Hi - Got a proble, need advice please.....

[Rob the vocalist]

Hi all,

This is my first post onto the forum, I'm hoping for help with a current sound issue.

 

I run a Mackie PA (CFX 16 Desk, SRM 450 powered cabs, 1501 Subs). My microphone is a Shure diversity wireless system (Model TN4), the other 6 mics are wired.

 

Issue ;)

The built in FX unit on the mixing desk leaves somthing to be desired, so I decided to upgrade to an outboard unit and chose an Alesis Midiverb IV.

 

Patching in an bypassing the built in unit was straightforward as was finding/adjusting suitable vocal effects on the Alesis.

 

When standing next to the desk/Mic Rx all is fine, when I move away from the equipment I get a buzzing/whining noise which sounds like the mic is about to 'drop out' and lose signal. If I turn the Alesis unit off the problem disappears and I can walk quite a distance with no drop out/noise. The problem also disappears if I turn off my wireless mic. The prob only occurs when both are switched on (Alesis + Mic), the wired mics don't have any issues

 

Any advice appreciated :** laughs out loud **:

 

Thanks

 

Rob

[dominicgross]

The only thing I can think of off the top of my head is the cables your using for the midiverb.

 

Make sure they are balanced: overwise they may be picking up interference from the wireless mike?

[Solstace]

Welcome!

 

I'd suggest it's quite likely (From previous bitter experience) that the Alesis unit may be producing the interference that you are picking up - especially if the antennae are sat anywhere within a few feet of the Alesis unit.

 

Without knowing with your level of experience, or the particular model of mic/receiver;

 

Have you tried replacing the mic battery/batteries? Gets me every time, even in the West End. If you get radio-mic problems, ALWAYS replace the battery as the first port of call.

 

Still not working? Well, if you have the option of moving the antennae away from the receiver unit itself, (usually they are attached via BNC's) then you could run BNC cables and move them so that one antenna sits either side of stage, which in turn may get them far enough away from the Alesis unit to rectify the problem.

 

If you don't have the option to move the antennae away from the back of the receiver unit... Can you re-tune the mic and receiver to a different frequency? Does it only happen in one venue, or have you had it working in some but not others? I'm assuming you've racked the receiver with the rest of your mixing gubbins - if this is the case you could un-rack it and place it nearer the stage (well away from the mix position) and run cables back to the mixer (you've not mentioned a multicore...)

 

Giving a go within this very forum ought to provide you with some food for thought if you're still stuck for ideas - if not, please ask away :** laughs out loud **:

 

C.

[audio]

We had this problem with a cheapo reverb and our school trantec R/F mics, moving the antennae away, as solstace suggests, solved the problem.

Give it a go

[Rob the vocalist]

Thanks for the replies.

 

To answer the questions/suggestions......

The Alesis is rack mounted 1u above the Mic Rx (the mic is a Shure TN4 'True Diversity - the one with two ariels). For ease of transportation etc (+ setup), I'd like to keep the units racked together if possible).

 

Experience? I've been a gigging vocalist for around 14 years, however my experience in tech matters is limited.

 

Brand new mic battery has been fitted - no joy.

The ariels are fixed and can't be shifted to a different place.

I've tried taking the FX unit out of the rack and moving as far away from the Mic RX as possible (Which is about 2 feet due to cable length) - no difference.....

 

Balanced cables, hmmmm. Hadn't thought of this. I assumed that I could use normal patch cables (guitar signal leads), I assume I thought wrong?

 

Any suggestions on what type/make of cables to try??

 

Thanks again

 

Rob

[Chris L]

The normal balanced cable for this would be just a stereo/balanced (they are the same) 1/4" jack (like guitar leads).

Makes; go for something with good strain relief on the connectors.

 

Chris

[Andrew C]

The normal balanced cable for this would be just a stereo/balanced (they are the same) 1/4" jack (like guitar leads).

Makes; go for something with good strain relief on the connectors.

 

Chris

<{POST_SNAPBACK}>

 

Stereo cable should be two individually screened cores, balanced should be a pair of cores twisted together with an overall screen. I believe guitars are normally unbalanced. The jack plug you need for balanced use are TRS (tip, ring, screen), but the de-facto pro connector is the XLR.

 

As for makes I use Deltron or Neutric.

 

Edit

The MidiVerb 4 has two 1/4†unbalanced inputs and two 1/4†unbalanced outputs.

These provide three different (analog) audio hookup options:

 

Page 19 here, so no point using balanced cables!!

[Chris L]

Sorry, my mistake, I was drawn by the fact that a lot of jacks that are really TRS advertise themselves as stereo.

 

Chris

[BlueShift]

perhaps I missed this in the thread so far, but where is the interference coming through? is it the Alesis's output (eg. when you mute the alesis on the desk, does the sound go away) or is it the mic's output.

 

I am assuming it is the latter, in which case definately make sure the cables are balanced.

[Rob the vocalist]

When I bypass the Alesis the interference goes away, as it does if I turn off the radio mic. Wired mics work through the Alesis no problem.

 

Re cables, (getting a bit confused -sorry, I'm not much of a tech) regardless of the outputs/inputs on the Alesis being unbalanced, will balanced cables provide better shielding from the radio mic and help cure the problem?

 

Thanks again to all for the help

 

Rob

[Chris L]

Yes, they will provide better shielding.

If that's where the interference is being introduced, then it will solve the problem. But if not, it won't. :P

 

Chris

[Rob the vocalist]

Cheers, I'll give it a whirl

[bonny]

Yes, they will provide better shielding.

If that's where the interference is being introduced, then it will solve the problem.  But if not, it won't. :P

 

Chris

<{POST_SNAPBACK}>

 

I was under the impression that balanced cables can only help matters if both the input and outputs on the two devices you're connecting are balanced.

[Andrew C]

Yes, they will provide better shielding.

If that's where the interference is being introduced, then it will solve the problem.  But if not, it won't. :P

 

Chris

<{POST_SNAPBACK}>

 

I was under the impression that balanced cables can only help matters if both the input and outputs on the two devices you're connecting are balanced.

<{POST_SNAPBACK}>

That would be my opinion too. However, I am loosing the will to live & all the diodes down my lefthand side.... :P

[Chris L]

...have this terrible pain" (ish)

 

Ahh, the inputs on the Alesis are unbalanced, that ruins that. The best option is therefore just to move it as far away as possible from the radio source or try changing the frequency of the UHF signal/s.

 

Chris