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7 Cable Method Woes


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Anybody using the 7 cable method? I set 7C method up using a new Marshall DSL40CR and an older Marshall DSL40C. I want distortion/overdrive going in front of amp and modulation effects after preamp in DSL40 FX loop.

Sound is cutting out substantially on newer DSL40CR. Older DSL40C working fine. 

Cable #1 Guitar=> Helix LT Guitar Input

Cable #2 Helix LT Send #1=> Amp#1 Main Input

Cable #3 Amp#1 FX Loop Send => Helix LT Return #1

Cable #4 Helix LT 1/4 Left Output => Amp#1 FX Loop Return Cable #5 Helix LT Send #2 => Amp#2 Main Input

Cable #6 Amp#2 FX Loop Send => Helix LT Return #2

Cable #7 Helix LT 1/4 Right Output => Amp#2 FX Loop Return


Copied 7 Cable Method patch from template.


Signal Path A going to Amp#1 panned left 100%. Signal Path B going to Amp#2 panned right 100%.


FX Loop block mix set to 100%.

Global Settings Send/Return #1 set to instrument, Send/Return #2 set to instrument, 1/4 outputs set to Line.


Signal Path A panned left to Amp#1 is working fine (older DSL40C). Signal Path B panned right to Amp#2 has signal (volume) loss in the effects loop.


Signal Path A output turns green indicating signal is going out. Signal Path B output does not turn green, although I have sound. If I turn FX Loop off on Amp#2 sound increases to normal.


Since Amp#1 is working fine I switched all the cables between Helix LT and Amp#1 and Amp#2. Amp#1 continues to work properly while Amp#2 continues to have sound loss. I swapped out with other cables I know are good so I am sure it is not a problem with cables.


I disconnected from Helix LT and jumped a cable between send and receive on the Amp#2 FX Loop. Sound volume level remained the same with FX Loop on and off. I also ran a pedal in the FX loop and had no sound loss.


I took Amp#2 to a skilled Amp technician. The guy builds his own Amps so I know he is qualified and competent. He cleaned Amp#2 FX Loop jacks. Checked everything and finds no problem.


Are there any other settings in the patch set up or global settings I need to consider? I am sure it has something to do with the signal interfacing between Amp#2 and Helix LT.


I found this on a Marshall Forum "some effects loops have a problem when an effected signal is mixed with an out of phase dry signal at the return point".


I called Marshall USA and actually spoke to a technician. The Marshall tech used to own a Helix so he completely understood my issues. He said if my effects loop is workimg fine with jumping and with a separate pedal there is no problem with the amp. Its still under warranty but I have to ship it to Mississippi for them to look at it.


Anyone have any ideas?



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Given that you're able to swap the amps and the same amp is still the one having issues, it seems pretty clear that it's something with that amp, although, what it is, I don't know. When you say sound is cutting out, how much is it? Can it compensated for by adjusting the Send level in the Helix's FX Loop for that amp? What happens if you disconnect the cables from Amp#2's FX loop? Is it still getting a good signal from the Helix's Send?

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Since AMP1 is working no matter how you cabled it up, why don't you try the 5 cable method using only the preamp of amp1


Cable #1 Guitar=> Helix LT Guitar Input

Fx Loop 1 block

Cable #2 Helix LT Send #1=> Amp#1 Main Input

Cable #3 Amp#1 FX Loop Send => Helix LT Return #1

Cable #4 Helix LT 1/4 Left Output => Amp#1 FX Loop Return Cable

Cable #5 Helix LT 1/4 Right Output => Amp#2 FX Loop Return Cable


Then if it's not working, swap cable 4 and 5 with Amp1 and 2's return.   If they problem swaps, then you might have a helix issue or the effects returns are expecting different levels or the output of the two preamps is different.


Still not working properly?  You could then switch to using AMP 2's preamp and see if AMP1 is now much louder.


Hope you get it figured out!

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Thanks for your comments. I have tried 4C with just problem amp #2. It works just fine when disconnected from Helix with a patch cable jumping FX loop send and receive. It also works fine with an MRX overdrive pedal. I think you are correct the returns are expecting different levels of output. I am boosting the output block by 10db as a work around to balance it out. I talked to a Marshall tech this morning. He said he is going to get specs on amp and Helix LT and let me know if i have an imbalance in impedance between amp and Helix. I'll post if I figure it out.

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