Direct box problem ?

[ripingitar]

I am trying to record a direct track along with my guitar amp track similtaneously so that later if i choose i can resample the guitar track if im not happy with my sound with guitar rig plug in... I have a PASSIVE direct box with A balanced xlr to go direct to the mixer and a 1/4 out to my amp ... problem is when i plug everything up .. I get excessive noise ... sounds like a ground loop problem ??? but may be coming from the pc??? tried different cables ...moving away from the pc .. plugging in equipment in different locations .... no help .. so i had to proceed with my tracks without a direct track!!!... should i have gotten a ACtive box ?? would that have been quieter ??? I even took the box apart looking for a bad ground ?? no luck ????
is there any modifications i can do to suppress the noise which is present through my amp and the direct signal /??

 

[boingoman]

A passive Di might not be the best choice for this, like you suspect. Not enough impedance. That would be my first guess.

Guitars like to see very high impedance, over 100,000 ohms. A passive DI will have 15-20,000ohms, usually. That gets paralleled with your guitar input, dropping the impedance the guitar sees to below 10,000ohms.

Is it noise like hiss, or hum? Hiss will most likely be impedance or something, a 60hz hum is most likely a ground loop.

If it's a hum, does the DI have a ground lift? If not, you can open up the mic cable and cut the shield to see if it helps.

 

[ripingitar]

its def more of a hum .. it has no ground lift its a cheap box ... i guess i need to upgrade .? to a better box ? ..

 

[slidey]

I regularly do just what you said & erm (I'm almost embarressed) an active behringer DI will do the trick

 

[ggunn]

its def more of a hum .. it has no ground lift its a cheap box ... i guess i need to upgrade .? to a better box ? ..

Try lifting ground on your amp.

 

[boingoman]

its def more of a hum .. it has no ground lift its a cheap box ... i guess i need to upgrade .? to a better box ? ..

You could open the box and cut the ground.

 

[ggunn]

You could open the box and cut the ground.

It would be simpler to open up one of the mic cable connectors and cut the shield.

 

[boingoman]

It would be simpler to open up one of the mic cable connectors and cut the shield.

Yeah, I already mentioned that, I figure I'd just mention the box, too.

 

[Micter]

Or just make sure the amp is plugged into the same outlet as the recording gear. It's not a good idea to lift the ground on the amp.

 

[ggunn]

Or just make sure the amp is plugged into the same outlet as the recording gear. It's not a good idea to lift the ground on the amp.

If it's a ground loop, plugging the amp into the same outlet may not help. I understand the potential safety issues regarding groundlifting amps, but if an amp and mixing board are connected through shield (which closes the loop) and the board is grounded, then the amp is still grounded when a ground lift is applied to its power cord, and this will usually stop the hum.

But IMO, the best option is clipping the shield of the low Z link.