Most modular users don't have a Voyager so I didn't get too much interest at Brighton but I did get some interest on Twitter and Muffwiggler and in particular from one wiggler whose frequent enquiries about its development has spurred me on to develop it. It has been very slow going due a number of reasons (not all connected to the module itself).
Output Adaptor RetrofitThe first reason for procrastination was due to an error in the design of the Voyager the Accessory Port. It was not suitably buffered, so if you hang a cable from it some of the signals become unstable and oscillate. Moog's remedy for this was a small adaptor board that you have to retrofit inside the Voyager between the main circuit board and the Accessory Port's ribbon cable (my understanding is this just affects backlit types, not the Old School version). This is a small circuit board that adds a 330 Ohm resistor in series with many of the signals; here is a link to an installation guide. The 330 Ohm resistance is enough to isolate the capacitance of the extra cable length which maintains amplifier stability (ED Note: If you want to understand about amplifier stability then this series of 5 short videos by Analogue Devices is the perfect intro, in particular video 4 which describes this problem nicely. Ideal for anyone designing with op-amps).
As you can see from the installation guide that fitting the adaptor is a bit much for some people to take on and I didn't want to encourage inexperienced Voyager owners to open up their expensive synth and potentially damage it or harm themselves (there is an AC mains hazard on the left if you don't disconnect from the mains). I don't yet have a solution other than to buy a Moog Voyager Output Adaptor for VX-351 and fit it if you are confident or get a music shop tech to fit it for you. You might already have one fitted if your Voyager has been used with the Moog VX-351.
Smaller, BetterThe second reason for delay is I increased the scope of what the VXP1 can do; I didn't want this to be a Eurorack rip-off of the VX-351. Rather than just a simple breakout panel it now handles each signal with active electronics as follows:-
- All signals are buffered and have the necessary gain and drive to give more Eurorack-friendly output levels.
- The smooth and step Sample and Hold outputs are replaced by just one output and a variable control to give an adjustable slew to Sample and Hold.
- There are more LFO waveforms.
- There are more noise options.
- The panel is narrower.
Here is the panel design that will go into production:-
Current StatusMarch 15th 2016
All the circuit design, PCB layout and mechanical drawings are complete. I will be checking, double checking for the next week before I commit to manufacture.
March 22nd 2016
Checking is complete and I found a few errors; well worth switching your mind off and coming back to it a few days later! The PCBs and the panel are now ready to get quotes and place orders.
April 9th 2016
The PCBs are now on order; expected delivery 22nd April.
May 26th 2016
The first set of PCBs have been built and tested and, in the main, work fine. I need to tailor the slew pot to optimise the adjustment range to give better control around the more pleasing portamento effect but that is minor. There are two problems: The first is I cannot get a quote out of my panel supplier to make front panels - they seem mega busy with far bigger orders - I'm trying elsewhere reluctantly. The second is the need for an output adaptor board fitted inside the Voyager (as the VX-351 has for backlit Voyagers). My alternative approach was not successful. I'm now designing my own output adaptor board.
SpecificationATTENTION: The first and most important thing that I need to get across here is that the VXP1 has been designed for the keyboard versions of the Moog Voyager. The Old School version has the same Accessory Port but does not have a touchpad so therefore does not support the Touch X, Y, A and Gate outputs. The RME (Rack Mount Edition) has an Output Accessory Port and does support the VX-351 and is probably OK BUT I have not been able to verify the extent to which it is compatible as there is virtually no information about the RME Output Accesory Port's signal set. Logic suggests it is very similar but I cannot yet guarantee how well the VXP1 will work with the RME. I will try and find out (maybe borrow an RME for a weekend - any offers?).
TOUCH Outputs (X, Y, AREA, GATE)This function produces TOUCH X, Y, AREA CV and GATE outputs in response to touching the Voyager's touchpad. X and Y vary according to where the pad is touched, AREA varies according to how much area on the pad is being pressed. The GATE turns on when the pad is touched.
X, Y and AREA are CV outputs that have an effective range of ±5V.
GATE is a 0V off and 10V on signal. The GATE LED illuminates when the pad is touched.
NOTE: The Touch outputs are not supported by the Old School Voyager; they will remain at zero volts. One possibility I'm looking into is to provide a modification to allow the 4 Touch connectors to be used as a mult. This would involve removing 4 resistors and adding 3 linking wires on the circuit board. Another possibility is to make X, Y and AREA into diode connected inputs to the GATE output. This would act as a logic OR gate. This would entail fitting diodes to 3 connectors and wiring them to a spare comparator chip and wiring that to the GATE output driver. These options would have to be ordered as an Old School variant with Mult or Diode options but I will publish details of how to modify or revert back to standard.
KEYBOARD Outputs (PITCH, VEL, PRESS, GATE)This function produces KEYBOARD PITCH CV, VEL CV (velocity), PRESS CV (pressure) and GATE outputs in response to playing the keyboard. PITCH CV is determined by which key is pressed, VEL by how fast a key is pressed and PRESS by how hard a key is pressed. The GATE turns on when a key is pressed.
PITCH is a CV output that is trimmable to 1V/octave (using the screwdriver adjustment on the front panel) and has a nominal range of -0.916V (low F) to +2.667V (high C).
VEL and PRESS are CV outputs that have an effective range of ±5V.
GATE is a 0V off and 10V on signal. The GATE LED illuminates when a key is pressed.
WHEELS Outputs (PITCH, MOD)This function produces WHEEL PITCH and MOD CV outputs in response to operating the Pitch and Mod wheels. The Pitch wheel is centre sprung to give 0V when not operated. The Mod wheel is not sprung and can be left in any position. Normally when the Mod wheel is fully rotated towards the player no modulation occurs (in the Voyager). However this position equates to -5V output. A jumper can be set on the VXP1 circuit board to provide either the standard ±5V range or a 0V-10V range. A 0V-10V range will allow it to operate a modular VCA to control modulation depth for example.
PITCH and MOD are CV outputs that have an effective range of ±5V but MOD is jumper selectable to have an effective range of 0V to +10V.