OptiPhase

Updated vintage optical phaser design

 

 

The OptiPhase optical phaser rack effect module compares to the Musitronics Mutron Phasor II.  Updated to use modern available parts, the OptiPhase sounds like stirring a cup of liquid music.

 

Description

The OptiPhase is an updated Mutron Phasor II design.  The Phasor II is considered by many to be one of the best phasers ever.  Vintage units in working condition bring high prices.  It does provide nice fluid, liquid phasing, but it had some problems, too.  It ran on wall power, which often brought some noise into the circuit.  It caused some tone sucking because the switching wasn't true bypass.  They also had a tendency to stop working due to their construction (see note at the end of this page).  And they had a fair amount of that background phaser noise.  All of these problems are addressed in the OptiPhase. 

There's one other difference between the OptiPhase and the original units.  The brand and model of the key optical components in the original circuit are unknown.  Those components are a light source and the photoresistors used in the phasing.  The exact properties of these components is key to the character of the phasing.  After much experimentation, we have settled on modern replacements for these components that sound very close to the originals.  You'll get those components in the standard OptiPhase configuration.  There are two trimmers in the circuit that are critical to adjusting the phasing.  Tiny, tiny adjustments make big changes in the sound.  You may prefer different settings, but keep track of your starting positions so you'll be able to get back to them easier if you need to...

While we were testing replacement components, we found some other components that sounded great, but different from the Mutron.  One of these is the basis for the OptiPhase Mellow Yellow configuration.  It has a little less low-end throb and can be set to different levels of liquidity using the trimmers.  There will probably be additional configurations added when we get time to experiment more with some of the other components we tried, others that sounded great but not like the Mutron.

 

Configurations

  • OptiPhase - compares to original Mutron Phasor II

  • OptiPhase Mellow Yellow - see description above

 

Options

  • Stages Switch - The Mutron is a 6-stage phaser.  This option lets you turn off the last two stages to give you a 4-stage phaser.  The Univibe is a 4-stage phaser...  The other setting on the switch is all 6 stages, of course.  See Univibe Switch Option description for additional information.
  • Univibe Switch - This switch lets you select either the Mutron capacitor values or the Univibe capacitor values for the first four stages.  Since the other parts of the circuit is different from a Univibe, and because you have two additional phaser stages, this won't make your OptiPhase sound like a Univibe, but it does provide some of that character, particularly when coupled with the Stages Switch to turn off the two extra stages. 

If you have only the Stages Switch, you get the Mutron sound, plus a unique 4-stage phaser sound.  If you have only the Univibe switch, you get the Mutron sound, plus a unique 6-stage Univibe-ish sound.  With both switches, you get the Mutron sound, the 4-stage Univibe-ish sound, the 6-stage Univibe-ish sound, and a unique 4-stage Mutron sound.

  • Blinking LED - Adds a second LED that blinks in time with the Rate
  • Custom Op Amp - Default is a 4558 op amp, like the original circuit.  You can choose a different pin-compatible op amp.
  • Input Capacitor - The original circuit used an input capacitor that trimmed off some bass.  By default, we use a value that lets all the guitar's bass come through.  If you want more or less bass to be allowed into the circuit, choose this option and let us know what you want.  This option is not presently switchable.
  • Custom Components - We use metal film resistors and a selection of capacitors that provide good tone and low noise.

 

Front Panel

  • On/Off indicator LED
  • Rate
  • Depth
  • Feedback
  • (optional) Rate LED
  • (optional) Stages switch
  • (optional) Univibe switch

 

Rear Panel

  • Audio In
  • Audio Out
  • On/Off Footswitch
  • On/Off Override
  • DC Power
  • DC Power LED

 

Module Width

  • 1.5" standard
  • 2" left wing and 1.5" right wing available if the Blinking LED option is not selected

 

Power Consumption (aprox)

75 - 80mA

 

Base Configurations

Part # Description List Price
MOD-OPTIPHASE-STD OptiPhase module $315
MOD-OPTIPHASE-MELYEL OptiPhase Mellow Yellow module $315

 

Options

Part # Description List Price
MOPT-OPTIPHASE-STAGES Stages Switch $19
MOPT-OPTIPHASE-VIBE Univibe Switch $39
MOPT-OPTIPHASE-LED Blinking LED $19
MOPT-OPTIPHASE-OPAMP Custom Op Amp $0 - TBD
MOPT-OPTIPHASE-INCAP Input Capacitor $0
MOPT-OPTIPHASE-CC Component Changes TBD

  

Free Tip! 

Do you have a misbehaving original Mutron - dead, sound cutting out, crackling/distortion?  There may be an easy fix.  While these units are built tough, they have one serious flaw.  All that stuff inside, which is kinda heavy, is suspended by being soldered to the pots, which are of course fastened through the top of the pedal enclosure.  Over time and after many stomps, the solder holding the pots to the board will crack or break, even though you may not be able to see it, even with a magnifying glass. 

If that is your problem, it is simple to fix.  You just need to reheat the solder - no parts removed or replaced, so you are still all original.  You probably won't even have to add any more solder, but possibly.  Just reflow it carefully and see if that fixes your problem.  Sometimes you have to reflow them a couple of times due to the way they are constructed, but it works great if that is your problem.  Just be careful not to burn/melt anything else or get someone to do it for you.