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Author Topic: Connecting this Mic to Icom IC-706MkIIg  (Read 752 times)
W1CEW
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« on: September 29, 2006, 03:02:57 AM »

So I have in my shack this mic:
http://www.eham.net/data/classifieds/images/202951.jpg

It is a studio mic, a Marshall MXL V67.  Pretty flat response.  Coming from it is one of those three prong studio connectors (from the phantom power supply).  Also using a Heil footswitch for keying.

Short of just buying a W2IHY box to connect the mic to the rig, is there some relatively inexpensive way to adapt this to the IC-706?  

Thanks for any suggestions!

Chuck

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KZ1X
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« Reply #1 on: September 29, 2006, 05:01:02 AM »

Looks nice.

It's easy to hook up ... very easy, in fact, *IF* you have the right connectors, the tools with which to attach them, and are handy with electronic hardware assembly (plus maybe a bit of actual interfacing, some resistors, maybe a transformer).  It would take 15 minutes, tops.

If you're looking for something off-the-shelf, that might be harder.  
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K0BG
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« Reply #2 on: September 29, 2006, 06:21:03 AM »

You have to be rather careful making your own RJ45 plug for the 706 (or 7000). There is 8 vdc on the mic input (pin 6), and 8 vdc on pin one. Short out pin one, and the internal 8 v regulator will fail instantly! Short out pin 6, and you'll eventually lose the surface mounted series resistor.

Icom sells an adapter for connecting a mic with their standard 8 pin, round connector, and I would suggest you buy one. Sure is cheaper than the tool to properly crimp on the RJ45.

By the way, the RJ45 plug IS NOT the same design as an RJ45 meant for telephone connections, albeit they look the same.

Alan, KØBG
www.k0bg.com
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N9XTF
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« Reply #3 on: September 29, 2006, 09:27:45 AM »

Alan,

I have made a number of mic pigtails for my MKIIG using Cat5 RJ-45 connectors, that work perfectly.  What is the difference in ICOM's version.  I may need to rethink what I have done.

Thanks,

Doug
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W1CEW
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« Reply #4 on: September 29, 2006, 09:37:22 AM »

http://www.mxlmics.com/condenser_mic/mxlv67g/mxlv67g.htm

Here's another pic.  Sure is a nice looking mic, ain't it?  So it has an impedance of 200 ohms.  The input for the 706 is 600 ohms, so probably need a 3 to 1 transformer of some type?

There are mini equalizers short of a W2IHY, yes?

I work in computers so should be able to finagle a RJ45 somewhere and pigtail it!

Thanks for all the thoughts on this.

-Chuck


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AA4PB
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« Reply #5 on: September 29, 2006, 09:53:13 AM »

According to the specs, that is a condenser mike that requires a 48V (+/-4V) phantom power supply. You won't get that kind of voltage from the IC-706. You'll need to build an interface that includes the phantom voltage, impedance matching, and signal voltage level matching (a preamp perhaps).

By far the easiest would be to purchase a small mixer. Many mixers provide much less than 48V phantom power so make sure you get one that provides that much voltage.
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W1CEW
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« Reply #6 on: September 29, 2006, 10:52:19 AM »

Yes, I should have mentioned that I already have the phantom power.  That's all set, and I had this working quite nicely using a W2IHY unit and my last rig, which was the IC-746.  Coming from the phantom supply is a studio connector, but I supposed it could as easily be a DIN or RJ-45 for that matter.  Probably I'd have to plug the Heil switch into the rear to key it, though.
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AA4PB
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« Reply #7 on: September 29, 2006, 03:46:36 PM »

The 3-pin connector on the mike is called an "XLR".

You will need to be VERY careful to isolate the phantom power from the radio with capacitors because the 48 volts will kill the radio.

Unlike RF systems, it is very common in audio work to use a low impedance source (the microphone at 200 ohms) to drive a higher impedance load (the radio at 600 ohms). The only question is whether the microphone has a high enough signal output to drive the radio. The easiest way to check that is to try it.

The microphone (and probably the output of your phantom supply) is a balanced system. Neither signal wire connects to ground. You will upset the phantom power if you try to ground one side. The radio on the other hand is an unbalanced system with one microphone lead referenced to ground. You will need an isolation transformer to connect the two sides. You will need a good quality transformer if you expect to maintain the frequency response of that microphone and you will have to be careful that it doesn't pick up hum from magnetic fields. Jensen makes high end transformers with mu-metal magnetic shields.

You could also try a professional audio direct box (DI). These are used to connect unbalanced outputs from music instruments to balanced microphone inputs. If you get a transformer type (i.e. NOT an solid state type) then they work quite well in reverse to couple your balanced microphone to the unbalanced radio input.
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W1CEW
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« Reply #8 on: September 29, 2006, 05:11:28 PM »

Hi Bob,

OK, that's right, XLR, I knew that. :-)

Well I'm about convinced that the easiest shortcut to getting this going right would be to just get another W2IHY box, because when all is said and done, I might want to be able to tweak the audio characteristics anyway.  Unless a Berringer mixer would magically solve the balanced/unbalanced issue, which I'm guessing not.

In which case, maybe I'll put the whole thing up for trade: Boom mic, shock mount, phantom power -- for a Heil Pro headset.  Wacky?

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