Lord of the Ring (Modulation) 2009 - Gearslutz · in another instrument-level or line-level signal, such as a guitar, bass, keyboard, etc. The Carrier Oscillator’s few controls

LOTRM 2009 © GregAE p 1

Lord of the Ring (Modulation)2009

If I had to choose just one Moogerfooger pedal to compliment the Voyager1, the choice would be easy; I’d pick theMF-102 Ring Modulator. Why? It’s because the Ring Modulator is the only Moogerfooger pedal designed to produce soundinstead of simply filtering sound or adding effects2. In fact, the Ring Modulator (RM) extends the Voyager’s sonic palette toan entirely new class of sounds that can’t easily be duplicated by other means. This feature alone makes the RM the ideal‘desert island’ pedal companion for the Voyager, but, as you will soon learn, it’s capable of much, much more.

What kind of sounds does RM produce? All manner ofbells, chimes, gongs, tubular bells and electro-metallictimbres, collectively referred to as ‘clangorous’ sounds.These sounds are distinctive because they containinharmonic frequencies, meaning that their harmonicspectrums aren’t based on integer multiples of afundamental frequency like those that appear in sawtooth orsquare waves. Whereas a sawtooth or square wave has anorderly series of decreasing harmonics, the overtones ofclangorous sounds can be spread far and wide across thefrequency spectrum, with varying amplitudes and phases.

By itself, the Voyager can produce only a limited range ofclangorous timbres with its built-in modulation capabilities.The MF-102 Ring Modulator greatly extends this range bygenerating a wealth of inharmonic textures, making it anexcellent accompaniment to the Voyager. So how can youmake the most of it, with or without a Voyager? Read onand find out!

Concepts

A Ring Modulator performs a simple arithmetic function: it takes two input frequencies, and generates the sum (F1 + F2) anddifference (F1 – F2) signals while suppressing the original frequencies. For example, if two sine waves of equal amplitudeare applied to the input, say one at 200Hz and one at 300Hz, the ring modulator will output two sine waves of equalamplitude: one at 500Hz (the sum) and one at 100Hz (the difference). The use of sine waves here provides a simple exampleto illustrate what a Ring Modulators does, but what happens if two complex waves are used instead of simple sine waves?The answer is that you get a complex result. The individual harmonics of each wave interact with each other, producing acomplex product of sum and difference frequencies. Such is the case with two square waves, as shown in Figure 1.

1. “Lord of the Ring (Modulation)” (aka “LOTRM”) was written a few years before Moog Music introduced the Little Phatty(‘LP’) synthesizer. While the Ring Modulator works equally well with the LP or Voyager, the LP’s lack of CV expansion jackslimits the interface possibilities of the Ring Modulator when compared to what can be done with a Voyager and VX-351 CVExpander.

2. Technically, this is no longer true. Long after LORTM was originally published online (in 2006), Moog Music released theMF-107 FreqBox, which can also produce sounds through its internal oscillator. The FreqBox can be used as a stand-alonesound source, much like the Ring Modulator’s Carrier oscillator.


Figure 1. Two ring-modulated square waves

Figure 1 shows the result of ring modulating two square waves together; one at 350Hz, and one about 100Hz. The view onthe left shows an oscilloscope display of the result, while the view on the right shows the corresponding frequency spectrum.Taking a closer look at the frequency spectrum, we see that ring modulation has produced two large frequency spikes at about250Hz and 450Hz (the respective sum and difference frequencies of the fundamentals) along with a complex series ofinharmonic overtones (there are actually more low-level overtones than the ones shown, but these appear below the displayed30mV level). The resulting sound can best be described as ‘bell-like’, owing to the complex nature of the overtones that wereproduced.

Component Parts

The Moogerfooger MF-102 Ring Modulator isactually made up of three separate ‘modular’components, all neatly combined into a flexiblemodulation package. The three components are aLow Frequency Oscillator (LFO), a VoltageControlled Carrier Oscillator (VCO), and a RingModulator. Each circuit can be used separatelywith the Voyager or other CV gear. The RingModulator diagram on page 5 shows how thesethree components interconnect and interact witheach other, with shaded areas used to indicateeach component.

Now let’s take a closer look at each of thesecomponents.


The LFO

The RM’s LFO is a basic Low Frequency Oscillator with a minimum of features. The RM’s LFOsports Rate and Amount controls, a two-position waveform selection switch on the front panel, andRate CV Input and LFO Output jacks on the back. The AMOUNT control adjusts how much of theLFO signal is fed to the Carrier Oscillator, but does not regulate the signal at the LFO Output jack. Thismeans you have to use an attenuator to adjust the LFO signal level if you are using it for external CVapplications.

The LFO’s RATE control has a range of 0.1 Hz to 25 Hz. The manual says applying a CV to the RateCV Input jack has the same effect as turning the knob, but what actually happens is that knob and theCV input combine to affect the rate. This means that you can adjust the RATE knob to maximum(25Hz), and then increase the rate further by applying a positive CV, or reduce it by applying anegative CV. Plugging an expression pedal into the Rate CV jack and setting the RATE knob tomaximum, you can increase the LFO rate to well over 1Khz (!) with the pedal pressed all the waydown. Conversely, by setting the RATE knob to 0.1 Hz and applying a negative CV, the LFO can gowell below the displayed 0.1 Hz rate.

The LFO ‘s panel switch selects between the two available waveforms. Selecting ‘Square’ produces asquare LFO wave as expected, but switching to the ‘Sine’ position actually produces a triangle wave,not a sine wave as depicted on the panel.

The Carrier VCO

The Carrier VCO is a wide-range, voltage-controlled oscillator that provides a constant signal sourcefor one of the Ring Modulator inputs. This allows you to use the Ring Modulator simply by pluggingin another instrument-level or line-level signal, such as a guitar, bass, keyboard, etc.

The Carrier Oscillator’s few controls are found in the MODULATOR section of the pedal. There is aFREQUENCY control knob to adjust frequency and a switch for high or low (HI/LO) frequencyoperation. In HI mode, the carrier oscillator operates in the audio range, from approximately 30 Hz to4kHz. In LO mode, the carrier oscillator acts like an LFO, with a range is from 0.6Hz to 80Hz. Back-panel jacks provide Carrier Output, Carrier Input and Frequency CV Inputs. The Carrier Output jack isbridged to the Carrier In jack, so that the carrier signal is automatically routed to one of the RingModulator inputs unless another signal is plugged in. The Frequency CV input accepts an expressionpedal or other CV. Like all CV inputs, applying a CV adds to the effect of the corresponding knob,extending the range of the oscillator above and below what the knob provides. As with the LFO,applying a positive CV value increases the oscillator frequency, while a negative value decreases it.


The Carrier Oscillator produces a triangle waveform as shown in Figure 2:

Figure 2. The Carrier Oscillator waveform

Although the Carrier VCO has a linear frequencyresponse, the actual response isn’t specified in themanual. Testing reveals that it’s not the typical 1V/octresponse – it’s more like 0.7V/oct. The fact that it islinear, however, means that the Carrier VCO will tracka linear control voltage. This is an important con-sideration that will be used to great advantage as weshall soon see.

The Ring Modulator

The Ring Modulator section is comprised of two parts: the Audio Input circuit and the RingModulator circuit. The Audio Input circuit has a Drive control to adjust the gain of the audioinput signal. By contrast, the Ring Modulator circuit itself has no user controls – its job is tosimply perform the arithmetic ‘sum and difference’ function described above.

The Modulator Mix knob works like a balance control, adjusting the balance between theAudio Input signal and the Ring Modulator output. When the Mix control is set to ‘0’, onlythe input signal appears at the Audio Output jack. When the Mix control is set to ‘10’, only thering-modulated signal appears at the Audio Output jack. Setting the Mix control betweenthose two extremes adjusts the relative balance.

Carrier In vs. Audio In

Since one of the RM’s inputs is labeled ‘Carrier Input’, it might lead you to think that there’s a distinction between the inputs of a conventional ring modulator, similar to what you might find on a Vocoder. There isn’t. A ring modulator simply creates the sum and difference products from the input signals, without regard as to which is which. The reason for the

distinction in the MF-102 is that the Audio Input has a DRIVE control to adjust the input gain (the Carrier Input does not have an equivalent control), and, more importantly, the Audio Input is the signal that is switched in BYPASS mode. Otherwise, the inputs really are equivalent.


MF-102 Ring Modulator Diagram


Back Panel

Voyager owners know that all control voltage inputs are identified by colored jack nuts on the instrument’s back panel.Red nuts are used to indicate control voltage inputs, while blue nuts indicate gate inputs. Unfortunately, none of theMoogerfoogers hold to that convention; all panel jacks are secured with the same black nuts. Instead of using colored nuts,Moogerfoogers use panel labeling to distinguish between control voltage inputs and other I/O, with black-on-white labelingidentifying the four CV inputs (Rate, Amount, Mix and Freq.), and white-on-black labeling used for all others as shown:

Footswitch

There’s not much to say about the footswitch that isn’t already covered in the manual. Activating the switch toggles the pedalstate between ‘On’ (green) and ‘Bypass’ (red). As pointed out in the manual, the pedal itself doesn’t have ‘true bypass’. Thesignal applied to the Audio Input jack always runs through the Drive gain circuit, whether or not the pedal is in ‘Bypass’mode. Of course, this also means that if no power is applied to the pedal, no output will result.


Cool Ring Mod Tricks

The MF-102 User Guide lists some ways of using the Ring Modulator, so I won’t repeat those here. Instead, this section willfocus on ways to get the most out of the Ring Modulator when paired with the Voyager.

1. Tuning the RM Carrier Oscillator

Let’s begin with the Carrier Oscillator. This first trick is the one that makes the MF-102 so valuable as a sonic resource to theVoyager. It also forms the foundation of the other cool tips to follow.

As mentioned earlier, the RM’s Carrier Oscillator has a linear CV response. This means you can use the Carrier VCO as anextra oscillator for the Voyager if you apply the right control voltage. To set this up, you’ll need your Voyager, the VX-351CV Expander, a few patch cords and the MF-102. Configure the signal routing as follows:

OUT

IN

VX-351ATTEN

PITCHKBD

MF-102 RING MODULATOR VOYAGER

EXTERNAL INFREQ

CARRIER OUT

Now perform the following steps to scale the MF-102 Carrier VCO3:

1. Turn off all Voyager oscillators, leaving Oscillator 1 ON. Adjust the Oscillator 1 wave to triangle, and set the othercontrols to provide a sustained, unfiltered sound. This will make it easy for tuning purposes.

2. On the VX-351, set the attenuator to about ‘7’ on the dial (i.e., the 2 o’clock position).3. On the Ring Modulator, set the LFO Amount control to ‘0’, switch the Oscillator control to ‘HI’, and adjust the

Frequency control to about mid-range (the settings of the other controls do not matter).4. Switch the Voyager’s External Input ‘On’ and increase the External Input level so that you can hear the RM Carrier

Oscillator. Adjust the level to equal volume with Oscillator 1.5. Hit and hold the low ‘F’ on the Voyager keyboard and adjust the RM’s Frequency control for unison tuning with the

Voyager oscillator.6. Hit and hold the high ’C’ on the Voyager keyboard and adjust the VX Attenuator for unison tuning between the carrier

and Voyager oscillator.7. Repeat steps 5 and 6 until the RM’s oscillator is scaled and tracks the Voyager oscillator across the keyboard.

With the Carrier Oscillator scaled for keyboard control, it can nowbe used just like any other Voyager oscillator. The Carrier VCOcan be tuned as a sub-oscillator to provide extra girth to a patch,a super-oscillator to provide ‘top’ to a patch, or a blending oscillatorfor interval tuning. Spend a bit of time exploring the possibilitiesthis fourth oscillator provides, but be aware that you may need toadjust the CV scaling a bit as things warm up and tuning drifts.Repeat steps 5 and 6 of the above procedure if you need to retune.

3. This procedure can also be used to scale the internal oscillator of the MF-107 FreqBox – try it!

No Glide Here

The VX-351 Key Pitch CV Output does not include the Voyager glide function. This means that when Glide is turned ON with the above configuration, only the Voyager oscillators will glide between notes; the Carrier VCO will be unaffected.


2. Squaring things up

Since the Carrier Oscillator is strictly a triangle wave, its usefulness can be limiting when combined with the Voyageroscillators. You can easily turn that triangle wave into something more interesting using a distortion pedal or similar deviceto clip the signal, turning that soft triangle wave into a crunchy square wave when the distortion device is adjusted to a highgain setting. Simply plug the Carrier Output into your effect device, and then route the device output to the Voyager ExternalInput. I’ve gotten very good results using a cheap ($15) Dan Electro FAB Metal pedal, although that any distortion oroverdrive pedal would probably work as well to force the signal to ‘flattop’. When setting this up, though, remember to keepthe effect devices output level down as you make adjustments, then turn it up to match the level of the Voyager oscillators.

This ‘waveform conversion’ trick works because a single, sustained wave is being processed through the distortion pedalinstead of several waves, i.e. chords. Also, because the triangle wave is a line-level signal, the distortion device is easilyoverdriven; helping to minimize the noise usually associated with high gain settings. Given the number of possible effectdevices that could be used here, your experience will certainly vary. If you have several such devices available, try them allto see what works the best.

3. Octave Doubling

This well-known trick only works with simple waveforms, like sine or triangle, but can be used to good effect in manypatches. The basic idea is to apply the same signal (“x”) into both ring modulator inputs. Since a ring modulator produces thesum and difference frequencies of the two inputs, the difference frequency for identical inputs is zero:

x – x = 0

while the summed frequency is twice the original (in other words, an octave):

x + x = 2x

This principle is easily demonstrated using the RM’s Carrier Oscillator. Keeping the scaled oscillator frequency connectionsin place, use a patch cord to connect the RM Carrier Output to the Audio Input. Connect the RM Audio Output to theVoyager’s External Input. Engage the pedal (Bypass LED will be Green) and, while playing, adjust the RM’s Mix control tohear the octave doubling effect.

With this configuration in place, you now have five oscillator signals available: two from the RM, plus three from theVoyager. By themselves, the signals from the RM resemble an organ-like sound, owing to their precise octave relationshipand pure tone. You can vary this sound by applying a control voltage to the RM’s Mix CV Input, allowing you to youdynamically adjust the balance of the two sounds.


4. Tracking Modulation

So far we’ve focused on the Carrier Oscillator, mainly using it to augment the Voyager’s three oscillators. It’s time to takethe rest of the Ring Modulator’s electronics for a spin and show what they can do.

Keep the Carrier Oscillator configured to track the Voyager’s Key Pitch, and connect the RM in the Voyager’s Mix/Out loopusing an Insert Cable as shown below.

OUT

IN

VX-351ATTEN

PITCHKBD

MF-102 RING MODULATOR

VOYAGER

MIX/OUTLOOPFREQ AUDIO IN

AUDIO OUTRING

TIP

INSERT CABLE

With this new configuration in place, select a Voyager preset (any one will do), and switch off all but one of the Voyageroscillators. Set the RM Drive knob to a comfortable level (about 9 o’clock on the dial should do it), set the Mix control to100% and engage the pedal (the Bypass LED will be Green). Play a few notes on the Voyager while you adjust the RM’sFrequency knob. Find a setting you like, and then play it up and down the keyboard. You’ll notice that the sound ‘tracks’your playing, because the relationship between the Voyager oscillator and Carrier oscillator is constant. This setup allowsyou to play electronic bells, chimes, metal bars – any ‘clangorous’ sound – chromatically.

In this configuration, the RM’s Mix control can be used to balance the modulated and unaffected sounds.

5. Ring Mod as VCA

Here’s a tip that combines several concepts already presented. We’re going to use the Ring Modulator circuit to adddynamics to the scaled Carrier VCO signal – in other words, as a VCA. To do this, we’ll apply an envelope control voltage tothe RM’s Carrier Input and use the Carrier VCO as our signal source. We’ll keep our scaled VCO connections as before, andmake a few new connections as shown here:

OUT

IN

VX-351ATTEN

PITCHKBD

MF-102 RING MODULATOR VOYAGER

EXT AUDIOINFREQ

AUDIO IN

AUDIO OUTOUT

IN

ATTENFILTERENVS

CARRIERIN

CARRIEROUT


With these signal routings in place, make the following settings:

1. On the VX-351, set the Attenuator for the Filter Envelope to about the 11 o’clock position.2. Set the RM Drive to 0, the Mix control to 100% and engage the pedal (the Bypass LED will be Green).3. Select a Voyager patch (any one will do), and make the following adjustments:

a. Turn OFF all oscillatorsb. Turn Ext Audio ON, and set the External Mix knob to about 9 o’clockc. Open the filter (Cutoff fully clockwise), set resonance to 0, LP/LP moded. Set the Filter Envelope Amount to 0 (mid position)e. Set the Filter Envelope Attack, Sustain and Release to 0, and set the Decay to 12 o’clockf. Set the Volume Envelope Sustain to max.

Play a few notes on the Voyager. You should now be hearing the filter envelope controlling the volume of the Carrier VCO,similar to a VCA. There will probably be a small amount of bleed-through, but it demonstrates the basic idea.

To work with this new capability, try shortening the Filter Envelope Decay while you turn on one or more of the Voyageroscillators (you may have to adjust the oscillator level and also the wave to best match the sounds). This tonal combinationwill give you a percussive attack coupled with a sustaining sound, creating a unique effect unlike any other Voyager patch.Also, try adjusting the Filter Envelope Attack and Decay controls for additional variation.

Note: Since the Voyager only has two envelope generators (Filter and Volume), the possibilities using this technique aresomewhat limited. Nevertheless, much can be explored using this method. Other CV sources, like an LFO, can be employedto achieve different results. Regardless of the CV being used, however, remember to attenuate the level before applying it tothe Carrier Input.

6. Drive as Waveshaper

In cool tip #2 we used an effects pedal to create a square wave. We chose this method to generate a crunchy square wavefrom a triangle, but that’s not the only way to get a similar effect. You can also use the RM’s built-in Drive circuit.The RM’s Drive control is used to adjust the gain of low-level signals, but at high drive settings can produce a soft clippingeffect on the signal, changing the waveshape. To examine the effect of high Drive settings, we processed a single Voyagertriangle wave through the RM’s Drive circuit, and used an attenuator to keep the RM’s output level in check. Viewing theresult with oscilloscope software, we observed the triangle wave get larger as we advanced the Drive knob. When we reachedthe 3 o’clock position, the wave began to flattop. As we continued to advance the knob, the signal became flatter. When theDrive control reached maximum, the triangle took on the appearance of a rounded square wave (shown in the second figure):

Figure 3. A triangle wave taken from the Voyager Mix/Out Loop, Oscillator 1 only, Mixer level = 10(value = 255), processed through the Ring Modulator, Bypass ON, Drive = 0, Mix = 0


Figure 4. The same Voyager signal, but with the RM’s Drive control at maximum, and attenuated to anequivalent level

The sound of the signal in Figure 2 is a bit like a filtered square wave – a mellow sound, but still buzzy. It’s not exactly thesame result as we got from the distortion pedal (the distortion pedal output contained sharper edges and had a brighter tone),but it’s still very practical as a medium-bright sound source.

Next, we returned the Drive knob to 0 and switched the Voyager wave to sawtooth, keeping everything else the same.

Figure 5. A sawtooth wave taken from the Voyager Mix/Out Loop, Oscillator 1 only, Mixer level = 10(value = 255), processed through the Ring Modulator, Bypass ON, Drive = 0, Mix = 0


Figure 6. The same Voyager signal, but with the RM’s Drive control at maximum, and attenuated to anequivalent level

As we observed with the triangle wave, as the Drive control is advanced the sawtooth wave increases in amplitude untilDrive reaches about the 3 o’clock position, where the waveform begins to change. With Drive fully clockwise, the wavebecomes a ‘smoothed sawtooth’ as shown in Figure 6 above. This sound is like a soft version of the sawtooth wave, butdifferent from what you can get by adjusting the Voyager’s Wave knob between sawtooth and triangle waves.

Both the modified sawtooth and triangle waves can be used as new sound sources for the Voyager or LP, adding to the sonicpalette.

Suggestions for Use with any Instrument

One of the best things I’ve ever read regarding the use of the Ring Modulator appeared in Moog Music's Moogerfoogerforums late in 2007. Forum member 'Narrowcaster' posted the following:

"There are a bunch (of settings I use on the RM), but here are a few that I'm using a lot:

Very slow freq, to make a nice deep tremolo, and then just a touch of very slow LFO, so the tremspeed is always varying a little. I find this adds enough variety to keep the trem from sounding toomechanical.

With fuzz guitar, I like to set the frequency just to the point where the effect switches from fasttrem to a growl (where you can start to hear the sum and difference tones, but the overallimpression is still a nasty fast wobble). Then I dial this in and out with an expression pedalplugged into MIX. It's great for soloing, and I use it almost the same way I would a whammy bar.But this effect needs to be dialed in to the region of the fretboard you're basing the solo around,because a freq setting that's nicely on the edge in one register will not be right for much higher orlower notes.

I really love, with pianos or clean guitar, setting up bell-like tones. For me that's usually with thefreq about 1/4-1/3 up in the Hi range, and mix at 50%.

One last one ... if you have access to an envelope follower (like on the MF-101 filter), it can be alot of fun to modulate the carrier frequency with it. Sometimes I use this on LO frequency rangesfor touch-sensitive trem speed, and sometimes on HI ranges for touch-sensitive scronk.”


Regarding his basic approach to using the MF-102 Ring Modulator, Narrowcaster wrote:

"I think of it in terms of four basic regions, and I like to call them: tremolo, growl, bells, andshimmer. Here's a quick explanation of how they come about. This is all explained in terms of whathappens when you keep the input frequency constant and slowly increase the carrier frequency.Also, the description below assumes you have MIX set to 50% (so that you are always hearing threepitches: input, sum, and difference).

For any given input frequency, when the carrier frequency is very low it will sound like tremolo.This happens because the sum and difference tones are so close in frequency to the input that theydon't sound like distinct notes of their own. You only notice them because they cause interferencepatterns (which is the trem effect). As you increase the carrier frequency, the sum and differencetones get farther away from the input frequency. At a certain point, it starts to sound like a roughgrowling effect, because you are starting to hear it as three different notes, but they are very closetogether. As you keep raising the carrier frequency past that, the spread gets greater and greater, soit really sounds like three different pitches. That's the range I call "bell tones." As you keepincreasing the carrier frequency even further, you reach a point where both the sum and differencetones will be *higher* than the input pitch. For a while this still sounds like bells, because thespacing of the three pitches is still relatively close. But as you keep increasing carrier frequency, thesum and difference tones begin to get so high that they sound like a very high shimmering soundcompletely disconnected from the input. A lot of people like to crank the carrier frequency and keepthe MIX almost dry, so they get just a little of this shimmer for ambiance."

Awesome advice, Narrowcaster! Thanks for allowing me to include your message here.

Finale

At this point, I hope you’re sufficiently intrigued to try some of the above ideas and techniques to see what you can createwith the MF-102 Ring Modulator. And if you’re looking to add a Moogerfooger to your setup, but don’t know which one tobuy, look no further. Head straight to your local music store and audition an MF-102! Regardless of whether you play guitar,bass, keys, or some other electronic instrument, a world of new sound possibilities awaits you!

Documents

Lord of the Ring (Modulation) 2009 - Gearslutz · in another instrument-level or line-level signal, such as a guitar, bass, keyboard, etc. The Carrier Oscillator’s few controls