Mixer problems – sound bleeding to other channels

Thanks to Howard for this question:

Hi Kenny

I get “bleed through” in my mixer when I source an ipod (or any mp3 player/laptop) into my mixer. I connect to Line 3 input and “crank it up” (the source output) to match the sound levels of the other channels.

I can’t stop the sound from bleeding through, even if the channel slide is all the way down. It bleeds through the fade selector switches too. The only way to eliminate the bleed is to turn down the source, but then the output is not high enough to match other sources (CD). Help!

Howard

Hi Howard

If sound still bleeds through when the volume of that channel is pulled right down it usually means that there is a problem at the mixer side of things rather than a problem with the iPod, laptop or mp3 player.

With mixing desks, two things immediately come to mind which can cause sound to bleed through where it shouldn’t.

The first possibility is that your mixer has poor circuitry or a problem with its circuitry.

Poor circuitry is a common problem in less expensive mixing desks, but even many good quality mixing desks can start to perform less efficiently after they get to a few years old. If the problem is a cheap mixer, there is no real solution except to live with the problem or buy a better quality mixer.

But if you use an expensive mixer that’s just become a bit ropey after a few years of wear and tear and gigging, you could ask your local electronics engineer to give it a service and that may be enough to fix the leakage. But don’t just hand it in to your local music shop and ask them to do a service on it though – ask to speak to the engineer first and tell him exactly what the problem is and ask him if a service will actually solve that particular problem (no point in paying out money needlessly).

In some situations a solution to leakage could be to buy a noise gate and insert the noise gate between the mp3 player and your mixer. You would then set the threshold of the noise gate so it will “gate out” any unwanted noise. However noise gates are really designed to stop unwanted noise such as hiss from devices which are supposed to be silent when switched off. From what I gather, you want your mp3 Player to still continue to play music while you have the volume turned right down. If this is the case, then a noise gate won’t help.

The next possibility is that your mixer is absolutely fine – it’s the mixer settings that are the problem.

This is especially true if you have a more expensive and complicated type of mixer with lots of different routing possibilities. The leak could be caused simply because the settings for that channel and/or the cabling for the mixer output are not set correctly and it’s bleeding some sound to areas of the output it shouldn’t.

You say you plug your mp3 player in to channel 3. That immediately suggests to me that something may not be correct because an mp3 player requires TWO input channels because it is stereo (a left channel and a right channel). I would expect you to have to use TWO channels on your mixer for your mp3 player (eg channel 3 for the left sound and channel 4 for the right sound). But if it’s a DJ type mixer you have, the channels may ALL be stereo, so although your mixer calls it “channel 3”, channel 3 has two stereo inputs. If so, then that’s ok.

Mixers, especially the more expensive mixers out there, often have the ability to route the input and output signals in a variety of different ways. So if you are using a monitor-out from your mixer to your amplifier instead of the standard main-out, this could cause leakage.

Similarly if you use the headphone-out from your mixer to your amplifier (which you should NEVER do by the way!) then that could cause leakage. in fact if there is anything set up in your mixer whether it’s an input or an output that’s not connected the way the mixer needs it to be connected according to its operating instructions, you can expect problems.

This is especially true if you don’t have all the input signals properly trimmed, or don’t the pan on each channel set correctly, or the output from the mixer to your amplifier isn’t coming from the correct output.

If everything attached to your mixer is connected and set properly, then the leakage is most likely to be down to the first possibility above (poor circuitry).

If you know what you’re doing, you may be able to sort the problem by doing something as simple as buying a can of compressed air from your local electronics shop and air-dusting the channel fader. That will remove any dirt and grime that could be stopping the fader getting right down to zero. However don’t even attempt this if you’ve never done it before and don’t know what you’re doing – these compressed air cans have a habit of malfunctioning from time to time and squirt a little bit of liquid when they should really only be throwing out air. Liquids and electronics are a BAD combination(!) so if you’re not sure, leave it to a qualified engineer, even if it does sound like a pretty simple job…

Kenny

UPDATE++UPDATE++UPDATE++UPDATE++UPDATE++UPDATE++

Thanks much Kenny!
It is a Gemini PMX1600 mixer used with a PV500 amp. It has always worked fine, but I’ve only recently attempted mixing in a laptop or iPod to it, so the bleed thru problem may be inherent in this unit. I use a mini to split cable to connect to the stereo input of Ch3 (or 4, doesn’t matter, same effect). I have started to get an intermittent white noise problem too (sometimes goes away when I cycle power to the mixer, but not always). Looks like it’s time for a new mixer…..
Howard

Hi Howard

Yes, the Gemini is a DJ mixer and generally DJ mixers tend to be not as good quality as recording studio / live music type mixers.

The white noise problem you mentioned may be an earth loop problem, especially if you notice it more when you have your laptop plugged in.

Some laptops have a known problem with earth loops but don’t always give off the type of buzzing you would expect to hear with an earth loop problem. Instead the laptop sounds as if there is interference coming through it which sounds a bit like low frequency white noise that’s breaking up a bit.

You need a ground loop isolator placed between the laptop and the mixer to stop the noise (around £15).