I've been trying to replace it (or at least prepare to replace it) for years now, and nothing quite gets it right. Yesterday I did a comparison (I'm not going to say "shootout") of the old MXR, reissue MXR big box, MXR micro flanger, and my attempts and mimicking it with the Eventide H9. All sounded good, but only the vintage one sounded extraordinary. I'm not sure how to describe it best, but the character of the sound (waveform, filtering, weight) is something special. (Not unlike the difference between an old fender amp, the tone master version, and an amp sim)
Over the years, I've tried and found wanting (in reverse chronological order)
MXR 117R. Sounds fairly close, super noisy at idle. Just as heavy as the original. Less volume drop.
Boss HF-2. Sounds good, but more chorus-y than deep swooshy.
PastFX Hot for Flanger. Kinda in the same ballpark but it sounds fundamentally different than the MXR ones to my ears. Still more chorus sounding. Lots of features (level, volume, "Waldo" switch --> I would have vastly preferred a "permafrost" switch instead!)
MXR Micro Flanger (reissue). Decent, sounds a bit better than the big box reissue, but limited in controls. Only Rate (speed) and Regen. Comparing it to the reissue, it seems like the invisible manual control is maybe 9:30 and the width is around 11:30. But sounds pretty good throughout the range, even if it can't quite do the super wacky. Light and small. Volume bump.
Eventide H9 Flanger (Modfactor). I can get this in the ballpark, but I haven't been able to get the turnaround on the waveform right and the filtering seems different. It can totally do HF-2 sounds and EHX Electric Mistress ones, however. No ability to play with the dials, of course. Or at least with out programming them / mapping to exp pedal. Hint: Turning down the EQ on the Diamond comp upstream actually makes the HF-2 and H9 sound a bit closer to the MXR filtering (Note to self: I could probably play with an EQ pedal to get even closer).
ADA PBF Flanger. The one I had sounded like everything I hate about flangers: thin, warbly, pitch shifting not in pleasant ways. It's been a few years, so maybe I'd be better at dialing it in now, but it just seemed "thin" overall.
Boss ME-5. Some good sounds but (obviously) Boss family.
Boss BF-2. Sounds good at what it is. Which is a metal storm drain (rather than the MXR's self excavated tunnel from under an avalanche)
Ibanez UE400 (FL301 circuit?) Sounds pretty good, but not full bodied enough.
Basically: I'm considering having my vintage one modded to address functional issues. (That said, it works fine in a bypass loop and even finer in the loop of a Boss LS-2 -- it just makes an already big and heavy pedal effectively bigger and heavier)
- Power jack
- New switch
- (maybe) LED
- (maybe) volume trim or something to address the drop out
- (unlikely) weight relief
I hesitate to send it off to some random tech because I love it so much (and that's exactly why I'm even considering the modifications in the first place!).