channel crosstalk

[paulfrench]

on the gain knobs, but I was looking at channel 13 which has markings for high/low z. sorry for the confusion

so, the signal in the unused channel doesn't start to go away until I lower the gain knob to 20db or lower

also, on gigs we are using almost every channel, so instead of calling it the "unused" channel, it's better called "incorrect" channel I suppose

[WK154]

on the gain knobs, but I was looking at channel 13 which has markings for high/low z. sorry for the confusion

so, the signal in the unused channel doesn't start to go away until I lower the gain knob to 20db or lower

also, on gigs we are using almost every channel, so instead of calling it the "unused" channel, it's better called "incorrect" channel I suppose

To be sure your input signal is at 0 meter position and  for test purposes nothing is plugged in to all other channels. The adjacent or other channels only go to 20db on their trim knobs before you see meter activity? That means you have 20db of additional noise somewhere in the circuit. Which MF version are you using? V3 has different meter scales. We are just dealing with channel input meters to be sure. On the channel with the input signal make sure you are at 60db of gain if the input signal allows it. We don't want to test the input source just the preamps. A clean source will help.

[paulfrench]

I'm running the latest MF with the latest firmware update.

I have an old Fostex test tone generator kicking around somewhere, would that qualify as a clean source?

[sam.spoons]

I'm running the latest MF with the latest firmware update.

I have an old Fostex test tone generator kicking around somewhere, would that qualify as a clean source?

I'm running MF2 on a DL1608, I have noticed this but never tested it, maybe I'll have a look.

I also have a Fostex tone gen and yes I'd say it would qualify.

[Greg C.]

One thing to bear in mind is that the metering on the DL goes down to below -60dB which is not something you'll find on most analog mixers, so you'll never see crosstalk with those. High res metering is something you find on digital desks these days and you are much more likely to see noise and crosstalk. You're not hearing it because -80 to -60dB is extremely low level. More expensive larger desks will have less crosstalk due to greater physical spacing and possibly better shielding between the preamp circuits. So this is probably a non-problem problem. The easy fix would be for Mackie to change the metering scale to be less sensitive

[paulfrench]

Well said Greg C.: "non-problem problem".

When a potential bride tells us she didn't book because she and her mother noticed the crosstalk issue, I'll start to be more concerned. That's not happening.

[WK154]

Since I don't have MF3 running I can only speak about MF2. Mackie has a habit of messing up meters so until I install MF3 I can't give you values on my mixer. The real estate used to display this is totally out of proportion especially for something that Mackie claims has only 3 points that are valid. Here is the link to MF2 measurements.
http://cacophony.aspinock.com/index.php?topic=636.msg5512#msg5512
They may have changed the meters on MF3. The accurate way to find out what if any significance this has on your sound system is to measure it with a RMS meter and as Greg pointed out may well be below hearing levels. The accepted threshold is -80dBu (in critical listening but not in live sound environments where you're lucky to have a noise floor of 60dB SPL) which of course means  that it's not just a mixer issue but a complete sound system problem. Muting the test signal and listening to the other channels is of course the quickest way I know how to check any relevance to this. Ears do come in handy at times.

[Greg C.]

Well said Greg C.: "non-problem problem".

When a potential bride tells us she didn't book because she and her mother noticed the crosstalk issue, I'll start to be more concerned. That's not happening.

The metering on my Avid Venue stops at -60dB. That 20dB difference down to -80dB is a substantial amount of added resolution. Quite honestly, it's not good for much except demonstrating the shortcomings of the mixer 

[paulfrench]

looks like the meters in MF3 go down to -100

i did see meter activity slightly above -40, but it was inaudible even with the headphone at max, and faders at max.

[WK154]

This all comes down to the gain structure of all your equipment were the idea is to have all the max's aligned and the noise floor fall's were it may and in live sound it's usually well below your room noise floor. This was mainly to see if your equipment had a fault.