We find that wiring a MFOS PCB to the front panel controls is both time consuming and often detracts from the overall finish. We are not able to alter the MFOS PCBs to make panel wiring easier so we approached the problem from a different angle. We chose to mount the front panel controls on a mini PCBs (breakout boards) that take the panel controls to a JST type XH socket into which is plugged a lead (not included with set but available separately). This lead is then dressed to the main MFOS PCB (or sometimes to other panel controls) and soldered into the respective pads. Many breakout boards have solderable jumpers for making common connections as well as thin tracks to cut where panel mounted resistors need to be connected inline with say a pot wiper. MFOS projects may require multiple breakout boards so we bundle these altogether and offer them in one ST Synth Panel Breakout PCB Set. The pack description will further describe the wiring colour code and what if any links need to be made or cut.
This method does have other advantages other than just time saving and appearance:
- Time saving
- Neater more professional appearance - improves resale value
- Takes care of common connections between panel components
- Has space to accommodate panel mounted resistors and capacitors
- Can improve reliability - have you tried soldering a diode, LED and a wire to one pin on a toggle switch on the 16-step sequencer?
- Makes fault finding easier
If you have any reservations about using connectors, then simply solder wires direct to the breakout boards. Takes longer but you still get all of the other advantages.
The boards are designed to fit our front panel component spacing so you will see references to pitch and whether it is in the 'x' or 'y' or both direction. At the time of writing, there was 30+ breakout boards developed for pots (using pot brackets), sockets (jack and banana), switches and LEDs. Whilst these will not take care of every panel component on over 40 MFOS projects, it will go a long way to achieving it. As we work through making up each MFOS project with these breakout boards, we will see where improvements can be made or even create more breakout boards to provide the best possible solution.
The panel PCBs can also be used with our YuSynth range. YuSynth PCBs are better laid out as regards panel wiring but can still take advantage of these breakout PCBs.
This pack contains the following breakout PCBs and offers a saving over buying them individually:
- 7210-702 x 3
- 7210-703 x 4
- 7210-704 x 3
- 7210-746 x 3
- 7210-754 x 2
- 7210-756 x 1
Whilst you can solder wires between the breakout PCBs and the main PCB, we do recommend using our JST cable assemblies. For the Soundlab Ultimate, you will need the following:
- 7210-106 x 6
- 7210-108 x 3
- 7210-109 x 4
- 7210-112 x 3
See the Build Guide tab for wiring information on how to use these breakout PCBs with this module.
Whilst our breakout PCBs make the task of building an Ultimate, it remain a fairly complex build and should only be undertaken by someone comfortable with electronics and soldering. We have taken all reasonable effort to document this build below but should you find any errors, please let us know by posting on the FAQ tab, thank you.
29 Jan 2019. Our thanks to Georg B from Belgium who has spotted a few errors in the text / tables which have now been corrected. The photos of the actual wiring remain correct.
18 April 2020. Thanks to Ian for pointing out a mistake in the description regarding the AR output wiring to the sockets and VCA / VCF AR Mod pots. It is now corrected
14 May 2020. Thanks to Martin for spotting the 2-way pot PCB showing the wrong colour wire being cut. Description is correct, orange wire goes to X48, yellow wire is cut.
Guidelines when building the MFOS Ultimate module using our panel PCBs, front and back panels, PCB holder and the MFOS main PCB.
- Assembled MFOS PCB #7210-074
- Front Panel #7210-574
- Back Panel #7210-874
- PCB Holder #7210-974
- 2-Way Pot PCB #7210-702 (3 reqd.)
- 3-Way Pot PCB #7210-703 (4 reqd.)
- 4-Way Pot PCB #7210-704 (3 reqd.)
- Banana PCB #7210-746 (3 reqd.)
- LFO Toggle Switch PCB #7210-754 (2 reqd.)
- Toggle Switch PCB 1x2y SP+DP #7210-756 (1 reqd)
- 6-way Cable Assemble #7210-106 (6 reqd)
- 8-way Cable Assemble #7210-108 (3 reqd)
- 9-way Cable Assemble #7210-109 (4 reqd)
- 12-way Cable Assemble #7210-112 (3 reqd)
- 25mm spacers with an ID of 4mm #TBA (4 reqd)
- M4 x 30mm Pan head screws #TBA (4 reqd)
- PCB Mounting Fixing Kit #7210-182
- Pot mounting brackets #7300-000 (30 reqd)
- Additionally you will need our Switchcraft Jack Sockets #7212-208 (Pack of 8)
Not all panel components use our breakout PCBs, some will require soldering direct but these will be described in the following guidelines.
Panel PCB Preparation
Make sure the solder bridges where specified are done before assembly as it is very difficult to solder G afterwards.
- Solder in JST headers noting that the slots in the socket housing point towards the top of the board on the pot
- Remove any anti-rotation lugs on the pots
- Insert pot into bracket and temporarily do up lock nut
- Insert pot with bracket into PCB and solder in position ensuring the pot bracket sits flat on PCB. Only solder the bracket lugs on the bottom of the board
- Repeat for remaining pots
- Remove pot nut
PCB #7210-703 (3 reqd) used for the VCO pots, no solder bridges required. All pots 100k Lin.
Mount the three VCO pot PCBs to the panel. Then wire up the power buses through R7 and R9 pads using busses 22 swg tinned copper wire with sleeving between the boards as shown in the photo below. The main MFOS circuit board spacer is quite close to the top pot on VCO 3 so it is worth cutting the wiper pin close to the pcb to avoid it touching the spacer.
The Mixer section uses a 3-way and a 2-way pot PCB. On the 3-way solder bridges A, B & G. On the 2-way solder bridges A & B. All pots 100k Log.
In the photo below, as well as fitting the pot PCBs, you can also begin populating the banana & jack sockets as well as the toggle switches. Note the green ground link wire between the 3-way and 2-way PCBs.
Next is the VCF 4-way pot PCB. Solder bridge F before assembly. All pots 100k Lin except resonance which is 10k Lin
The next 4-way pot PCB is for the Attenuator. Solder bridges A, B, D, F & H. An unforeseen class between the bottom corner of this PCB and the blue banana socket, apologies for this. It is a quick fix though and requires cutting away the PCB corner as can be seen in the second photo below. All pots 10k Lin.
The AR Gen 2-way pot PCB next. Solder bridge C + two wire links between R2/R3 & R5/R6. Both pots 1M Log.
The next 4-way pot PCB is used for the VCA and LFOs and requires a wire link soldering between R10/R11.
Now the LFO toggle switch PCBs #7210-754. These PCBs were designed just for the Ultimate. Make sure that the middle toggle switch of the three is the centre off type (3-way). Solder the JST in position first then with the switch already fixed to the panel, align the switch and the PCB then solder.
The S&H 2-way pot PCB is next and uses 1M pots, Solder wire links between R1/R2 & R5/R6
Next is the AR gen switch PCB 7210-756. Solder bridge L2.
Finally for the breakout PCBs is the VCO banana socket PCBs. These are simply placed over the socket connections and soldered. Use a 40 to 50W iron and make the solder connect quickly.
So, that's all of the breakout PCBs mounted and we move to the wiring phase.
Back Panel Wiring
Before we wire to panel controls to the main MFOS PCB, there is additional wiring required. Firstly, a 0V common is required to most of the pot PCBs. This is easily achieved by soldering a solid 22 swg tinned wire through the Gnd pads on the pot PCBs like this:
The attenuator pots only need local wiring.
|2||Red||Ch 1 Out Socket|
|3||White||Ch1 In Socket|
|5||Orange||Ch 2 Out Socket|
|6||Green||Ch 2 In Socket|
|8||Violet||Ch 3 Out Socket|
|9||Grey||Ch 3 In Socket|
|11||Black||Ch 4 Out Socket|
|12||Red||Ch 4 In Socket|
The 8 jack sockets need a common ground connection linking them all together and onto the S&H pot PCB Gnd pad.
7 yellow links between banana sockets are next (ignore the yellow link below link 6)
Most of the panel components should now be in position, some that have not been mentioned yet include:
VCA 100k pots
Output level 10k pot
Red LEDs in LFOs
Green LED in S&H
Yellow LED in Repeat Gate
You will also need to wire a 0V common to the above (cathode connections on the LEDs)
Plug in Mixer JST on 3-way pot PCB, cut yellow and blue wires as not needed. Solder white, green and grey wires to the commons on the toggles switches on VCO1, 2 & 3 respectively.
Plug in Mixer JST on 2-way pot PCB, cut black and yellow wires as no needed. Solder Green to noise output sockets and white to the Ext input jack socket.
Solder orange and white wires from the VCO toggle switches to their respective banana socket PCB as per the photo below.
Plug in VCF JST, cut grey as not needed.
- Take three additional lengths of wire, we used an off cut of green, blue and grey.
Plug in LFO switch PCBs JSTs.
- On LFO1 JST, run the black wire to R6 pad and the blue wire to R5 both on the VCA/LFO pot PCB
- Run the white wire to LFO 1 banana output sockets
- On LFO2 JST, run the black wire to R9 pad and the blue wire to R8 both on the VCA/LFO pot PCB
- Run the white wire to LFO 2 banana output sockets
- Take a length of orange wire and solder one end to LFO 2 output sockets and the other end to the CW connection on the LFO 2 Mod pot on the VCA section (in the photo below, the pot is in the upper left hand corner).
Run a length of white wire from the wiper of the output level pot to the pole of the output jack socket.
Erratum - The green wire from the VCF JST is shown going to the cw connection of the VCA AR-Mod pot, this is incorrect. That particular green wire actually goes to X81 on the main PCB. See description above for the correct wiring of the VCA AR-Mod pot cw connection. Also, the 2-way pot mixer PCB shows the orange wire cut, it should be the yellow wire that is cut, the orange wire goes to X48.
Now plug in the remaining JST connectors. Dress the VCO cables with cable ties.
Take the MFOS PCB ready mounted to the PCB holder and fix in the upper right hand corner with 1 screw.
Solder the VCO JSTs to the MFOS board as follows:
Note the way we have dressed the cables, if you follow this and the remaining wiring, the 300mm JST tails will be long enough and the PCB holder will be removeable to allow for future maintenance.
Wire the VCO JST connectors from the banana socket PCBS:
AR Gen Switch PCB
|6||Green||0V (Pad to the side of Q12)|
VCA/LFO Pot PCB
Mixer 3-Way Pot PCB
|1||Black||0V (just below X49 pad)|
|3||White||S10 common (already wired in a previous instruction step)|
|6||Green||S11 common (already wired in a previous instruction step)|
|9||Grey||S12 common (already wired in a previous instruction step)|
Mixer 2-Way Pot PCB
|3||White||Ext Input socket MXD (already wired in a previous instruction step)|
|6||Green||Noise output sockets (already wired in a previous instruction step)|
VCF 4-Way Pot PCB
|4||Yellow||0V (pad just above C51)|
S&H 2-Way Pot PCB
AR Gen 2-Way Pot PCB
LFO1 Switch PCB (do not cut, leave full 300mm length)
|1||Black||R253 CW (already wired in a previous instruction step, R6 on LFO1 rate pot)|
|3||White||LFO1 outputs (already wired in a previous instruction step)|
|7||Blue||R253 Wiper (already wired in a previous instruction step, R5 on LFO1 rate pot)|
LFO2 Switch PCB (do not cut, leave full 300mm length)
|Black||R265 CW (already wired in a previous instruction step, R9 on LFO2 rate pot)|
|White||LFO2 outputs (already wired in a previous instruction step)|
|Blue||R265 Wiper (already wired in a previous instruction step, R8 on LFO2 rate pot)|
That is all of the JST wiring completed but there are a number of individual components that require wiring. Assuming you have dressed the cables from the JSTs as per the photos above, it will still be possible to lift up the PCB holder and unplug JST in order to gain access to the reminaing components.
You should have plenty of coloured wire from those snipped off from the JST connectors. Colour is not important but included below so you can trace on the photosd if you need to. So, the remaining wiring is:
- Noise Output banana sockets X50 - green
- S&H Input sockets X70 - brown
- S&H Output sockets X73 - pink
- S&H Trig Out socket X74 - orange
- LFO2 Mod VCA wiper X68 - yellow
- AR Mod VCA wiper X69 - violet
- LFO1 LED X96 - blue
- LFO2 LED X105 - pink
- S&H LED X111 - orange
- Output Level pot CW X67 - violet
- Repeat Gate LED X112 - blue
- Repeat Gate Output sockets X77 - green
- AR Gen push button switch red wire to +12V on VCO 3 PCB (R7 pad), other terminal on switch to X87 - yellow
- AR Gen Gate/Trig banana socket X90 - green, jack socket X91 - brown
- VCF Log CV banana sockets X52 - pink & X53 - white, jack socket X56 - blue
- VCA Ext CV banana socket X65 - red & X66 - white
- VCO1 Log CV banana socket X11 - blue, Log jack socket X13 - Violet
- VCO2 Log CV banana socket X26 - blue, Log jack socket X28 - violet
- VCO3 Log CV banana socket X41 - blue, Log jack socket X43 - violet
Time to dress those cables using cable ties.
The Mix Out jack socket is wired to the MFOS PCB using a screen single core cable (#7300-615). On the MFOS PCB, the screen is soldered to a 0V ground connection just above X110, the signal wire is soldered to a 2k resistor which in turn is soldered to the top end of R131.
Below is the completed module
We like to put a thin smear of heatsink paste between the tempco resistors and their adjacent matched transistors.
Followed by encapsulating using a hot glue gun. Not everyone uses this method but seems to work for us.
Wiring is now complete except for the +/-12V supply whcih depends on your own system. We solder in a 3-core cable with a plug on the end which we use for power distribution in our racks. Next is a visual inspection and we also apply power before inserting chips to check for correct polarity across one of the IC sockets. The completed module can be housed in our modular cabinets or in our 9U hardwood case.
No posts found