Shure Mic hookup

[Malcontent297]

Hi All,

New member to the forum and new to radios. Go easy on me guy's....
Is it possible to run a shure SM58 voice microphone with a Cobra 142GTL base?
Is there anything special I need to know or do to make it work?

Thanks,

Malcomb

 

[GnG8d]

That mic has an XLR output, but you'll need a pre-amp which most likely will take the XLR. Then you'll need to build a cable to go from the pre-amp to the radio. You'll have to decide on a pre-amp before you know what kind of cable to build.

 

[Robb]

Yes; I corrected the spelling on the mic.
Yes; it can be done as 359 pointed out.
Ham operators do it all of the time with their radios.
CBers are just getting hip to it as of late.

 

[Malcontent297]

Thanks 359 & Robb,

Darn, spell check corrected Shure, (Sure it’s Shure) and I missed it......:blush:
Thanks for fixing it for me... How embarrassing.........

359, do you have any recommendations for a pre-amp?
Where would I find one?
Are there any spec's I should look for?
I can probably handle making up the cording for it.

Thanks,

 

[Robb]

ART makes a tube preamp that sell for $30 @ 'Guitar Center'. It will work nice; but you will need to use the unbalanced output (1/4 inch Tip/Ring/Sleeve plug; not the XLR/balanced output) to go to the radio. The mic to the preamp uses a XLR cable; a 6 ft cable will work best. You will have to figure out the pinout on the radio to get it right. The 'audio' wire into the radio is the "+" from the mic preamp output; and the PTT on the radio is where to wire the footswitch to. You might have to build/buy a footswitch. Easier to buy -than to build- that part.

Be careful with the output gain of the mic preamp into the radio. If it is too high; it may damage your radio's audio chip. Be careful...

 

[mackmobile43]

ART makes a tube preamp that sell for $30 @ 'Guitar Center'. It will work nice; but you will need to use the unbalanced output (1/4 inch Tip/Ring/Sleeve plug; not the XLR/balanced output) to go to the radio. The mic to the preamp uses a XLR cable; a 6 ft cable will work best. You will have to figure out the pinout on the radio to get it right. The 'audio' wire into the radio is the "+" from the mic preamp output; and the PTT on the radio is where to wire the footswitch to. You might have to build/buy a footswitch. Easier to buy -than to build- that part.

Be careful with the output gain of the mic preamp into the radio. If it is too high; it may damage your radio's audio chip. Be careful...

Is that a 1/4'' stereo phone plug?

http://www.guitarcenter.com/ART-Tube-MP-Studio-Mic-Preamp-105798490-i1171932.gc



* Provides Superior Preamplification for: Microphones, Instruments and Line Level Sources
* Analog VU Meter
* OPL Output Protection Limiter
* Hand-Selected 12AX7A Vacuum Tube
* Variable Input and Output Gain Controls
* Provides over 70 dB of Gain
* +48 Phantom Power Switch
* Phase Reversal Switch
* XLR and 1/4" Inputs and Outputs
* Portable, All-Steel Construction
* Excellent as Tube DI
* Built-in Brickwall Limiting
* 20dB gain switch

ART Tube MP Studio Mic Preamp Specifications:

* Input Connections: XLR (balanced), ¼"TS (unbal)
* Output Connections: XLR (balanced), ¼"TS (unbal)
* Input Impedance XLR: ¼" 2K ohms, 840k ohms
* Output Impedance XLR: ¼" 600 ohms, 300ohms
* Maximum Input Level: XLR +14dBu
* Maximum Input Level, ¼" +22dBu
* Maximum Output Level: XLR +28dBu
* Maximum Output Level: " +22dBu
* CMRR >75dB (typical @ 1kHz)
* Frequency Response: 10Hz to 30kHz, ±5dB
* Dynamic Range: >100dB (20-20kHz) typical
* Total Harmonic Distortion (THD): <0.1% (typical)
* Maximum Gain:
* XLR to XLR 60dB (typical)
* ¼" to ¼" 44dB (typical)
* XLR to ¼" 54dB (typical)
* ¼" to XLR 50dB (typical)
* Equivalent Input Noise (EIN):
* XLR to XLR -129dBu (A weighted)
* ¼" to ¼" -105dBu (A weighted)
* Dimensions 5.0"H x 5.5" W x 2.0"H
* Weight 1.5 lbs.

ART Tube MP Studio Mic Preamp Includes:

power supply

 

[GnG8d]

Behringer also makes a tube type pre-amp for around $30 called the UltraGain MIC100. W2IHY also makes some stuff that will provide the pre-amp plus some processing, but it's more costly.

 

[WR0220]

A little clarification - using the 1/4" Stereo/TRS (Tip/Ring/Sleeve) jack would provide a balanced signal, not unbalanced. You need to use the 1/4" mono jack (Tip/Sleeve) if you want an unbalnced signal.

I prefer to use the XLR balanced signal throughout the entire chain up to the point of injecting the audio signal into the radio. It (and the TRS jacks) offer better protection against interference. Run an XLR cable from mic to preamp, and another XLR cable from preamp to radio. Convert the balanced signal to unbalanced by connecting the shield and audio - wires of the XLR cable to the common lug of the radio mic plug. Connect the audio + wire of the XLR cable to the audio lug of the radio mic plug. For the PTT circuit I use a single conductor shielded cable. Connect the conductor wire to the transmit lug of the radio mic plug and the shield to the common lug of the radio mic plug. You can terminate the other end of the cable several ways. The easiest would be to solder a N.O. momentary switch directly to it. I prefer a 1/4" mono inline jack. Then you can plug a hand or foot switch into it. If the switch ever fails you can simply unplug it and plug a new one in. I've been using the ART Studio V3 preamp for a couple of years now. It has several preset audio levels and individual input/output gain settings. The 600 ohm output matches nicely to several of the radios I have.

 

[Malcontent297]

A little clarification - using the 1/4" Stereo/TRS (Tip/Ring/Sleeve) jack would provide a balanced signal, not unbalanced. You need to use the 1/4" mono jack (Tip/Sleeve) if you want an unbalnced signal.

I prefer to use the XLR balanced signal throughout the entire chain up to the point of injecting the audio signal into the radio. It (and the TRS jacks) offer better protection against interference. Run an XLR cable from mic to preamp, and another XLR cable from preamp to radio. Convert the balanced signal to unbalanced by connecting the shield and audio - wires of the XLR cable to the common lug of the radio mic plug. Connect the audio + wire of the XLR cable to the audio lug of the radio mic plug. For the PTT circuit I use a single conductor shielded cable. Connect the conductor wire to the transmit lug of the radio mic plug and the shield to the common lug of the radio mic plug. You can terminate the other end of the cable several ways. The easiest would be to solder a N.O. momentary switch directly to it. I prefer a 1/4" mono inline jack. Then you can plug a hand or foot switch into it. If the switch ever fails you can simply unplug it and plug a new one in. I've been using the ART Studio V3 preamp for a couple of years now. It has several preset audio levels and individual input/output gain settings. The 600 ohm output matches nicely to several of the radios I have.

WR0220,
Thanks, I'm a picture/schematic kind of guy. That's exactly what I needed to see.
You lost me with the balanced and unbalanced, but I'll figure it out.
I have 3 Tube guitar amps at home and they all use 1/4" phono plugs so I have plenty of mono and stereo plugs around.
Is there any magic to the N/O switch? My guitar footswitches have buffers to keep them from popping when actuated. Will that be a problem for the radio as well?

 

[Robb]

The PTT switch will not make a 'pop' when broadcasting. At least, most radios don't.
No buffer needed. You want to use a momentary switch; not a full 'on/off' switch. I use a TASCAM foot switch that started life as a switch for a reel-to-reel tape machine. I got it used; think I paid $10 for it at a consignment shop.

 

[Robb]

The PTT switch will not make a 'pop' when broadcasting. At least, most radios don't. No buffer needed. You want to use a momentary switch; not a full 'on/off' switch. I use a TASCAM punch in/punch out foot switch that started life as a switch for a reel-to-reel tape machine. It has a momentary switch in it. I got it used; think I paid $10 for it at a consignment shop. It has a 1/4" tip/sleeve on one end; so I soldered an inline 1/4" female to the cable (as described in that graphic) for the PTT.

Easy to do.

If you get 'hum' in the transmitted sound using the balanced preamp output (which is correct - BTW); you may need to use a 1:1 isolation transformer there as well.

 

[WR0220]

The balanced to unbalanced signal conversion is pretty simple. All you do is connect both the audio negative wire and the shield of the XLR cable to a common ground point - the common/shield lug of the radio mic plug. This illustration may help:

How to Wire an XLR to a 1/4" Jack

Think of the 1/4" jack sleeve in the illustration as the common/shield lug of your mic plug.

A N.O. momentary switch of decent quality will do the trick for activating PTT. The N.O. means that the circuit is open when the plunger is at rest, and the circuit is closed when you depress the plunger. If you have the 1/4" mono inline jack and plug laying around you may want to consider using them, but you will still need to fabricate or purchase a foot/hand switch. Putting the 1/4" jack/plug combo in the circuit is personal choice but not mandatory.

Most preamps and mixers have a built in DI (direct input) box (also known as a matching transformer) so impedance matching between the mic and preamp/mixer usually isn't a problem. You do want to pay attention to the output impedance rating of the preamp/mixer you use though to insure it is a good match to the radio you plan on using. Otherwise (like Robb mentioned) you will need to use a DI box/matching transformer between the output of your preamp/mixer and the radio input.

If you are familiar with creating a daisy chain of effects between your guitar and amp just use the same line of thinking with the daisy chain you create between your mic and the radio input.

 

[GnG8d]

A N.O. momentary switch of decent quality will do the trick for activating PTT. The N.O. means that the circuit is open when the plunger is at rest, and the circuit is closed when you depress the plunger. If you have the 1/4" mono inline jack and plug laying around you may want to consider using them, but you will still need to fabricate or purchase a foot/hand switch. Putting the 1/4" jack/plug combo in the circuit is personal choice but not mandatory.

I got tired of chasing foot pedals around and bought some miniature momentary switches from RS and made a hand keyer from a AA flashlight housing. But if you are only keying a mic, a foot switch is pretty handy.

 

[Robb]

Put a piece of velcro on the whole back of the pedal - and 'bingo' - NO more movement.
Just so long as there is a piece of carpet underneath it...

BTW - if you read my signature; you will see just how much you can put in line. Some guys go a lot farther than I do - by a far cry. They use pretty exotic/expensive studio gear and get a real broadcast-quality sound. But what I have and use does very well without spending 1000's of dollars. If you have some outboard gear, some it might be incorporated if it isn't being used for anything else. A Behringer preamp and digital EQ isn't necessary; but it does help create a quasi- broadcast quality sound. So does the sonic maximizer...

 

[GnG8d]

Yeah, I riveted two foot switches side/side to a strip of aluminum, but I just got tired of looking for foot switches. If I was only keying a mic, a foot switch is fine. But I key a mic and two different amps, so it got hectic.