YuSynth MiniMoog Transistor Ladder VCF
A bare double sided PCB 75x100mm (no need for the wire jumper links shown on the PCB layout) for the Yusynth MiniMoog transistor ladder synth module. These PCBs are manufactured by Soundtronics with a percentage of the sale going to the creator of the YuSynth - Yves Usson. These are early days for the YuSynth Modular Synth at Soundtronics, our plan is to stock PCBs for all of the projects as well as components, kits and front panels. This is going to take time but will eventually be as comprehensive as our MFOS range.
No components are included with the PCB but check out our Synth Components section where you should find what you need. We do suggest visiting the YuSynth MiniMoog Transistor Ladder VCF project page for detailed information including Yves panel layouts but a summary is shown below.
We have spotted a few of errors on the YuSynth designed PCB, nothing serious though:
- R31 next to T1(T2 see below) is incorrectly labelled on the PCB, it should read R33
- U2 is U1 and U1 is U2
- Rxx27 is R31 (56k)
- T2 is T1 and T1 is T2
Well, it was meant to be! Yves Usson could not possibly avoid building a clone of this very successful and famous filter: the Minimoog VCF!
This filter has a sound of its own that contributed to the success of many songs during the 70s and 80s.
The aim here was to design a quite faithful copy of this mythic filter while using components that minimize the burden of selecting a great number of matched transistors. This is why he used cheap transistor arrays (CA3046). As for all the other filters of the YUSYNTH project, he has added an input and an output buffer to adapt this filter to the input and output levels of his modular system.
Because, the YuSynth power supply standard is +15/-15V, some values of resistors had to be modified.
NOTE: for Eurorack a pair of jumper must be add and the values of resistors R24,R26,R27 must be changed.
The PCB can accept a choice of three types of power connector, it can be either a Synthesizers.com 6 pins MTA connector, a MOTM 4 pins MTA96 connector or a 10-pin Eurorack connector.
The module is designed to work with a +15V/0V/-15V PSU
Click on the schematic thumbnail above for the circuit diagram.
Basically the circuit is built around the original core of the EMS filter, though Yves had to change some resistor values to compensate for the fact that the active components (NPN,PNP and JFET) are modern counterparts and some of their characteristics are different from the original parts.
The major additions are : a quadruple OPA that is used to buffer the various inputs (audio, CVs) and the output. The values of the resistors of these buffers may be adjusted to audio and CV levels of any modular system. Next, he introduced a voltage control input of the RESONANCE. Finally, a 78L12 and a PNP transistor to convert the power supply levels from +15V/-15V to +12V/-9V .
NOTE : the value of R47 can be changed to adjust the output level as see fit.
The wiring schematic image in the above thumbnails show the panel wiring to the pots and sockets etc. Note that the PCB silk screen has T1 and T2 swapped over. T2 and T3 presets pins are a rather tight fit in the PCB so care is needed when being inserted.
Setting and Trimming
V/Octave tracking :
- Apply 0.000V to the V/Oct input
- Turn the frequency knob fully counter-clockwise in order to measure 0mV at the base of Q1 (node between R9 to R11)
- Apply 1.000V to the V/Oct input
- Adjust T1 in order to measure 18.2mV at the base of Q1
- Apply 5.000V to the V/Oct input
- Check that you have 91.0mVat the base of Q1, if not adjust T1
- Apply 0.000V to the V/Oct input
- Set the filter to auto-oscillation (EMPHASIS turned fully clockwise)
- Connect a keyboard (CV/GATE) to the V/Oct input
- Play a tune and check the goodness of the tracking
- Slightly adjust T1 to achieve a good chromatic tracking.
Frequency range :
- Apply a sinewave with frequency 32Hz to the audio input
- Emphasis potentiometer to minimum resonance (fully counter-clockwise)
- Turn the frequency knob fully counter-clockwise
- Adjust T2, in order to mute the 32Hz signal.
- Emphasis :
Adjust T3 in order to reach auto-oscillation near 95% of the full range of the EMPHASIS pot.
The parts list below is direct from the YuSynth website.
The parts list excludes knobs although we have standardised on the Cliff KM20B but it does include 1/4" jack sockets. All parts are available individually (use the part number in the search box above) or as a components kit that excludes sockets and knobs.
|U1,U2||CA3046 Intersil, CA3146 and CA3086 are possible substitutes||7212-505||2|
|Q2,Q3,Q4,Q5,Q6,Q7||BC547 matched by pairs||7212-495||3|
|R16,R28,R33, R26*||1K *1k2 for +15V/-15V PSU 1K for +12/-12V PSU||7163-051||4|
|R26*||1.2K* for +15V/-15V PSU 1K for +12/-12V PSU||7163-053||1|
|R24*,R27*||220K *270k +15V/-15V PSU 220K for +12/-12V PSU||7163-107||2|
|R24*,R27*||270K* +15V/-15V PSU 220K for +12/-12V PSU||7163-109||2|
|C4,C5,C6,C7||47nF matched quads to 1%||7212-792||1|
|T1||500 ohms 10/15 turn trimmer||7212-853||1|
|P5||50K reverse audio potentiometer (ALPHA)||7300-110||1|
|Jk1,Jk2,Jk3,Jk4,Jk5,Jk6||female jack socket||7212-206||6|