Marshall JCM 800 2205 Noisy FX loop

[octodoom]

Hi guys, not really sure this is the appropriate forum to ask this but here it goes.
About a year ago I bought an '84 JCM 800 2205 (the dual channel 50 watt head), and it's a proper beast. The tone is great and I'm really happy with it's performance so far, but it always produced too much hum and hiss.
In order to solved this I took it to a tech, and got the amp back 3 weeks ago. Apparently none of the amp's previous owners had done any "up keeping" at all, no tube or capacitor replacement, nothing.
So I got the amp back, and most of the hiss and hum went away, but there was some still some hum going through. I started checking everything, from my guitar, to my cables, my pedals, and my power supply. With some research I found out I was making a couple mistakes, I was powering both my front of amp, and FX loop chains with the same power supply, and some of these pedals were daisy chained. So I got another power supply, now I have one power supply for my front of the amp pedals, and another for my FX loop pedals, and no daisy chains. Both power supplies have isolated outputs.
Also got new patch, and instrument cables for my entire rig (some cables were also producing some hum). Now, with all this, most of the hum went away, but there is still something there, so I tried to find exactly where the hum's coming from, and found out it's in my FX loop.
If I'm just running my front of the amp pedals without an FX loop, the amp is dead silent, no hum at all. If I'm running my front of amp pedals, and a cable going from send to return in my FX loop without any pedals in the loop, the amp is also dead silent (no hum or additional noises). But when I add my pedals to the FX loop, that's when the hum starts.

So my set up is:

guitar -> fuzz, tuner, wah, OD, compressor sustainer -> amp --> Fx loop send --> boost, chorus, delay, phaser, smartgate, EQ -> Fx loop return -> cab (marsahll 4x12 1960 AV)

I got a 5 slot electrical plug, that powers all of it, then I just plug that one to the wall plug. The entire set up is grounded as well. Also I've checked all my pedals individually and I don't have a faulty or "noisy one" in the chain.

Is there a possibility that somehow there's a ground loop happening here? I thought of getting the ebtech hum eliminator and place it after the EQ, but I'm not sure this will solve the problem, and I'm not really keen on just spending money for no reason.

Do any of you guys have any idea of what could be causing the hum? And, will a hum eliminator solve my issue?
I am slowly going nuts because of this, so all feedback and advice is more than appreciated and welcome.

Thank you so much for your help in advance.

 

[South Park]

Did you put the FX loop in . Is it A shielded cable you may a ground loop try cleaning the jacks

 

[octodoom]

Thank you so much for the reply. Yes all cables are shielded I believe, and all jacks have been throughly cleaned. Also the Fx loop is original, the amp hasn't been modded. Also when I run a cable from send to return in the FX loop, without pedals (same cable going out and going in) I don't have any hum whatsoever.
Maybe a ground loop is happening in my power supplies?

 

[South Park]

The FX loop in connected to the grid that is how the hum starts . Some times the switch on the jacks can make noice .

 

[octodoom]

@South Park Thanks for the advice. I'll have another at the jacks today.

 

[tce63]

@South Park Thanks for the advice. I'll have another at the jacks today.

to the forum, a great place

Cheers

 

[Gunner64]

My 2205 was hissy in the loop. More so than other amps I have with loops.

 

[octodoom]

@tce63 thank for the warm welcome.
@Gunner64 Is there anything I can do to improve this? Or is this just the way the amp naturally behaves?

 

[TXOldRedRocker]

I see you have boost in the FX loop. Of all my pedals, those produce the most noise. Does the hiss still happen if you completely remove it temporarily? (Plus, I've never had boost in my FX loop, always in front with only time based effects in the loop.)

Once, I had some unexpected levels of hiss and found that one pedal had a patch cable that was 98% plugged in. The pedal worked, but it was picking up RF like crazy. Once found, just pushed it the rest of the way in, and hiss gone. Unlikely, but worth a try.

Also, I never let the patch cables touch. As in, don't put the pedals so close that the cables going in and out of pedals touch each other. Depending on the pedals, that can hiss too.

I do use two Ebtech Hum X's, one for each amp, and they help.

Now, my all tube Marshall amp, Fender too, produces hiss the more gain I use, Nature of tube amps, in my opinion. So I have a noise gate after all my boost pedals, and for me that works great! I use the TC Electronics Sentry, which I think is the best out there, though many, many people will have a different opinion. I see you use a Smart Gate, which I have no experience with, but not sure why that isn't taking care of the hiss for you.

If the hiss is just the nature of your setup, there are other additions that may help...
* Electro Harmonix Hum Debugger pedal.
* ISP Decimator pedal line.
(I'm going to get the ISP Decimator II G String, just because I want to play with it.)

Good luck, and keep us updated please.

 

[octodoom]

@TXOldRedRocker Thanks for the feedback man, I actually do have my pedals close enough my patch cables touch (honestly never thought that could be a problem), so I'm gonna make sure I give more space between the pedals, and give that one a try. As you also said I do use my boost in the Fx loop, I enjoy just a clean signal boost, only volume nothing else and I feel like the FX loop in the best place to keep it, and I have tried removing the boost from the Fx loop chain and there is no difference unfortunately in hiss or hum.
Regarding the smart Gate, it works super well in removing all the Hiss and Hum, the only problem is I use my clean channel a lot and the smartgate "cuts me off" prematurely, so I loose a lot of sustain and note length, thus using the smartgate doesn't completely solve my problems.

Yet again, gonna make sure there is spacing between my pedals so the patch cables won't touch, also gonna read up on the Electro Harmonix Hum Debugger and the ISP Decimator (maybe that can solve some of the issues). I'll try to keep you updated on the situation.

 

[Mitchell Pearrow]

Hi guys, not really sure this is the appropriate forum to ask this but here it goes.
About a year ago I bought an '84 JCM 800 2205 (the dual channel 50 watt head), and it's a proper beast. The tone is great and I'm really happy with it's performance so far, but it always produced too much hum and hiss.
In order to solved this I took it to a tech, and got the amp back 3 weeks ago. Apparently none of the amp's previous owners had done any "up keeping" at all, no tube or capacitor replacement, nothing.
So I got the amp back, and most of the hiss and hum went away, but there was some still some hum going through. I started checking everything, from my guitar, to my cables, my pedals, and my power supply. With some research I found out I was making a couple mistakes, I was powering both my front of amp, and FX loop chains with the same power supply, and some of these pedals were daisy chained. So I got another power supply, now I have one power supply for my front of the amp pedals, and another for my FX loop pedals, and no daisy chains. Both power supplies have isolated outputs.
Also got new patch, and instrument cables for my entire rig (some cables were also producing some hum). Now, with all this, most of the hum went away, but there is still something there, so I tried to find exactly where the hum's coming from, and found out it's in my FX loop.
If I'm just running my front of the amp pedals without an FX loop, the amp is dead silent, no hum at all. If I'm running my front of amp pedals, and a cable going from send to return in my FX loop without any pedals in the loop, the amp is also dead silent (no hum or additional noises). But when I add my pedals to the FX loop, that's when the hum starts.

So my set up is:

guitar -> fuzz, tuner, wah, OD, compressor sustainer -> amp --> Fx loop send --> boost, chorus, delay, phaser, smartgate, EQ -> Fx loop return -> cab (marsahll 4x12 1960 AV)

I got a 5 slot electrical plug, that powers all of it, then I just plug that one to the wall plug. The entire set up is grounded as well. Also I've checked all my pedals individually and I don't have a faulty or "noisy one" in the chain.

Is there a possibility that somehow there's a ground loop happening here? I thought of getting the ebtech hum eliminator and place it after the EQ, but I'm not sure this will solve the problem, and I'm not really keen on just spending money for no reason.

Do any of you guys have any idea of what could be causing the hum? And, will a hum eliminator solve my issue?
I am slowly going nuts because of this, so all feedback and advice is more than appreciated and welcome.

Thank you so much for your help in advance.

To the forum
I would also recommend what Southpark has already replied.
I am no tech, but that is my guess, plus I don’t use many FX .
Cheers
Mitch

 

[octodoom]

@Mitchell Pearrow Thanks for the help dude. Gonna try what both you and SouthPark suggested too.

 

[Gunner64]

@tce63 thank for the warm welcome.
@Gunner64 Is there anything I can do to improve this? Or is this just the way the amp naturally behaves?

There is a fix somewhere for it, it involves changing some components I believe. I don't use many effects so I never really used the loop much, so I never researched it any further than that.