The Tangerine Dream, Module Details

(Note: This page is under constant construction as it will be a launch pad for upcoming online “How-To” videos on modular synthesis.)

A 6-Sided Hexagon, approximately 35″ Across. Each face is designed to hold five. 8-3/4″ tall by 3-3/4″ wide modules.

My Build Rationale: I wanted a completely analog modular synthesizer for developing sounds and demonstrations. The only digital component is the MIDI Implants that are used, and this is only to enable the use of modern keyboards and allow some control through Ableton Live. You really need to have a passion and patience if you want an analog synth like this. They are temperamental, hard to keep in tune and complex patches are almost impossible to replicate. If you develop a sound you really like, you need to document your patch (could have dozens of cables) and record it for later use. That is why most people turned to hybrid synths with digitally controlled VCOs and the concept of pre-configured patches. But for a live adhoc performance… they are pretty cool!

All of the Printed circuit boards are available through several dealers. They are not kits, you just get the bare board and source your own components. People who would like to build their own modules, and who have little experience in electronics, would be best served by joining Electro-music.com. There is numerous resources and assistance in the online forums for most of the circuits listed here. You will a decent multimeter, soldering iron and an oscilloscope. You can’t possibly expect an analog synthesizer to function as designed without one. Most of the circuits used are designed by Ray Wilson and can be found on his site. I chose Ray’s designs for several reasons:

  1. They are relatively inexpensive and ‘play’ nice with others
  2. They can be built from fairly easy to find components and the flexible designs allow for easy substitutions of capacitors, opamps, etc.
  3. His printed circuit boards are the highest quality. The lead spacing and pad sizing are perfect.

Thomas Henry designs are also top quality. I do intend to add a couple more from him when I get the chance to build them. Most of his designs can be adapted from +/-15VDC to +/-12VDC

Here is the TH555 VCO under construction. Use high quality polypropylene, polyester, mylar, Silver Mica and C0G/NP0 capacitors where necessary. Don’t go cheap here. Note also the Tempco soldered into the top of the matched transistor pair.

TH555 VCO under construction

 

Here is a video of VCO Calibration

Face 1

2 – MFOS VCOs These are awesome VCOs designed by Ray Wilson. They are easy to calibrate, track really well if you build with matched pairs of transistors and connect with a tempco. The sine wave output IMO is one of the best in any VCO.

2 – TH555 VCOs These VCOs are designed by synth legend Thomas Henry and based on the 555 timer chip. Moderately easy to calibrate, and excellent performance on the sine wave. These (along with the X4046) also require matched pair transistors and a temperature compensating resistor

TH X4046 VCO Another Thomas Henry design using a 4046 phase lock loop. Really awesome sounds and harmonics with this VCO. It will also require a couple resistor changes to accommodate 12V operation.

 

Face 2

YuSynth (Mini Moog) transistor ladder VCF Yes, this design is based on the famous Moog ladder filter and sound well… like a Moog ladder filter. It is imperative that you have a transistor matching utility that can properly measure Vbe for BC547C transistor or see if you can purchase 3 matched pairs online from any of the DIY forums.

MFOS State Variable (12db) VCF

MFOS 24db VCF Both of these VCFs are beautifully designed and track perfectly using many different VCOs. Please read Rays notes on VCA performance and improvement before starting these circuits.

MFOS Dual VCA Nothing is really special about this VCA, it is very inexpensive to build and does the job perfectly

MFOS Quad Timbre Bank. The Quad timbre bank is basically 4, pre-patched VCF & VCA circuits. The standard VCF->VCA patch is probably the most used, especially when multiple, simultaneous VCOs are being used. This module seriously gives extra play room!

Face 3

MFOS Dual AR Envelope   This is a perfect envelope generator for most patches. Easy to build, and inexpensive.

MFOS ADSR Envelope   Another EG from Ray, but this on adds two other segments in the profile for additional control.

MFOS Delated Modulation Module  This module is a hardware version of the classic LFO->VCA<-EG that gives sound its vibrato effect. Since this patch is almost always used, I use this module so I don’t have to occupy the LFO, VCA and and envelope generator.

MFOS Ring Modulator  Another great design. The only detriment to this design is the use of the Analog Devices AD633AN multiplier chip. They are very expensive, and one of the most expensive ICs in the whole project (or any other synth I have built). They are readily available on ebay for dirt cheap, but they are also one of the most forged, and counterfeit chips on ebay. Spend the $16 and get a real one from Mouser or DigiKey electronic suppliers.

 

Face 4

MFOS 8 Stage Phase Shifter  Hey, why do you need 8 Stage Phase Shifter? The modules on Face 4 are basically used to alter the wave shapes. A Phase shifter, actually modifies parts of a waveform by offsetting its phase with the ‘normal waveform’ and provides really cool modulation effects . You can also plug an electric guitar into the signal input jack for some added fun and effects.

MFOS Sample and Hold with VC  Standard sample and hold that allows its sample rate to be modified with CV. High the pitch, the faster the sample periods. This module used polypropylene capacitors to ‘Hold’ the sampled signal. They can still be had, but are getting fairly rare.

MFOS Wave Freaker   This wave modifier turns waves inside out, on their head and bends things into really cool sounds.

Lord of the WAH!    The Lord of the WAH! is an old school “Cry Baby’ Wha inductor guitar effect, but made for synths. It actually uses and older inductor design found in dozens of guitar pedals. This circuit also uses a moderately expensive That2180C VCA chip. And yes, you can also plug a guitar or any other mic level device into the module and modulate the sound from your synth. Tons of fun, and really unique sounds can be designed when patched to with all the other things. That is why modular synths excel from all-in-ones.This module will require 4 resistor changes to enable 12V operation.

MFOS Noise Module  noise is necessary for creating many sounds. This module is very good at giving a little more control over the quality (clarity and frequency) of the noise.

 

Face 5

MFOS 4 Channel mixer  Designing sound cleanly and effectively requires ample mixing capability all the way through the patch. I use a  large 24 track mixer, another small Behringer 12 channel portable mixer and I still found myself needing more in the early stages of a path. I may mix the outputs of 2 or 3 VCOs, VCFs, or VCA into a single audio signal needed for a small part of a large patch. Using this small 4 channel mixer is perfect. Although it is fairly clean, I substituted the TL072 OpAmps with OP275s and used audio quality capacitors throughout. Doing so, really reduces any hum, noise and sounds that can drive you crazy trying to trace.

MFOS CV echo module  This is a digital version of the Old School Spring Reverb Project I did a while ago. This module, like so many others, uses the Princeton Technologies PT2399 chip for the reverb and echo effects. Comparing the two will yield very different sound profiles. I prefer the spring reverb for classical rock type sequences and sound, or blues type synth riffs. However, it is not as responsive (in a controlled way) as the digital version. If you want an electronic dance beat, or more modern sound this module will certainly deliver. The spring reverb is also not conducive to external vibrations. Imagine a slinky in a 50 gallon oil drum, falling down the stairs when it is bumped, even the slightest amount.

 

Face 6

Power Control with Dual programmable MIDI to CV interface 

Power Supply: This PCB is available from many vendors including SynthCube and ModularAddict (not promoting these two, but they are the main North American distributors for MFOS PCBs). I have to say, it is one of the best power supply designs for the budget conscious builder. I used a 110VAC to 25VAC centre tapped transformer for each circuit. Always, Always, Always.. give yourself plenty of headroom when building power supplies. The power supplies are rated at 1.5 Amps each, and I use a 1.5 amp fuse for the whole synth. With all the modules installed, I am sitting at 750-800mA total across both supplies (I keep them fairly balanced). Also consider that dozens of circuits are turning off and on, OpAmps are driving much of the circuitry in this synth and a hefty capacitor bank keeps everything stable throughout.

MIDI to CV interface: These tiny little devices are amazing. They are basically thumbnail sized circuits that are literally taped to the back of the panel. And provide excellent MIDI to CV conversion. I have used it successfully with many MIDI controllers and Ableton Live to provide MIDI signals. These devices change the digital messages into CV voltages that I can use to control VCOs, VCAs, VCFs, etc. Each one can be configure to provide two independent MIDI message to CV conversion channels. So one channel can provide the CV for pitch, while the second can be used to provide modulation. tremolo, aftertouch, or another pitch control for a second VCO.

MFOS CV Gate expander  Eventually, I will add a second one of these modules to the synth (I have 2 – 1/2 spaces left). This module provides exact copies of CV and Gate signals, with unmeasurable delay. Most patches require multiple CV and Gate signals, and this is one of the best designed modules out there.

MFOS Voltage Quantizer  What is a voltage quantizer? Basically it takes linear variable voltages and turns them into discrete voltage steps. Example, if I had a knob it my sequencer that goes from 0 to 1 Volt, the CV output would be in the exact voltage, so many of the notes heard would be out of tune. Many analog synthesizers utilize 1 Volt per octave. Looking at a piano keyboard, there are twelve keys per octave. The quantizer takes a variable voltage input and outputs a fixed voltage, over a specific voltage input range. Example: the sequencer outputs 0.01 through 0.08 volts into the quantizer, the quantizer outputs 0.0833 volts exactly, or the voltage required for the first key pressed.

MFOS LFO  Although you could use this as a sound generator for low frequency audio signals, it is mostly used to modulate other VCOs. This design is very inexpensive, robust and very stable and predictable.

Barton Music Arpeggiator & Expansion   Michael Barton produces dozens of really inexpensive and cool modules. This arpeggiator is really flexible and stable. The notes above and below the one being played are dead on. Almost every MIDI controller these days comes with an arpeggiator, they are all meant for providing arp effects on etc note being played. Whats nice about a dedicated arpeggiator module, is that I can use it with any CV  and many of the effects that rely on modulation. Basically, I can arpeggiate the modulation control for some really cool sounds.

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