Stop Humming!

[cnsky54]

I could use a good suggestion or two - I have two 100W Carvin amps that are fed out of a Roland GR20 guitar synth, and I want to record onto my Tascam 2488. I like the stereo effects on the synth, so have two identical amps with identical speaker setups. And they hum like crazy! I first isolated power circuits, and tried turning off everything in the house to no avail. This morning I unplugged the input cable into an amp and it stopped the hum. By experiment, I found out that both amps will operate silently UNTIL both are plugged into the synth. They are perfect alone, but somehow cause each other to hum. It wasn't the house wiring or the synth or my computer or anything, just these two boxes annoying each other. Does anyone have a past problem that sounds like this? Should I stick to mono?

john g

 

[mikemorgan]

I think the line out on the GR20 is more like a keyboard out at -20db and would be better impedence matched to a PA instead of guitar amp. Why not just plug the synth directly into you board, and record from there?

 

[cnsky54]

I may have to record direct in, but would sure like to figure out the problem! The hum persists with other solo effects, loop stations, etc., and with the synth out of line, and other guitars. If I turn amp A off then B will still have a 60hz hum in it until I pull the input line out of A, then silence resumes. Is my house not grounded well? Should I run a long extension out to another 120V plug on a different circuit to isolate the two machines?

j

 

[mikemorgan]

Do you have the two amps patched together somehow? I don't think a balanced cable between the two would matter, but it might be worth a shot.

 

[cnsky54]

No, they are on opposite corners of a rectangular room, plugged into different outlets (but probably the same power circuit), and they feed into speaker boxes that they sit on, but the only connection between them is the guitar or synth or floor box...

 

[boingoman]

Make sure all your shit is on the same circuit, first of all. Try using an extension cord and power strips to plug everything in. If that doesn't work, a box like an ebtech hum eliminator might. You have a ground loop, one amp's ground is sitting at a different potential than the other's.

The dumbass cure is to remove the safety ground from one of the amps by breaking off the ground pin or using one of those 3-2 adapters, because the signal ground is is hooked to the chassis along with the safety ground. Doing either makes you a dumbass.

 

[cnsky54]

And that, gentlemen, is it! Thank you both - the common Fuhrman power bar got rid of the hum, and I'm plugged directly into the console for now, which is much simpler. Now I have no more excuses for not getting something done today...

john

 

[boingoman]

Now I have no more excuses for not getting something done today...

john

We can probably help with that, too.

 

[Grizzly]

I could use a good suggestion or two - I have two 100W Carvin amps that are fed out of a Roland GR20 guitar synth, and I want to record onto my Tascam 2488. I like the stereo effects on the synth, so have two identical amps with identical speaker setups. And they hum like crazy! I first isolated power circuits, and tried turning off everything in the house to no avail. This morning I unplugged the input cable into an amp and it stopped the hum. By experiment, I found out that both amps will operate silently UNTIL both are plugged into the synth. They are perfect alone, but somehow cause each other to hum. It wasn't the house wiring or the synth or my computer or anything, just these two boxes annoying each other. Does anyone have a past problem that sounds like this? Should I stick to mono?

john g

Well I had a simular problem untill I plugged everything into a UPS with a battery back up. All of the hum went away. Try that you can get a good UPS for around $75.00 it's a cheap fix

Griz