how to mod a reissue phase 90 to be more like a vintage MXR unit
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just found this in my travels on HC. this is from dunlop themselves.
1) Removing the Pre and De-emphasis will result in a slightly higher noise
floor while raising the headroom at 1.3Khz +3dB and 7.2Khz +12dB. Procedure:
Remove C11 (.01MF) and C12 (680PF).
2) Removing the feedback around the Phaser circuit will diminish
regeneration. This will result in a mellower effect, reduce the midrange
frequency response, and sound more like the earlier SCRIPT MXR Phase 90s.
Procedure: Remove R28 (24K).
3) For lowering the overall effect output change R7 from 150K to a 100K
or -3dB reduction, R7 150K to a for -2dB reduction. This modification
should only be done in conjunction with modification #1.
Modifications #1 and #2 can be done separately or together.
also:
1. There is a trimpot internal to this effect. It's located at the top of the board covered in epoxy. I took the board out and was able to get to the pot from the other side. I was then able to remove the epoxy, reassemble and adjust to see what it did. Basically it kind of acts as a bias adjustment. If you turn it all the way to the left or right, there is no phase. Within the middle is where the phase is, and it's a very small portion of that middle, so any mild adjustment will have extreme results. The results are not one of effect level like some people think. What the pot does is make the phase wave inconsistent in its peak. Example, low peak, low peak, high peak, etc. Until you reach that sweet spot where the phase is consistent. Not having it set right also makes the effect sound rather thin and metallic, so after all of this fiddling, in my opinion, it's best to LEAVE IT ALONE (Hence, the epoxy, duh...). If you must tinker, be sure to mark where it was to begin with, because it will be very difficult to find since you don't have much room to play with.
i think it would be cool to put R28 on a switch so you could bypass it at will. additionally, you could (if there is room in there) put a 50K pot in place of R28 to vary the feedback for different sounds.
1) Removing the Pre and De-emphasis will result in a slightly higher noise
floor while raising the headroom at 1.3Khz +3dB and 7.2Khz +12dB. Procedure:
Remove C11 (.01MF) and C12 (680PF).
2) Removing the feedback around the Phaser circuit will diminish
regeneration. This will result in a mellower effect, reduce the midrange
frequency response, and sound more like the earlier SCRIPT MXR Phase 90s.
Procedure: Remove R28 (24K).
3) For lowering the overall effect output change R7 from 150K to a 100K
or -3dB reduction, R7 150K to a for -2dB reduction. This modification
should only be done in conjunction with modification #1.
Modifications #1 and #2 can be done separately or together.
also:
1. There is a trimpot internal to this effect. It's located at the top of the board covered in epoxy. I took the board out and was able to get to the pot from the other side. I was then able to remove the epoxy, reassemble and adjust to see what it did. Basically it kind of acts as a bias adjustment. If you turn it all the way to the left or right, there is no phase. Within the middle is where the phase is, and it's a very small portion of that middle, so any mild adjustment will have extreme results. The results are not one of effect level like some people think. What the pot does is make the phase wave inconsistent in its peak. Example, low peak, low peak, high peak, etc. Until you reach that sweet spot where the phase is consistent. Not having it set right also makes the effect sound rather thin and metallic, so after all of this fiddling, in my opinion, it's best to LEAVE IT ALONE (Hence, the epoxy, duh...). If you must tinker, be sure to mark where it was to begin with, because it will be very difficult to find since you don't have much room to play with.
i think it would be cool to put R28 on a switch so you could bypass it at will. additionally, you could (if there is room in there) put a 50K pot in place of R28 to vary the feedback for different sounds.
Post edited by Unknown User on
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it's easy if you know how to properly desolder. it's pretty simple. the hack way is to clip the resistor but it's better to desolder it.