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ADA Preamps => MP-2 => Topic started by: Kim on July 27, 2016, 06:08:54 PM

Title: MP2 weird noise...
Post by: Kim on July 27, 2016, 06:08:54 PM
Just the other night at rehearsal I noticed that my MP2 is suddenly acting strange.
It would kind of "burp" or ring out at the end of a palm mute on my normal heavy patch.  If I had to actually try to describe it in words, I'd say it sounds like you're hearing an electrical zap.  lol    So I thought the Noise Gate needed to be adjusted, but that didn't really help get rid of that extra "zap" sound afterwards.  Some more tinkering showed me that if I lowered the Voicing down one step, it went away and everything was fine again.  Same results if I kept the same Voicing I normally use on my heavy patch but reduced the Drive and/or OD somewhat.

Anyone else thinking what I'm thinking now that it might just be the tubes?

 I haven't changed them since I've had the MP2 (it's been what, 6-7 years now?) and can't even remember what kind are in there.  I do have a spare pair hanging about that I can try, so I'll find out about that tomorrow night. 
Title: Re: MP2 weird noise...
Post by: vansinn on July 28, 2016, 01:23:38 AM
Did it also loose a touch of [distortion] gain?
If so, it sounds a Bit like how one of my MP-2's suddenly lost a touch of gain several years ago - only, I didn't experience your stated zap behavior.
Back then, MJMP suggested a specific component likely being the cause, but I don't remember which one.. think it was a transistor..
Title: Re: MP2 weird noise...
Post by: MarshallJMP on July 28, 2016, 02:09:47 AM
I think I talked about the resistor R913.Hey Kim check your high voltage, see if it's higher then 190V.There's a testpoint called HV were you can measure it.
Title: Re: MP2 weird noise...
Post by: rnolan on July 28, 2016, 04:50:25 AM
Hey Kim, if you check out the MP2 noise mod instructions it's got a good picture to show the test point MJMP is talking about.  The resistor in question (R913) is under the left tube (looking from the front).  At the test point I get: MP1#1 = 188.9v (still has original R913), MP2#2 = was 187.8v (has new R913 now and noise mod and measures 191v), MP2#3 = 189.9 (has new R913, prior to resistor change it was 194.8 and noisy) but not what your describing.

Obviously some new tubes can't hurt  :thumb-up: , and 6 or 7 years is a while...
Title: Re: MP2 weird noise...
Post by: Kim on July 28, 2016, 07:08:22 AM
Thanks guys. It didn't seem to lose any gain or volume.  I was told that my MP2 already had the Noise Mod done to it before I received it, so I assumed that wasn't going to be the problem.  But....I will check the voltage anyway when I get that chance. May as well since it gets opened up for tubes anyway.   :thumb-up:
Title: Re: MP2 weird noise...
Post by: rnolan on July 29, 2016, 09:16:24 AM
Hey Kim. one of the MP2s I bought had had the noise mod done but not R913  :dunno: , so just the caps it seems ? So I changed out the resistor.  Anyway, as you say while its open for tubes ...  When you pull the old tubes out you can check if R913 has been replaced.
Title: Re: MP2 weird noise...
Post by: vansinn on July 30, 2016, 01:54:29 AM
I'm pretty certain R913 was replaced on the MP-2 Kim got back then ;)
Also, I doubt this resistor, though sitting in the HT/plate supply, would change abrupt enough to cause the sudden change Kim describes.
But check it anyways.. :sleezy-eyes:


"90% of network problems are routing problems.
9% of the remaining 10% are routing problems in the other direction.
The remaining 1% might be something else, but check the routing anyway."

  -- unknown
Title: Re: MP2 weird noise...
Post by: Kim on July 30, 2016, 03:31:33 PM
Ok, I finally have a chance to play with this.  lol

The Update:
I haven't unracked or opened anything just yet.  I simply made the normal connection from the MP-2 Recording Outs (fx processor in Loop) to my puter and played my main patch through this Home Recording setup.  Nothing sounds out of the ordinary, so now I will try another angle.  I don't have Frick and Frack here at home with me, so I'll now connect to the Quadtube and try it again with more volume than what my nearfield monitors have.
Title: Re: MP2 weird noise...
Post by: Kim on July 30, 2016, 04:23:14 PM
Update #2:

I can't seem to replicate the weird shit I experienced at rehearsal.   :dunno:

What's different from there? 

So, I guess all I can really do now is to unrack the MP-2, open it up to do the usual microphonic tap-tube test, and check that HV voltage.  Be right back...


Title: Re: MP2 weird noise...
Post by: Harley Hexxe on July 30, 2016, 04:46:08 PM
Kim, were you still using the Recording outputs in your live rig?
Title: Re: MP2 weird noise...
Post by: Kim on July 30, 2016, 05:30:46 PM
Kim, were you still using the Recording outputs in your live rig?

No.  I simply used them here at home to get the speaker sim and connect to and use my puter, software, and nearfield monitors.  Test #2 required the Stage Outs to be used. These went into the Quadtube power section and using those speakers at a considerably higher volume. 

Update#3:
Noise Mod is confirmed, and R913 has been replaced.
Noise Gate Chatter-Shutter-Upper R611 has also been replaced.
I have 195.2 Vdc at HV test point.   :whoohoo!:

And the tubes:
Tube Town 12ax7 Classic in V1
JJ ECC83S in V2
Both pass the "microphonic pencil tap test" easily.

I'm satisfied here.  Next rehearsal I'll bring the other guitar and either verify or eliminate that part of the equation.
Title: Re: MP2 weird noise...
Post by: MarshallJMP on July 31, 2016, 02:13:41 AM
195V is a bit high,could be that the R913 is going up in value.
Title: Re: MP2 weird noise...
Post by: Harley Hexxe on July 31, 2016, 06:29:35 AM
Kim, there could be a short developing in a cable somewhere ::)
Title: Re: MP2 weird noise...
Post by: Kim on July 31, 2016, 08:14:48 AM
195V is a bit high,could be that the R913 is going up in value.
Is that a bad thing?  I was under the impression that above 190 was good....

Kim, there could be a short developing in a cable somewhere ::)
Hmm...I will add that to the list of things to verify.
Title: Re: MP2 weird noise...
Post by: MarshallJMP on July 31, 2016, 08:32:34 AM
Should be around 190V,usually if the voltage goes up so does the resistance of R913.
Title: Re: MP2 weird noise...
Post by: rnolan on August 01, 2016, 05:48:27 AM
Hey Kim, see my earlier post re my MP2 values, e.g. MP2 #3 had noise mod but not R913 and measured 194.8 and was noisy.  I replaced R913 and it measured 189.9 and noise reduced.  Seems you want to be as close to 190 as you can but not more and slightly less is better ?
Title: Re: MP2 weird noise...
Post by: vansinn on August 01, 2016, 11:46:32 AM
@MJMP: Do you think a thin film [R913] resistor would created less noise?
Those do produce less spot noise, but whether this will matter in a HT plate regulator circuitry is :dunno: to me..
Title: Re: MP2 weird noise...
Post by: Kim on August 01, 2016, 07:26:06 PM
Ok, I should just go ahead and replace that R913 then, correct? 
Title: Re: MP2 weird noise...
Post by: MarshallJMP on August 01, 2016, 11:30:57 PM
As for noise don't think it will matter a lot.

@Kim,well maybe best you replace it.
Title: Re: MP2 weird noise...
Post by: Kim on August 02, 2016, 08:36:39 PM
Now we're getting somewhere. 

Tonight I did some more troubleshooting at rehearsal.  It's not the guitar, or cables.  Not even the preamp or fx processor for that matter.
The one thing in my rack that I couldn't check at home....the MT200.   :facepalm:   So I found that if I lowered the Presence on the MT200 to 0, the strange noise following a palm mute went away.  And raising that Presence all the way up resulted in that strange noise becoming a real squeal.   Must be bad tube(s) in the MT200, so I'll swap them out next rehearsal. 
Title: Re: MP2 weird noise...
Post by: Kim on August 04, 2016, 08:22:50 PM
Update:   different tubes swapped in the MT200 changed nothing.  More troubleshooting......So I checked my pedals (that I didn't bring home with me last time)  ::)  and there it was. Taking one pedal out of the equation cleared it up.  I'll deal with that over this weekend.

Really glad it's not the ADA stuff, but I will still change out that resistor that went a bit out of spec anyway.   Thanks for the help!  :wave: 
Title: Re: MP2 weird noise...
Post by: rnolan on August 06, 2016, 10:45:19 PM
Hey Kim, cool, glad you found the issue, which pedal was it ?
Title: Re: MP2 weird noise...
Post by: Kim on August 08, 2016, 07:19:31 PM
Hey Kim, cool, glad you found the issue, which pedal was it ?

Well, when I took the Mel9 out of the chain at rehearsal the funny business stopped.  But....here I am trying to replicate the problem at home again and coming up empty.  This is starting to really get on my tits here.   I brought all the pedals home and ran into both the QuadTube and the Crate G60XL with no problems.  FFS I can't keep dragging ALL my gear home and back to rehearsal, rinse and repeat twice a week.

Maybe some kind of electrical loop?  I have the Crate, Mel9 adaptor, and the Quadtube all plugged into the same power strip here at home.
At rehearsal the Mel9 adaptor is plugged into a power strip that is not shared with my rack gear.
Stan video'd the problem; if he'd send that to me or upload it somewhere I could show you guys what's going on.   
Title: Re: MP2 weird noise...
Post by: Kim on August 08, 2016, 08:25:23 PM
Here's the vid.
https://www.dropbox.com/s/b5xwhznxqnnbziv/VIDEO0082.mp4?dl=0 (https://www.dropbox.com/s/b5xwhznxqnnbziv/VIDEO0082.mp4?dl=0)

You can hear that noise just before the Reverb tails. 
Title: Re: MP2 weird noise...
Post by: MarshallJMP on August 09, 2016, 12:13:11 PM
I wanted to open it and I had to ask permission to look at it?? Is this normal?
Title: Re: MP2 weird noise...
Post by: Kim on August 09, 2016, 08:36:12 PM
I wanted to open it and I had to ask permission to look at it?? Is this normal?

Sorry I posted wrong link.  Try it now.    :)
Title: Re: MP2 weird noise...
Post by: MarshallJMP on August 10, 2016, 08:34:25 AM
Ok got permission so ...  :lol:
Title: Re: MP2 weird noise...
Post by: Kim on August 11, 2016, 04:58:19 PM
What do you make of that?  Could be just that resistor out of spec?  I'm ordering some new ones this weekend...
Title: Re: MP2 weird noise...
Post by: MarshallJMP on August 12, 2016, 01:53:17 AM
It's hard to hear ,I hear something but it's very short.So go ahead and replace the resistor and see what happends. It will go in value anyway so at some point you will have to change it.
Title: Re: MP2 weird noise...
Post by: Kim on August 17, 2016, 03:49:38 PM
New resistors arrived today.   :whoohoo!:

Funny though...the 240k ohm 1/2 watt ones are the same physical size as the 3Mohm 1/4 watt ones. The package says they are 1/2 watt though.

I'll bring my rack home tomorrow night so sometime this weekend I'll get on that.
Title: Re: MP2 weird noise...
Post by: MarshallJMP on August 17, 2016, 04:14:22 PM
Then you didn't get a metal film? Maybe a carbon?
Title: Re: MP2 weird noise...
Post by: Kim on August 17, 2016, 07:45:41 PM
Both are Yageo Metal Film. 

Mouser Part #'s:
603-MFR50SFTE52-240K
603-MFR-25FTE52-3M

^ Exactly as printed on Packing Slip and baggie stickers.    :dunno:
Title: Re: MP2 weird noise...
Post by: MarshallJMP on August 18, 2016, 02:35:52 AM
Okay just checked the data sheet and they come in 2 sizes ,the regular ones and the miniature types. You have the miniature so these are smaller and the same size as carbons.
Title: Re: MP2 weird noise...
Post by: Kim on September 14, 2016, 05:48:16 PM
Finally got around to changing those resistors.  ::)
194.2 vdc at the test point.
Will check the actual operation at rehearsal tomorrow evening....
Title: Re: MP2 weird noise...
Post by: Kim on September 22, 2016, 08:28:00 PM
Update:

Didn't get to do that rehearsal last week, but tonight everything sounded fine.  So while I'm  :dunno:  I'm also  :whoohoo!:

 :thumb-up:
Title: Re: MP2 weird noise...
Post by: Harley Hexxe on September 23, 2016, 05:38:01 AM
Update:

Didn't get to do that rehearsal last week, but tonight everything sounded fine.  So while I'm  :dunno:  I'm also  :whoohoo!:

 :thumb-up:

     When something like that happens to me, it always shows up at the most inopportune moment :facepalm:
Title: Re: MP2 weird noise...
Post by: Kim on September 23, 2016, 04:02:29 PM
When something like that happens to me, it always shows up at the most inopportune moment :facepalm:

Yep I can believe it.   But after all that tail-chasing I was doing before, it sure felt like a "Win" for me.  Even though changing the Noise resistor didn't seem to affect anything as evidenced by the Test Point voltage, I feel like maybe it was the other Gate resistor that must've been the culprit.   
Title: Re: MP2 weird noise...
Post by: rnolan on September 23, 2016, 09:38:19 PM
Hey Kim, glad it's working for you again  :thumb-up: .  So it seems the new R913 lowered it 1 volt ?  (previous 195.2v now 194.2v).  The R611 "should" just affect noise gate chatter ?
Title: Re: MP2 weird noise...
Post by: Kim on September 24, 2016, 10:36:59 PM
I think it actually was a "chatter" thing that I was hearing. That resistor had been previously replaced, but perhaps that was the one that went bad...
Title: Re: MP2 weird noise...
Post by: rnolan on September 24, 2016, 11:00:29 PM
Cool, good to keep in mind for future trouble shooting  :thumb-up:
Title: Re: MP2 weird noise...
Post by: Kim on November 28, 2016, 06:41:56 AM
HUGE update here.

The resistors I had changed really had nothing to do with my "problem".    :crazy:  I'll explain...

I originally had my MP-2 rack set up as I normally would always have my previous MP-1 racks set up. 
Everything in Series:  MP-1 > FX unit > poweramp.  The poweramp Level stays about 75-100% and I'd control the overall level with the FX unit's Output Level.  Once the preamp patches, fx patches, and everything's all dialed in this worked great.  So I automatically wired up my MP-2 rack the same way when I got it with no problems.  Later on, I changed the routing to put the FX unit in the Loop (something I would never, ever do with the MP-1) because I figured this way I now had options.  I could now take advantage of the MP-2's pretty darn nice Recording Outs if I ever needed or wanted to, and the FX would appear in those Outs.  If I would happen to use the Recording Outs in the old version "Series" routing, no FX would be present in those Outs, just preamp...which might be fine if I were to do some kind of W/D/W setup but I'm not interested in doing any of that.

So that "problem".   I was still using the FX unit's Output Level to control overall level, and when I needed to turn it up a bit, I was overdriving the Loop and causing all kinds of bad artifacts to pop up and generally just blowing everything past the Gate.  :facepalm:  It wasn't always apparent with the Clip LEDs, but that's what was happening because turning the FX Output Level back down cleared it all up.  I could've kicked myself.  So I went through and re-optimized all the levels across my presets and patches and now my overall level is controlled by the MP-2 Output Level, as I always should've done in the first place. 
Case Closed, and everything is back to fine. 

 ;) And by "fine" I mean raining doom, despair, fire and destruction down among the forlorn, the downtrodden, the tired and forgotten.  :headbanger:

Title: Re: MP2 weird noise...
Post by: Harley Hexxe on November 28, 2016, 07:21:07 AM
Never say "Never" O dispairate Prophet Of Doom ;D
Title: Re: MP2 weird noise...
Post by: MarshallJMP on November 28, 2016, 08:25:52 AM
Thanks for sharing this, it isn't always a technical problem.
Title: Re: MP2 weird noise...
Post by: rnolan on November 28, 2016, 06:22:35 PM
 :whoohoo!: go Kim. glad you got it sussed  :thumb-up: . I don't know if you do this ? but assigning a CC expression pedal (if you have one) to the MP2 stereo master vol (done in system edit menus) works a treat for your overall vol control (also controls the cab sim outs).