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Great Mic Sound for your CB or Export Radio-final

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  #1  
Old 11-02-2010, 03:33 PM
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Arrow Great Mic Sound for your CB or Export Radio-final


Previous article: http://www.worldwidedx.com/installat...-part-4-a.html


Summing up . . .

So by now we know what mic and preamp we want and have either purchased a Heil cable or built one out of stuff we already had. Hopefully, we also have chosen a really fine mic and didn't spend too much. Some Hams have spent $3000-5000 on their audio chain alone, incorporating a mixer, high-end preamp, reverb unit, compressor, noise gate, and limiter. The simplicity and cost of a professional mic and preamp alone will do more than enough to get real hifi sound without resorting to this extreme. Don't even bother going farther than this simple arrangement, unless you want to take the time and toils to understand professional sound systems and recording gear. It can take a lot of cash and time too and little benefit will be realized - unless you just want to compete with others that have gone the distance and feel you want to explore some more.

There are usually two knobs on a preamp; one controls the mic gain into the preamp and the other controls the output the goes into your radio. When setting the gain on the preamp input; be sure to start with the mic level @ 12 or 1 o'clock. When adjusting the output control, just keep the output knob/level barely cracked open. Too much output power from the preamp into your radio can also pop the preamp that is already in your radio. Most radios have a mic gain control; keep it set fairly low as well. Just use and watch your modulation meter so that it doesn't exceed 100% modulation. You can do this by simply giving it the 'ahhhhh' sound into the mic from 4 inches away - and then adjust the preamp output to ensure 100% modulation. This is an important thing to do; as nice audio needs to be clean in order to be effective with the gear you are now using.


Other items to be considered . . .

A push to talk switch - either by hand or foot - is necessary. You can take a simple $.50 SPST momentary switch and wire it to the jack on the cable as Heil does with their cables (that is how I made my own cable - BTW). Or - even wire it right into the radio's mic plug itself and then drill/mount it in the mic stand if you want. I use a TASCAM tape recorder cue footswitch that is spring loaded and already has the 1/4 inch male plug/cable on it; it looks just like the MFJ footswitch. But MFJ and Heil make both the footswitch and handheld push to talk switches. They cost around $30-40; but you can really do this portion for next to nothing if you want to save the bucks.

A desk mic stand will also be necessary when using a pro mic. There are many different kinds/models; most any will work. A simple $15/new or $5-10/used mic stand will do; no real need to spend more than necessary. Some hams gos as far as using a overhead extendable/retractable - which is nice but will cost quite a bit too. I use a simple desk mic stand with my condenser mic and paid only $15, it works just fine and I am quite pleased with it as it is.

Another item that I consider necessary, is a mic wind screen. They cost anywhere from $15 to $40 and work equally well. They are a low tech device that gives a high tech result. That fine mic you've chosen will benefit greatly by having a windscreen that will remove the 's', 'p', and 'b' wind blasts. This will keep your audio as smooth as silk and won't break the bank. Recommended. You can also build your own out of some panty hose and a needlepoint form; but it is really easier to buy one right off of the shelf for the amount of money you have to spend ($15) vs the work to make your own. Mount it 1/2 inch away from the mic and then you can get up close to the mic without blasting it with wind from your mouth as you speak. Don't even bother with the foam style wind screens; they just don't work as well - even for a dynamic type mic.


Options . . .

One can opt for a small mic mixer - like the Berhinger 4 channel mixer - instead of a stand alone mic preamp that we've already discussed. This will offer a two band EQ, phantom power for your condenser mic, and has an 'effects loop/'buss' that allows for other devices to be inputted with your sound with (you can adjust the wet/dry level that will control the percentage of effects that you put into this loop). Such as adding a reverb unit, a compressor, limiter, or noise gate. It is advisable to run the the compressor/limiter/gate after the mixer; then run the reverb unit through the effects loop ('send' and 'return') in the mixer for best results.

These mixers doesn't have 'tube emulation' for that nice tube sound; but the preamp it provides will be very clean with a lot of gain. You will only need to use one of the four channels it provides; but the buss it has as an extra allows for using more outboard gear (compressor, reverb, etc...) They only cost between $50-60 and are necessary if you do plan to expand your audio capabilities. It will use the same cord you made, as it has a balanced output. You can also use the mixer's built-in head phone output to monitor what it sounds like as it is going on the air.

It is the outboard audio gear that you might use with the mixer that will get expensive. A nice and modestly priced reverb unit would be a Lexicon for $200. Or you can opt for the lower priced Alesis Miniverb and spend less than a $100. A compressor/limiter/gate made by Alesis can be found for $125/used and will provide dedicated functions that can improve the audio. But these are the lower cost items; as many high end audio components for a professional sound ramps up very quickly. The best condenser and a decent preamp will still be 90% of what will be heard - go with a quality condenser and forget the rest. Or you might find yourself as an audio junkie spending thousands on the audio gear and only a fraction of that on the radio.


Conclusions . . .

IF you have done this all correctly, the regulars that you talk to daily will notice a vast change in your sound and say so. If you made the cables and footswitch yourself; then you probably did this project for less than or about $150-200. Some may spend more; but that is too easy to do. If you stuck to my recommendations for mics - you should be on target with the budget. I hope you had as much fun as I did building mine and enjoying the compliments of a very clean audio transmit that lacks coloration - yet an abundance of natural sound. It should sound like you are standing in the same room with them - if conditions are decent and their receive is capable of it.

Many Cobra/Uniden radios are capable of high quality audio transmit. Many Export radios are too. If your radio doesn't transmit as well as it could after these improvements; then chances are it wasn't very good to begin with. Regardless of what radio you do use; the improvements made should be very noticable. If they aren't you can opt to use another radio or have it looked at by a tech to see if it is performing as it should. Most techs can also improve the transmit audio as well as the receive audio bandwidth.

I use a different cable hook up with the same mic and preamp for my Ham radio. The Kenwood has an ACC2 plug on the back that will bypass the onboard Kenwood mic preamp. An external preamp will always work better and cleaner. Some late model Icoms and Yaesus have a similar ACC2 plug as well. So, if you do get your Ham license, you can also use these concepts and materials on a Ham rig with great results too. Until then, you can enjoy transmitting on CB - with a legal and better audio - for only slightly more money that you would have spent for that Silver Eagle or Turner+3.
Enjoy . . .





Top:
Behringer 4 channel mic mixer

Bottom left to right:
MFJ foot switch
Mic stand
Wind screen
Attached Images
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Old 11-02-2010, 04:55 PM
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Nice artical Robb.


T23

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  #3  
Old 11-16-2010, 12:12 PM
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Best to have the windscreen 1/2 to 1 inch away from the mic.
Easy to build this screen, and they work quite well too.
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Old 11-21-2010, 06:26 PM
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Default Enhanced Audio

Thanks for the good read, Robb.

I stumbled accross enhanced audio quite by accident about 15 years ago and have been doing it ever since. I had a pretty decent radio...AR 3500....and wanted to add a little quality to my voice. Came accross an old EV 664 large element dynamic and tied it to the switch of an old stock mic. Worked great.

Folks I talked with said it sounded good but it didn't have that big audio presence. I think what they meant was that I didn't have that loud, overdriven crappy audio that a lot of folks wanted. Please realize I am talking 27 meg AM here. I have always monitored myself with a second radio so I knew what I sounded like. Then I incorporated a D.O.D. 512 effects processor and I was off. What fun I had and still have.

I now have another 664 mic (outstanding 50 year old mic) and am using an ART Studio V3 tube pre into a Lexicon MX 200 Dual Processor into a Yamaha MG 102c mixer. Got a couple of other mics I change up on occasion...a Nady ribbon with the voodoo labs transformer change out, an AT 2020 large diaphragm condenser and a Electro Voice Mercury 911 1950's Elvis mic plus a few others to play around with. This all goes into my Kenwood TS-440S. The Kenwood audio combined with these components is outstanding. The tube preamp set with the input at 75% and out put at 50% into the processor set with full compression and very slight reverb makes my station sound like what you hear when you are listening to a good FM station. I have used it on SSB but it just flat shines on AM.

Thanks again for the posts, Robb. It is a great hobby and it is ever-changing. I am glad to see the articles posted as I have been asked many times how I get thet big, smooth, studio audio sound. I just say I got a new mic!

Mike

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Old 01-04-2012, 06:50 PM
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Thanks.

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Old 01-14-2012, 05:06 AM
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Quick question for you Robb if i might?

600ohm stock handheld mic (as per stats on the FT-950)

replacement mic Audio-Technica ATM61HE (i see entry level Heil mics are 1000ohm)
ELEMENT Neodymium Dynamic
POLAR PATTERN Hypercardioid
FREQUENCY RESPONSE 50-18,000 Hz
OPEN CIRCUIT SENSITIVITY -51 dB (2.8 mV) re 1V at 1 Pa
IMPEDANCE 600 ohms
OUTPUT CONNECTOR Integral 3-pin XLRM-type

will be using the new Heil CC1-XLR-Y-BAL cable (to eliminate a history of rf)

600=600 so should be no issues correct?
i'll be using the radios internal dsp for now
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Old 01-15-2012, 07:11 PM
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There is a lot of info missing from this thread.
Every radio is not deisgned the same for audio response and if AM and SSB are included, there are large differences between the modes.
.
On AM it depends on the frequency response (audio bandwidth) of the radio's audio circuit as to what you can 'force' through it with any outboard equipment and mke.
Same thing for SSB.
To expand on this, use SSB for an example.
A peticular radio has a 2400 hz wide filter bandwidth.
The audio input circuit cuts the low end audio sharply at about 200 to 300 hz.
The SSB filter begins it's sharpe rolloff at say 2600 hz or 3db down the curve.
This would be the basic 'window' you have to drive audio through (300 to 2600 HZ) no matter what is done to try to widen it out with addon equiment.
To enhance this radio situation, the input low audio response needs to be lowered in frequency to at least 100 hz.
Then a mike with lower end output needs to be used.
On the upper side of the audio response, the filter would need to be changed to an upper limit beyond 3000 hz.
Then you can use outboard equalization to custom full per the voice, the mike and the room acustics.
On AM mode the radio ususally has a wider response but may still be limited by the same input audio circuit frequency response design that is used for SSB .
If done carefully, a stock radio can be enhanced to a noticable degree within it's limits.
.
Lastly, the receiving end radio has to have nearly equal overall audio response to recover what it received from the enhanced transmitter setup.
This requires a wider audio receive frequency response and a qualty speaker , not some little 3"er.
As a last comment to show when it is 'over done', many drive with too much low end audio on SSB and this becomes hard to tune in the midsts of a SSB roundtable. With a ham rig, I can cut off the low end of the objectional station with my reveive EQ. and 'fix' the problem. The station doing the excess low end EQ. waists his effort on me for that part of his audio efforts.
Remember that what you hear from any radio is compairative/subjective to another radio.
On commerical AM radio your hearing bandwiths as high as 8000 hz.
On FM your hearing out beyond 10k.
You can't do this on CB or ham without causing a commotion from other users who will complain about the bandwidth you take up given the channel and frequency spacings (room) involved. So there can be a down side if done to excess.
Good luck.

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Old 01-15-2012, 09:41 PM
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Nice write up! It was very well thought out. I'll have something to think about.
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