Effect loop hum

[Setzer]

I was experimenting today with different effect box sequences,just checking things out trying some fx that I havent used for a while etc.

I have a DC5 and I dont really use many fx boxes but I have an old Boss DD2 in the effects loop so I took it out of the loop to try it before the amp and when I tried that I became aware of a hum that is present when I use the loop and disappears when the loop is unused.

I checked the DD2 in front of the amp and no hum from the pedal and then tried a couple of different pedals in the loop and the hum appeared with each pedal I tried.

Has anybody any idea if this hum is normal,or is there something wrong.

Thanks in advance.

 

[4Eyes]

it sounds like ground loop. try to disconect ground/shield wiring on one of the signal cables in your FX loop (cable from Fx send to effect pedal in or effect pedal out to Fx return). it might hepls.

 

[Setzer]

Thanks for the idea 4eyes.

I tried it but unfortunately it didnt make any difference at all.

The hum is a real pain as the delay doesnt sound anywhere near as good in front of the amp as it does in the fx loop,plus its got a hair trigger effect level knob which is easily controllable in the loop and a real nuisance when going in the front.

 

[4Eyes]

and what about both signal cables in Fx loop?

 

[6L6C]

A few thing s come to mind since you are using the loop with the DD2, I assume you have the mix control at 100% (not that you have to).

Try the following so you can at least pin point were the hum is coming from, for the following keep the loop mix at 100% even if you don’t normally run it like this. Also keep you foot switch for the DC-5 hooked up.

Just take a cable and put it in preamp out to power amp in, nothing in between just a straight patch, kick the effects loop on (if it’s not already) Is there any hum? If there is hum try another cable but even if there isn’t try another cable anyway. Assuming there is no hum so far we just ruled out the preamp tubes and also found two good cables for the effects loop. Another thing are you using shielded cables for the loop?

Another thing to look for. Are you using a transformer for the DD-2 or any other pedal? Might be a ground loop. Let’s put the DD-2 back in to the loop (make this the only pedal in the loop to start). Run the DD-2 on a battery, how does it sound? If it is still humming at this point? If so let it hum go to the channel volume your amp is currently on and gradually turn it down the hum will go down in volume yes , but does the hum disappear at a certain point while turning it down?
If this is the problem the DD-2” input can’t handle the preamp out signal. Hopefully this is not the problem.