Boosting a JCM 900 for Solo

Discussion in 'Marshall Amps' started by 1+9+8+7, Aug 15, 2019.

  1. 1+9+8+7

    1+9+8+7 Member

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    So I'm running my 900 on the B channel with medium gain, nothing crazy. I've got my effects pedals in front of it, basically a Boss compressor, drive and EQ. At the end of the chain I've got a guv'nor mk1 I used to boost for solos. The issue is, the guv'nor doesn't really boost the volume much, it really just adds a bit more compression.

    Is this because I've left no headroom in the amp? If I back volumes of pedals off I don't get the same drive or punch...
     

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  2. John BNY

    John BNY Well-Known Member

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    I use a boost pedal through the effects loop on my JCM 900 DR, and it works great.
     
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  3. Lance Chambers

    Lance Chambers Well-Known Member

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    There is an old FX Loop trick that we could go into detail about but let's stick to common practice first. Signal boosts in the front; signal altering in the loop. :jam:
     
  4. 1+9+8+7

    1+9+8+7 Member

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    I don't think any pedal I'm using, maybe other than the EQ would alter the signal. Care to go into more detail re this old FX loop trick?
     
  5. Lance Chambers

    Lance Chambers Well-Known Member

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    It's actually so simple most don't even know about it. You run the sound in reverse. :jam:

    Most Marshall amps have a "Level" control function in the FX Loop (FX mix knob on front of some units). Set your sound with the FX Level at it's maximum compression, etc.,........(-10db cut) when playing rhythms. When it's time for your solo simply hit the FX button to turn OFF the FX Loop and you get an instant 10db gain in your signal chain...........re-engage the FX Loop after your solo for the same cut during the remainder of the playing.

    FWIW: Marshall actually has this same tip listed in some of their amps documentation.

    BTW! Your pedal chain is incorrect. :cheers:
     
    Last edited: Aug 15, 2019
  6. 1+9+8+7

    1+9+8+7 Member

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    Turn off the FX loop? How can you do that in a 900?
     
  7. ampmadscientist

    ampmadscientist Well-Known Member

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    You need to put a clean boost in the effects loop, not in the front input.
    The front input will just compress the signal more and more.
     
  8. Lance Chambers

    Lance Chambers Well-Known Member

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    You can A/B channel switch for varying signal boosts on a JCM900................They share the same EQ. :cheers:
     
    Last edited: Aug 15, 2019
  9. John BNY

    John BNY Well-Known Member

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    Sticking a boost pedal in the effects loop will give you the solo boost you need. I use the boosta grande pedal and it’s perfect for gigging, because you can boost both the clean and OD channel for solos.
     
  10. mk2 steve

    mk2 steve Well-Known Member

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    On a mkiii or slx... not on a dual Reverb. That has a clean and dirty channel. Not a simple MV jump like the other two. Channel A has less gain than channel B and is voiced differently
     
  11. Lance Chambers

    Lance Chambers Well-Known Member

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    Please read the comments thoroughly folks. :facepalm:

    You can A/B channel switch for varying signal boosts on a JCM900................They share the same EQ.
     
  12. mk2 steve

    mk2 steve Well-Known Member

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    I can read, thanks. The 900 doesn’t have the FX loop button that you referenced. It cannot be switched on and off. Switching to the clean channel will not perform the solo boost that OP wants. FX loop level is the same on both channels on a 900 and cannot be footswitched on and off.
     
    Last edited: Aug 15, 2019
  13. 1+9+8+7

    1+9+8+7 Member

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    So the compressor, overdrive and eq are actually in a single unit. I'm using an old Roland GP-8.

    Chain looks like:
    Guitar > GP-8 (comp 》OD 》EQ) > Guv'nor > 900

    The GP-8 has an effects loop after the EQ and before the last 2 modulation effects in the chain. So I'm think of either putting the Guv'nor there, or leaving it where it is, and using it almost in reverse. Setting the GP-8 to my lead tone/ volume and then using the Guv'nor engaged to hold the volume back for rhythm then dis-engaging the Guv'nor for a lead boost....

    Might be a bit backwards and not sure if anyone else has ever done this but I think it could work. Will try it later today.
     
  14. WellBurnTheSky

    WellBurnTheSky Well-Known Member

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    This. MXR Microamp, CAE/MXR MC401, TC Spark, or any clean boost put in the FX loop will do the trick.
    Alternatively, try an EQ pedal (MXR, Boss, Source Audio, or any other), so you can roll off some top and bottom end and push some mids, plus a tad more volume.
    Either option will get you there.
     
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  15. anitoli

    anitoli Well-Known Member

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    Maybe your band mates could try an old school remedy, which is back off on their volumes when the solo kicks in. This worked for ever in the 70's-80's.
     
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  16. Buzzard

    Buzzard Well-Known Member

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    Why can’t some of you f’ers ever get it through your heads when referring to jcm 800’s and 900’s ,that you need to state which model your taking about.
     
  17. John BNY

    John BNY Well-Known Member

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    Good point. I assume he doesn't have the DR.
     
  18. 1+9+8+7

    1+9+8+7 Member

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    Apologies. 4100 100w hi gain dual reverb
     
  19. mk2 steve

    mk2 steve Well-Known Member

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    Why? If he had the SLX or MkIII he wouldn’t have this issue as they have built in dual master volumes. The DR does not.

    Run a boost in the loop, something like an MXR micro amp or an EQ with the level bumped. That’ll give you your solo boost.
     
  20. John BNY

    John BNY Well-Known Member

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    I didn't know the SLX or MKIII wouldn't have this issue. But, problem solved since he has the DR.
     

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