Sequential Pro-One – modifications and upgrades (part 3)

Part 3 of our Pro-One upgrade trilogy provides hints for a new CPU, MIDI kits, and some very simple modifications. The material for the latter can be purchased in any hardware store for a few Euros, and lend the Pro-One a higher degree of stability …

Sequential Pro-One Synthesizer

First, however, an after-thought on the side panels of the Pro-One. These may be had not only in the USA, but also in Europe. Strictly speaking, any experienced craftsman musician could manufacture them himself, but entrepreneurs / professional carpenters often have better access to noble woods.

One company in question is based in London / UK and can be found on Mint Case. The provider not only offers side panels for the Pro-One (and a complete Pro-One wooden case as well), but side panels for a large number of synthesizers – from the Korg Mono/Poly to the new Behringer vocoder …

Sequential Pro-One Synthesizer Wooden End Panels
Sequential Pro-One Synthesizer Wooden End Panels

Now to the insides of the Pro-One. From today’s perspective, the computer-technical facts of this 1981 synthesizer are ridiculously elementary. There is the ROM and RAM area of ​​the Pro-One, for example, which is tiny. It is not surprising that the sequencer can only store a maximum of 40 steps and that it immediately loses its memory when the instrument is switched off.

An upgrade brings some light into this digital darkness: Music Technologies Group (MTG) is the manufacturer of a CPU which not only extends the Pro-One sequencer memory to 256 steps, but also ensures that sequences are retained after the instrument is switched off.

Sequential Pro-One Synthesizer - New CPU

“The MTG Pro One Turbo replacement CPU Module is a drop-in replacement microcontroller for the Sequential Circuits Pro One’s 8021 CPU (AKA P8021/8021H/P8021H). Plug-n-Play! No soldering required!”

For another option, Music Technologies Group offers a MIDI kit (IN / OUT), in which, as a special feature, the Pro-One arpeggiator / sequencer is MIDI clock syncable (MIDI IN) and can transmit its data to the exterior (MIDI OUT). In addition, the Pro-One keyboard can be used to play other MIDI synthesizers polyphonically (!) …

Sequential Pro-One Synthesizer  - MIDI Kit

Kenton Electronics should also be mentioned. The company offers a Pro-One retrofit kit that can receive pitch bend / mod wheel / filter cutoff frequency and sustain MIDI values ​​(with a range of a respectable 60 notes).

So, finally, to our two last suggestions, which again concern the hardware of the Pro-One. One of the few unpleasant aspects of this instrument is the instability of the pots. Fastened directly to the (one and only) large main board, they are not screwed to the panel and therefore lack stability. They feel shaky – they don’t feel good.

Sequential Pro-One Synthesizer

This problem can be tackled very easily with washers. Assuming the diameters of the washer and the knob match, this modification is not detrimental to the appearance of the Pro-One. To the contrary: The washers and the aluminum knob caps (mentioned in part 2 of our trilogy) contribute to a coherent overall impression of the instrument, above and beyond the stability that is gained.

Of course, such a modification needs to be considered carefully, since you have to attach the washers to the panel with glue (superglue?). Ideally this should be done with light pressure against the potentiometer axis at the moment of sticking, in order to alleviate the wobble factor (the original problem) once and for all.

Sequential Pro-One Synthesizer

Once glued on the Pro-One, the washers cannot be easily removed – at least not without leaving stubborn residues. Caution is advised! Take your time – work slowly and precisely. You don’t want to ruin your Pro-One.

In most cases, removing the pasted washers won’t be an option anyway. Since a Pro-One with stabilized potentiometers is a lot more comfortable to operate (and also looks much better!), you will hardly want to revert it back to its original condition.

Sequential Pro-One Synthesizer

Another – even simpler – modification is the rear stabilization of the Pro-One metal housing. If you look at the innocent simplicity with which Sequential accommodated the inputs / outputs on the main board and from there (via holes in the housing) to the outside, you wonder why the company didn’t invest in 7 spindle nuts as binding (and stabilizing) elements.

This is no criticism, of course. The Pro-One was designed, manufactured and sold as an inexpensive instrument. Therefore, it had to be assembled with just a few quick steps. Especially in the first two years – 1981 and 1982 – this great monophonic synthesizer was manufactured non-stop, with an output of up to 50 pieces a day. So it’s no surprise there wasn’t time for mounting extra spindle nuts.

Sequential Pro-One Synthesizer

But what was missed in the early 80s can be made up for today. The threads are there, so it’s just a matter of the few seconds needed to mount the nuts and stabilize the rear side of the Pro-One. A slight pressure against the rear wall is recommended during assembly, making the jacks protrude a little more and facilitating the mounting of the spindle nuts.

Sequential Pro-One Synthesizer

The result is not only a visual upgrade, it also gives the Pro-One significantly more stability. In addition – now we are back to the optics – the spindle nuts with the silver Pro-One / Sequential badges and the aluminum pot caps (if they have been added) effect an even greater visual harmony.

Sequential Pro-One Synthesizer

This ends the trilogy of Pro-One upgrades. All modifications – even the handling of that superglue – are of course at your own risk. The individual articles serve primarily to illustrate some options of improving the hardware of this classic synthesizer – if you want to.

Sequential Pro-One Synthesizer

The fact is: only a small investment is required to diffuse the dominantly cheesy, plastic look of the original. A few washers, nuts, wooden parts or aluminum knob caps are enough to achieve a balance between the instrument’s SOUND and (after upgrades) its valuable DESIGN.

Sequential Pro-One –
modifications and upgrades (part 3)

CPU Upgrade
MIDI Upgrade
Simple poti stabilization
Simple rear side stabilization

Sequential Pro-One – modifications and upgrades (part 1)
Sequential Pro-One – modifications and upgrades (part 2)
Sequential Pro-One – modifications and upgrades (part 3)

Sequential Pro-One – best vintage monophonic?

Filed under 2020, General, Stories

“Es genügt, einen Ton schön zu spielen” sagte der Komponist Arvo Pärt im Jahre 2005. Diese Aussage ist ebenso einfach wie ich auch exzellent: Es braucht kein Meer an Tönen, denn entscheidend ist der Klang. Dass so mancher Vintage-Synthesizer der 70er und 80er Jahre teils unerreicht hochwertige Klänge liefert, steht außer Frage. Doch tatsächlich leben wir “heute” in einer nahezu perfekten Zeit. Einerseits hat man – mehr oder weniger – noch Zugriff auf die Vintage Analogen, andererseits wird auch bei Neugeräten die wichtige Komponente des hochwertigen Klanges wieder zunehmend berücksichtigt. Doepfer, Cwejman,, MacBeth, Moog, GRP, Studio Electronics, COTK, John Bowen und andere Hersteller bauen hervorragende Synthesizer, die den “Klassikern” in nichts nachstehen. All diesen (alten wie neuen) “großartigen” Instrumenten ist Great Synthesizers gewidmet. _________________________________________________________ In 2005 composer Arvo Pärt said: “Playing one tone really well is enough”. In other words, it is sufficient to play one tone 'beautifully'. I agree with that. All musical efforts are focused on the sound itself. Although I studied classical music (piano and drums), it’s the electronic sound that inspires me. Synthesizers are the epitome of new sounds and exciting tonal spheres. Today, many companies produce high-quality - excellent! - synthesizers: Doepfer, Cwejman, MacBeth, Moog, GRP,, COTK, Studio Electronics, John Bowen and others. It's their products I'm really interested in ... apart from Vintage Synthesizers, which I have been collecting for 20 years. Subsequent to our former websites Bluesynths and Blogasys, Peter Mahr and I have now created GreatSynthesizers. We hope you like it.

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