Author Topic: Noise on unconnected channels  (Read 736 times)

robmcl

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Noise on unconnected channels
« on: February 16, 2018, 04:48:07 PM »
My XR18 shows a signal on several channels that have nothing connected.  The "noise" on the meter disappears when I switch any channel to USB input, so that should indicate an issue specific to the combo jack inputs.
Ihave tried the initialize function as well as downloading and reinstalling the firmware (both 1.16 and 1.13) with no change
Anyone else seen this problem?   Suggestions on a fix? 

WK154

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Re: Noise on unconnected channels
« Reply #1 on: February 17, 2018, 05:00:35 PM »
I noticed that on your pic ch15 48V is on. Does the noise disappear if 48V is off? This would clearly indicate a Warranty trip to B... You could measure the Phantom power if you had a scope (DC is blocked) the AC component would be picked up in the preamp.
When in doubt KISS

RoadRanger

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Re: Noise on unconnected channels
« Reply #2 on: February 18, 2018, 02:50:13 AM »
Inputs that aren't connected will pick up crap out of the air. Just shut them off...

WK154

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Re: Noise on unconnected channels
« Reply #3 on: February 18, 2018, 03:07:26 AM »
Yeah RR but why pick on Ch 9,10,15,16 only? To bad the LR was muted that would have given more info.
When in doubt KISS

robmcl

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Re: Noise on unconnected channels
« Reply #4 on: February 18, 2018, 12:14:51 PM »
Thx.   Yes I had 48v on and off with no effect.   Read somewhere to turn it on and leave the unit powered on for extended "burn-in".  Was worth a shot (nothing to lose) but again no change.   LR muted/unmuted also no change.   At this point it seems to be a bad pre-amp and prob a warranty return.

WK154

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Re: Noise on unconnected channels
« Reply #5 on: February 18, 2018, 10:40:26 PM »
My guess is that 2 A/D converters (CS4272 two channels) bit the dust. Remember all visual indicators (meters) are derived from digital data (after the A/D). In any case a Warranty return.
When in doubt KISS