Code 100H FX Loop



I have recently acquired a code 100H and cab and am learning how to use it to get the best from it. I have found i can never seem to get my solo playing to cut through and it needs a boost. I planned on using the FX loop with my boost pedal but i get no effect whatsoever. My leads are all good and the pedal works - i just cant seem to get any response from the FX loop. Can you please help?

asked 13 Mar 2019 at 10:29 AM

matthew richards
First off, as the baseball adage goes “Don’t blame the glove for your errors.” Now, let’s get down to business...

1)Make sure pedal works with a different amp.
2) Make sure your effects loop is working by testing different pedals
3) Unplug headphones from front of cab (headphones turn off fx loop).
4) connect fx send to pedal in, pedal out to fx return
5) Make sure your cables are plugged correctly and work properly.
6) set eq on pedal to flat neutral and turn up pedal gain/ vol 100%

This should remedy all your problems, as long as fx loop is working on your amp. I run an eq as a boost pedal, too, and I’ve run it through the front and the fx loop depending on my pedal board set up. The code by itself is a monster and a boost will definitely help your leads slice through the mix. My bandmate plays a 150 w Mesa boogie and my Code slices through it like a samurai sword. I love this thing.
- Mark Solis 24 May 2019 at 09:22 AM
Answers: 5


I have the 100H running thru a 4X12 cab.  See if this is how you have it all plugged in as mine blows they heck out of my basement walls loud!  I run my guitar thru an MXR eq pedal then run that thru the front of the amp, all your effects placed in the front end will then go thru the preamp.  I then take a tubescreamer and will hook that up in the FX Loop, here is the how.  Take a guitar cable and place it in the send on the fx loop, this goes into the input of your pedal.  Next take another cable and place in to return of the fx loop, this then goes into the output of your pedal then the fx loop is complete.  Any effects in the fx loop are post preamp.  This will boost your volume loads so make sure that both the volume and master volume are down before you turn it on.  I have run Les Pauls, 6, 7, and 8 strings thru doing this and it is super loud.

Another way to do this is you are using a multi effects pedal is to run that into the return all alone if you are running your guitar thru your effects pedal, this disables all the controls on the amp and you are then using the amp as a PA so to speak.  All of your effects, volume come thru with the effects pedal knobs you can adjust.

Couple ways I use it.  If you need more patches I found this site with literally 1,000s of em.  This is not related to Marshall's website but has some really good patches that work great

answered 13 Mar 2019 at 06:00 PM

Steve R (15)


As Steve said, If your using headphones you wont hear any fx in the loop. Kinda sucks.

answered 15 Mar 2019 at 06:01 PM

Robin Morgan


The only mod you should run theough the front are wah pedals. Run your boost through the fx loop, since the loop is biased and will keep the signal clean and unchanged between bypassed and on pedals. Make sure your headphones are unplugged otherwise your f’d loop will be non active. 

answered 28 Mar 2019 at 01:38 AM

Mark Solis (2)
if I try another one and it's the same, then it's bye bye Marshall. Which will be a shame as I've been using Marshall amps for a good 20 years. Redtube Beeg Spankbang - KINGA danie 24 May 2019 at 03:03 AM


Using hearphone will resolve the issue. Thank you very much.

answered 26 Jan 2020 at 04:36 PM

kilein mikein


Is there a legitimate reason using headphones disables the FX loop?

This doesn't make any sense to me.

answered 28 Jan 2022 at 12:34 AM

Bruce Perry
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