MXR Phase 90

[Rob A]

The cheerful little orange box. I used to have one back in the late 70's, long since gone.

I'm posting cause I bought one today for a little bit of nothing. If you poke around the web at all, you'll find plans for modifying the more recent versions of this to improve a certain degree of midrange clipping/harshness/distortion in the modern version of the design. You can also choose to pay big bucks for a vintage "script logo" version (before Dunlop took over and screwed it up I guess), or a current one that is a reissue attempting to recreate the old school vibe.

For me, cheapness is a serious virtue, so I grabbed up a vanilla recent version of this pedal used and set out to carry out the "R23 mod." I also recorded a bit of before, during, and after for your listening enjoyment.

With the stock circuit, I agree that this pedal basically is unusable. The harshness you get in the upper mids is truly nasty. Here's an audio clip that kind of shows it at its worst disadvantage:
http://shup.com/Shup/374771/phase-90-1.mp3

So the first step is to remove the feedback resistor R23. This second clip represents the sound after that change:
http://shup.com/Shup/374773/phase-90-2.mp3

The second step is to remove the two capacitors C11 and C12. this is optional, but it can improve the tone further. I decided that I couldn't stand the thing distorting so badly, so out they came. Here's the improvement:
http://shup.com/Shup/374782/phase-90-3.mp3

And a short musical selection using the fully modded Phase 90:
http://shup.com/Shup/374785/phase-90-4.mp3

I think it's a vastly improved sound. As good as the vintage pedal? I can't really say. I have used exclusively software phase shifters for recording since I got my suitcase, but this pedal modded is likely to find a semi-permanent place in my rig.

Drawbacks:
- There's no wet/dry control on this pedal, so you have to either put it in an FX return to get that mix control, or live with the lack of it. There's a trim pot inside that you can tweak the wet/dry mix with, but that's not really satisfactory. Mine's in the loop on my mixer, and it really livens it up to mix in a bit of dry sound with the phased sound.
- No feedback control either. Deal with it.
- It's mono. Maybe that doesn't bum you out, but I like the stereo phaser sound.
- Recently made ones use surface-mount components, making  then slightly harder to mod. Mine was through-hole and dead easy to modify with nothing more than wire cutters.

Upside:
+ There are ten zillion of these out there, so you can almost definitely find one cheap.
+ The frequency response is such that it actually improves my noise floor slightly, believe it or not. The 120Hz power supply buzz gets damped pretty well by mine (not eliminated or anything).
+ Cheap!
+ Easy to mod.
+ Cheap!

So if you have a Phase 90, and you think it sucks, go here to find out how to do the R23 mod:
http://www.erikhansen.net/pedal-mods/mxr-phase-90-mods
Concise version: clip out the three marked components in this pic:
http://www.erikhansen.net/diy/phase90scriptmod.jpg
You'll get a much more usable pedal.

If you don't have one, go get one. Phase 90 + Rhodes go together like hot fudge and vanilla ice cream. Don't get suckered in on the upmarket ones (like the 74 handwire or the EVH version), buy the low end one and get after it yourself.

Is the bestest phaser ever? Nope. Too few knobs to even be in the running. But it's a nice addition to the signal chain.

[Tim Hodges]

Thanks for that Rob, very detailed!!

I was looking into getting one (one of the "vintage" remakes) so your post will save me a few ££ when I decide to get one.

T

[Mark II]

Brilliant post, Rob.
I have a phase 90 aswell and heard about the R28 mod but didnt thaught that it would be that improving soundwise.

I have just checked if I have a SMD version.
It's not, I have to warm up the iron  

Cheers
Mark II

[Rob A]

Actually, the traces on the board are really small and delicate. I'd recommend not using the iron and just cutting out the components. I know it seems kind of irreversible, but I can't imagine wanting them back in the circuit.

[Mark II]

True. And using the cutter is much faster.
I have bought mine last year and it's build up pretty much like the one on the foto linked above. No PCB mounted parts. Easy to mod.
I cut out R28 and both Cs and I like the new sound.
Much more less harsh, as you described.
Thanks for your advice, Rob.
kind regards

Mark II

[Ben Bove]

Wow - heard about the mod but thought it was eh, not big deal.

Your examples are totally night and day.  I've got one of the remakes and have always noticed the "crunching" but thought that was just part of the sound.  

When I get a moment I'll mod it.  Just wish I had certain recordings done after I found this out.  

Thanks for being thorough as always

[Michael]

I couldn't deal with the sound of a stock Phase 90 and recently was thinking about buying one just to do that mod.  Craigs List here I come! Nice write up Rob!

ANyone try that Phase 45?

[chava]

I made the change yesterday afternoon after I read this post, and I love the results.  I used to only use the pedal with the speed turned way down, just to fatten up the sound, but this little mod really does the trick. Definitely less harsh and more lush at any setting. Thanks for the tip, Rob!

[Dan Belcher]

I did this mod myself as well a year or two ago, and it really does make a world of difference.  However, I later got an old Small Stone phaser off eBay and use it 99% of the time. It's very similar to the Phase 90 sound, just slightly creamier in my opinion.

[Rhodesman88]

If you like the MXR Phase 90, try a Behringer PH9.  Nice copy of te MXR and inexpensive too.  Usually on eBay for $29.95 and some sellers have no shipping.  Runs on 9V battery or external power supply from Behringer.