how to tweak internal trim for phase 90

Discussion in 'Effects, Pedals, Strings & Things' started by tedm, Oct 8, 2005.

  1. tedm

    tedm Gold Supporting Member

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    I just got a used phase 90 with the R28 mod done, and it works fine, but I'm wondering if there are any tweaks to know when the internal trimmer is set just right? I'm playing a clip here with the speed set to the delay (les paul to tube screamer to Phase 90 to Echo Park to amp):

    (have tried the phase 90 in all positions, and so far like it after TS, and before delay)

    http://www.tedm.com/mp3s/reggae1.mp3

    Thanks!
     
  2. britishampsrock

    britishampsrock Member

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    not sure, but i do like te clip
     
  3. tedm

    tedm Gold Supporting Member

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    I appreciate the feedback!

     
  4. fuzzface

    fuzzface Active Member

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    sorry, but where is the r28 mod done??
     
  5. tedm

    tedm Gold Supporting Member

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    will probably provide details, I purchased mine with it already done, something about clipping or removing a cap or resister near one of the jacks.

    BTW, there is more than this mod to make a reissue a 'script' version, I think mods to 2 other caps or resistors, and possibly even the # of IC's in newer ones vs older ones.

    However, this is apparently a major mod, not that some folks prefer these without the R28 mod, so if you make the mod, I'd ensure it's easily reversible.


     
  6. dave-o

    dave-o Member

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    I think its one of those things you have to do by ear. I built the BYOC version, its supposed to be an exact copy. I just kept fiddling with the trim till it sounded good to me. Nice playing!
     
  7. tedm

    tedm Gold Supporting Member

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    Thanks! Also, for info. on mods, here is a link:

    http://www.erikhansen.net/diy/phase90diff.htm

    I'm pretty happy with the tone after tweaking the trimmer while playing, but I might open the whole thing up and do the C11/C12 cuts to make it more "script" like if I end up opening the thing again.

     
  8. tedm

    tedm Gold Supporting Member

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    Here's a clip with the trimmer tweaked to give a tad more pronounced phase than the earlier clip, not sure which I like better, probably the more subtle phase cycle, or in-between where it was and where I moved it to.

    Wish there were some external control for that trimmer.

    big Speed knob is about the same (around 11 O'clock), amp and delay settings varied a bit.

    http://www.tedm.com/mp3s/phase3.mp3
     
  9. tedm

    tedm Gold Supporting Member

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    OK, I went in and removed C11 and C12 to make this reissue even more script like.

    I can't tell much from the C11 and C12 removal, but I can tell a lot from the slightest tweak of the internal trimmer.

    Since I can't play any VH tunes, I am wondering if someone who has or has heard a script Phase 90, if it sounds like this:

    http://www.tedm.com/mp3s/phase4.mp3

    the playing is a LP bridge to tube screamer to Phase 90 (speed knob at middle - noon) to slightly overdriven amp. no delay fx.

    Is it close??
     
  10. tubes4tone

    tubes4tone Supporting Member

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    Last night I performed several mods to "scriptify" my new Dunlop Phase 90 pedal. For reference, I have a block logo 90 that has the scripty circuit (single opamps), so I was able to do side-by-side comparisons.

    I got my info from here:
    http://www.diystompboxes.com/smfforum/index.php?topic=37893.0
    I used the MXR Phase 90 to Script.gif file as my main reference, but I didn't do all of the mods that he has listed. The picture of the actual PCB with the components labelled was an immense help, enabling me to accomplish the mods in less than an hour, including disassembly and sound testing in between. The mods I actually performed were:

    Remove R28 (just like everyone else does) - not a huge change to my ears. Still had some strong mid or high-mid peaking compared to the block-scripty. This was accomplished by lifting one leg of the resistor from the board and folding it back under. That way, I don't lose the part if I want to change it back. Lift the LEFT leg as it appears in the picture of the PCB.

    Remove R32 and C11 This was actually accomplished by lifting BOTTOM leg of R32 ONLY (as it appears in the picture) which removes both components from the circuit. Again, both components can stay on the board and not get lost.
    Remove R31 and replace with jumper (Do this at the same time that you remove R32 and C11) This is the one component that you actually have to remove, but you could tape it inside the battery cavity to save it for later. Take a small piece of wire and solder it into place where the resistor was. Tone wise, this removes the "pre-emphasis," which is essentially boosting the high end a bit. Trying the pedal after this step made it significantly darker than it was before modding, and even darker than the block-scripty.

    Remove C12 Again, just lifted the LEFT leg of a cap to save the component. I actually lifted the wrong cap at first and no sound came out at all, but I quickly fixed it! This final mod brought the missing high end (from R32 and C11 removal) back into the pedal.

    To my ears, it now sounds so close to my block-scripty that I'm not going to worry about any more mods. These mods are essentially "free" since you don't have to buy any components; you're just REMOVING parts from the board (except for the wire jumper that you add). I thought about removing the footswitch and making it true bypass, but I don't think it will work because of the way everything is attached to the PCB.

    The author of these mods (link above) has several other suggestions for component removal and replacement, but these seem to me like they will offer a diminishing return, and are more difficult to do (replacing the trim pot, for instance). Like I said earlier, the pedal sounds so close to an original that I don't feel the need to mod it any further and risk damaging the pedal.
     
  11. tedm

    tedm Gold Supporting Member

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    Wow, you really went the whole mile. So how does the sound compare to my reissue with just the r32, c11, and c12 removal??

     

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