EMW-200

The differences between the EMW-200 and the EML-200

There are two main differences between the EMW-200 and the EML-200. The first is that on the EML-200 there is a MIC AMP module that is nothing more than a microphone amplifier. In the 70s the mixers were very expensive pieces of equipment and having a mic amp nearby could have seemed a good idea. On our EMW-200 we replaced this module with a LFO or Low Frequency Oscillator that can be used to modulate the VCOs or other modules on the machine.

The second difference is that on the old EML they used a spring tank on the Reverb module that on our model was replaced with a Digital Delay line. The main reason that lead us to do that is that the spring tank is a sensitive device that can suffer damage from excessive vibration and the ones that produce a good reverb effect are the big ones. Adding a spring tank to our project, and doing it the right way, would raise the equipment dimensions and final price to an unacceptable level.
After some consideration, several tests and a special design for our delay unit we decided to use this module. It was carefully designed to have a vintage sound and was proved to extend the equipment possibilities and timbral range.

The Master Oscillator

                                   
MASTER OSCILLATOR MODULE                                                                                EMW-200 Waveform (YELLOW / shown on top)    -    EML-200 Waveform (GREEN)

The Master Oscillator on the EMW-200 uses the same core circuit used on the EML-200, however we made a few improvements. One was made in the sine wave waveshaper circuit, we modified it in order to produce a more precise sine waveform, as seen on the above image. Another improvement was the replacement of the less reliable mechanical rotary switch with a digital controlled mechanical micro relay system, this way the range adjustment could use a normal potentiometer, what guarantees future replacements if necessary. Note that only the control circuit is digital, the signal path on the entire module is completely analog.

The Voltage Controlled Oscillators

The Voltage Controlled Oscillators on both machines, the EMW-200 and the EML-200 uses the same transistor type VCO, we only made minor changes in order to improve the frequency range. On the EML-200 the circuit starts operating at aproximately 10Hz and stops at 10KHz. On the EMW-200 the VCO range goes from 1Hz to 17KHz.
Its important to know that the VCOs on both machines do not respond to standard 1V/oct. control vontages, so in order to obtain a musical scale its necessary to use an analog sequencer.
The video below shows the EMW-200 and the EML-200 VCOs in operation, the waveforms can be viewed on the oscilloscope screen.

 The Delay module

The Delay module on the EMW-200 uses a special design that emulates a vintage echo chamber, it is very usefull and has controls for the Delay Time, Repetition (regeneration) and Effect Mix. A demonstration video below shows the Delay module in operation.

The Switch module

The Switch module on the EMW-200 (as on the EML-200) is an analog switch circuit that works intercalating two audio signals. These singals enters the module thru the A (11) and B (14) inputs, which has a gain control associated with each one. The switching frequency can be controlled by the SW. FREQ. potentiometer and the time relation between the two signals can be controlled by the A/B ON TIME control. The video below shows the Switch module in operation.

The Filters

There are two filters on the EMW-200 and they are of the exact same type found on the EML-200, one is a Highpass and the other is a Lowpass filter, both are 6db/oct. These filters give a very characteristic tone to the synthesizer sound, almost like an effect that dips things into a dark or misty athmosphere. They are not usual filters as we are used to see, they are simple and have unusual characteristics, but their simplicity turns out to be a powerfull feature and at some extend gives to this machine its sound personality. Below is a little demo video that exemplifies and shows the two filters in action.

On the next video you will be able to hear the two filters being used on a more complex patch.

Here is the patch sheet for this FILTER FUN patch:

Description:
The triangular waveform from the MASTER OSCILATOR feeds the SAMPLE & HOLD module on the WAVE SHAPER.
The two SAMPLE & HOLD outputs goes to the swing (freq. mod.) inputs of the two VCOs, n.1 and n.2.
VCO n.1 output goes to the SWITCH (A) input and the VCO n.2 output goes to the SWITCH (B) input.
One SWITCH output goes to the LOW PASS FILTER and then to the MIXER input (29).
The second SWITCH output goes to the DELAY input and the DELAY output goes to the HIGH PASS FILTER input.
The HIGH PASS FILTER output goes to the MIXER input (26).
One LFO output goes to the SWITCH Pulse input.
The MIXER output goes to the mixing console.

Note: The MIXER could be adjusted to produce a stereo effect that would make this patch a lot more vivid and interesting. Its something we will show on another demonstration and I hope you can try on your EMW-200.

The Wave Shaper module

The Wave Shaper on the EMW-200 is a module composed of 4 submodules, a sample & hold (SAMPLER), an oscillator with pulse width control, an A/D (Attack/Decay) generator and a Ring Modulator. Beyond that there is a switching system that selects 4 ways to feed the modulation input of the ring modulator module and a manual trigger for the attack/decay generator.
On our EMW-200 we made a simple upgrade adding a switch to configure the pulse input (20) to work as a pulse output from the internal oscillator or to allow the attack/decay generator and the sample & hold to be triggered by an external pulse.
On this module we also replaced the mechanical rotary switch with a digital controlled relay system.

The Sample & Hold (SAMPLER) submodule

On the first image below it is possible to check the original triangular waveform (yellow) that is generated by the Master Oscillator (3) and the resulting waveform (green) present at the Sample & Hold output (21). The second image show the Sample & Hold output when fed by the Noise source.

The Sample & Hold can be fed by any waveform on the EMW-200, including the Noise source from the Master Oscillator module. The following demo video shows how the Sample & Hold operates and its effect on a triangular waveform and on the noise source. In order to hear the Sample & Hold effect we connect its output to the VCO n.1 modulation input.

The Oscillator submodule

The Oscillator on the Wave Shaper module has two controls, RATE and WIDTH and it is used mainly  to trigger the A/D generator. An output signal from this oscillator is present at the (20) connector when the IN/OUT switch is positioned down. When this switch is facing up the A/D generator can be triggered by an external signal.

The Attack/Decay Generator submodule

The A/D generator on the Wave Shaper module is a very usefull tool as a modulation source for other modules. On the EMW-200 this circuit was updated in order to produce a very precise waveform, with an ultrafast attack and a wider time range. Shown below is the image of the waverform produced by the EMW-200 A/D Generator.

The Ring Modulator submodule

The Ring Modulator submodule on the Wave Shaper is very flexible, mainly because its modulation input can be selected between several sources through the MODE selection switch. Here is a description of the functions of the MODE switch:

With the MODE switch on the MAN. and AUTO positions the Ring Modulator modulation input is fed by the A/D generator output.
- On the MAN. (manual) position the A/D will only be triggered manualy by the MAN. switch on the front panel.
- When the MODE rotary switch is on the AUTO position the A/D is triggered by the internal oscillator.

- On the RING position the Ring Modulator modulation input receives signals from the modulation (23) input connector only.
- With the MODE switch on the PULSE position the Ring Modulator modulation input is fed by the internal Oscillator pulse output.

This completes the description of this complex and usefull module, but beleive me, nothing like the practical experimentation in order to hear the results and feel the full power of this module. It was very well planned by the EML people and it is the heart of the EML/EMW-200.

One more demo video showing the versatility of the Wave Shaper interacting with just one VCO.

The Mixer

The Mixer on the EMW-200 is an exact replica of EML-200 mixer, it is a very flexible and well planed module. It has two sections of three channels each that can be addresses to L (Left), R (Right) and Stereo output jacks, this allow us to create very dinamic stereo images where separated sound elements can appear and/or move within the stereo field.
The lower line output jacks (37, 38 and 39) has output levels of -3db in relation to the ones on the upper line. The Mixer works with DC and audio signals. This is a very straightforward module, its versatility allows various routings of the signals generated by the EMW-200 in a easy way.

On the following simple example we enter with a noise sound on the first channel of the No.1 Mixer (left) and with a sine wave sound on the first channel of the No.2 Mixer (right). You can check that changing the PAN knobs causes the sound to alters its place on the stereo field.

The Ring Modulator module

The Ring Modulator mixes two signals on a special way, it uses the MODULATOR signal to alter the CARRIER signal amplitude. With low frequency signals it can be used as a VCA, where 0 Volts do not allow any Carrier signal appearing on the Output. Here is a video that uses the VCO No.1 signal as a modulator for the square wave from the Master Oscillator.

The LFO module

As explained at the begining of this page, on the EMW-200 the MIC AMP. module present on the EML-200 was replaced with a LFO. It provides the equipment with more useful resources to alter and modulate the sounds. The LFO has a RANGE switch (SLOW / FAST), two selectable waveforms (SQUARE / TRIANGLE), a potentiometer to control the Frequency and two outputs.
On the next video you can see the LFO modulating the VCO No.1 frequency.

Technical Specifications

 Dimensions and Weight

Width (front): 41cm.
Height: 22cm.
Depth: 17cm.
Weight: 3.7Kg.


Electrical specifications

Voltage: 110 or 220 VAC (selectable)
Power consunption: < 20 W.
AC power connector: tri-polar power socket (computer type)

Front panel Audio and CV connectors: mono 3.5mm (J-2)
The stereo outputs (38) on the mixer module are 3.5mm stereo jacks.

Gate / Trigger input voltage range: 5 to 15V.
Gate / Trigger voltage threshold: 2.5V.
Gate / Trigger output voltage: 5V.

Internal power supply for the modules: +15 / -15V.


Master Oscillator

Waveforms: sine, triangular, square
Noise type: white
Frequency range: 0.02 to 18KHz.
Output voltage: 10V. (+/- 5V.)


VCOs

Waveform: sawtooth
Output voltage: 10V. (+/- 5V.)
Frequency range: 1Hz to 18KHz.


Delay

Delay time: 20 to 350ms.
Repetition range: one to infinite
Average frequency range (no direct signal): 15Hz to 4KHz.

Frequency response curve (20ms / no direct signal):

Frequency response curve (Direct signal):

Switch

Frequency range: 0.25 to 50Hz.
Duty cycle range: 5 to 95%


Low Pass Filter

Topology: 2-pole multiple feedback
Attenuation: 6db/oct.

Frequency response curve (all closed):

High Pass Filter

Topology: 2-pole multiple feedback
Attenuation: 6db/oct.

Frequency response curve (all closed):

Wave Shaper

Internal Oscillator:
Frequency range: 0,27 to 28Hz.
Duty cycle range: 2 to 98%

Internal ring modulator:
Type: transconductance multiplier cell
Carrier input range: 0 to 15V.
Modulator input range: 0 to 15V.

Attack/Decay Generator:
Output voltage: 10V.
Minimum attack time: 0.8ms.
Maximum attack time: 1.4s.
Minimum release time: 1ms.
Maximum release time: 3.5s.

Sample & Hold:
Output voltage: 10V. (+/- 5V.)


Mixer

Type: 6-channels with 2 sub-groups (L) and (R) AC-DC mixer
Upper output jacks: 0db.
Lower output jacks: -3db.
Pan controls range: 0 to 100%


Ring Modulator

Type: Analog balanced modulador
Carrier input range: 0 to 15V.
Modulator input range: 0 to 15V.


LFO

Waveforms: triangular, square
Frequency ranges: 2 (Slow and Fast)
Slow frequency range: 0.42 to 220Hz. 
Fast frequency range: 8Hz to 1.2KHz.
Triangular output voltage: 8V.
Square output voltage: 10V.