SC20H FX Loop Noise Concern

Discussion in 'Marshall Amps' started by S-Page666, Nov 22, 2020.

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  1. S-Page666

    S-Page666 New Member

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    Hi all,

    I purchased a brand new SC20H recently, and ultimately, the amp rules. The tone is everything I've ever looked for. Classic 80's Zakk Wylde tone when boosted with an SD-1. I love it.

    HOWEVER, there seems to be some FX loop issues, and five minutes of research was enough to verify that I'm sadly not alone on this matter. It appears the SC20H is notorious for FX loop flaws. Volume drop and true bypass-pedal popping are seemingly common issues. I'm having another issue which I haven't come across anywhere as of yet. My FX loop is noisy. Very noisy. When the loop is disengaged, the amp works perfectly. Once the loop is on however, a loud hum kicks in (regardless of whether any pedal is on or not). I mostly only use a BOSS DD-3 in the loop. And I've tried moving the pedal several feet from the amp to no avail.

    I'm just wondering whether this is commonplace for these heads and I just suck it up for the sake of the awesome tone. Although having a noisy loop is a total pain in the ass as delay in the loop is critical for my playing style. I emailed Marshall and they described it as abnormal. They suggest I send it back to the place of purchase, which is 1800km's, so I'm reluctant, in the case that they just confirm its not a faulty device just a faulty design and I'm without the amp for weeks.

    Some advice would be wonderful!
    Thanks.
     
  2. Sustainium

    Sustainium Well-Known Member

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    Try to compare it with a different new amp, that should let you if your amp is faulty.
     
  3. Gene Ballzz

    Gene Ballzz Well-Known Member

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    Is loop on with a cable in place of the pedal (FX LOOP SEND to RETURN) also noisy? If not, that DD-3 stomp box may be presenting an impedance and/or signal level mismatch.
    Just Askin'
    Gene
     
  4. pedecamp

    pedecamp Well-Known Member

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    Is it noisy when the loop is on but no pedals plugged in?
     
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  5. junk notes

    junk notes Well-Known Member

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    DD-3 on a power supply or battery? If it is a ps, then is it a Boss PSA?
     
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  6. Gene Ballzz

    Gene Ballzz Well-Known Member

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    @S-Page666
    Where are my manners? I totally forgot to :welcome: you to the forum! You should definitely read the responses to you questions!
    Just Sayin' Hi,
    Gene
     
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  7. Ingolf

    Ingolf New Member

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    Hi @S-Page666,

    Welcome!
    If you turn the master volume past 4-5 the volume drop vanishes completely.
     
  8. JBA

    JBA Well-Known Member

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    -The volume differential is well known but more of a bonus than an issue. So I don’t know what to tell you here..?
    -The pop, if you get it just when tapping a pedal in or out can be unacceptable to some or solved by a buffered pedal by others.
    -Noisy loop. It’s the first time I’ve heard of this one and I can confirm mine doesn’t have this issue. Follow some of the posted suggestions to ensure you are reporting the root cause and not a bum ground on a cable or something. If it’s still noisy then you are super unlucky and have a rare issue with yours. In this case I’m sorry a return isn’t simple for you because that the best path forward.

    Show the dealer by phone or video and get an agreement ahead of time. It’s new so this should be replaced, not repaired. Line it up to buy a new one, have it shipped then send the defective one back for refund. This way you don’t go without. ;-)
     
    Last edited: Nov 22, 2020
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  9. Kutt

    Kutt Well-Known Member Gold Supporting Member

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    You said it hums with the loop button engaged while no pedal is in the loop, right? If so then yes I hate to say that you lkely have a bigger problem than the inherent design. Do whatever it takes to get a replacement and don't pay a penny more in the process. This is on Marshall, not you.

    I wanted an SC20H earlier his year. But the FX loop oddities were something I wouldn't tolerate. Like you I use a delay in the loop for a touch of depth. In the end I ponied up a little bit extra money and got a Friedman JJ Jr. instead. Zero regrets. Just something for you to consider as well if the Marshall doesn't work out.
     
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  10. S-Page666

    S-Page666 New Member

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    Thanks all for your helpful responses, and for welcoming me to the forum!

    I've done some troubleshooting.

    When the loop is ON and NO pedals connected (a cable going direct from send to return only) there is NO excessive hum or noise.

    Therefore I assume the problem isn't with the amp. I've tried three different pedals in the loop (on their own and in a series) and they all make noise (BOSS DD-3, BOSS SD-1, WAMPLER REFLECTION)

    Therefore I can probably further assume the issue probably ain't with the pedals?

    Pedals powered by a T-REX FUEL TANK JNR. Could it be my power supply? My cables?

    Very strange though. Never had any problems with my Orange Rockerverb FX Loop using the same gear in the same way in the same chain.

    Thanks in advance. I appreciate the help.
     
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  11. scozz

    scozz Well-Known Member Gold Supporting Member

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    I know you don’t want to return it, and I understand why, but there is definitely something wrong with your amp.
     
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  12. WellBurnTheSky

    WellBurnTheSky Well-Known Member

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    From what you describe, I'd say either the power supply or one of the cables. Try switching cables one at a time. Also try with just one pedal, powered with a battery.
    Also, to entirely eliminate the amp as the cause, try using just a jumper cable in the FX loop (no pedal, just the cable).
     
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  13. JBA

    JBA Well-Known Member

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    I would try one pedal at a time. Try different cables with that pedal, then try batteries if you happen to be using a common pedal power supply. Also plug your amp in somewhere else in the house. If if it still hums then you have a problem with the amp. The cable in the loop will eliminate certain faults but if the amp has a fault that impedes its noise immunity then your pedals or a long cable in the loop might bring on the same noise.
    Best of luck!
     
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  14. pedecamp

    pedecamp Well-Known Member

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    So with the loop on and a jumper cable plugged in no noise, is it quiet with nothing in the loop?

    Try a 9v battery in each of your pedals through the loop to see if all is quiet to see if you pedal power supply is the culprit, maybe due for a new power supply.
     
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  15. S-Page666

    S-Page666 New Member

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    When I tried solely with a jumper cable the amp still made noise once I engaged the loop, however, much less than with a pedal in the loop. Should there be no difference in noise level whether the loop is engaged or disengaged?

    I then tried various other methods:
    - using a battery
    - changing cables
    - different pedals altogether

    Strangely, the noise level changed with these different configurations, but there was ALWAYS noise.

    I'm concluding this amp is a dud. Time to contact the retailer.
    Is this a rarity for Marshall? Faulty gear? This is my first Marshall valve amp (had a SS MG combo years ago) and I expected the highest level of quality that the name and reputation 'Marshall' carry. I am disappointed. Should I chalk this down to a one-off and request a replacement SC20H, or am I rolling the dice again?

    By the way. Thanks for all of your help. You guys are absolute legends and have saved me so much research. I'm very grateful.
     
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  16. S-Page666

    S-Page666 New Member

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    Yeah I'm thinking that too, now.
     
  17. JBA

    JBA Well-Known Member

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    It’s your amp. Mine gets quieter (master below 5) when I engage the loop and this is because of the well known volume “taper” effect when using the loop. Personally I’d do a return / exchange cause this amp’s a keeper. Your issue is not a common one. Matter of fact you’re the first case I’ve personally heard of. Maybe someone else could chime in..?
     
  18. pedecamp

    pedecamp Well-Known Member

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    Yeah have the retailer order you a replacement, tell them you want to hang onto it while you wait for the replacement otherwise you'll have nothing, it could take months!
     
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  19. Kutt

    Kutt Well-Known Member Gold Supporting Member

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    I've noticed a trend over the last few years with loop weirdness and switching weirdness on different Marshalls. I had one of the latest DSL20 heads and for brief time I had it there was channel switching/indicator light oddness going on. I ended up returning it. I've heard similar stories from the same DSL lineup. In fact my DSL100HR is in for a warranty repair right now for static noise (not tube related. The tech has isolated it to the Resonance circuit). Then there is the volume drop on the SC20's.

    Moral of the story, while your specific issue seems to be uncommon there is a larger pattern with bugs and faults at higher numbers over the last few years from what I've observed. Could be from cost cutting measures/low tolerance parts, inexperienced engineers, or both.
     
  20. S-Page666

    S-Page666 New Member

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    I've had to send the amp back to the retailer for them to check and possibly repair (Australian Consumer Law dictates the retailer can attempt to repair a faulty product prior to offering a replacement or refund). So we'll wait and see. Hopefully they provide a full report following inspection. I'll keep you guys posted.
     

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