De Modules Notes

Malekko/Wiard Xmix[modifier]

Posted: Thu Jan 12, 2012 5:57 Post subject: XMIX vs. Mixolator

The XMIX is different than the Mixolator.

The Dual Mixolator is a CA3280 based implementation of Lester Ludwig's GLAP (Generalized Linear Analog Processor, based on the unobtanium CEM3330 EN#127(5)). This uses a single gain cell with crossfading and panning done by addition and subtraction of phases. Works fine, but can't do super precise math like the XMIX.

The XMIX is designed to work with calibrated 1 volt per octave sources and does math to within 1 millivolt (1 cent) error.

The Mixolator (GLAP) was never intended for that kind of extended DC accuracy.

Hope that clears it up.

application suggestions[modifier]

Wiard XMIX - analog x/y mix module

The XMIX is a versatile mixing/crossfading utility module with Wiard flair. There are level controls for the two inputs (X and Y). The Y input can be inverted via a switch. Z controls the balance of X Vs. Y. Z has a CV input, along with an attenuator for CV amount. Positive and negative outputs are provided, as well as an Expand input which provides a unity input to chain the output of other modules (such as another XMIX).

Some uses for the XMIX:

- A 2 > 1 Mixer - CV crossfading - A signal inverter - Audio rate amplitude/crossfading modulation - With a single input, you can use the XMIX as a linear VCA - Input different waveforms to create new wave shapes - The X input normals into the Y input when nothing is plugged into Y. Invert the Y input with the switch, and crossfade the X signal VS the inverted version of itself

The XMIX is 8hp wide, 25mm deep, and consumes approximately 45mA power.

There is a three pin connector on the PCB that goes hot-ground-cold.

Connect this to an XLR or TRS and you have a low impedance balanced send, with out needing a D/I box on stage.

Or if you need to send quad. Each channel can work as a high impedance unbalanced to low impedance balanced converter / send channel.

I always noticed how there are big long cables going to the final mixer in polytonal patches and stuff. It occurred to me what we need for synthesizer is "distributed mixing". Bring the channel strip to the module, and make them chainable so you can just plug the output of one into the "expand" input of another. Make 2, 4, 6, 8 channel mixers as needed.

Mixing: There are two styles of mixing, the classic two knobs controlling volume and the newfangled "DJ" style crossfader type. So that thar XMIX needs to support both. Center detent knob on Z makes two gain of 0.5 mixers from X and Y and you can put two 10 volts P-P in and get 10 V P-P out. No clipping at supply rails.

Now a switch is just a really fast crossfade. So we can use it as a SPDT switch too and with no "clicking". The control voltage rejection on the XMIX is plenty good enough to get rid of control voltage bleedthru, but if you switch between two signals with different DC levels, mathematics says it MUST click. Use your head.


1. If you fade from nothing to something it is a simple linear VCA.

2. If you fade from a sine to a sawtooth or square wave it does "filterless filtering" like on the Buchla 258 mix control.

3. If you run SQR2 from the Oscillator to ZMOD, set Z at the center detent, run any two of the other waveforms to X and Y, you get PWM like waveform animation with lot's of wavecycling as you vary the PHASE control on the oscillator. Or put an LFO into PHASE MOD for repeated cyclic stuff.

4. Set Z to center detent, Put sine wave with no DC offset into X input (normaled to Y), set Y polarity to negative, Set X and Y full on. You will hear nothing, we canceled the carrier for you at the center detent of Z control. (Your Welcome!) Now run some piano chords into the ZMOD input and turn it up. Instead of the usual garbage you get from balanced or Ring modulators, you will hear eerie beauty. (try it).


Take a random voltage like a Noise ring output and run it to a multiple. Run the multiple to the inputs of two Malekko Attenu8 modules. Run one to the Y input of the XMIX, run the other through a Quantizer and then into the X input of the XMIX. Set X and Y controls to max.

Now you can crossfade between a wide range unquantized random voltage and a smaller range quantized random voltage. Done slowly this has the subjective effect of bringing the opera glasses into focus. Very subtle, but VERY musical.

More Tricks and Techniques for the XMIX.

1. Synching LFO reset to keyboard gate signal. The synch input on a sawtooth core oscillator is a little cap that goes to the 5 volt peak reference. A negative going spike on this forces an early reset to zero and restarts the VCO(LFO).

What we need is a device that gives both positive and negative versions of a GATE signal. Such as plugging the GATE signal into the Expand input on an XMIX. Take the plus XMIX output to the envelope generator and the negative XMIX output to the "Synch" input on the LFO.

2. Logic ORing of gate signals: Take one gate to the "Expand" input and one gate to the "X" input. Set "Z" to max set X control to max. XMIX plus output is logic OR of gate signals.

3. Logic "ANDing" of Gate signals: Take Gate one to "X" input of XMIX set X to max. Take Gate two (keyboard) to ZMOD input of XMIX, set ZMOD to max. Set "Z" as needed for effect. XMIX plus output will be high only if both Gate one and Gate two are high.

4. Pulse Roll generation: Sometimes what you want is a repeated set of pulses when a keyboard key is held down. Sometimes called an "Auto" mode this allows strums and rolls (for Marimba maybe). With an Envelator set to "Cycle" mode, the high time of the SQR output is set by the A control and the off time is set by the D control. Using the Patch #3 with a repeating set of pulses sets as Gate one (X) allows the keyboard to gate on and off a repeated set of pulses like a marimba roll.

5. Pulse Burst Generation: If Patch 3 is used with the SQR outputs of two Evelators, the "ON" time of the Envelator into ZMOD will give bursts of pulses from the Envelator connected to the X input at the XMIX plus output.

6. ADSR Envelope summing: As Ralph Burnham's pointed out in Elecronotes Magazine an ADSR is only the mixture of an AD unit with an AR unit. Take two Envelators, set the first to AD set the second to AR. Run keyboard Trigger into AD section Gate in, run keyboard Gate signal into AR section Gate in. Run AD Envelator plus output to X input of XMIX and X control to max, run AR Envelator section into Y input of XMIX, set Y polarity to plus and Y control to max. The ADSR envelope is available at the XMIX plus output with the XMIX "Z" control acting like the old "Sustain" control. The "ZMOD" input can be used as voltage controlled sustain level input.

Did I mention HOW to use this as a balanced (ring) modulator? Make sure the X & Y knobs are at full.

1. Connect your carrier sine wave (or whatever) to the X input. 2. The Y input is normaled to the X input so the carrier is going to X + Y. 3. Switch the Y input polarity to negative (minus). 4. Monitor the plus output. 5. Adjust the Z control to get the best carrier null. 6. Now run anything into the Z control input (modulator), ZMOD is the volume for the modulation input.

Have a new experience! You can even run piano chords through it without turning to garbage. The secret is the -60 dBv value of the second harmonic in the sine output from the Oscillator. Since you get two sum and difference frequencies from each harmonic in the modulation, if you have a second harmonic in the carrier, you get 4 frequencies. So you need an extremely clean sine carrier to go from awful to eerie beauty.

As an example, tum the oscillator to 384 Hz (the key of the song) and listen to "Claire de Lune" on piano through the balanced modulator. It is not recognizable because you have inverted the melody line!

jimmyambulance wrote: is there any way to do PWM on the uncle?

The XMIX module has the functions to do the inverting and mixing for classic PWM. It also has the function needed to replicate the Buchla 258 waveshapers which crossfade from a sine wave to either a square or sawtooth.

This moves from a low harmonic content signal (the Buchla 258 has about 3% THD on the sine) to a higher harmonic content signal. This is the same thing a VCF does, but without the VCF. Personally I like the sound of this so called "filterless" filtering and wanted to make sure it was available in the system. You can use an Envelator for this of course, and the ZMOD control on the XMIX allows you to control the "filterless" sweep effect.

The same thing applies to the Anti-oscillator crossfading from the triangle to the Mayhem output similar to the Buchla 259 waveshaper.

VC Panning[modifier]

Yes of of course you can do voltage controlled panning with two XMIXs.

Consider one left channel and the other one right channel.

Run a mono signal you want to pan in Y on the left channel and X to the right channel.

Set each Z control to minimum. Wire both ZMOD inputs to a 0 to 10 volts source.

At zero volts ZMOD the mono signal will be 100% in the left channel. With ZMOD at 10 volts, XMIX1 is completely turned off an XMIX2 is completely on.

Setting ZMOD to the middle will produce 0.5% of each channel in the output XMIX.

When two XMIX are joined together it becomes a 4 into 1 mixer, right?[modifier]

Yes, connect plus OUT to expand input of next section.

A) Can they still operate as two, 2 into 1 mixers?

Not if the expand input is connected to a previous XMIX.

B) Can it operate as a 4 into 1 with two channels crossfading two source and the other 2 channels being mixed in?

Yes, the expand input is simply added to the output mix without affecting any other functionality. Gain accuracy POSSIBLY degrades by 1 millivolt per chained unit (DC accuracy). The output op-amp is an OPA2134 which has a noise figure of 8nv/Hz compared to a 741 which has a 45 nv/Hz noise figure. You should be able to chain up to 10 (20 input mixer) before it is as noisy as an old Peavey PA mixer.

C) Will they operate as two VCA's mixed together?

Yes, they are two VCAs, but one is wired to work the opposite of the other. No, you can not use the VCAs independently.