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Author Topic: MP-2 with loud "humming" noise.  (Read 12536 times)

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WAR_in_D

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MP-2 with loud "humming" noise.
« on: Time Format »

Recently picked up an MP-2 and only got around today to finally getting it up and running..  Well, it's pretty darn noisy and in my search online for info on how to remedy this situation I ran across this site.  During my search, I found a couple of videos on youtube showing the resistor change for the noise mod and the noise gate chatter but I noticed upon checking out the "mods" section of this site that there is a lot more involved in doing the "noise mod" correctly.  The youtube video I found listed the part number for the R913 resistor, but upon searching Mouser for that particular part number it says the part is no longer stocked and Voodoo mods listed the ADA MP series preamps under the gear that they no longer modify due to a lack of available parts with which to rebuild them with..

I guess my question is, is there a current detail parts lists with readily available part numbers and what not to do the noise mod?

Any help you provide would be greatly appreciated.  I found MarshallJMP's website through the forum earlier today and shot him an email.. It seems to me that he's the resident guru when it comes to the MP's..  So, I'm hoping that I'll be able to get the information needed to get this thing up and running clean again.

Thanks in advance..
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rnolan

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Re: MP-2 with loud "humming" noise.
« Reply #1 on: Time Format »

Hey WAR_in_D, I bought 2 MP2 noise mod kits from MJMP recently, he had to wait for all the parts to come and then sent me everything (parts wise needed). Then lots of soldering to do. As you say, there's quite a bit to it.
If your MP2 isn't the last EPROM upgrade (v1.41), that's worth doing as well, easy mod to do, just swap out the EPROM, MJMP has them (http://www.marshalljmpmodshop.net/miscellaneous_parts_and_replacement_tubes.htm). The version will display as it turns on (or take off the top and check the sticker on top of it). And also the tubes are probably due for a change, check the tube (http://adadepot.com/index.php?board=38.0) discussion for ideas.
MJMP is indeed the resident guru  :bow: but there's a few others here with lots of under the hood knowledge.  :thumb-up:
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WAR_in_D

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Re: MP-2 with loud "humming" noise.
« Reply #2 on: Time Format »

Thanks for the reply..  Yes, the tubes will definitely get replaced and the newer EPROM is already on the way as it's currently running the older version.  I'd kind of gotten away from playing for several years and recently gotten back into it.  I've tried some of the newer amps out there (and some of the older), but nothing really caught my fancy like my old rack system did.  So, I've been on the hunt to rebuild it.  I kept most of my processing gear (Quadraverb II, BBE 462, etc..) but needed a pre and power amp.  Luckily, I found a nearly mint and unmodded MP2 that had all the Midi controllers with it (MXC, Quad Switch, and ADA Expression Pedal).  The only problem is this darn hum.

I'm thinking Tung Sol's for the replacements.  For a high gain, low noise tube they seem be one of the better choices.  In the past on other tube driven amps/preamps, I've usually run an assortment of vintage tubes and newer stuff.  I believe in my other MP2 I had (which was years ago), I had an old vintage Ei and something else.. Probably a newer Electro Harmonix as I always seemed to have some of those hanging around but I remember that combo being pretty sweet tone-wise in there.

Anyway, enough ramblin about that.. LOL  I know in the other thread you asked me to describe more about the hum.  After doing a bunch of reading on this site to get an idea what to test.. Here's what I'm hearing.  On the clean channels, it's pristine.  No unwanted noise, or weird stuff going on.  On the dirty channels, as long as the tube drive is lower than about 6 it's not too bad but the more you crank up the tube drive it starts humming pretty badly.  I haven't been able to make it "motorboat" but it's basically unplayable otherwise. 

I'm basically clueless when it comes to diagnosis of this unit, so any help would be greatly appreciated.

 
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rnolan

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Re: MP-2 with loud "humming" noise.
« Reply #3 on: Time Format »

With MP2 I've found on the high gain sounds/voices you need to use the NR (gate, I run mine on fade not cut and dial in the threshold) (the MP2 has lots of gain... >:D ) but from warm vintage (5) and down it's fine not required.
As you will no doubt read elsewhere here, I'm a big fan of the Mullard long plate re-issues tubes for MP2, brings it alive (I find  >:D ).
My 2nd MP2 came with a pair of EH tubes, best thing I did to it was put in some Mullard long plates... IMHO.

How do you have it patched ? gain structure can have a big influence on hum, not that the noise mod won't help BTW.
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WAR_in_D

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Re: MP-2 with loud "humming" noise.
« Reply #4 on: Time Format »

Appreciate the input.. but as bad as this hum is, I have to think that something is amiss.  Especially since the first one I had was never this loud, not even close.  Even with the factory presets where the noise gate is running, I can still hear a really pronounced hum going on in the background.  Good info on the fade vs. cut though with regard to noise gate.  I never realized there was an option for that and the fade is what I'm looking for.  When I owned the first MP2, I despised the noise gate for that very reason...  it wouldn't just fade out, but cut off abruptly and I hated that.

I did see your posts about the Mullards, and now you've got me considering them as well.  As far as patched, I'm not sure what you mean?  I had sold my previous rack case, so I have another one on order so I didn't have my Furman Power Conditioner in the mix yet.  As I tested it, it was straight up MP2 into the power amp with nothing in between and just running the stock presets.

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rnolan

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Re: MP-2 with loud "humming" noise.
« Reply #5 on: Time Format »

OK so patch is straight Guit to MP2 to power amp to cabs ? If that's humming and leads are all ok (good qual etc) and gain set right (ie power amp up full (ish)) MP2 out on 1/2 to 3/4 ish guitar up full (BTW what guit and what PUs ?), sounds like noise mod territory ? I've got 2 MP2's and while I've bought the noise mod kit (for both) neither of them really need it at the moment, so I'm thinking when to install (I need to find a good solderer LOL). New tubes may help BTW.
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WAR_in_D

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Re: MP-2 with loud "humming" noise.
« Reply #6 on: Time Format »

Yes, straight up MP2 to power amp to 4x12 cab... Guitar is an 87 Les Paul Custom with Tim Shaws. 

I think the problem may be solved though!  I tried a different power outlet, and put the power conditioner in the mix and it sounds much, much cleaner today.  Yesterday, when I was messing with it I could hear the hum even when the guitar wasn't plugged into the MP2.  The original MP2 I had always had a bit of background hum in it, which honestly I attributed to the guitar I was using at the time not being up to snuff but it may have just been normal for it.

I don't hear any hum now in the background of even the highest gain presets while playing thru them, although without the noise gate engaged it's pretty noisy when the volume is opened up wide on the guitar and not playing.  I don't think that is odd though, for something with that much gain.  I'm still trying to figure out you get the "fade" you're talking about though.  I saw the "gate" or "fader" option in the noise gate, but how do I go about setting it?

Man, I really appreciate all your help and I'm glad to have it working at last.  I really wasn't looking forward to replacing all those caps and resistor.. Although, I'd still like to have the kit around as I'd like to put that in there one day. 



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rnolan

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Re: MP-2 with loud "humming" noise.
« Reply #7 on: Time Format »

MP2s' aren't fond of bad power (I often run off a generator, in the end I bough an UPS to decouple me and smooth the power supply).
Sounds like a normal MP2 that just needs new tubes and v1.41 EPROM from what you are saying, not that the noise mod won't help (it wasn't invented/conceived for no reason, and I've got 2 kits ready to go...).
So the NR settings are Status:in/out, Mode: Gate/Fader and right arrow to Threshold (when it will kick in), to set select prog edit, NR, (displays status and mode (use right/left buttons to move between each option (Status, Mode, Threshold)), what the arrow points at is what will change with Yes:up/No:down), then store the patch.

so on my old rhythm patch (see MP2 patches) which is now my over the top lead, Status = in, Mode: = Fader, Threshold = 80 and the voice is Ultimate Hi Gain, Drive 70, OD 100, Master 77... The high gain patches in MP2 need the NR mostly for when your not playing LOL. Most of my playing these days is on the Voice 5 Warm Vintage (my current rhythm/lead patch) which doesn't need the NR and is still more distorted than I sometimes want.
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WAR_in_D

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Re: MP-2 with loud "humming" noise.
« Reply #8 on: Time Format »

Cool, I'll check the settings next time I'm in there..  I really appreciate your help.  Well, two out of the three things you recommend are in process of being taken care of.  I've got the 1.41 Eprom coming and I just ordered a matched pair of the re-issue Mullards..  Was originally going to go with the Tung Sol, but you swayed me on those. LOL

Will look into the noise mod when I can get some information on what I need.  I see you keep saying you bought two of the noise mods, but haven't put them in yet.  Is there somewhere I can buy the kit ready to go, just need to have installed?



 
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MarshallJMP

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Re: MP-2 with loud "humming" noise.
« Reply #9 on: Time Format »

Just send you an email about the noise mod.
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rnolan

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Re: MP-2 with loud "humming" noise.
« Reply #10 on: Time Format »

Will look into the noise mod when I can get some information on what I need.  I see you keep saying you bought two of the noise mods, but haven't put them in yet.  Is there somewhere I can buy the kit ready to go, just need to have installed? 
, MJMP will be in touch, he put the 2 kits (well collection of all required parts) together for me and sent them to me. So I have all the parts required, just need to find someone much younger who's good with a soldering iron. I'll do my spare MP2 first I think.
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WAR_in_D

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Re: MP-2 with loud "humming" noise.
« Reply #11 on: Time Format »

Just send you an email about the noise mod.

Thank you sir.. I've sent a reply back with a few questions.. I'll look forward to your advice.
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MarshallJMP

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Re: MP-2 with loud "humming" noise.
« Reply #12 on: Time Format »

Just replied,let me know if you have more questions.
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WAR_in_D

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Re: MP-2 with loud "humming" noise.
« Reply #13 on: Time Format »

Just replied,let me know if you have more questions.

Will do, appreciate the info.  With the holidays I've been kept pretty busy with all the family gatherings and now just getting past New Years.  I'll be in touch after this weekend for sure to get this moving forward.  Thanks again.
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MarshallJMP

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Re: MP-2 with loud "humming" noise.
« Reply #14 on: Time Format »

No problem. :thumb-up:
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