RM50 very noisy fx loop

[buriedorburned]

I used it RM50 combo for a jam today, and I had a Zoom MS-50G running though the fx loop. I know the amp used a line level fx loop, and the Zoom has worked very well with it.
However today with the amp turned up to band levels (Both the Master and module level at noon), even when it was not engaged, it was very noisy.

Now the RM50 itself is a fairly noisy amp, and the module (Ultra XL) is also a very high gain, so there's added noise. But the hiss with the Zoom in the fx loop today was horrible. As soon as I removed it, the noise was much better.

Is there anything I can do to help this?
The Effects knob on the amp was at noon, could that have been part of the problem?
I use a tubescreamer and ISP Decimator out front.
Could it be the Zoom pedal?

Any help greatly appreciated!

 

[VitaminG]

could be dirty jacks on your loop. Spray some contact cleaner onto the tip of a cable and work it in and out of the jacks to remove any oxidation.

 

[webrthomson]

The loop itself is tube driven so it's worth checking if you can put a quieter tube in that position (or possibly lower gain?) - I can't remember what the tube layout on the RM50 is, but I'm sure that someone will chime in with that!

Other than that and the sockets if you are using a lot of gain it and finding it noisy at gig level volume a noise gate might well be the way forward. There are lots of good ones out there - ISP Decimators are what I use and they are pretty good - I've got the version 2 G string pedal.

http://www.isptechnologies.com/portfolio/decimator-ii-g-string-pedal/

By the sounds of it you need one that will go in the loop and in front of the amp both the G String decimater and the Boss NS2 will do that, thought I've not used the NS2 in that fashion.

I'd try things in order of expense first so jack sockets, tubes, noise gate - mainly because I'm mean

Hope that helps - let us know how you get on!

 

[Jaded Faith]

If the noise was greatly improved when you removed the Zoom, that's the variable that's causing the issue. The signal flows through the loop circuitry whether you have anything in the loops or not. If the noise was less sans the Zoom, there's your issue.

 

[JKD]

For the record...I believe the FX loop is driven by v2 in the head.

v1 is closest to the input Jack, v3 (Phase Inverter) is closest to the big power tube pair........so v2 is the other one.