Rob the vocalist Posted May 3, 2005 Author Share Posted May 3, 2005 Hmmm.......... so giving balanced leads a whirl will make no difference, despite improved shielding?? Moving the unit away from the Rx is not possible.... Have I reached a dead end?? Rob Link to comment Share on other sites More sharing options...
david.elsbury Posted May 3, 2005 Share Posted May 3, 2005 Well, since you have narrowed the problem down to the Alesis FX unit, maybe you could get another FX unit... but I'm guessing that that's not one of your options.David Link to comment Share on other sites More sharing options...
Rob the vocalist Posted May 3, 2005 Author Share Posted May 3, 2005 Not really an option, nothing wrong with the unit (Plus I've had it less than a week)Just the compatibility with/interference from my Shure wireless mic - which was unexpected. Link to comment Share on other sites More sharing options...
bruce Posted May 3, 2005 Share Posted May 3, 2005 Not really an option, nothing wrong with the unit...apart from it screwing up your radio mic :P(Plus I've had it less than a week)Does this mean you just bought it? Any chance of swapping it for something else? Some random thoughts: 1. What happens when you don't have the fx unit in the audio circuit, but still powered on. Do you still get the interference? I'm guessing you do...2. Does the Alesis have an external PSU? Have you tried swapping that for another of similar spec? PSUs - especially switch mode ones - can be noisy.3. Are both units CE approved? CE approval should (but often doesn't) place limits on both emissions and susceptibility to interference. Not that it helps much.... :P4. Have you tried re-routing the cabling and moving PSUs?Just the compatibility with/interference from my Shure wireless mic - which was unexpected.<{POST_SNAPBACK}> So we have 2 units, stuck right beside each other in a rack, which interfere with each other. The interference is probably enhanced because they're so close together. So the solutions are obvious. You either (a) move them apart, or (b) change one of them. You say (a) is not an option - why? Is the rack really so small? One last idea - this is probably a complete red herring - but try taking them out of the rack, setting them up in the same configuration, stacked up with some bits of paper between them, and see if the problem goes away. I once had a system (which used a cheapie 1U mixer) which had terrible hum problems, which were caused by an earth loop through the rack mounting bolts. Isolating the chassis from the rack solved this... Bruce. Link to comment Share on other sites More sharing options...
paulears Posted May 3, 2005 Share Posted May 3, 2005 I think that the problem is probably harmonics from the clock frequency generated in the alesis. Distance will prove it. un rack the Alesis and move it away slowly, if the problem goes away, then it's a proximity effect and distance (annoying though it is) is the only solution. What's probably happening is that one of the harmonics falls close to your operating freqency - giving the front end of the shure a hefty dose of signal that either swamps the agc, or simply desenses the input sufficiently to make your mic signal appear to be very low and noisy. I have a yamaha dsp effects unit that can't live in the same rack as a sennheiser rx. Just one of those things really. Although the Alesis has a metal case, there are loads of 'holes' in it and the screening isn't good enough to stop the radiation. SO - try the distance test first. Then try a frequency shift, quite a big one if you can. paul Link to comment Share on other sites More sharing options...
Rob the vocalist Posted May 3, 2005 Author Share Posted May 3, 2005 Lots to try in the last two posts, thanks for the help guys.I'll try all the stuff and report back, (not tonight though - footy's on!) Link to comment Share on other sites More sharing options...
Chris L Posted May 3, 2005 Share Posted May 3, 2005 Just because I am interested, would there be any way to 'isolate' the unit from the radio mic signal, like earthing the rack? (would that do it?) Chris Link to comment Share on other sites More sharing options...
Simon Lewis Posted May 3, 2005 Share Posted May 3, 2005 Stopping the breakthrough will depend on the physical construction (metal, plastic, presence of small holes etc.) of the two devices, the earthing topology (whether it adheres to AES48 - aka the "Pin1 problem"), the selectivity of the RF front end, the degree of RF supression on input cables / connectors etc., etc. Even then, the sheer physical proximity (effectively the RF is picked up in the 'nearfield' of the generating device) means that the usual rejection methods may fail. Therefore, in many cases, an earthed rack simply will not cure the problem. Simon Link to comment Share on other sites More sharing options...
2Loud Posted May 3, 2005 Share Posted May 3, 2005 Hi There, Just an observation, last time I used an Alesis was ages ago and from memory all Alesis units that I've seen or used have an outboard power supply that is AC-AC step down and not the normal AC-DC that you would have on the radio mic.When you say that you bypass the verb the interference on the mic goes away, are you bypasing the unit by unplugging the in's/out's or by some other means?What I suggest you try is to spearate the power supplies cause they are more than likely stuck in the back of the rack on top of each other, failing that it sounds as if you could have a faulty earth somewhere.Alll the best. Ric Link to comment Share on other sites More sharing options...
Rob the vocalist Posted May 3, 2005 Author Share Posted May 3, 2005 I'm bypassing the unit electronically (using the built in bypass function on the Alesis), it stays plugged/patched in. The noise disappears when its bypassed. Rob Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.