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Author Topic: Help with mp1 - low distortion and "sputtering"  (Read 1455 times)

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Cstecker

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I have an original mp1 that does not give me near the distortion that it used to.  First off, the solid state channel works fine.  The clean tube and dist tube channels are the only one affected.  The unit has new tubes which test fine.  The clean channel actually has more gain and volume than the dist channel. The sound also "sputters" and "spits" as you play.  Any ideas where to start.  I had a technician look at it and he gave it back saying it would take quite a bit of time to troubleshoot and would cost more than I wanted to spend to find the problem.
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MarshallJMP

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I would start with some measurements, do you have a multimeter?
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Cstecker

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No I don't have a multimeter.  Let me update you in my problem.  I got another mp-1 and it worked great for a few days, then started doing the same thing!  So I'm thinking it's something I'm doing?  I play a strat with the Clapton active mid boost circuit into a GCX audio switcher before it hits the ADA.  I did not have this issue until after I installed the mid boost?  The signal is also going through a buffer on the GCX.  Could I be overloading the input on these MP-1's and frying something?
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Iperfungus

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My suggestion would be to do a test in more simple condition:

1) use a different guitar with a standard pickups configuration and no boost or active stuff
2) remove the MP-1 from the current chain
3) use a simple setup: guitar, MP-1, power amp + cabinet (or an amplifier)

If you've another unit, you can also A/B test them.
But use a simple rig.

Then, buy a good multimeter: it's always a good idea to have one!  :thumb-up:
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ADA MP-1 (modified by MJMP)
Marshall JMP1
TC Electronic G Major
Alesis Quadraverb GT
Zoom 9150
Advance Tube Technologies TA '70 tube power amp
Marshall Valvestate 8008 power amp
ADA B200s power amp
Behringer FCB1010 MIDI controller
Zoom 8050 MIDI Controller
Zoom FP01 Expression pedal
Blackstar HTV 212 stereo cabinet with 70/80 Celestion speakers
Rivera Pubster 25
Blackstar Fly 3 amp + external speaker

Stomps, stomps, stomps...and stomps (Bogner rules!): TC Helix phaser, Xotic RC Booster, TC Sentry noise gate, Bogner Ecstasy Blue, Bogner Ecstasy Red, Mad Professor Royal Blue Overdrive, Sonic Research Turbo Tuner, TC Flashback delay


1987 PRS Custom
1988 Fender Strat Plus
2014 Fender Modern Player Strat
2016 Custom assembled Fender Strat
2013 Gibson SG Standard
1995 Gibson Les Paul Studio
1991 MIJ Ibanez RG570FM TB
2016 MIJ Ibanez RG655M SPM
2002 Bruno Traverso Custom "Tommy" Silky
2017 Kramer Baretta Special
2010 Simon & Patrick Woodland CW acoustic

Cstecker

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Already tried that.  Yesterday I retired strat with passive pickups and took the preamp out of the rack and wired straight to power amp.  I even reloaded all factory programs.  Same issue. I feel like the Ada is not getting the full input signal?  The input led never lights up, only the od1 light occasionally lights when I hit the strings real hard.  All of the patches sound weak like they are not getting enough signal?
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Iperfungus

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Already tried that.  Yesterday I retired strat with passive pickups and took the preamp out of the rack and wired straight to power amp.  I even reloaded all factory programs.  Same issue. I feel like the Ada is not getting the full input signal?  The input led never lights up, only the od1 light occasionally lights when I hit the strings real hard.  All of the patches sound weak like they are not getting enough signal?

Mmmmmmh....MJMP, input jack issue?  :dunno:
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On the run again!

ADA MP-1 (modified by MJMP)
Marshall JMP1
TC Electronic G Major
Alesis Quadraverb GT
Zoom 9150
Advance Tube Technologies TA '70 tube power amp
Marshall Valvestate 8008 power amp
ADA B200s power amp
Behringer FCB1010 MIDI controller
Zoom 8050 MIDI Controller
Zoom FP01 Expression pedal
Blackstar HTV 212 stereo cabinet with 70/80 Celestion speakers
Rivera Pubster 25
Blackstar Fly 3 amp + external speaker

Stomps, stomps, stomps...and stomps (Bogner rules!): TC Helix phaser, Xotic RC Booster, TC Sentry noise gate, Bogner Ecstasy Blue, Bogner Ecstasy Red, Mad Professor Royal Blue Overdrive, Sonic Research Turbo Tuner, TC Flashback delay


1987 PRS Custom
1988 Fender Strat Plus
2014 Fender Modern Player Strat
2016 Custom assembled Fender Strat
2013 Gibson SG Standard
1995 Gibson Les Paul Studio
1991 MIJ Ibanez RG570FM TB
2016 MIJ Ibanez RG655M SPM
2002 Bruno Traverso Custom "Tommy" Silky
2017 Kramer Baretta Special
2010 Simon & Patrick Woodland CW acoustic

Cstecker

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I have an mp1 version 1 with rear input mod and version 2 that this has happened to.  I've tried both front and rear jacks and I get the same thing.
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Harley Hexxe

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Hi Cstecker,

    First of all, welcome to the Depot!

    Have you tried spraying out the input jacks with Deoxit, and swabbing them out with a Q-tip? It's a long shot, but what do you have to lose? This could be a resistor going south in the input stage, or it could be a diode going bad.

    Harley 8)
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Cstecker

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 Thank you. Yes I have cleaned the input and output jacks. The solid-state channel on both units seems to sound fine to me?   I'm wondering if this could be an issue on the tube board? I have changed tubes and that makes no difference at all.
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Harley Hexxe

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It's possible, but you'll need a multimeter to check some voltages on the board.
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MarshallJMP

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Re: Help with mp1 - low distortion and "sputtering"
« Reply #10 on: Time Format »

The input will never lit up, that's normal, the OD1 led does at higher OD1 settings.(also depends on the T2 trimpot).

If the SS sounds good then it could be a problem on the tubeboard.It's just strange that it happends with both MP-1's.
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Cstecker

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Re: Help with mp1 - low distortion and "sputtering"
« Reply #11 on: Time Format »

Ok guys, I got them both working again.  It turned out just being the tubes! I feel stupid.  I bought new tubes weeks ago and that did not work.  I even sent the older mp1 to the shop and the tech said the tubes tested fine.  He did not fix it at the time because that unit has several mods in it that weren't done very well and he couldn't find good schematics for it.  I also told him I didn't want to put much money into fixing it.  I don't know if reloading the presets had anything to do with it when I changed tubes but I'm just happy to be up and playing again.  Thanks for your suggestions!
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MarshallJMP

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Re: Help with mp1 - low distortion and "sputtering"
« Reply #12 on: Time Format »

Okay great !!
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Harley Hexxe

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Re: Help with mp1 - low distortion and "sputtering"
« Reply #13 on: Time Format »

Hey Cstecker,

   I've bought new tubes that were crap right out of the box before, so that comes as no surprise. In the future, you might think about getting tubes from Doug's Tubes in New York.  The chances of you getting a bad tube from him seem to be highly unlikely.

    Harley 8)
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