Loopback setup

GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

desol

Well-known member
Joined
Jun 20, 2005
Messages
2,122
Hey guys

Could someone possibly give me a hand figuring out my loop back setup? I'm trying to get things setup to do a test like Aaron Rash's in the lab (neve test sweeps) in REW, and I'm having some difficulties. I've always had this same problem with loop back setups, feedback. A few days back I tried to set things up, and I literally got the burning smell coming out of the mic pre.  :-\  I'm kinda at my wits end with this and I don't wanna keep screwing with it and possible hurting something, if I haven't already. It's kinda weird cause I've built a decent amount of gear, but I'm having issues with this basic little measurement setup.

Can anyone give me run down of the basic do's and don't's to make sure of? Do I need to have certain inputs turned off? I know it should be easy...just in and out.

I have an MBOX 3 interface for the computer. I'm assuming I need to have my output turned way down when going into the input of the mic pre, cause a mic level signal is so small.

 
Hello,
If you're getting feedback, this means that your input signal is being resent to your output with some gain added to it.

You need to turn off all analog monitoring possibilities on your interface; probably the Mbox has a control that allows either the signal from your software or the input signal from the interface to be sent to the output. it needs to be set to NOT allow input signal in the output.

Good luck!

Best regards, Rogy
 
Thanks Rogy. Everything seems to be fine with my unit(in regards to the burnt smell)...thankfully.  :mad:

Appreciate the reply. Hopefully this serves as an example for someone else of what NOT to do.  ;D

 
desol said:
Thanks Rogy. Everything seems to be fine with my unit(in regards to the burnt smell)...thankfully.  :mad:
I would really suggest one needs to build an attenuator that would match the input with the max output level.
For example, if the max output level is +20dBu and the max input level at minimum gain of the mic input is -5dBu, a 25-30dB attenuator would do the job.
Typically you would run measurements at about 0dBu output, and need to pad the mic input.
However, in your particular case, the MBox max input level with Pad is +24dBu and the max output level is +10, so you should have no problem.
 
Thanks for your reply Abbey...  :)

I haven't attempted to test the pre's again. I'd really love to get it figured out; every time I've tried this something has gone wrong.
Be nice to reliably measure the gear I build.  :eek:
 

Latest posts

Back
Top