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Looking for help expiermenting with mic and preamp

C

cjruger

Active Member
Aug 13, 2012
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After reading Robb's write up on Hi fi audio for cb, I want to start expiermenting. I'm looking for help wiring up a dynamic omnidirectionl radio shack micto run into my base setup. I have 2950dx and an older cobra 29gtl. I'm going to try in in the cobra.
My plan is to start with a preamp, I think the preamp built into my peavey 112 acoustic guitar amp will work. It has 1-4" and xlr jacks in and out and phantom power capable.the manual says it can be fed into rack gear or voice processor.
What I need help with is how to wire up the cord out of preamp into the cobra mic jack. I know i need to wire a switch in also.
Can I use the 1/4 jack mic or do I need xlr mic?
If I can use the 1/4 cable, how do i splice it into the 4 pin cobra connector? As in which wire go where

Any help is apreciated
 

Forgot to reply to your PM; sorry.

You probably could use the preamp; but why bother if you don't use a decent mic? That is the whole point, to use a mic that has a very flat response so that your voice audio is a more accurate representation of reality. I say this because many popular power mics skew the freq response quite a bit. Not to mention you won't need to use an equalizer on the mic likw you would for a cheaper/less capable mic. Recommend either a Shure SM-58 or one of the MXL large diaphragm condenser mics; around ~$40 for either choice/used.

You will have to wire up a cable that adapts the output of the mic preamp. You will use the audio hot and connect it to to the audio wire on the Cobra. You will also have to fashion a push-to-talk switch to actuate the transmit function in the radio. If you read all of those articles, it even shows a schematic in how to wire up a 4-pin Cobra radio. Might want to read the last couple of articles once again.
 
Ok thanks,
Just want to use the mic i have to see if i can even get this working , then will look at a better one.
I studied the diagram but am confused as to what the bottom left diagram is showing. Is that the xlr to cobra plug? If so where does the 1/4 switch jack wire go to?

Eta after reading it a few more times i think i got it

So would the better mic and pre amp i have be better than my d104 tug i have?
Ultimately I would like to run thru audio software on the computer and eventually find a how to to mod the radio to have the wider band width
 
so i found a shure sm58 for 40$, i attempeted to wire it to the radio with some but not good sucess. It is xlr in to the amp but i only had a 1/4 jack mic cable to run out, so i wired that to the 4 pin connector via Robb's instructions for the xlr cable, it did somewhat work when transmitting but i cant get it to work well. it would feed back to the speaker in the guitar preamp. I tried several different ways of wireing it but could get it to work right. so I ordered a couple xlr cables to modify and attempt again.
 
So does that box replace the need for a preamp? You can run the shure sm58 into that and into the radio with nothing else?

Grogan said:
Not sure of what your budget is but http://onairdesigns.us/ has some nice stuff to make your conections and even keying the mic easy. I have one and use it today.
Shure PG-48, Berhinger XEYNX 802 mixer and the box from on air designs.....
Click to expand...
 
Update:
I used the line out on the pre amp instead of pre amp out and it works great, I talked to a station on am and ssb about 50 miless away and said it sounded great, it needed a little more lows but really sound good.
 
So what output level from the preamp looks the best into the mic jack?
The manual for my preamp i have has these options. the 1st did not work well, had to turn everything way down and reports were didnt sound well, the second seemed to work well. the last,(xlr out) havent tried yet but will when the cable comes in. as far as the output levels what is best for the radio?


Preamp Output: 1/4 jack
Load Impedance: 1 K ohm or greater
Nominal Output Level: 0 dBV, 1 V RMS

Effects Send: 1/4 jack
Load Impedance: 1 K ohm or greater
Nominal Output Level: -10 dBV, 300 mV RMS

Direct Output: (transformer balanced) (xlr jack)
Load Impedance: 600 ohms or greater
Nominal Output Level (Post EQ): -3 dBV,
0.7 V RMS
 
Last edited:

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