ASM2 Whats Not Included

What's NOT included in the
ASM-2 PCB and Component Kits

The question is often asked

Question: "I am buying the ASM-2 PCB and ASM-2 Component Kit but what else do I need to buy to complete my analogue synthesiser?".

Although the answer is actually fairly simple, explaining why is a bit harder. Anyway I hope to do that below.

Answer: The answer to the question is:-

The ASM-2 pcb offers the builder all of the basic modules required to construct an analogue synthesiser which includes:-

If you purchase and build an ASM-2 PCB and Component Kit then, unfortunately, it wouldn't work!!! Why???

Well the first part of this answer requires you to study the schematics for ADSR1, ADSR2, VCF1, VCF2, VCLFO1, VCLFO2, Glide, Noise and Sample & Hold. Close inspection of these modules shows that they require some pots to complete the circuit. For example, the ADSR modules require pots for ATTACK, DECAY, SUSTAIN & RELEASE. Without these the circuit just can't operate. Similarly for the other modules. The VCOs, VCAs and Ring Modulator are the only exceptions here as they will operate without any additional hardware.

However, even fitting these components to the unit will not give you an operational system. As an absolute minimum we now need to supply power to the board. The ASM-2 includes on-board circuitry which provides the main regulation circuitry required for table and reliable operation of the board but even this unit requires external power which is provided by some form of pre-regulator circuit. In its simplest form this could be one (or possibly two) wall-warts or plug-packs. In its more desirable form it is a built-in AC-DC power supply. This built-in power supply itself may be a commercially manufactured unit or can be home-made (as long as you are FULLY aware of the potentially LETHAL voltages you will be working with when constructing such a unit!!!!!!!). The circuit requirements for the pre-regulator are very simple as shown in this recommended schematic for our RAW-DC unit. The only additional items required to complete this power supply are a mains lead, an ON/OFF switch and a fuse.

Question: Right, so we have built our ASM-2 pcb, we have added the basic pots as listed above and we have attached our AC-DC power supply, will it work now?

Answer: Yes...... and No!!. Yes, because if you stick a scope on to some key points around the board you will see that the VCO's are oscillating, the VCLFO's are oscillating and the Noise module is making lots of noise. No, because you can't `play' the unit yet and you can't hear anything either!!

The last one can be quickly addressed by grabbing a pair of, preferably, high-impedance heaphones and tapping in to the various points mentioned above.

The next problem we need to address is the fact that none of the modules are connected to any of the other modules so our sound generating path stops at the point where the sounds are generated. To fix this problem we need to connect various inputs and outputs together to create a `signal path' through our generated sounds can be fed for modification, such as filtering and mixing, and then fed to an audio amplifier wher we can hear the sounds we are creating.

This is where we move into the next degree of difficulty in answering the question:-

Answer: As Homer Simpson would say.. doh!.. An even tricker question. The problem here is that everyone has there own ideas on how they want to connect their synthesiser. Some people want the total flexibility of a patchcord system them allows them to connect just about any output to more or less any input. At the other end of the ladder some people just want to be able to turn their synth on, twiddle a few knobs and make sounds. Whilst other people want something in between. At this point you should quickly read Appendix B from the ASM-2 manual which briefly summaries these three systems. This is a crucial decision point for the builder as it will seriously affect the complete design of the system including the design of the case, front panel, quantity and type of pots and switches as well as the material points such as nuts and bolts. There is no simple nor easy solution to this problem but my personal preference is for the semi-patched system which offers a good compromise between the flexibility of the patchcord system and the `instantaneous-nous' of a hardwired system. The semi-patched system is also generally more practical in the size of the case that is needed for it. Much smaller than a modular but, usually, bigger than a hardwired unit.

Having chosen the type of synthesiser you are going to build we can then move on how to approach the topic of connecting the module inputs and outputs. For a patchcord system the only real question to address is the type of connector you wish to use and this is covered in Appendix B. This decision will somewhat be governed by the size of the case you intend to use and also will be affected by the design of the front panel. For the other two systems it is common to start with what is termed the `normalised' configuration. In this configuration we define the `normal' connections that will be made and used when `playing' the synth in normal use. For example, it is common to feed the outputs of the VCO's in to one or more of the filters so that you can tailor the harmonic content of the signal and to then feed this `filtered' signal to the VCA's so that you can control the envelope or loudness of the signal. Both the VCF and VCA normally derive their control signals from one or more ADSR's. This `normalised' signal path is achieved by wiring the relevant outputs to the appropriate inputs. In most case you will want these individual paths to have a `level' control so that you can adjust the quantity of each signal being manipulated and this is done through the addition of pots in the signal path. Even in a normalised system there is the need to provide options for some signals. For instance you may want to have a VCLFO control the modulation of a VCO. The modulation control itslef will still go through a pot but you will want to include a switch so that you can select, for example, either the square or triangle outputs from the VCLFO. You can see these extra switches in the Korg Mono/Poly picture in Appendix B.

Another governing factor in your design decision is the case. If you have metalwork or woodworking skills then you may wish to build your own case in which case (!) the shape and size will be of personal preference. For those of us less mechanically inclined you will want to use a ready-made case. Unfortunately your choices tend to be fairly limited in this area unless you have a large budget to throw at it. Nice-Racks will custom build a very nice wooden cabinet for you. A number of suppliers offer various forms of the popular 19" Racking system or you might strike lucky and find a decent size case in your local hobby or electronics shop. As part of the design requirements for the ASMx-Genie family I needed to find a case that was a suitable size yet readily attainable around the world (shipping costs for cases to other countries can become quite prohibitive) and, ideally, not too expensive. I eventually settled on a range of aluminium cases commonly used as video/camera cases or toolkit cases. The size of these appears to be fairly consistent and the price generally very good. On top of this the cases, being made from aluminium and wood, are very easy to work making the task of drilling holes for the few cables and connectors required a simple task even for the least skilled amongst us. With a case chosen it is then a matter of designing the front panel.

Before getting stuck in to the actual task of laying out your front panel you now need to thumb through your favourite supplier of pots, knobs, switches and LEDs. The exercise now is to choose the style of knobs you want in your synth, choose a range of pots that will fit them. then select a range of switches and then some LEDs. If your design includes panel connectors for patchcords etc then you also need to select hem at this point in time as well.

Having made these choices you need to determine how much panel space each item requires making allowance, where necessary, for the size of the item itself. For example, most switches generally have a larger body footprint than may be required on the front panel for finger access to the toggle. However, if you place these components too close together (based on your finger access requirements) you may find that the switch bodies interfere with other items on the panel including mouting rails for the panel where switches are mounted close to the edge of the panel. Similarly pots may have a much larger body than the knobs chosen. When I am designing front panels I like to work on a horizontal spacing of 45mm or more (with 40mm being the absolute minimum) and a vertical spacing of 40mm (with 35mm being the absolute minimum). This approach allows enough room for text and labels to be applied around the component and provide good finger access. Going for smaller spacing usually means compromising the text/labels for the components and can restrict your range of pots, knobs and switches available to you. I also like to lay my panels out on a grid system. This does mean that where you have a number of switches in a module that you do waste panel space nut I generally find the overall appearance of the grid system more gratifying. Having said that, both the ASM1-Genie and ASM2-Genie bend this rule. The ASM1-Genie bends this rule in the area of the patchcord connector section at the bottom of the panel. As this area does not require continual finger access, the reduce space does not compromise the user operation. The ASM2-Genie bends this rule to a much lesser degree. In the MIDI-CV and VCO 1 section you will note a couple of switches and LEDs squeezed in between the grids. Again the impact on the user is fairly minimal.

The other impact on your design of your choice of hardware, case size and panel layout is the number of components you can fit on the panel. Modules like the VCO's and VCF's are equipped with a number of inputs to allow a variety of signals to be fed in. In general there will be a minimal configuration/requirement that will dictate the minimum number of components that `have' to be fitted but there will also be the desire to cater for additional inputs where possible. For example the VCO's should have both a FINE and COARSE control plus there will be at least one LOG FM input (usually from a keyboard or similar controller). In addition to these it is desirable to provide pulse-width modulation of the squarewave and to cater for one or more additional modulation sources such as low-frequency modulation via a LOG FM input for effects like tremolo. You will, inevitably, find that you will need more `holes' on your front panel than you have room for and you will need to trim your design or change to a bigger case and/or a different panel design.

You can see these sort of affects in the ASM1-Genie and ASM2-Genie which both use the same sized case. The ASM1-Genie uses the ASM-1 pcb which had fewer modules on it. A study of the block diagram and front panel for the ASM-1will show that we have managed to incorporate nearly all of the available input and output points in the design and achieved, through the patchcord section, a fairly flexible system. The ASM2-Genie uses the newer ASM-2 pcb which includes a larger number of useful modules. However the inclusion of these additional modules in the ASM2-Genie has meant that we have had to sacrifice several features of the ASM1-Genie. The first obvious one being that the ASM2-Genie is no longer a semi-patched synth but is now a hardwired synth. Also, a closer inspection of the block diagram and front panel will reveal that we do not have quite as many input/output options on some of the models. It is important to note here that these limitations in the ASM2-Genie design are NOT a reflection of the ASM-2 itself but are specifically governed by the size and design of the case and front panel.

With all the above points considered and then applied to your design you should now have an operational synthesiser ! ....

Your synthesiser is certainly now operational. With a suitable amplifer connected to the output of the VCA(s) you can certainly generate a variety of sounds. You will need to use something like the VCLFO or Noise module to generate trigger signals for the ADSR(s) to allow the VCF(s) and VCA(s) to function, and you will want to connect the VCO(s), VCLFO(s) and/or Noise modules to the VCF(s) as your sound source but you won't be able to `play' it.. not yet.

One more final step has to be considered before we can say you have finished system. Control of most of the modules in this system is via `voltage control' (the concept of voltage controlled synthesis was originated by Robert A. Moog) and this extends to the control of the system as a whole. The most common controller used has been the keyboard. Earlier designs of keyboard generated two fundamental control voltages:-

These controls can actually be connected directly to the ASM-2 and provide you with a fully functional system. However these types of keyboard are not as common today and there is also a requirement by many users to use alternative methods of control. A common approach to fit this need has been to utilise the MIDI system and incorporate a MIDI to Control Voltage converter (MIDI-CV) which allows the system to be connected to a much wider range controllers. The MIDI-CV simply generates appropriate KOV and GATE signals in response to pre-assigned MIDI commands received via the MIDI port. The KOV signal is fundamentally fed to the VCO's to define the operating frequency of the VCO's whilst the GATE is fed to the ADSR as trigger signal. With a MIDI-CV fitted you have the option of adding additional control options such as MIDI controlled modulation of a VCO (tremolo). There are a number of MIDI-CV kits on the market including the popular PolyDAC(X).

With the addition of this module we have finally arrived at the end of the construction and it is time for you to plug in to your sound recording equipment and start producing the next `Oxygene' masterpiece!.... woohoo!

So, using the ASM2-Genie as a frame of reference for your complete synthesiser you will need the following
additional items.

Answer: It is planned that a kit of parts will be made available. However, the main reason these items are not currently provided in a kit is that we don't want to restrict you in achieving what you deem to be a `synthesiser'. You might not want the style or colour of knobs that we supply or you may want more inputs on `this' module and not use `that' module or even go for a different style and size of case. Not been a mega-big commercial company that can afford to alienate and lose a few customers because the product doesn't meet their specific needs it is better for us to offer the basic sub-components and allow the builder the freedom to go where ever their imagination and desire takes them. Having said that we do appreicate that some constructors do not have the skills or desire to go through this `design and construction' process and would rather have a `complete kit' and just get on with building and playing with the kit. With those builders in mind we anticipate making the ASM2-Wizard a pre-patched, modular system.

For those builders who decide that the ASM2-Genie does satisfy their needs I am happy to quote on a full set of components as listed in the attached BOM.