Sort of CB related question & problem! Help Please

[chalkers]

Hi guys and gals,

Sorry for the bizarre question but I've hit a dead end and you guys are the only people i can think of that may be able to help. I've just purchased a large ex MOD mobile speaker array for announcements at our local village day and it only has a CB type mic input. Three wires; ground , audio & PTT. What I need to do is wire a bog standard wireless mike in, XLR, 1/4 Jack? the type you get from maplin or just a normal hard wired stage mic. Is it just a case of wiring in the mic between ground & audio and putting a permanent connection between PTT and ground so the mic is always live? Dont want to blow the circuits as I dont know the difference in output between Stage mics and CB mics. Basically can you wire a normal stage mic to a CB radio? Hope that makes sense?

Many thanks and kind regards,

Charlie

[cjay]

Makes sense and I think it would work but your problem is going to be pops, squeaks and buzzes over the speakers if you leave it 'keyed' all the time and don't mute the mike. (standard function on most if not all the wireless stage microphones I've ever used (used to 'do sound' for DJs, bands and some studio stuff))

I wonder if you could use one of the Bluetooth CB mikes for it, that'd have PTT capability.

Studio mikes tend to be 600ohm impedance if my memory serves, they can be 'balanced' for noise immunity over long distances and can need 'ghost' power which I think is usually 48V so it'd be worth checking the audio in pin on the connector to see if there's a ghost power supply.

[chalkers]

Thanks Cjay. The cordless mike has its own mute button and the base station for it has a mono unbalanced output which makes life easy. Will check on the phantom power, good point, hadn't thought of that.
C.

[chalkers]

Do CB mics in general require a phantom power?

C.

[cjay]

Generally not but there are that use power from the rig. Never run across one that uses 48V though, as far as I know that's a professional thing for studio use.

[darkone]

XLR out will probably be line level. You may well need to throw a 20 or 30db pad in line with the mic input.

[chalkers]

Thanks CJ, if i find out which wires are PTT and audio I'll check for any phantom power. Darkone, had a look and the out from the mic base station is a mono 1/4" jack. Can you please expand on what you mean by a 20 or 30db pad?
Cheers C.

[darkone]

The XLR line output will be much too loud for the mic input. You need to reduce it.

Reading for you:http://www.uneeda-audio.com/pads/

[cjay]

XLR out will probably be line level. You may well need to throw a 20 or 30db pad in line with the mic input.

Yes, of course. Did I mention it was a long time ago?

[kr0ne]

An XLR connector does not necessarily mean a line level output... although it almost certainly does mean a balanced output!

Unless there is some (powered) preamplifier built into the mic somewhere (possible with radio mics I guess, I don't really have any experience with them), then the output will be mic level.

It won't help with the PTT part, but probably the most versatile thing you could do would be find a few spare pennies to buy a cheap mixing "desk" and hook this in. I say "desk" but I'm really talking about those tiny things about the size of a video tape with only a very few input channels. You can usually pick stuff like this up really cheaply and they will allow you to connect pretty much anything you want - line level, mic level, instrument level, balanced XLR, unbalanced 1/4" jack, stereo phono etc. etc. etc.

[cjay]

From a radio mic receiver it's entirely possible it could be line level though it may be line, adjustable or mic level. Or switchable between the lot.

[kr0ne]

Makes sense...

[cjay]

It's the best thing about standards, there are so many you can choose from.

[kr0ne]

Yeah, that's why a desk of some sort is so handy for anything like this... it's kind of like a big super-adapter. Mixing multiple audio sources together is just an added bonus!