Anyone make a case for *not* doing mods on DRRI?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by joegrant413, Jan 16, 2008.


  1. joegrant413

    joegrant413 Member

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    I just found a tech where I live who would be happy to do the mods on my fairly new DRRI. He'd add the reverb and "vibrato" to the Normal channel. (Yes, I keep hearing this is simple mod... anyone can do it... but I'm not going to...)

    I want to make this mod because I think the normal channel sounds superb -- with or without dirt pedals -- and I love the reverb.

    Are there downsides I should know before pulling the trigger? One I know is voiding the 4.5 years left on the Fender warranty. The other is the potential, I suppose, that the Normal channel won't be as pristine as before... but I haven't heard anyone mention that.

    Anyway.... can anyone offer reasons I *should* not make this DRRI mod and just leave the amp alone?

    Thanks,
    -- Joe
     
  2. jjasilli

    jjasilli Member

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    Lot's of people like this mod. However, it does change the circuit path and gain structure of the 1st channel. So it will be different.
     
  3. phsyconoodler

    phsyconoodler Member

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    You could actually use the normal channel for what is was designed for:an effects loop with an eq.Plug your guitar into the reverb high input and your input of a delay or whatever into the low jack.Then take the effect output and plug into the high input of the normal channel.Voila!You have reverb,deay and a great level & eq for the effect.No need to make a 'clone' of the reverb channel out of the normal channel.
     
  4. John Phillips

    John Phillips Member

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    It's not that simple a mod on a reissue. It is on an original, but the RI is built on a PCB and is harder to modify.

    Doing this mod will make the Normal channel sound like the Vibrato channel less the bright cap, so if you prefer the tone of the Normal channel, you do not want to do this. In fact you could make the Vibrato channel sound much more like the Normal channel far more simply by removing the bright cap - which is an easy mod.

    It's quite a lot of work, will void the warranty, probably won't give you what you want, will be as difficult to put back if you don't like it, and there's a much simpler way of getting reverb on the Normal channel that involves doing nothing to the amp whatever:

    Plug the guitar into the #1 jack on the Normal channel. Jumper from the #2 jack to the #1 jack on the Vibrato channel. The two channels are out of phase with each other, so you need to keep the Vibrato channel's volume much lower than the Normal, but if you turn the reverb up further than normal, that will work. The Vibrato channel tone controls will also work on the reverb to some extent.
     
  5. joegrant413

    joegrant413 Member

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    Thanks, phsyconoodler,
    I've tried something similar, but probably not exactly the same thing. Do you notice any phase cancellation probs? I'll probably give what you say a try, so one other question... are you turning up the reverb and turning down the volume on channel 2?

    Thx,
    -- Joe

    P.S. I have a LS-2 line selector being shipped. I might play in the picture hear for ways to split, combine, or mix signals.
     
  6. joegrant413

    joegrant413 Member

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    Hey John Phillips,

    Look like we were posting at the same time! Thanks for the advice. If I explore the jumpering more, it would nice to have a way to avoid the phase cancellation. I believe Radial has a box that includes phase inverting, but that probably more $$$ than I care for.

    Again, your cautions are very timely and appreciated!!

    -- Joe
     
  7. Rick1114

    Rick1114 Supporting Member

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    There's a guy on the FDP forum who's linked a scematic of the DRRI "reverb to normal channel" mod to his user profile. He goes by fritzthecat or something like that. The mod is relatively easy, but many consider modding PCB amps a big hassle because it's much less forgiving to repair screwups and it's not "easily" reversible because the traces start to lift if you keep experimenting on them.

    For myself, I like the Vibrato channel better because of the extra gain stage (the reverb driver). If you mod the normal channel for reverb it will also have the extra gain stage and sound slightly brighter as John Philips described. So you may want to leave it as is. If you do not use the vibrato because its off the charts bright you can just do the bright cap mod!

    I actually experimented with mine quite a bit with new coupling caps, tone stack, and different bright cap values. I completely removed the yuck factor from the vibrato channel and gave it a litlle more natural drive - YMMV.
     
  8. John Phillips

    John Phillips Member

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    That's largely my experience as well. They're pretty reliable until they develop some minor fault - which could be fixed easily with a little care - but they get worked on by techs who don't like and don't respect PCBs, don't seem to understand how to do simple jobs on them without causing more damage, and end up making far more problems - sometimes irrepairable to what I would consider a proper standard, if they do things like cutting out the PCB and bodging in a different type of pot because they couldn't be bothered to get the correct one (for example), which I have seen all too often.

    They do have an inherent problem with the flying leads from the boards to the tube sockets being too flimsy, and they will break with repeated flexing.
     

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