channel crosstalk

[paulfrench]

Anyone else experienced this?: audio signal from one channel is showing up on another meter on the mixer. The level shown on the improper channel is minimal. I'm pretty certain that this is a physical rather than software issue as it happens with adjacent channels on the DL1608. By that I mean audio from keyboard channel 15 "leaks" into vocal channel 5. At first, we thought the mic just needed a shock mount, but later found that this signal crosstalk happens even with the vocal mic unplugged.

[Wynnd]

Extremely low levels of crosstalk might be normal.  What you seem to be describing doesn't sound normal.  Call Mackie, but you might want to try resetting the mixer first.  If that doesn't work, it might be a bad mixer and need to be replaced.

[paulfrench]

Thanks for the reply. I just updated to the latest Master Fader, which prompted the firmware update. Would the firmware update have done a reset as you recommended?
I'll have to put some signal through the mixer to test it out tonight.

[WK154]

If you can believe the Mackie specs (I don't) on the DL1608 you should not see any signal on the adjacent channel. Crosstalk is rated at <-120 db and the meter scale is stated to be -90 dB (implied dBFSC) at the bottom. That leaves 30 dB before you should see anything. This is measured with the input signal of 1 Khz. Not clear if adjacent channel is shorted (pin2-pin3 on xlr ) or just open. You either have a lot of RF or a defective DL.

[RoadRanger]

The crosstalk between a used channel and one that has nothing plugged into it can be quite high and this is normal. Having a proper impedance device plugged in lowers the crosstalk from other channels bigtime.

[WK154]

The crosstalk between a used channel and one that has nothing plugged into it can be quite high and this is normal. Having a proper impedance device plugged in lowers the crosstalk from other channels bigtime.

I'm well aware of that  hence my question about what's plugged in an of course Mackie doesn't state their test conditions.

[paulfrench]

So, I've done some tests with a mic plugged in. The signal showing on the unused channel registers from -80 to about -60, and happens on most of the pairs, but not all. Also, the signal is visible, but I can't hear it. I listened with the unused channel soloed, and also muted the plugged in channel (even muted the plugged in channel was passing visible signal to the meters), and turned the plugged in channel down while cranking the unused channel. No sound from the unused channel showing "ghost" signal. Weird. It's showing on the meter, but it's not audible. So, I guess if it can't be heard, it isn't there, right? Maybe this is like the old tale "if a tree falls in the woods......."  or "Currently residing in the WTF file." Hmmm.

Other than this weirdness, the mixer has been really great through 50 gigs this year.

[WK154]

Let's approach this another way. You stated that you did about 50 gigs with the DL and it never was noticed before? Or you are now experiencing this recently? Without going into a rigorous test setup what have you found over your years 50 gigs that changed?

[paulfrench]

Somewhere in the middle of the summer, I noticed this happening during setup. My first thought was that it was the vibrations from the keyboard player hitting his keys and the sound transferring through his vocal mic mounted on the keyboard stand. After unplugging the vocal mic, the meters were still showing low level reaction to his playing. So, I'd say I first noticed this after 20 gigs. Nothing in the setup changed in that time, other than the ideas I tried as possible solutions. ( trying new cables, shock mount for the vocal mic)

Tonight is the first time I've taken the time to explore this further. It's very odd that it shows up on the meters, but can't be heard, at least in the headphone output. I'm next going to try monitoring through the main xlr outs. I didn't have time to set that up tonight.

[paulfrench]

RoadRanger, I will try again tomorrow using balanced inputs on the adjacent channels and see if that changes anything. Thanks.

[Ampli]

Sound more that the gain knobs are not turn to minimal (of the channels that aren't in use)
This is also discussed somewhere here in the past

[ijpengelly]

I've seen this happen before, haven't noticed it as much recently with being able to hide unused channels, as the original posted suggested no actual crosstalk is occurring, just that MF was showing a reading. It wasn't even necessarily on adjacent channels. I think it was / is a quirk in the software. I'll have to see if mine still does it.

[WK154]

Been there before but you can't find anything in this mess. So here it is again with the iPad docked and V2.1.1 of MF the readings should be ~-40 on the meter scale when the trim is at 60 dB gain (max) and the input in this case is a 1 Khz signal adjusted to 0 on their input channel meter scale. There is no adjacent channel issue they all respond the same. There is about a 5-7 dB reduction for 100 ohms or 0 ohms compared to being open. To get no visible meter signal  you need to cut gain on adjacent unused channels back to 45-50 dB on the trim pots. If not used reduce gain (trim pot) to 0. If you using 3.01 MF then leave the digital trim at unity. You won't see the digital trim change on the input meter anyways. No quirk in the software AFAIK.

[paulfrench]

 ijpengelly: I'm Glad to hear someone else has seen this. Yeah, my feeling is the same:some software quirk. As long as nothing audible is happening, I'm not gonna worry about it.

WK154: reducing the gain pots lessened the issue, but I had to go below unity to totally eliminate it.

Thanks for the input guys.

[WK154]

ijpengelly: I'm Glad to hear someone else has seen this. Yeah, my feeling is the same:some software quirk. As long as nothing audible is happening, I'm not gonna worry about it.

WK154: reducing the gain pots lessened the issue, but I had to go below unity to totally eliminate it.

Thanks for the input guys.

I don't think you understood so I clarified the previous post. Please re-read. "Go below unity" on what?