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  • MXR/EVH Phase 90 - true bypass?

    Are either the EVH Phase 90 or the MXR Phase 90 true bypass? I have found a site and read about altering older MXR Phase 90 pedals to true bypass, and that the older pedals can suck signal (tone) as they just switch output, but what I cannot seem to ascertain is if the newer pedals (like the EVH Phase 90) have been updated to true bypass or not.

    If someone can suggest an alternative that gives the same phase effect/tone and is true bypass, I'd be interested in that as well.


    Thanks.

  • #2
    New wans r not tru bypass.

    educate yourself!

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    • #3
      Indeed, none of the MXR's are true bypass. If you keep a fully buffered (Boss or similar) pedal or other pedal always active in front of it, you will most likely not notice any serious tone loss. The problem is worst when the MXR pedal is the first thing the guitar "sees" (either because it is physically first in line, or because the other pedals in front are true bypass and turned off).

      If I were serious about the true bypass thing, I'd get a '74 reissue Phase 90 and have it modified for true bypass. There's also the Retro-Sonic phaser and the BYOC one, if you fancy other colours than orange...

      /Andreas
      The Power List

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      • #4
        The Custom Shop and EVH models have pretty good buffers in them.
        Guitars: Suhr Pro Series S2, Gibson Les Paul Standard Faded 50's neck w/Wolfetone pu's.
        Amps: Blackstar HT-5, Diezel 1x12cab, Vox DA-5
        Effects: Boss TU-2>Cry Baby GCB-95F>MXR CS Phase 90>Keeley TS-9 Plus Mod>BYOC Analog Chorus>MXR Carbon Copy>ISP Decimator> amp.

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        • #5
          OK, that answers a lot of questions, thanks a lot for your help.

          In my setup there will be a buffered pedal (tube screamer) in front of it, so together with using one of the ones with better buffers will hopefully solve the problem. I will try it first - I was wondering if it was a waste of time and I should just cut to the chase and get a looper, but it sounds like if I get one of the later models and put it where I want it in the chain, it might work.

          Thanks again.

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          • #6
            In my setup there will be a buffered pedal (tube screamer) in front of it, so together with using one of the ones with better buffers will hopefully solve the problem. I will try it first - I was wondering if it was a waste of time and I should just cut to the chase and get a looper, but it sounds like if I get one of the later models and put it where I want it in the chain, it might work.
            Yes, it should work. The low impedance output from the (fully buffered) tube screamer is well equipped to deal with the impedance loading of the MXR. If it's one of the modern reissue pedals, the loading is less than with the older ones (or with the '74 reissue). But the tube screamer will probably be able to drive either one just fine.

            I still wouldn't count out the '74, though - I hear it sounds spectacular, which is a quite important aspect too...

            /Andreas
            The Power List

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            • #7
              I have a couple MXR Phase 90s, including the newest EVH and they're all serious tone suckers. I talked to the MXR tech at Dunlop and he recomended I try raising the input impedance a bit, but that would make it noisier. On Revision E, mine, this resistor is location designator R14. Just try changing the input termination resistor from its current 1MEG to a 1.5MEG if you want to try.
              Straight-Jacket memories, and Sedative highs... the Good Old Days.

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              • #8
                Yup, the problem is that in bypass, the input impedance in the MXR ends up in parallel to the input impedance of the next pedal. Equal impedances in parallel divide to half their individual values, and raising one of them only raises the total a little. If the MXR is 1 meg, and the next pedal is 500K (not an uncommon figure), the total input impedance will be 333K. Raising the input z on the MXR to 1.5 meg will only raise the combined total to 375K.

                This is why the MXR method of adding a buffer to the front of the circuit, to raise its input impedance, will never be more than a stopgap measure. If they wanted to fix it properly, they could have placed the buffer in front of the switch instead - then the total input impedance the guitar "sees" would have been 1meg, regardless of what pedal follows it. Either that or wire for true bypass, where the input impedance would have been irrelevant. As is, the performance of the MXR in bypass will be subject to change depending on what's in front of (and after) it. Stick a buffered (Boss or similar) pedal in front of it, and the problem all but goes away. Run the guitar straight into the MXR with a 500K pedal following it, and you'll lose a lot of treble and punch...

                /Andreas
                The Power List

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                • #9
                  makes you wonder why MXR just don't add a decent input buffer. I guess they would have to respin about 20-25 PCB's but they must have done that recently for all the RoHS regulations.
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                  • #10
                    there is an internal trimpot in the evh phase 90,what is it function??

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                    • #11
                      no, but the tonefactor nebula is. and that is bad ass
                      check out my sweet dealzzz, I got tons of them

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                      • #12
                        makes you wonder why MXR just don't add a decent input buffer.


                        Well you'd think they'd do something... killer pedal otherwise.
                        Straight-Jacket memories, and Sedative highs... the Good Old Days.

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                        • #13
                          I unplugged my EVH phase 90 and with the effect off the signal still passes through - doesn't that mean it's true bypass?
                          Gibson 2006 '58 VOS Les Paul
                          Gibson 2009 Les Paul Traditional
                          Gibson Flying V with SD JB/Jazz pickups
                          PRS McCarty
                          EBMM Axis Super sport
                          Keeley compressor, Skreddy Mayo, MXR EVH Phase90
                          Bogner 20th anniversary XTC with matching 412
                          Suhr Badger 18 and matching 112 cab
                          TC Electronic GMajor2
                          Voodoo Labs GCX&GCP, RJ mini amp gizmo
                          Martin HD28

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                          • #14
                            I'd really like to find out who started that myth way back when - it seems that no amount of information is enough to kill that one off...

                            Anyway, to answer the question:
                            No, it just means that the bypass line is passive (not passing through any active circuitry). A pedal that passes signal in bypass when powerless can be true bypass, but in most cases it is "hardwire" (also known as "half-assed") bypass, where the circuit is permanently connected to the input jack and the switch only selects the output signal.

                            A true bypass wiring will disconnect the fx circuit completely (at both ends) from the bypass line, which is something the simple "power off test" will not detect.

                            /Andreas
                            The Power List

                            Comment


                            • #15
                              makes you wonder why MXR just don't add a decent input buffer. I guess they would have to respin about 20-25 PCB's but they must have done that recently for all the RoHS regulations.



                              Probably because they've been making the pedal this way for years and people are still buying a lot of them. The phase 90 must be the #1 selling phase pedal.
                              Check out my band the OIDS

                              and the OIDS myspace page

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