Phase IV

Phase Modulator / Frequency Shifter

Phase IV is a program to run on Electrosmith patch.Init() that can perform phase modulation and frequency shifting by quadrature modulation, as described here.

How it works

The incoming signal(s) are fed into a Hilbert transformer, which outputs an in-phase/quadrature pair. We can then phase-shift the signal using a balanced modulator, where we modulate it with another in-phase/quadrature (sin/cos) pair.

Depending on the blend of the sin/cos pair, we can achieve an arbitrary phase shift of the incoming signal. If we let a signal control the sin/cos blend, we could use that to modulate the phase.

If instead the sin/cos pair are components of a quadrature oscillator, we will get a frequency shifter.

We can use either an internal sine oscillator for the modulation or an external one.

There is also a mode to output only the in-phase and quadrature components for the modulation signal, to be used with another module that performs balanced modulation, such as Joranalogue Collide 4. This means you could use Collide 4 to perform phase modulation as well as frequency shifting.

The inputs, outputs, and controls are as follows:

• CV_OUT_2/C1 LED: Lights up when in Mono->Stereo mode (see below).
• B7: Switches between modes for the controls CV_1?CV_4 when pressed in (Mono->Stereo or Dual operation).
• B8: Up = external oscillator, down = internal oscillator.

Normal mode (B7 not pressed)

• CV_1: Coarse frequency
• CV_2: Modulation depth
• CV_3: Fine frequency
• CV_4: CV modulation depth

Alternate mode (B7 pressed)

• CV_1: Volume of I/Q outputs
• CV_2: High-pass filter frequency
• CV_3: Mode from CCW to CW:
  • Phase mod 1 stage
  • Phase mod 2 stage
  • Phase mod 3 stage
  • Phase mod 4 stage
  • Frequency shifter
  • I/Q out phase modulation
  • I/Q out frequency shifter
• CV_4: Low-pass filter frequency

CV inputs

• CV_5: V/Oct left
• CV_6: V/Oct right
• CV_7: Mod depth left
• CV_8: Mod depth right

Signal Inputs and outputs

• IN_L: Left input
• IN_R: Right input/modulation input
• OUT_L: Left output / I-output
• OUT_R: Right output / Q-output

When B7 is held, it switches modes. In addition, when using the internal oscillator, it switches between using L/R inputs as dual independent signals or converting IN_L to stereo by applying a Hilbert transformer before the modulation. CV_6 and CV_8 will only be used when running in dual mode.

NB: Since B7 has a dual function, if you press it to change alternate parameters, you will need to press it again to return to the Mono/Stereo mode you were in before.

Diagrams