Tags: VCA module

Notes: The Erica Synths Black Ring-Xfade is an extremely versatile module for sound shaping. It consists of two unconventional ringmodulators/waveshapers, a crossfader that works both for audio and CV and a VCA. Unlike conventional ringmodulator that works only with a signal present on both signal and carrier inputs, the Black Ring-Xfade passes through the signal without alteration, if no carrier is present, but low level signals on the carrier input result in unique waveshaping. Add the crossfader between two ringmodulators (or as a separate unit) topped up with the VCA, and you have an amplitude modulation powerplant in 10HP!

Ring1 CV; Ring2 CV
These are the ringmodulator carrier (CV level) level controls. Unlike conventional ringmodulator, this one passes signal unaltered, if RING CV is turned down. With increasing Ring CV level a slight waveshaping turns into proper ringmodulation.

Xfade
This is a manual Crossfade control. This fades smoothly between signals patched into XFADE IN1 and XFADE IN2. The XFADE CV is added to the knob position.

Coupling
Set the Crossfader mode - AC is optimized for use with the audio signals, DC - for control voltages (but it will work fine with audio, as well).

Ring 1; Ring 2
The green LEDs give visual feedback on signal levels, applied to XFADE IN1 and XFADE IN2 respectively.

Vol CV
Select the VCA CV response. A 0-10V setting is intended for use with the envelope generator, a -5V - +5V setting - for nice tremolos with a LFO.

Xfade IN1; Xfade IN2
These are the Crossfader inputs. They are normalled to the Ringmodulator ouputs, so, if nothing is patched here, you can crossfade between two ringmodulated signals.

Xfade CV
This is the Crossfader CV input. The CV is added to the XFADE knob setting.

VOL CV
This is the VCA CV input. The VCA is post-crossfade - it controls the amplitude of a resulting signal after the crossfader. It will also work with low frequency control voltages applied to the XFADE Ins - nice for designing unconventional modulations.

Ring1 Out; Ring2 Out
These are the ringmodulator outputs.

Xfade Out
This is the Crossfader output and the main output of the module.

Ring2 In; Ring2 CV
These are the second Ringmoduator signal and carrier inputs respectively. These two are normalled to the RING1 inputs, and if no signal is patched here, the duplicate the first Ringmodulator. Interesting trick is to set RING CVs at different levels and crossfade between two ringmodulator signals.

Ring1 IN; Ring1 CV
These are the first Ringmoduator signal and carrier inputs respectively.

Fade L; Fade R
The red LEDs indicate the crossfader position.

Xfade CV LVL
This is a crossfade CV level attenuator. By adjusting it you can control a span of fading between inputs.

Specs:
Audio level 10Vptp
CV level (full span) -5V - +5V
Power consumption +38mA, -32mA
Module width 10HP
Module depth 35mm

Notes: Alpha Duo is a stereo precision VCA with ring modulation, overdrive and distortion.

Alpha Duo's VCAs have three modes:

1) Two quadrant, for classic VCA behaviour
2) Four quadrant, where the VCA responds to both positive and negative Gain CVs. This creates a classic ring modulator.
3) In four quadrant separate (4S) mode, each of the two VCA channels is controlled by separate gain CVs, turning Alpha Duo into two independent VCA/ring modulators.

Alpha Duo also features three drive modes.

1) In Drive Mode zero the overdrive circuit is not active, giving a clean signal.
2) Drive Mode One is a tube style soft overdrive. Like a tube, the positive and negative parts of the waveform are distorted differently, producing a pleasing, warm fuzz.
3) Drive Mode Two is a harder clip - more like a transistor amplifier - for a harder edged distortion.

Alpha Duo's signal path is DC coupled, so it's great for processing CVs as well as audio.

Specifications:
Width: 10HP
Depth: 22mm excl. power cable. Approx 32mm inc. shrouded power cable
Power Requirements:
+12v: 200mA
-12v: 50mA
+5v: 0mA

Inputs:
Signal (Zero attenuation): +/-5v nominal, +/-12v max
GainCV [Zero attenuation]: +/-5v nominal
Pan CV [Zero attenuation]: +/-5v nominal

Outputs:
Dual/Stereo: +/-5v nominal, +/-11v max