Noise when jumping channels

Discussion in 'Marshall Amps' started by Mats Raknerud, Jul 16, 2020.

  1. scozz

    scozz Well-Known Member Gold Supporting Member

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    I think maybe @Martin Adams has a very good suggestion. Do you have a known good 12AX7 @Mats Raknerud?


    Oh BTW,...:welcome: to The Marshall Forum!!
     
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  2. Gene Ballzz

    Gene Ballzz Well-Known Member

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    This is incorrect, mostly. Two separate input channels (HIGH TREBLE #1 through one triode and NORMAL #2 through another separate triode) that DO share the same EQ later in the circuit! These two separate input channels get "mixed" together in parallel just after the volume/LOUDNESS pots, yet before another gain stage/cathode follower and then the tone stack.

    If amp is new, I would NOT get it repaired, but instead replaced! There is a defect (possibly two different defects) and I would not depend on some repair tech outside the factory to correct it in a bullet proof manner! I would be absolutely adamant with the retailer about this and demand a refund if they won't take care of the replacement at no cost to you! A NEW amp should function perfectly, right out of the box!

    It would help to know generally where you are located?

    And :welcome: to the forum!

    Just My $.02,
    Gene
     
    Last edited: Jul 16, 2020
  3. Mats Raknerud

    Mats Raknerud Member

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    Btw. This all seems even worse with humbuckers. With the strat I can move around and find a pretty quiet spot. Not with the Gibson 335. I think the 335 has unwaxed pickups.

    It seems like the strat is almost capable of canceling out the noise if I find the exact right spot. Like it normally would be with a single coil with a fair amount of gain. But yeah, as you can se in the video it's a lot more noise than you would normally get with these settings.

    Also having the output power of the amp dropping I would assume there's something very wrong. The gain stays pretty much the same, so something weird is going on after the preamp.
     
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  4. Mats Raknerud

    Mats Raknerud Member

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    Thanks.

    Yes, I have taken one out of another working amp. And swapped the preamp tubes in the Marshall one by one. No change.
     
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  5. Mats Raknerud

    Mats Raknerud Member

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    Yes, you're absolutely right.

    I've emailed Thomann. I live in Norway. So it will probably get shipped back to them. :)
     
  6. marshallmellowed

    marshallmellowed Well-Known Member

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    Do you have anything in the FX loop?
     
    Last edited: Jul 16, 2020
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  7. Mats Raknerud

    Mats Raknerud Member

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    Brand new.

    Nothing in the loop. Same with the loop bypassed. (bypass switch on the back)
     
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  8. marshallmellowed

    marshallmellowed Well-Known Member

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    OK, so that eliminates any ground loop possibilities. There seems to be an issue with the input jacks (wiring, contacts...). It's a bummer, but your best bet is to return it for another amp.
     
  9. WellBurnTheSky

    WellBurnTheSky Well-Known Member

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    They're great. My old bass player had an issue with an amp he had purchased, they dispatched an UPS delivery man to collect it the next day. And since they didn't have the exact same amp head available, they offered him a replacement for a higher value.
    I've bought lots from them, and always was super happy with them.
     
  10. Im247frogs

    Im247frogs Well-Known Member

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    ]
    Now that is difficult to believe. I have a couple home built amps, and a couple built by people who know what they're doing and ALL of my Tele's are noisy as SHIT thru all of them unless they're in humbucking mode. And they're all shielded, shielded output jack wire etc.
     
  11. tce63

    tce63 Well-Known Member Gold Supporting Member

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    Thomann are great and will sort it out for you, they arrange pickup and send you a new one :applause::applause::applause:

    I live in Sweden by the way.

    TC
     
    Last edited: Jul 16, 2020
  12. South Park

    South Park Well-Known Member

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    Try a balanced cable you may have a ground loop in the cable
     
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  13. marshallmellowed

    marshallmellowed Well-Known Member

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    Not sure what that means, and not possible. The ring of standard patch cables are grounded on both ends. The input jacks are mono, and not designed for balanced cables.
     
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  14. South Park

    South Park Well-Known Member

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    It is the cable that goes between the head and the cab . It not the same as The guitar cable . Some times the cables can pick crap and send to the grids that might be what it is doing
     
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  15. Mitchell Pearrow

    Mitchell Pearrow Well-Known Member VIP Member

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    :welcome: To the forum
    I do hope you get your amp issues worked out.
    They are killer amps.
    Cheers
    Mitch
     
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  16. South Park

    South Park Well-Known Member

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    The way you stop RF is a grid stopper the a 68 k resister on the shielded cable on V1 pin 2 the grid . You might have a oscillation condition . This is a big problem with high gain amps
     
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  17. Chris-in-LA

    Chris-in-LA Well-Known Member

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    Brand new? With all these issues? Take it back. That volume drop issue seems to suggest that your amp is broken.
     
  18. WellBurnTheSky

    WellBurnTheSky Well-Known Member

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    So it's not balanced cable, it's speaker cable (non-shielded, usually bigger gauge). And if this was the source of his problem, noise would be constant, as he didn't plug/unplug it (and thankfully so).

    And wtf are you talking about, SV20H "high gain amp" ? It's about as remote from that as could be...
     
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  19. DC135er

    DC135er Member

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    Sounds to me like a preamp tube is going bad or is microphonic. Jumping channels shouldn't create any him at all.
     
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  20. Mats Raknerud

    Mats Raknerud Member

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    Hi guys.
    just wanted to chime in and say that Thoman sent me a new amp and paid for the shipping of both return of the old amp and for sending me the new. :)

    happy days.

    Now if Covid19 could just go away maybe I could get some gigs again.
     
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