Using Mobilepre to check my preamp
 

I'm a bit new to this and am trying to use Avid Mobilepre to see why my custom-made preamp has developed a hum. I'm using a M-Mobile Avid Mobilepre MK II. I've found the Mobilepre drivers and will update them on the laptop. Do I need the Avid pro tools too, to install Mobilepre to do the test, if I'm using Audacity to see and save data or just ignore it? I don't have the CD and have looked for the software, but without luck.
I've connected the XLR cable left and right (one at a time, seperately) from preamp out to Mobilepre in. None of the buttons in from are depressed. Gain on XLR in (left or right) is turned all the way up to maximum. A signal went from preamp, thru the Mobilepre, to laptop via USB. Audacity (V 2.0.6) is set to Mobilepre as the input source. It records but at a low volume. The data's useable. Here's a screenshot of the left xlr being played back. Am I using the best settings in audacity to record a hum?


I'm using these tests to isolate if the hum is coming from ground loops, components or another source.

Am I using the best settings and is there a better way to do this?


Screenshot link:

https://imgur.com/a/pMYhmr6

https://imgur.com/a/pMYhmr6

Re: Using Mobilepre to check my preamp
 

Welcome to the DUC. You should not need Pro Tools to troubleshoot this.

"I've connected the XLR cable left and right (one at a time, seperately) from preamp out to Mobilepre in." This is incorrect. Doing it this way means you are feeding a preamp out(line level) into a Mic-level input. You should use a cable with XLR at the preamp output and TRS at the MobilePre input.

"Gain on XLR in (left or right) is turned all the way up to maximum. "Again incorrect, or an indication that something is not working correctly. Feeding a line-level signal into the XLR input SHOULD be causing it to be extremely over-driven and distorted.

Repeat the test using the proper cable and start with the MobilePre GAIN all the way down. Set the preamp gain to give the proper meter reading on the preamp(and let us know what that preamp is). Once the preamp gain is set correctly, bring up the MobilePre gain enough to give a decent recording level into Audacity. If it still doesn't sound geed, try plugging the mic into the MobilePre XLR input and verify the mic works(and tell us what mic it is)

Re: Using Mobilepre to check my preamp
 

Thanks for correcting my process. I run some tests this weekend.

Re: Using Mobilepre to check my preamp
 

One question: Is the signal strength the same going into the Mobilepre at the XLR front inputs the same or different as the 1/4" inputs in the back; because it says line-level does it mean its being amplified before even turning the gain knob?

Re: Using Mobilepre to check my preamp
 

Usually(some manufacturers have their own ideas of how things should be:rolleyes:), it means a 20-30db pad is added, but GAIN knobs still work(why ask this when you can test it for yourself?:o

Re: Using Mobilepre to check my preamp
 

I don't want to introduce gain from Mobilepre to recording to the laptop. How do I do this? Also is there a spec for the minimum and maximum gain coming from the Mobilepre?