Connecting Multi-FX using 4CM
4CM allows you to put all the effects within a Multi-FX in their correct places (in front of the amp or in the amp’s loop). However, for 4CM to work, your Multi-FX unit must have a built in effects (FX) loop. If your Multi-FX does not have an FX Loop: stop reading now. You are sunk. Choose from your tough choices above or buy a new Multi-FX with an FX loop.
Do not confuse the Multi-FX FX loop with the Amp’s FX Loop. These are two different things. Just because you have one, it does not follow that you have the other.
The good news is that most recent, higher-spec Multi-FX units have their own built-in FX Loop. This is certainly the case with the Line 6 HD500 and Boss GT-10/8. Other vendors support FX loops in their products and many older models from Line 6/Boss have them too (check the specifications for the Multi-FX online if you are not sure).
The manufacturers intend this loop to allow you to add other external effects into the chain controlled by the Multi-FX but, using some fancy cabling and setup, this loop can be used to position the individual effects where you want them – either ‘in front’ of the amp or in the Amp FX Loop.
The way 4CM works is by running your Amplifiers entire pre-amp section within the FX Loop of your Multi-FX. You can then put your compressor/distortion/wah-type effects before the Multi-FX Loop and the delay/modulation type effects after the Multi-FX FX Loop. Sorted!
This is confusing to get your head round though so let’s have a couple of diagrams. First, this is a diagram that just shows the physical cabling …
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Figure 4 - 4CM Cabling
OK. Now a diagram showing the routing path through the amp. Note the arrowheads showing where your guitar’s signal goes through the chain, through to the speaker(s).
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Figure 5 - 4CM Routing
And finally, the big one! showing the effects themselves, the pre amp (with volume, tone and gain controls) and the power amp (with master volume and presence controls … where installed). Notice how the entire amp-pre-amp is now within the Multi-FX Effects Loop.
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Figure 6 - 4CM Chain
OK, so that is the basic idea. Note: on the JVM, the Master control is implemented after the effects loop - as per the diagram. On some other amplifiers the master control is implemented before the effects loop. In this case the output volume on your effects unit becomes the master control for the amp and you may need to turn the master control on your amp way high to provide a signal into the effects loop