NGD: JP2C and a potential problem

Discussion in 'Gear & Equipment' started by efx1138, Aug 16, 2019.

  1. efx1138

    efx1138 SS.org Regular

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    Hi all,

    I just bought a brand new JP2C from a local store here. Importing these things to Sweden takes time and after 5 months it finally got here. I took it home and set it up through my Suhr RL IR and powered it up. That's where my issues began. At some settings it sounds fine but at higher gain settings there's a horrendous squeal coming from the amp itself. It seems mainly dependent on the gain level and the master volume setting on channel 2 and 3. The MV especially I can't put above 4 without it squealing at high gain levels. Am I wrong in thinking these are tubes that might have gone bad in the transport over here? The 5-band eq does not affect the loudness of this squeal as much as the preamp settings to do which led me to believe it might be the preamp tubes.

    The settings I have tried are all from the manual so I'm assuming I should be able to run them but there's no way I can, especially with Shred on. I made a couple of videos illustrating the problems. This is the sound of the actual amp, the monitors are turned down to 0. It's a bit quiet but when running through the monitors it's unusable.

    I'm not a tube expert so I thought I would ask here. Including a pic anyway of the setup. I would really love to get this working so any input on this great appreciated :)

    [​IMG]



     
  2. Jacksonluvr636

    Jacksonluvr636 SS.org Regular

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    Well tbh I cannot even hear the squeal in the video BUT. It is a common thing on this amp, the manual even mentions it. back off the gain a bit.

    With that said I did have a faulty preamp tube when I bought mine brand new so that wont hurt to swap some out.
     
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  3. Adieu

    Adieu SS.org Regular

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    Uhm...have you owned tube amps before?

    The squeal appears less pronounced than the sound of you operating the knobs.

    And you're not even touching your guitar strings are you? High gain tube amps get noisy cranked.
     
  4. StevenC

    StevenC SS.org Regular

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    That's strange. My Twosie doesn't make that noise and I run a lot of gain and loud enough. It's not a quiet amp, way noisier than my Diezels, but it's no louder than my JVM and others I've tried with that amount of gain.

    If it's a sound coming from the head itself and not a speaker, maybe check there's nothing obstructing the fan.

    HNAD, hope you solve the issue. I'm so jealous of your Distressor!
     
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  5. Adieu

    Adieu SS.org Regular

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    PS wait, monitors? Set to 0?

    And you're running that reactive load piece of junk and god knows what else?

    OK...TROUBLESHOOTING 101:

    Step 1: plug amp directly into a cabinet of appropriate wattage
    Step 2: plug guitar directly into front input of amp
    Step 3: place BATTERY POWERED pedal through effects loop
    Step 4: place adapter powered effects plugged into a surge protector running off a wall outlet from a different room
    Step 5: remove surge protector
    Step 6: use same outlet / shared power strip
    Step 7: if and only if you get this far with no noise do you add stuff like reactive loads, monitors, etc

    Obviously test for noise at each step. Cycle through effect steps for each individual effect and combinations thereof. Oh and use new cables or cables tested ok with other amps
     
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  6. efx1138

    efx1138 SS.org Regular

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    Thanks for the input guys, I'm not running anything else with the amp, just guitar into front and then through the RL. Amp powered from the wall and not a powerstrip. I don't have access to a cab right here. I made another video where the volume through the monitors are set at listenable level, this sound you should be able to hear. It's definitely coming from the amp head itself. Fan seems ok, doesn't seem like anything is overheating. In the vid here I'm not even running with shred on, just channel two with a moderate amount of gain.

     
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  7. Adieu

    Adieu SS.org Regular

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    That IS weird. And you're saying this noise is coming from the amp not the speakers, but depends on the volume the speakers are set to??????

    Are your monitors powered? Use separate outlets. And make sure those outlets use real grounds, some cheap outlets and power strips don't actually have grounds at all

    Oh also, are you running same voltage as the amp is designed for, or using a voltage converter for an imported amp?

    Might be some kind of ground loop... reminds me of running a laptop hooked into a TV and a stereo for watching movies in the early 2000s, and every time I received an SMS message on a phone located anywhere near this rig, the plasma tv would get waves across the screen and the speakers would warble. It was literally somehow being picked up by the pre-cellphone area stereo system, and somehow went through the power strip or through the laptop and came out as noise on the modern plasma tv as well.

    Then I used separate power strips or something and it stopped
     
    Last edited: Aug 16, 2019
  8. Jacksonluvr636

    Jacksonluvr636 SS.org Regular

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    I hear it now.

    It is not weird for that amp. It happens with every JP2C, again read the manual.

    I will say your squeal definitely happens a little earlier than mine did which really sucks because unless I used an outboard boost I liked the gain way up on that amp.

    Seriously read the manual though man. It is a must the controls on that amp are a bit unique and if I am not mistaken the treble also controls the gain, or something weird like that.

    Try to turn the treble to 10:00 instead of 1:00 and see the difference.
     
  9. Jacksonluvr636

    Jacksonluvr636 SS.org Regular

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    Also edit....Sorry I see you did actually read the manual. At least about the settings but the manual does discuss the squeal.
     
  10. mnemonic

    mnemonic Custom User Title

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    Bare in mind those master volume settings would be very loud though a cab.

    It could be the reactive load, I think they can sometimes cause weird ground loops. The Suhr is one of the best ones though.

    Have you tried it with the reactive load, but with nothing from the line out? (either from the load or the amps slave out).

    It could be a tube problem, I have heard of tubes making noises from vibrations but not experienced it myself. If you have spare tubes, try swapping them in.

    The only other time I’ve had noise coming from an amp head was from the output transformer, with a heavily loaded down amp. Huge amount of current flowing though the output transformer so it ‘sings’, normally it would be so loud from the cab you wouldn’t hear it. But i don’t think that’s the issue here, unless the power amp is just oscillating a ton when the master goes up high.

    does Presence knob setting affect it? Turning presence down should increase negative feedback (for the high frequencies) and reduce oscillation. That is, if the presence knob works like a normal amp, I think it may not for the Mesa Mark series amps.

    Next step should be to try a cab, thus eliminating the load box
     
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  11. MASS DEFECT

    MASS DEFECT SS.ORG Infiltrator

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    ^What he said. Try a cab and see if it squeals like that. My JP2C will squeal at those volumes if me and my guitar is close to the amp. Other than that, I run my presence pretty high, gain at about 3pm, no shred, the amp is relatively quiet provided there is some distance between me and the amp. 10 o'clock on a JP2C is already gig volume.
     
  12. efx1138

    efx1138 SS.org Regular

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    Wow, lots of responses. Thank you guys, I appreciate the input. As far as power goes, the monitors are on a separate outlet from the rack unit which runs the Suhr and the amp is on its own outlet as well so they are all separate.
    I did just try something that yielded an interesting result. If I had the Reactive Load hooked up as normal but took out the cables going from the unit to the audio interface the sound stopped completely. I plug those cables in and it starts again. I get that a crappy speaker cable might interfer somehow but I wonder why those cables would affect the amp, any ideas?

    *update* this is interesting. it seems that the noise is introduced when the cables from the reactive load is hooked up to the audio interface, even if it's turned off..
     
    Last edited: Aug 16, 2019
  13. HeHasTheJazzHands

    HeHasTheJazzHands greg rulz ok

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    I remember my Mark III and Mark IV would squeal like a mooootherfucker. It's the design of the amp, I believe. Just very, very noisy beasts.
     
  14. Shask

    Shask SS.org Regular

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    Weird ground loops man, lol. They happen everywhere.

    I have a JCA tube head, and I get massive hum if I even plug a power supply into some pedals that are turned off, and plugged into a different Mesa head that is turned off. Makes no sense, as everything is not even turned on, but it still causes massive hum for whatever reason.....
     
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  15. MASS DEFECT

    MASS DEFECT SS.ORG Infiltrator

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    That's why sometimes I just let the Tube Amps and the pedalboard gather dust and fire up the AX8 and the power amp. No freakin cables and ground loops to contend with. Quiet, no hum, no buzz.
     
  16. efx1138

    efx1138 SS.org Regular

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    Yeah, that seems to be it. If I unplug everything except the reactive load and the amp the squeal goes away. Good to know it isn't a faulty amp at least :) Thank you all for all the responses!
     
  17. rexbinary

    rexbinary MOD King

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    I know if I have my Two-Notes Captor too close to my amp it will squeal just like that. Especially at higher volumes. It sounds just like what I hear in your video. I keep my Captor on the floor now.

    EDIT: I know you have a Suhr Reactive load, but this advice from Two-Notes would probably still apply.

    http://support.two-notes.com/knowledgebase.php?article=327
     
    Last edited: Aug 16, 2019
  18. efx1138

    efx1138 SS.org Regular

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    Yeah, I thought of that as well and I tried to keep them separate to no avail. But it seems to boil down to this. I can have the Reactive Load and the amp connected in my room and it will be fine. The second I connect anything to any other of 3 available sockets in the room like my computer or my rack units the sound comes back.

    So it seems like a ground loop issue then but I have no idea how to even begin to fix that.
     
  19. Shask

    Shask SS.org Regular

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    Probably a pro quality power conditioner to get clean power. Something like this.

    https://www.sweetwater.com/store/detail/P1800AR--furman-p-1800-ar
     
  20. Flick

    Flick SS.org Regular

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    I have the same amp. Had the same issues as I dial it in for death metal. A Fortin Zuul in the loop while running the key input on the zuul is the best result I’ve found.
     

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