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Author Topic: MP-1 volume drop  (Read 10315 times)

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revhed666

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MP-1 volume drop
« on: Time Format »

gday guys have had this problem for a bit and its preventing me from gigging my rack setup. random volume drops from the MP-1. i cant reproduce this problem and it seems whenever i try and troubleshoot it, it wont occur so i am yet to determine the MP-1 as the exact cause. i do run it in stereo with a marshall jmp-1 which does not experience the same issue. with no patch changing the MP-1 volume will drop a noticeable amount, sometimes flickering back and forth. sometimes it seems almost a permanent drop and i compensate by upping MP-1 master gain from 2.0 to 3.0 to even things out. it may stay like this for some days or weeks but sooner or later it changes back again and i readjust the patch levels. dont go crazy trying to work this out as i cant be absolutely sure its the MP-1 but i'm hoping u may have a solution. will try different tubes but they are mullards only a few years old and had very little use. cheers and beers
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Soloist

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Re: MP-1 volume drop
« Reply #1 on: Time Format »

Hello revhed666,
What else are you running in your rack? I too run an MP1 and JMP1 simultaneously from time to time.
Are you using a mixer? Does it happen just running the MP1 alone?
To make it easier just post your signal path, it may be something other than the MP1.
For example I was running a Gmajor 2 after my pre's. The noise gate setting that worked great for the JMP1 choked out the MP1.
Or it could be an issue with the way you split your signal.
Either way someone here will be able to figure it out.
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Live Rig:
Fractal Audio FM3 ver 1.06
Boss GT 100 ver.2.11
Switching- Radial Engineering Big Shot I/O v2 - Radial Engineering Pro D2 Stereo Direct Box
Power - Live Wire Power Conditioning Distribution System
Monitors  - (2) FRFR-112 Headrush Stage monitors
Axes - Charvel So Cal Pro Mod-Jackson DK2MQ Pro-Jackson USA Soloist-Ibanez RG3XXV
ADA gear: MP1- MP2 - MT200
Studio gear- way too much to list.

rnolan

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Re: MP-1 volume drop
« Reply #2 on: Time Format »

Hey mate, how'sitgoin ? (I'm assuming you're a fellow Australia  :wave: ). Hey no worries,we'll help you sort it out. A Soloist said detail your patching (this goes with that at Susan's...) and we'll work through it with you.  I can think of a few possible culprits (input jack (it takes the most wear and tear), output pot, needs a clean) but I need to know more how you plug it together (which will lead no doubt to further questions LoL).

Some basic maintenance though, clean input jack (well all jacks) and pots with some decent contact cleaner (may well fix it), a good thing to do regardless.  At this age it's worth changing out the input jack (well all of them really but that's a bit more ambitious).  Now we can't source them (MP1 input jack) anymore but you can do the input jack mod (changes the back input from line level to inst level) and replaces the front jack.

Cheers R
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Studio Rig: Stuff; Live Rig: More Stuff; Guitars: A few

revhed666

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Re: MP-1 volume drop
« Reply #3 on: Time Format »

Yeh mate Aussie all the way ;)
Signal path
EMG 81/707》
Behringer rack tuner 》
digitech GSP1101 》
GSP 1101 mono fx loop out split with Y cable 》

LEFT: JMP-1 》DBX stereo 15 band EQ 》STEREO Sonic Crapuliser 》GSP 1101 loop return left 》Gsp 1101 line out left 》 Marshall EL34 100/100 Power amp left

RIGHT: MP-1 》DBX EQ 》Sonic Crapuliser 》 GSP1101 loop return right 》 GSP1101 line out right 》 marshall power amp right

Its a bastard intermittent problem that no amount of cable or jack  jiggling can reproduce. Hopefully its a tube. Obviously i thought the Y cable was a potential trouble spot. I bought every Y cable on ebay and worked my way through them. Of course the cheapest had the most solid connection. The sockets were slightly larger and loose fitting on the more expensive cables go figure.
U guys helped out before when a chip controlling the eq was faulty. I also upgraded the eprom at the same time. Will put tubes in now and try the maintenance tips and see what happens. And report back when i have something...or nothing haha
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MarshallJMP

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Re: MP-1 volume drop
« Reply #4 on: Time Format »

Do you have a gain (distortion) or volume loss?
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revhed666

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Re: MP-1 volume drop
« Reply #5 on: Time Format »

Only volume to my ears but there may be a gaim loss masked by the JMP pumping along just fine. IIt happens so infrequently its hard to be exactt. Played for an hour with different tubes. Stripped down to MP-1 and power amp. No issues. Except crappy tone haha. it really needs all the other gear to make this thing work for me. Will keep playing and troubleshooting and see what happens. Thanks forcthe help
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Soloist

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Re: MP-1 volume drop
« Reply #6 on: Time Format »

Try swapping sides... JMP1 to the right, MP1 to the left. See if issue persists. I never had any luck with "y" cables.

When the tubes in my Mesa 50/50 power amp started to go I had a volume drop intermittently but I think it was both sides. How old are your tubes in the Marshall power amp?
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Live Rig:
Fractal Audio FM3 ver 1.06
Boss GT 100 ver.2.11
Switching- Radial Engineering Big Shot I/O v2 - Radial Engineering Pro D2 Stereo Direct Box
Power - Live Wire Power Conditioning Distribution System
Monitors  - (2) FRFR-112 Headrush Stage monitors
Axes - Charvel So Cal Pro Mod-Jackson DK2MQ Pro-Jackson USA Soloist-Ibanez RG3XXV
ADA gear: MP1- MP2 - MT200
Studio gear- way too much to list.

rnolan

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Re: MP-1 volume drop
« Reply #7 on: Time Format »

Hey mate, well interesting way to patch it so you are combining the JMP1 and the MP1 tones and sending one to left and the other to right.  If MP1 -> poweramp L/R works without issue, the seems maybe a drop in GSP1101 send level into the Y cable. Hey MJMP, could a difference in the JMP1 and MP1 input impedance be an issue ?
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MarshallJMP

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Re: MP-1 volume drop
« Reply #8 on: Time Format »

No I don't think so.
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rnolan

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Re: MP-1 volume drop
« Reply #9 on: Time Format »

Ok so Y lead should be fine (albeit there will be a bit of a volume drop splitting the signal)
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Systematic Chaos

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Re: MP-1 volume drop
« Reply #10 on: Time Format »

Could also be the respective channels of either the DBX EQ or the Sonic Crap thingy.....
Remove both DBX and Crapuliser from your signal chain and run only the GSP1101, JMP1, MP1, Poweramp....see if that cures things.
Add first the DBX, play and check, then the Crapuliser....
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revhed666

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Re: MP-1 volume drop
« Reply #11 on: Time Format »

Cheers for the help guys ive been on the road. I did pull the MP-1 from the rack replaced the tubes with Mullards purchased at the same time. No other cjanges or cleaning as yet. Straight to power amp. Same tone. No volume issues over a few hours of jamming over a few days. but now theres a single loud pop every 15 mins or so.  Reassembled rack setup. No volume issues. Pop still occurring. Curiously to balance the preamps i now have the MP-1 master on 2.5. Before it was either 2.0 or 3.0 depending if the volume drop had occurred or not. Maybe it is just tubes. So i should look at an A/B splitter box to replace the Y cable? Good tips guys thanks
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rnolan

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Re: MP-1 volume drop
« Reply #12 on: Time Format »

Mmm, that pop doesn't sound good, may be indicative of the original problem, could be a cap going off ?
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revhed666

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Re: MP-1 volume drop
« Reply #13 on: Time Format »

Stranger and stranger. Full rack setup today. Nothing changed. Loud pop every 15 mins replaced with dull thump every 5 mins. Pulled everything one at a time till it was nothing connected to power amp. Power amp connected to speakers. Still there. Both sides. Ok was gonna get it serviced as the presence knob is dodgy. Soooo at this stage it seems original problem was pre tubes. Saw an A/B box on ebay. Sorry fone wont let me paste the URL. battery only powered the LED for A or B channel indicator. $30. Is this any diferent to a Y cable? If it matters have just moved to an old house. The power box looks literally 100 years old. Does not even have a modern safety cut off switch. Might this cause some anomalies? Just wanna jam jeebus
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revhed666

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Re: MP-1 volume drop
« Reply #14 on: Time Format »

Same thump with old or new speaker cables too. So definitely appears power amp related....maybe ;)
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