Help understanding the correct Marshall head FX loop operation with a Syn2?

[TheBukman]

Hi all
Waiting for my new Syn2 to arrive this week with a couple of modules. It will mainly be used for recording.

I will be using it through a low watt Marshall SC20h studio head (JCM 800 version reissue) and using the power section of my Marshall to drive my Syn 2 preamp modules through. From there I will go out to Fryette PS2 load box for recording out and feeding my guitar Cab.
I also plan to use the Marshall head as my 3rd preamp option.
I will run my delay and reverb effects through the Fryette FX Loop or in the box so no effects will be used in the above setup at all except for a drive pedal through the front of the chain after my guitar.

So my main query is around how I set up the Marshall FX loop correctly for the 3 channel scenario. The Marshall has a series effects loop with an on-off switch at the back. I haven't used the effects loop before so just a bit confused about what the on-off switch exactly does.

Could someone pls confirm the following -
- I assume I need to run the Syn 2 line out straight to the Marshall FX return so it directly feeds the power amp when I want to use the Syn2 modules as preamps?
- I assume I don't need to use the Marshall FX send output at all?
- Do I also need to leave the Marshall FX loop switched off for the 3 channels to work ok while switching everything via the Syn2? I am really hoping I don't need to keep toggling the amp effects loop switch on and off whenever I want to use the Marshall preamp.

The Syn2 manual doesn't seem to talk about an amp FX loop on off switch and only says where in the amp loop I need to connect hence my confusion and hoping someone can help.

Is anyone aware if the above setup would be the same for a Mesa Boogie Mark V head which also has FX loop switching?

 

[j4q0]

An FX loop is an insert between a preamp section and a power section, in this case of your Marshall head.
The FX on/off switch will either bypass (off) or insert (on) the connections of the send/return jacks of the head.

Therefore:
Switch OFF: you won't be able to hear anything that you have connected into the return jack.
Switch ON: you will be able to hear anything you have connected to the return jack.

If you want to use the preamp section of the head as an option, then the preamp input needs to see a signal, therefore you need to connect the SYN2 with the 4 cable method as described in the manual, in which case you will use both the input of the head AND the FX send jack to complete the signal path going from your guitar, through both the head and the SYN and then into the load box.

And, since you want to be able to hear the SYN2 which is inserted in the FX loop of the head, then the FX loop must be switched ON.
The channel switching of the SYN2 will allow you to switch between the 2 modules and the head's preamp section, the latter happens when the SYN2 is in bypass mode.

 

[TheBukman]

Thanks very much for the detailed explanation. This has been very helpful