Jaded Faith
Well-known member
I have been meaning to write this up for about 5 months now, so here it goes:
Many MTS users have noticed issues with their amps picking up odd radio broadcasts. This is only observed on some amps and in certain locations when there is a cable plugged into the input jack. It does not matter if the cable is plugged into a guitar or not. The cable is simply breaking a short to ground when it is plugged in and acting as an antenna. Higher gain modules will make this more pronounced as they amplify the signal to higher levels of gain than a clean. Many Marshall amps also have this issue. I have owned 6 MTS amps and it was hit or miss regarding this problem. Some have this fix straight from the factory: my current RM20 did, my RM4 did not.
A simple fix for this is to remove the input board from your amp and solder a 1000pf ceramic capacitor between hot and ground on your 1/4" input jack. You have to carefully remove the nut that holds the jack to the front plate of your amp and the whole board will come out. A 1kV 1000pf ceramic cap is then soldered between the tip and center solder joints for the input jack on the bottom of the PCB. This will short the radio signals to ground rather than amplifying them through your amp. Your tone will not be affected. Here is a picture of my RM4 with the cap added:
Feel free to ask any questions and hope this helps!
DISCLAIMER: AS YOU ALL KNOW, THERE ARE DEADLY VOLTAGES INSIDE TUBE AMPS. BE SURE TO UNPLUG AND DISCHARGE THEM BEFORE OPENING THEM TO WORK ON THEM. IF YOU ARE AT ALL UNSURE HOW TO DO THIS, TAKE YOUR AMP TO A QUALIFIED TECH TO DO THE WORK FOR YOU. ALTHOUGH THIS IS A VERY SIMPLE TWEAK, I TAKE NO RESPONSIBILITY FOR ANY DAMAGE TO YOU OR YOUR AMP.
Many MTS users have noticed issues with their amps picking up odd radio broadcasts. This is only observed on some amps and in certain locations when there is a cable plugged into the input jack. It does not matter if the cable is plugged into a guitar or not. The cable is simply breaking a short to ground when it is plugged in and acting as an antenna. Higher gain modules will make this more pronounced as they amplify the signal to higher levels of gain than a clean. Many Marshall amps also have this issue. I have owned 6 MTS amps and it was hit or miss regarding this problem. Some have this fix straight from the factory: my current RM20 did, my RM4 did not.
A simple fix for this is to remove the input board from your amp and solder a 1000pf ceramic capacitor between hot and ground on your 1/4" input jack. You have to carefully remove the nut that holds the jack to the front plate of your amp and the whole board will come out. A 1kV 1000pf ceramic cap is then soldered between the tip and center solder joints for the input jack on the bottom of the PCB. This will short the radio signals to ground rather than amplifying them through your amp. Your tone will not be affected. Here is a picture of my RM4 with the cap added:
Feel free to ask any questions and hope this helps!
DISCLAIMER: AS YOU ALL KNOW, THERE ARE DEADLY VOLTAGES INSIDE TUBE AMPS. BE SURE TO UNPLUG AND DISCHARGE THEM BEFORE OPENING THEM TO WORK ON THEM. IF YOU ARE AT ALL UNSURE HOW TO DO THIS, TAKE YOUR AMP TO A QUALIFIED TECH TO DO THE WORK FOR YOU. ALTHOUGH THIS IS A VERY SIMPLE TWEAK, I TAKE NO RESPONSIBILITY FOR ANY DAMAGE TO YOU OR YOUR AMP.
