Blofeld Reverb Mod (concept)

Room enough for a reverb?

Upgrading the Blofeld with proper Studio-grade reverb and outputs – a medium-level mod for the brave at heart. CONCEPT ONLY, NO PROOF-OF-CONCEPT YET.

Ever since I saw a friend‘s Sledge synth, which is essentially a Blofeld dressed up by star designer Axel Hartmann, I thought about using the unused space in the Blo for an expansion. I dreamed up a concept of a knobby Blofeld controller mod which I dubbed „Frankenfeld“, but I will never realize it – building a controller of that complexity is quite some work to do.

I have been playing the Blofeld a lot recently, and I love it as much as ever, which made me think about a decent reverb as an extension. The obvious decision would be forking out 400 Euros for a Strymon Big Sky – everybody does that.

I do not like two things about this setup. First, lots of additional wiring. Another power supply. And second, using a Lexicon MX200 with my Oberheim Matrix analog synth, I have noticed that it is sometimes hard to get the input to an external reverb to the right levels.

Which made me think: how about using a second-hand Lexicon MX as an all-digital output processor and output stage?

The advantages:

  • No additional wiring.
  • MIDI-controllable decent master reverb.
  • Presumably much better anlog output.
  • Blofeld gains a digital SPDIF output.


  • Messing with your Blofeld – modding the housing is impossible to reverse
  • Headphone output
  • Master reverb and preset might not be as useful as one thinks, especially with multi patches

The main question remains whether there is really enough room in the Blofeld for the Lexicon PCB. Although I think that there are loads of space in the Blokeys, and that the MX200‘s electronics might consist out of a processor PCB and a front panel PCB like its predecessor MPX200 (service manual here), I have not looked yet. And there are about 30cm of usable space on the Blofeld‘s top, while the front panel needs about 45cm, so it has to be cut down in some way.

But what would life be without challenges.

The MX Mod

  • Skills needed: advanced-level soldering. recklessness.
  • Tools needed: Soldering station, metal drills and saw.
  • Materials needed: plastic PCB mounts, some cable, front cover.
  • Time needed: about one afternoon.

So this is what would have to be done:

  • Get a Lexicon MX200
  • Choose either of two configurations:
    • Rewiring the Blo‘s outputs to the MX‘s outs
    • Keep Blo‘s „Dry Out“ and MX‘s „FX Out“ (easier)
  • Take it apart and prepare the FX/Processor board. Remove Analog In, SP/DIF, and (in the Rewire Blo config) Analog Out.
  • Prepare the Blofeld: Take out its main board. Remove MIDI Out. Patch up SPDIF out: Solder a shielded cable to Pin 69 of the NXP 56371 DSP (datasheet) – this is an SPDIF output which you may use as a digital input to the MX200.
  • Drill holes for the Analog Out and MIDI OUT. Drill holes for the encoder and the displays.
  • Solder MX200’s MIDI In to Blofeld‘s MIDI Out. Solder SPDIF connection. Test. Smile.
  • Mount the MX‘s front panel board. Mount the MX‘s processor board.
  • Connect MX to power supply.
  • Additional options for upgrading:
    • Replace Blo‘s power switch (really switch power off instead of the electronics)
    • MIDI Thru

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