitor' control that determined the volume of the signal coming out of the additional headphone socket on the front. This allowed the operator to determine what the next sound effect cue sounded like while the main volume was down which was more useful than the original tone control as EQ and effects would be added externally. As the M400 has no cycling mechanism the 400FX were supplied with eleven additional tape frames in cases (1260 sounds in all) to make it equivalent to the original FX console. It was claimed by Streetly that a set of tapes could be changed in two minutes. I can confirm that, with practice, that this time can be easily improved on (especially with the help of an assistant). About ten 400FX's were made between 1970 and 1984 although another twenty or so standard M400's were converted and sold as FX machines to various broadcasting companies around the world.

A conversion kit was also made available that allowed the owner to make their own tapes based on standard 1/4" tape. This meant that only two sounds were available on homemade 'custom' frames. Only four controls to worry about, volume, tone, pitch plus track selector and only 35 keys (G - F). Although fabled to be extremely unreliable I was in a band that gigged two M400's for several years and they never once let us down (I still have one of them). The secret was to load them into the van last, take them into the gig and power them up on arrival so they could warm up and then play every note to make sure nothing had stuck in transit. One of the enemies of a Mellotron is change of temperature as this can cause condensation to occur on parts like the capstan, this can cause a tape to stick thus breaking it. A padded cover was available called the Protecta-muff that looked like bondage trousers for a Mellotron (all straps, buckles and black PVC) that protected the instrument in transit and made it easier to carry as it had handles. The M400 was also slightly modified and supplied as the 400 FX console, see FX Console for more details. There was also the Mark V, a two manual derivative that used the same tape frames, that was produced in small numbers. The Novatron is also an M400 although the name was changed when Streetly Electronics lost the rights to the name when Mellotronics was sold off. [caption id="attachment_68" align="aligncenter" width="310" caption="Patrick Moraz with Novatron in one of the later publicity shots"][/caption]

The Mellotron - Mark V

A variation on the M400 that also holds memories of the original Mark I was the Mark V that was basically two 400's side by side with a common capstan.

To make the instrument narrower and to give it a more modern 'thrusting' look the controls were mounted in front of the two keyboards and the cabinet was covered in black tolex. The controls were the usual M400 Volume, Tone and Pitch plus Reverb (not present on the M400). Outputs were stereo and a headphone socket was provided. Only 30 were produced in total between 1975 and 1984. After the enforced name change in 1977 the model became known as the Novatron Mark V but these are extremely rare.

The Streetly - M4000

The next picture shows the tapes after they have been threaded. This is an easy job as all the tapes are attached to a bar that is held in place by the 2 yellow finger bolts at the rear of the machine.

HEIGHT: 34" (86cm) WIDTH: 34" (86cm) DEPTH: 22" (56cm) WEIGHT: 122lbs (55kg) POWER SUPPLY: Transformer tapped at 115V, 220V, 240V 50 or 60 cps. Single phase. Consumption 75 VA. OUTPUTS: 1. Unbalanced line output via 2 circuit jack, 2. 3 volts into 5K ohms, via foot swell pedal, 3 volts into 600 ohms without foot swell pedal. SIGNAL TO NOISE: Better than -55dBM. TAPE VELOCITY: Normal 7 1/2 i.p.s. Variable speed range +/- 15% REPRODUCE FREQUENCY: 50 HZ - 12KHZ Reproduce characteristic modified NARBT standard. TONE CONTROL: 12 dB cut at 10 Khz REPRODUCE HEADS: Low impedance: 3MH: 35 in total.

1. Remove the cabinet lid by holding from the rear and lifting upwards. 2. Unclip the left and right key end blocks. 3. Release the four RED knurled finger screws which hold the keyboard assembly. Lift upwards clear of the instrument. Place on a clean surface. 4. Remove the aluminium tape storage box lid located behind the capstan bar. 5. Release the two YELLOW knurled finger screws that hold the rear tape clamp bar in position. 6. Lift the bar upwards and toward you until the tapes are in a vertical position just before the front tape guides. 7. Slowly lower the bar into a position behind the front tape guides. Locating pins at each end of the clamp bar should be rested in the points provided - coloured YELLOW. 8. Release the two BLACK knurled finger screws. Lift the complete tape frame slowly upwards until completely clear of the unit. 9. Place in the tape frame box to avoid damage. Fitting the tape frame is the reverse of the above procedure. All knurled finger screws must be secure to avoid assemblies coming out of adjustment.

Replay Heads (1) Cleaning It is recommended that the replay are cleaned at least every 3 -6 months depending on the amount of use of the instrument. Proceed as follows:- Expose the heads as if removing the tape frame. Using a smooth, clean cloth with a little Methylated Spirit or Carbon Tetrachloride clean each head methodically and polish immediately with a clean portion of the cloth. (2) Demagnetising The heads should be demagnetised once every 12 months or on fitting a replacement head block assembly, when a head block has been tested using a meter or a head has been in contact with a magnetised instrument. Proceed As Follows:- (a) Expose the head block as if removing the tape frame. (b) Release the retaining springs at the four points on the head block. (c) Disconnect the output lead of the head block. (d) Using a demagnetiser carefully demagnetise the whole head block taking care not to switch the demagnetiser off in the vicinity of the head block. Most demagnetiser manufacturers give detailed instructions of this operation which should be followed. REMEMBER A MAGNETISED HEAD CAN PARTIALLY ERASE A RECORDING.

KEY ADJUSTMENT 1) The depth of movement of the keys is controlled by the aluminium bar supported about 8" from the front of the keyboard on top of the keys. The height of this bar is adjusted at the factory to give a maximum depth of key movement of 3/8". 2) KEY TENSION (or touch) The key tension is determined by the 2BA Nyloc Nuts, retaining the key leaf springs at the rear of the keys. By turning each nut clockwise the key tension will increase and the key will rise. In manufacture, keys are adjusted by the above method until the key rises and just comes into contact with the bars above the keys. When all the keys are just touching the underside of the bar, a further 1/4 turn is applied. This is the standard key adjustment. 3) PRESSURE PAD ADJUSTMENT Pressure pad adjustment is achieved by turning the 4BA screws protruding from the top of the keys nearest the front of the instrument - hereinafter called the PAD ADJUSTMENT SCREW. Assume that the pad is not pushing the tape into contact with the reproducing head at all. Clockwise movement of the pad adjusting screw will cause the pad to move down under key pressure and with the correct adjustment allow the tape to play. The pad adjustment screw should be turned gently clockwise until sound is just heard - at this point ONE further complete turn should be applied. 4) PINCH ROLLER ADJUSTMENT This adjustment is effected by the second 4BA screw nearest the rear of the key. Correct adjustment is a full 2 turns beyond stall. To achieve this setting turn the pinch roller adjustment screw anticlockwise until the point is reached where the tape slows down and just stops driving. At this point the screw should be turned 2 full turns clock-wise. This is the correct adjustment.

Tape Replacement As before, the manual says:- Replacing a Tape A tape may be replaced with the tape frame in or out of the unit. There follows a description of how this is achieved with the tape frame in the unit. 1) Remove cabinet top lid and front panel. 2) Remove key end blocks by lifting upwards. 3) Remove keyboard assembly by releasing four red finger screws and lifting the assembly upwards clear of the unit. 4) Remove the tape storage box lid. 5) Release the tape to be replaced by undoing the appropriate screws on the rear clamp bar. 6) Pull the tape out of it's position in the storage loops and release the other end of the tape. The replacement tape will be supplied with it's start outermost and this should be placed under the clamp on the rear clamp bar. Proceed As Follows:- 1) Feed the remaining tape on the spool into the tape storage box and remove the tape from the spool. 2) The end of the tape should then be placed under the clamp on the front tape bar. 3) Using service tool 'K' push the tape down on either side of the support roller so that it goes in two loops between the separators. Continue pushing the tape down until the tongs are fully down, then leaving them in place and feeling upwards between the two separators, catch the two loops on the first and second fingers. Pull the loops down on the first and second fingers. 4) Take the spring loaded pulley assembly and break open one side to give access to the rollers. 5) Lift the tape loops onto the appropriate rollers and snap shut the assembly. 6) Check that the height of the tape loop is correct, if not adjust from the front clamp bar. The tape must now be positioned so that it's start is accurately placed over the re-producing head. Proceed As Follows:- 1) Replace the tape storage box lid and the keyboard assembly. 2) Switch on the instrument and tap the key in question. 3) If a delayed sound is heard, release the screws on the rear clamp bar and slowly pull the tape through until the attack of the instrument recorded on the tape responds on tapping the key. 4) Check all tracks in a similar manner. 5) Tighten clamp bar screws and replace end blocks and cabinet panels. Replacing a set of tapes is the same for as for a single tape.

First the ideas that didn't make it! The first incarnation of the M4000 was to be a VST plug-in, this idea was scrapped very quickly as it has so little to do with Streetly's normal business of supplying physical instruments. Next version was a table top M400 style solid state sample replay machine (I must find the pictures of that). A space model was built but tests with a rough prototype of the innards showed that sample replay technology did not satisfy the core requirement of sounding exactly the same as an original tape replay instrument. Even with simulated wow and flutter single notes were convincing but chords were not in back to back tests.

[caption id="attachment_131" align="aligncenter" width="475" caption="The prototype of the digital replay version of the M4000 - the idea was scrapped.   L - R John Bradley, Norm Leete, Nick Magnus and Martin Smith"][/caption]

So it was decided that the M4000 would be a real tape replay machine but that it would be able to cycle like the original Mark II but be similar in shape and size to the original M400. An aim that turned out to be a bit more difficult than it originally sounded and it took a bit longer than we thought it would.

Anyway, the aim of the M4000 was to take the best attributes of the Mark II and redesign those using modern techniques mainly from the ground up. The problem was to squeeze the cycling mechanism into a keyboard not much bigger than a standard M400. The slight increase in size was an opportunity to scale up the height to that of the old Mark II. The method of cycling had to change quite radically as there was no space for the guide tape. The first attempt used a servo driving a DC motor (just like the Mark II) but that wasn't accurate so a new system was designed resulting in the first cycling machine with a microcontroller and software - whatever next!

The M4000 has two extra stations making the total eight (two more than a Mark II) giving easy access to 24 sounds not counting the mixed sounds you get by putting the track selector between tracks. The range of sounds available as standard varies from standard favourites, through less common examples to new sounds - here is the standard set...

Station One Track A : MKII Flute Track B: MKII Violins Track C: Cello

Station Two Track A : String Section Track B : Eight Voice Choir Track C : Church Organ (real)

Station Three Track A : MKII Brass Track B : MKII Tenor Sax Track C : MKII Trombone

Station Four Track A : Male Choir Track B : Female Choir Track C : Boy's Choir

Station Five Track A : M300A Violins Track B : Russian Choir Track C : Sad Strings

Station Six Track A : MKII Church Organ (electronic) Track B : Ian McDonald Flute Track C : MKI Clarinet

Station Seven Track A : Vibes Track B : Watcher Mix (3 violins / brass) Track C : Orchestra

Station Eight Track A: Bass Clarinet Track B: Cor Anglais/Oboe Track C: Medieval Woodwind

Church Organ is awesome, MkII Church Organ is actually a Lowrey through a Leslie, Bass Clarinet is superb, String Section is  violins / violas / cello. It should be pointed out that blending between tracks has been improved so unlike the M400 there is a smooth transition between tracks. This selection is the standard set, you can specify custom sets if you wish. Still only four controls to worry about, volume, tone, pitch plus track selector and only 35 keys (G - F). However you also have a display and four buttons to control the cycling. Here is a close up of the control panel... [caption id="attachment_92" align="aligncenter" width="558" caption="The M4000 Control Panel - Note extra display and buttons for cycling"][/caption]

Cycling is achieved by selecting the target station with the up / down buttons and then pressing the cycle button. When stationary the inch button can be pressed which then allows you to offset the start position of the tape (using the up / down buttons) and also store a user offset for each station. So finally what does it look like? Well the best description I can come with is "a grown up M400" judge for yourself as here is the first production M4000 in all it's glory… [caption id="attachment_93" align="aligncenter" width="611" caption="The M4000 Production Version - less scruffy than the prototype above"][/caption]

There will also be a two manual version called the M5000 which will be even closer to being a modern Mark II.. Finally here is an internal view of the completed machine, notes the drums at front and rear that store all the tape and the chain that synchronises them... [caption id="attachment_94" align="aligncenter" width="611" caption="The M4000 Production Version - the keyboard removes easily for maintenance."][/caption] ]]> 125 2009-07-03 00:02:45 2009-07-02 23:02:45 open open the-next-step-for-streetly-m4000 publish 3 0 page _edit_lock 1246576310 _edit_last 2 _wp_page_template default 528 phdiux@xrvcod.com http://ezymgqmmrhxu.com/ 188.92.75.82 2010-01-19 00:19:07 2010-01-18 23:19:07 wndqgqilegoi, [url=http://fjkiedlqxarw.com/]fjkiedlqxarw[/url], [link=http://lqelfekdypyg.com/]lqelfekdypyg[/link], http://gqfntivzcmqz.com/]]> spam 0 0 531 lrxkdi@pivnxa.com http://udvaeouvpmel.com/ 67.223.232.71 2010-01-23 03:35:40 2010-01-23 02:35:40 fxfmtipfmpas, [url=http://gcgmitidusos.com/]gcgmitidusos[/url], [link=http://bwomvojnsosu.com/]bwomvojnsosu[/link], http://ryhcpxjmwsgd.com/]]> spam 0 0 527 jdmjll@pdxipx.com http://ddpnzbtpbypa.com/ 92.63.97.147 2010-01-17 04:11:59 2010-01-17 03:11:59 jjksingrrwcw, [url=http://dxhgtqurqpzp.com/]dxhgtqurqpzp[/url], [link=http://ovzaxirbhqnu.com/]ovzaxirbhqnu[/link], http://irfvskmemzkv.com/]]> spam 0 0 529 lyjkyn@kmetqa.com http://vsqdcyqsenop.com/ 168.243.69.98 2010-01-19 05:03:24 2010-01-19 04:03:24 unhmrmgaycwq, [url=http://tkzhaphtkonm.com/]tkzhaphtkonm[/url], [link=http://bllnqfpdiagl.com/]bllnqfpdiagl[/link], http://rimdyyppbvhq.com/]]> spam 0 0 532 joenbaldwin@gmail.com http://www.paydaytown.com 207.81.166.116 2010-01-25 01:16:48 2010-01-25 00:16:48 spam 0 0 http://www.normleete.co.uk/?attachment_id=131 Thu, 02 Jul 2009 23:07:40 +0000 http://www.normleete.co.uk/wp-content/uploads/2009/07/digitron-prototype.jpg 131 2009-07-03 00:07:40 2009-07-02 23:07:40 open open digitron-prototype inherit 125 0 attachment http://www.normleete.co.uk/wp-content/uploads/2009/07/digitron-prototype.jpg _wp_attached_file 2009/07/digitron-prototype.jpg _wp_attachment_metadata a:6:{s:5:"width";s:3:"475";s:6:"height";s:3:"356";s:14:"hwstring_small";s:23:"height='95' width='128'";s:4:"file";s:30:"2009/07/digitron-prototype.jpg";s:5:"sizes";a:2:{s:9:"thumbnail";a:3:{s:4:"file";s:30:"digitron-prototype-150x150.jpg";s:5:"width";s:3:"150";s:6:"height";s:3:"150";}s:6:"medium";a:3:{s:4:"file";s:30:"digitron-prototype-300x224.jpg";s:5:"width";s:3:"300";s:6:"height";s:3:"224";}}s:10:"image_meta";a:10:{s:8:"aperture";s:1:"0";s:6:"credit";s:0:"";s:6:"camera";s:0:"";s:7:"caption";s:0:"";s:17:"created_timestamp";s:1:"0";s:9:"copyright";s:0:"";s:12:"focal_length";s:1:"0";s:3:"iso";s:1:"0";s:13:"shutter_speed";s:1:"0";s:5:"title";s:0:"";}} http://www.normleete.co.uk/?p=134 Mon, 06 Jul 2009 14:41:57 +0000 http://www.normleete.co.uk/?p=134 [/caption] There, I've said it, but perhaps I should add some justification for such a bold statement. The Mini Moog has become a synthesiser icon and as such has become steeped in folklore and legend, people boast of it's prowess and it has become the synth to be seen with. This is unfortunate because in the wrong hands it is not an all rounder and can cause disappoinment (I am sure this is the source of quite a few secondhand or unused Mini Moogs). To fully understand the Mini Moog you must ask yourself the question, why did Bob Moog and his team design it? If you consider what synthesisers were like in about 1968-69 they certainly were not designed for live performance. So I think his intention was to produce a synthesiser OPTIMISED for live performance. If you view a Mini Moog from this perspective and compare it with something contemporary such as the ARP2600 I think he succeeded. If I had to choose between the two then I would plump for the Mini Moog as I consider it to be a true musical instrument and not some sort of 'sound lab' (I had an ARP2600 for many years but when I had to make the difficult choice it was the ARP that was reluctantly sold). The way the main panel hinges up, the space around controls, the clear layout and the large white lettering all assist rapid patching in the four bars leading up to your searing lead synth solo on a dimly lit stage. For such solos the Mini Moog has all the performance controls needed (the first synth to have mod and pitch wheels). The main features in more detail... CONTROLLERS: To the left of the 44 note F-C keyboard are pitchbend and modulation wheels plus on / off switches for glide (portamento) and decay. On the hinged front panel are Tune (used quite often!) the Glide control and Modulation mix. The modulation mix allows any combination of VCO 3 and the noise to be used as the modulation source. OSCILLATOR BANK: Three VCO's; VCO's 1 and 2 having triangle, triangular sawtooth, sawtooth, square, wide rectangular and narrow rectangular waveshapes. VCO 3 replaces the triangular sawtooth with a reverse sawtooth that is more useful as a modulation source. VCO's 2 and 3 have additional tune controls (plus or minus a fifth) and all three oscillators have a six way pitch switch (32' - 2' plus 'LO'). VCO 3 can be disconnected from the keyboard CV while it is being used as a normal LFO. Oscillator tuning is quite an issue on these instruments and varies between examples because of component tolerances. Later examples have a different oscillator board that is much more stable once it has warmed up (critical parts of the circuitry are heated). Earlier examples (before 10175) have a mainly transistor based design whose stability can questionable (although I know one early example whose tuning is perfect). If you are thinking of buying one check the stability of over a period of about twenty minutes and see if it settles down by comparing it with the (handy) built in 440Hz tuning reference. MIXER: Five input mixer with a level control and mute switch for each input. Inputs are form the oscillator bank, an external audio input and a white / pink noise source. The audio input also features the brightest overload indicator you will probably ever see! MODIFIERS :The output of the mixer is hardwired into a 24dB / octave (classic transistor ladder design) with cutoff frequency and emphasis (resonance) controls. There is also a depth control for the dedicated 'filter contour' (envelope generator). Keyboard tracking is handled by two switches giving off, 1/3V / octave, 2/3V / octave and 1V /octave, The output of the VCF goes directly to the VCA that has its own dedicated 'loudness contour'. The envelope generators are both a slightly unusual attack, decay, release design where the decay control determines both the initial decay and release rate. The previously mentioned decay on / off switch forces the release to zero when off. A strange idea but not as bad as it sounds once you get used to it!

OUTPUT: Has a main output control plus mute, a headphone socket and level control and a switch that adds a calibrated 440Hz tone to the output to assist tuning the instrument (also used quite often!). Finally there is a mains switch and indicator.On the top edge of the hinged rear panel are all the input and output sockets. Curiously missing is a keyboard CV output (although this can be added by the technically adventurous).

So there you have it , in my opinion, one of the best designed synthesisers ever manufactured and if I was forced to choose just one synthesiser to own then this would be it.

• DX1 - Voice structure of two DX7's but with larger LCD and better user interface, seperate controls for envelopes, weighted 73 note keyboard with poly-aftertouch, high quality wooden case and a list price of 9500. A true professional's instrument.

• DX5 - similar in function to a DX1 but in a more conventional case (like a larger version of the DX7). With a 76 keys, this time without the poly-aftertouch, this instrument is still a large keyboard but in my opinion if you had the space for it this is an ideal studio master keyboard and it is easier to understand than the DX7 because of the improved control layout. A bargain especially at the sort of silly prices you sometimes see them go for second-hand.

• DX7 - The ideal all rounder of the range for both studio and live.

• DX7-IID - Not a simple upgrade but a complete range of redesigns, only loosely based on the success of the original, that was released in 1987. One version, the DX7-IIFD, included a floppy disc drive for voice parameter storage. The DX7S was also released at the same time for the semi-pro market which was nearer to a straight re-hash of the original DX7 (complete with small LCD, although it was back-lit this time). A module (19" rack mount this time) called a TX802 was also made available.

• DX9 - same size and case as a DX7, this original partner to the DX7 was an odd part of the range as it was a four operator synth without velocity. This makes it much easier to understand but also eventually quite limited. Expect to pick one up for next to nothing, although I personally would go for a DX21 or DX11 for a cheap 4 operator FM synth.

• DX11 - part of the third wave of FM synths, a much more compact keyboard and now multi-timbral. Effectively a keyboard version of the TX81Z module, which strangely came out long before the DX11. Four operator but with additional waveforms other than sine waves, this is the best bet of the cheaper FM synths.

• DX21 - Part of the second wave of FM synths. At this point Yamaha had seemed to have decided that no-one was going to get the hang of programming these synths so they included 128 sounds in ROM that could be retrieved into the normal program locations. Only four operator the DX21 could, for the first time on an FM synth, produce splits and layers as well as having a chorus. Sadly velocity could only be sent via MIDI, as the keyboard fitted was not capable of sensing velocity itself.

• DX27 - similar to the DX21 but without the split / layer facility. 192 presets in ROM that could be accessed directly and only needed to be put into user RAM if edited.

• DX100 - mini-key version of the DX27 and could be used as a strap on MIDI remote keyboard, complete with conveniently placed real time controllers that fell to hand when being played standing up. Great fun - used to have one and regret selling it now.

• TX816 - Has to be mentioned for the total overkill factor as this was a 19" rack mount setup with eight TF1 modules in it, each module was equivalent to a DX7. The only time I ever had a chance to use one of these it was being driven by a DX7 so that was equivalent to NINE seperate DX7's! As each TF1 can remember a tuning offset then calling up a patch on the DX7 controlling the rack would, through sysex, put the same patch in each TF1 but with the tuning offset intact. This results in truly monstrous sounds. Was also available as the TX216 with just two TF1 modules.

• V50 - odd one out as although not a synth with 'DX' in it's model number this was the last of the pure FM synths and the only one that was a workstation. In effect this was two DX11's plus a drum machine, sequencer, disc recorder and effects.

Diagram showing a pair of DX7 operators in a Modulator / Carrier configuration

Algorithm Example - see text for explanation

• VCOs that can be used as VCLFO's (all three).
• RING MOD that can be used as an additional VCA.
• VCA with exponential response for percussion sounds that bite.
• Excellent interfacing with external audio signals. Including an ENVELOPE FOLLOWER that can trigger the synth from external audio signals (cheesy drum machines are a good source).
• NOISE SOURCE that goes right down to a rumble and can also be used as a modulation source.
• VOLTAGE PROCESSORS that can do nearly anything to a control voltage coupled with excellent interfacing with external control sources such as a sequencer. (MIDI interfacing through a MIDI-CV converter is also very straight forward).
• SAMPLE and HOLD that can accept inputs other than WHITE NOISE and that can be externally clocked.
• Stability of tuning that is surprisingly good for it's age and it is fairly easy to fix (although it rarely goes wrong).

ARP 2600 - History

ARP 2600 - Features

1. MICROPHONE PRE-AMPLIFIER with three gain ranges, ENVELOPE FOLLOWER that is pre-patched to the preamp output plus a RING MODULATOR with AC and DC coupling and inputs that are pre-patched to VCO1 and VCO2.
2. VOLTAGE CONTROLLED OSCILLATOR VCO 1 with sawtooth and square wave outputs. There are modulation inputs from KBD, S/H OUT, ADSR and VCO2 (sine) all being fed into a CV mixer that is part of the VCO (another ARP innovation). Frequency can be controlled by coarse and fine sliders plus a switch that selects audio or LF mode. For all three VCO's audio mode frequency range is between 10 Hz and 10 kHz without any reference to octaves. LF mode is between 0.03 Hz and 30 Hz.
3. VCO 2 with sine, triangle, sawtooth and pulse outputs. There are modulation inputs from KBD, S/H OUT, ADSR and VCO1(square). Frequency can be controlled by coarse and fine sliders plus a switch that selects audio or LF mode. There is also a PWM control plus a PWM input pre-patched to the NOISE generator.
4. VCO 3 with sawtooth and pulse outputs. There are modulation inputs from KBD, S/H OUT, ADSR and VCO2(sine). Frequency can be controlled by coarse and fine sliders plus a switch that selects audio or LF mode. There is also a manual PWM control.
5. VOLTAGE CONTROLLED FILTER / RESONATOR VCF has coarse and fine sliders to control cutoff frequency plus a manual RESONANCE control. Audio inputs are pre-patched into a mixer that is part of the VCF. These inputs are from the RING MOD, VCO1(square), VCO2(pulse), VCO3(sawtooth) and the NOISE GEN. Modulation inputs are from the KBD CV, ADSR and VCO2(sine).
6. ADSR and AR ENVELOPE TRANSIENT GENERATORS have such extras as a manual push button plus the ability to select the gate source. GATE and TRIGGER outputs are also available.
7. VOLTAGE CONTROLLED AMPLIFIER has an initial gain contol plus modulation inputs from AR and ADSR. Unusually the sensitivities of the inputs are different, one is linear and the other is exponential. Audio inputs are from VCF and RING MOD.
8. MIXER and REVERBERATOR has inputs from VCF and VCA and converts the mono output via a PAN control and a stereo reverb spring to stereo.