ADA Depot - A Forum To Support Users of ADA Amplification Gear
ADA Preamps => Original MP-1 => Topic started by: anto84 on March 06, 2016, 03:47:46 PM
-
Hi, last week I bought a second hand Mp1 Classic..now I have the chance to buy an original MP1 too at an half of his prce..but there's a problem!
. The seller says the Mp1 "sometimes" has a drop out volume problem. While playin presets volume become low suddenly. He doesn't know what the problem (and the solution) is.. all he knows is that he never changed tubes and the internal battery..
..So my questions:
- It is possible that the dropping volume problem is caused by the very old tubes and/or is maybe the almost dead battery?
- If they're not the problem..what it can be? Is something that can be solved and repaired from an electrician?
Thank you all!!
-
Hi, l'm giving you a quick answer but some expert like MJMP or Rnolan would more abble to solve your problem.
-Yes old tubes can affect your volume, replacing it will definitely helps (if the previous owner never replaced it , don't even think twice, do it !)
-No the battery is used for internal memory. Your mp1 can run without battery but you have to put back your preset after each reboot
-But the tubes could not be the only cause of the issue.
So stay tuned for more info
TG
-
Is it a volume problem or a gain (distortion) problem?
-
That's the first question I make to the seller. He says seems a volume problem... But I wouldn't be surprise if it was a gain problem that he has confused for a volume one..
He added that the problem that take place only "sometimes"
-
Well ask him,this way we can narrow down the problem.
-
Hey anto84, while I'm pretty confident that between yourself and more particularly MJMP you could sort out the problem, do you really want to take this journey ? To answer all the questions we are going to ask you as we attempt to trouble shoot the issue, you really need to have the MP1 at hand, plugged in. So you would need to buy it (unless he gives you a return policy or whatever ?). So what seems a cheap MP1 may cost a bit more, at least $50 for a new set of tubes... These kind of intermittent problems can be hard to sort out, hey it may be an easy fix ? You may be better off looking out for a MP1 in good nick with no issues, preferably with new(ish) tubes (and better MDRT and noise mod).
Eg The difference between a Volume drop and gain drop will help determine where in the circuit the problem is.
Not to say that MJMP may be able to narrow it down fairly quickly and give you an idea of what you'd be buying...
Anyway happy to help, just thought I'd ask.
Cheers R
-
Well a gain problem is usually either the tubes or the input jack.
-
My thoughts as well, and both relatively easy to fix. Also the input jack is the component that takes the most wear.
So anto84, when the volume drop happens, is the sound (distortion) still the same just suddenly softer, or do you loose all the distortion...
-
Seller say sound is the same just with volume drop..
-
Ok, that implies the issue is after the tube board/stage, ask if it makes any difference if chorus on/off ? Is he using the FX loop ? (when the drop happens ?), does the headphone out drop as well (when it occurs) (if no it would imply output jacks..??)
input > tubes > eq > FX loop > chorus > output pot > output jacks is kind of the signal flow.
I seem to vaguely remember an issue with the chorus chip sometimes ??? MJMP will know ?.
New output pot and jacks are always a good idea in a MP1 at this age
-
He can't answer to those questions anymore cause he has sell all his musical gear except the mp1 and a rack multieffect,,,guitar and cabinet are gone...
From what you're saying It seems to understand that the prolmem when the volume drop doesn't affect the gain is more serious than a normal gain loss... And here my doubt concerning the cost for it to be repaired...
-
Well it's probably not just put in new tubes (something you need to do every couple years regardless), it may not be more serious, you could take a chance on it, it may end being a simple fix (eg new output jacks or maybe they just need a good clean ??). Hey if you decide to go for it we're happy to help sort it out. I suspect though your trying to get a take on what may be involved (ie should you buy it, hence my earlier question, do you want to go on this journey ?). And anyway, if it just happens here and there, while you'd want to get that sorted (particularly for live gigging) it doesn't mean you can't use it.
-
Volume drops can also caused by a bad V2 tube,other possible culprits are,the front vol pot,output jacks.
-
Ok, after a phone call with the seller..some news:
He says that, as said earlier, he seems to remember that when the drop volume happens, the gain stays the same and only the volume drop ut. He added that touching a bit the frontal input jack the volume came back to normality...until next drop out
Are those elements enoughfor you to unveil the cause of the problem?
-
does this happen on all 3 voicings?or just on the 2 tube voicings?
-
He can barely remember the software version (1.38 of course) so the previous ones was the max I can pretend from him..
The fact that touching the input jack, the volume came back to normality what could it mean?
-
Well if it's a V1.38 it could be the input jack,most of these start to fail.So it's possible if you change it the problem will be solved.Problem is i can't find them anymore so it's best to replace it with the rear jack mod.
-
Hi thanks for the answer.
So if the input jack is the problem..can't be replaced with a similiar one with the same specs? I'd be happier not modding by myself..I'm a mess with soldering and wires! :facepalm:
-
Hi Anto, sounds good for you : you get a mp1 for cheap and soon it's gonna be fixed
You lucky guy ! :thumb-up:
-
The rear jack mod (http://www.marshalljmpmodshop.net/miscellaneous_parts_and_replacement_tubes.htm) is reasonably easy to do and any tech would have no problem doing it for you
-
I ended buying the Mp1 so in a few days it will arrive at my destination.
I'll be able to provide you way more detailed information regarding the problem of the unit...and I hope we can figure it out toghether the solution! ...I'll be your eyes..you all guide my hands please!! :wave:
-
Ok we'll get it in working order :thumb-up:
-
Hi guys..Mp1 arrived at home 1 hour ago. I opened it to remove some dust. I plugged my guitar with old tubes (to eliminate tube related problem from the possible cause of the volume drop)
I'm playing trough it and I confirm that the problems are not the tube..the volume drop happen only when touching the frontal output knob (so it's not, I suppose a inpunt jack problem). The knob make the some noise of a old guitar tone pot ..it begins to scratch every time i touch it and it it goes to a position where the mp1 is totally muted...then you move a little bit the knob and the volume stays until next "finger touch" of the knob.
So it's not a volume drop...as I thought... it's not lowering gain/volume thing but a totally disappearing volume thing.
Suggestions?
UPDATE: the input jack has some problem too. With the jack in if I hold the jack down from the outside with my hand from the othe volume go away too.... I
-
Well it seems you need a new front vol pot and a new input jack.
-
And where I can find they? The effect send/return knob too is scratchy when moving....
-
Well if you want i have these.
http://www.marshalljmpmodshop.net/miscellaneous_parts_and_replacement_tubes.htm
-
I'll try intensively the unit for a couple of days to see if the problem happens when playing with the guitar in a rehearsal situation.
What I noticed in a 2 hour test is that if I don't touch the knobs there are no problems...
If the scratches/drop volume continues to show only while moving the output and send knobs maybe I can live with that, cause when I leave they in position the unit is perfectly working.
Oh..just another question..Look at the picture of my Mp1..do you see some mods made or does it looks stock? (I'm asking cause the unit comes with a short 13,7 inch cable and I remember that the Mp1 I had 10 years ago was way more noisy than this one...
Thanks!
]http://(http://i304.photobucket.com/albums/nn161/gyzmo1/DSCN2060_zpsyw2rckjf.jpg) (http://s304.photobucket.com/user/gyzmo1/media/DSCN2060_zpsyw2rckjf.jpg.html)
-
Looks stock to me,can't see the tubeboard.Can you take a pic of that one?
-
Of course! Here's the pic. Loaded with a brand new matched pair of jjecc83s
Can I ask you how you use the send/return level knob on the rear of the Mp1? It is better to leave it on the max and and adjust the level from the effect or better set the multieffect (pedal or rack) level at max and adjust the Mp1 level to taste?
I noticed an increment of +- 1 dB of the overall volume leaving the Mp1 loop lepel knob at max with loop in even when the effect is bypassed (think of a delay pedal when you press it to bypass). To have the same volume it seems you should set the Mp1 level knobs to 9.5/10...funny
(http://i304.photobucket.com/albums/nn161/gyzmo1/DSCN2061_zpsj1dta9cr.jpg) (http://s304.photobucket.com/user/gyzmo1/media/DSCN2061_zpsj1dta9cr.jpg.html)
-
The MP1 loop is a tricky beast, some like it some don't. It's a serial loop (inserts into the signal path), and the knob is a dual ganged pot so when you turn up the send it turns down the return and vs versa. Also there is always signal on the send, switching it in or out toggles the return. Try setting it half way and adjusting the FXs' input and output to suit. Adjust it such that there is no increase or decrease in overall level when it's switched in/out (unity gain)
-
Looks stock to me,don't see any mods or parts that are replaced.
One i thing i noticed,you see that vactrol next (left) to the trimpot (on the second pic),it's that black part with 2 wires coming from the top the pcb.These are very close to each other,try to pull them apart a bit.This vactrol controls the OD1 volume.There's a second one (for OD2) near the V2 tube,i also can see that these wires are also close to each other,so do the same thing here.
-
Thanks!! Just did what you said to do...
(http://i304.photobucket.com/albums/nn161/gyzmo1/DSCN2062_zpshsm9u9cs.jpg) (http://s304.photobucket.com/user/gyzmo1/media/DSCN2062_zpshsm9u9cs.jpg.html)
-
Ok,well done!
-
Update: Yesterday I put some contact cleaner oil. Today no pot scrratching ...no jack input problem at all..
NO MORE VOLUME D R O P ! yeahhhh :banana: :banana-dance:
-
Excellent :thumb-up: good to hear :whoohoo!: MP1 heaven. How are you going with the FX loop ? BTW that pot and jacks could also use a clean. As you work out how best to patch it into your rig, apart from the A/B main outs, you can also get an output signal from the loop send (albeit mono and no chorus) and the headphone out (careful with level, you get allot of level on the phones out) which is stereo and also has the tops wound down a bit (similar to a cab simulator but not as sophisticated), but you can use it for direct recording.
-
I made a lot of test with the effects loop (which I tend to use only for delay or reverb of my Boss ME5..) comparing the MP1 and the MP1 Classic loops behaviours
Delay level from me5 at 6 on 7 max available; MP1 level knobs at max: MP1 win over Classic loop.
But as I begin to move the MP1 loop level knobs more than a 15% of his course..magic vanishes and the MP1 Classic loop seems more "professional",,,Difficult to explain..
-
The classic loop is quite different, like the MP2 it has a stereo parallel loop so you can program the return mix level to mix in FX with the dry signal, with the parallel loops (Classic and MP2) it's best to run the effect at full wet and use the return mix level to balance with the dry signal.
The MP1 loop is mono and serial as in the effect is inserted into the dry signal path and you need to control the mix balance (dry/effect) with the effect's mix setting(s) (and tweak the effect input and output levels to balance with the loop send/return level knob). The classic and MP2 loops are much better for lots of reasons. Some of the Classic's "enhanced" features (eg stereo parallel loop, cab simulated outs etc) were precursors to the MP2's feature set. I didn't see Classics in Australia, I went from MP1 straight to MP2 when they were released here.
As I said previously, some like the MP1 loop and get it sorted, some don't like it and patch FX in other ways, the most common is probably MP1 A/B out > FX L/R in, FX L/R out > power amp L/R in. (dubbed the 4 cable method (4CM)).
-
The classic doesn't have a parallel loop like the MP-2,it's also a serial loop since it doesn't have a mix knob.Just a line /instrument level button.
The idea of the one pot loop level in the MP-1 was quite good but it didn't work out so well in the end.Some effect work pretty good some don't.
-
So Mp1 and Mp1 classic have a serial loop either.. So why they have a different behaviour?
-
:whoohoo!:
Good for you anto