D/I inst input question- one hums one doesn't

mixsit

Well-known member
Last few sessions we've been experimenting with AKG-240 phones to mic the upright bass. Yeah ;)
Anyhow, I started with a Chameleon 7602 and it worked out well enough. But the D/I at its min gain, was running hot enough to where I thought that pre could be getting into saturation, so we swapped tonight to a RNP.
Now -both at similar levels, where the 7602 is dead quiet the RNP has a not loud but notable hum. So, pulled up the manuals, the 7602 1/4 in is balanced (I didn't know this -or at least had forgotten) and the RNP is unbalanced.

The phones go TRS extension cabled to the D/Is, and in both cases signal only comes from the 'left ear.
So I'm curious what's going on here. I thought the Chameleon being balanced might be doing common noise rejection? But if it were, shouldn't it be picking up from both ears as well?
It's getting late, an' I'm confoosed :facepalm: ;)
 
If anything I'd guess you're getting the difference between the two ears, which could leave much less desired signal (maybe why you're not overdriving anymore) and so the noise is greater in comparison. That noise might not be coming from the phones themselves - you're right about the noise rejection in the balance connection.
 
If anything I'd guess you're getting the difference between the two ears, which could leave much less desired signal (maybe why you're not overdriving anymore) and so the noise is greater in comparison. That noise might not be coming from the phones themselves - you're right about the noise rejection in the balance connection.
Thank you for your help.
I could see that first idea being true- but for with either pre I'm only getting sig from one ear- which is where I loose it trying to figure this.
To compare the two's gains as they use different scale methods for the indicated input gains, for about the same record level, RNP was at ' +15 ' , the 7602 indicates ' +55 ' ( I think I need a refresher on that but IIRC it means the source's sensitivity-
The 7602 was patched through a 160xt as well (not compressing-) Had +20 extra make up gain to play with in comparing the too last night. The only thing that comes up at all on that rig is the normal hiss' ..and room noise :D
 
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