MFOS Eight Stage Phase Shifter

phase_shifter_3Music From Outer Space is probably most famous Synth-DIY website. It’s author, Ray Wilson has developed huge amount of various modules and can offer wide variety of DIY-kits: module PCBs, noise generators, complete modular synths and even vocoder. Today I’m gonna tell about Eight Stage Phase Shifter module which Eurorack version I had pleasure to build recently.

How it works

Flanger is very popular modulation effect based on mixing audio-signal with slightly delayed copy of itself. The delay time is modulated. This cause constantly changing comb filtering of the initial signal. MFOS Phase Shifter allows to get such effect in several ways. See the block diagram below.

phase_shifter_block

The core is chain consisting of eight serially connected phase shifting cells. The signal is taken from the output points after 4th and 8th cells. Delay speed can be controlled by internal LFO (two waveforms) and by external CV. Device has 2 audio-outputs. The first is always connected to 4th cell’s output and the second output brings input signal mixed with one of 2 available points mentioned above: 4th and 8th stage.

phase_shifter_1Following controls are available:

  1. Audio-input socket
  2. 2 CV-input sockets
  3. 2 Audio-output sockets
  4. 4-Stage/8-Stage switch
  5. LFO waveform switch
  6. Signal level knob
  7. LFO Speed knob
  8. LFO Depth knob
  9. Feedback amount knob

DIY-kit

MFOS modules are distributed exclusively as printed circuit boards. Most rare components are also available separately, but full kits are available only for big projects such as modular synths. PCBs are relatively expensive (20 USD for Phase Shifter), but it is partly compensated with low shipping costs. I got my order as small packet without any packaging, stickers or business cards, which became trandy.

phase_shifter_2The schematic is optimized for very common components which are widely available in any electronic store. I had entire list already. Board is quality made (2-sided, masked, silkscreen) and looks like typical american thing: large size, large holes with wide borders, components are placed not very close to each other. it solders really fast, although build speed is very reduced because of need to connect every panel element to board with wires. In my opition, the universality of the PCB is it’s main flaw: even holes for molex or header power connectors aren’t provided. I had to make little additional board to make module eurorack-compatible. I have built this thing with my own panel design which is available here.

Functionality

What I need to say about sound quality. BOM allows to use 5% carbon film resistors, but Ray Wilson says that 1% metal-film resistors is recommended to reduce noise. I have chosen carbon-film resistors where allowed and found noise audible even if there is no audio signal connected. I can’t say that is a big problem because audio-signal pads noise very effectively. Though, Ray Wilson admit that this phase shifter is far from L. A. Studio equipment. Also, switching LFO waveform causing loud pop. In my case, even module restarts.

For me, personally, flangers sound better with slow sweeps, so I found a bit uncomfortable that all slow range (less than 1 Hz) of the speed knob is narrowed to one-two hours of the knob. Nevertheless, the sound is beautiful! The most interesting detail is that module provides pseudo-stereo effect when switch is on «8-stage». This effect has comfortable, moderate stereo-field width. Following audio-sample is recorded with Speed knob at 8 hours (Tri.) and Feedback knob around 3 hours.

Summary

Music From Outer Space modules are vary hard-core, likely dedicated for real DIY-nerds: the building process takes much time. The pros are good PCB quality, low power consumption (10ma/bus) and large availability of used components. Cons are missing optimization for perpendicular mounting and missing holes even for power connectors. The effect itself sounds good but it’s to be improved in the terms of useability. For example: very nice option would be simple LFO speed range switch.

modularsynth.ru rating: 6/10

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