A question about basic audio processing

[cjruger]

I am interested in learning about audio processing. Read a bunch of threads about it here. Im wondering if the following will work

I have for my mac, protools and garage band to play with some audio processing. If i use a simple vocal mic running into the computer thru the software, and out of the computer into a audio cable the runs to the ppt mic for the cb. The audio wire on mic is cut and attached to the audio out of computer and the shields are attached to each other. If i key up mic and put audio into vocal mike will this work?
Also is some sort of amplification needed?
What will this sound like compared to a d104 desk mic?

Sorry if im way off here im still trying to figure it out

 

[Robb]

Yeah; you can. You will need a few things to do it right.

First, getting a mic plug for the radio; don't hack up a working mic as you may need it in the future.

Second, you will need to get a momentary switch to use as a push-to-talk switch. Another inexpensive part.

Third, an audio xformer (can be bought at Radio Shack) so that the high level output from the computer will allow the signal through and get the impedance where it needs to be for the radio's input.

In addition, you will also need some mic cable that has shielding in it so that you don't get hum in the line as well. This will go between the radio input and the computer output; so you will need to use/get the appropriate 1/8" plug for the sound card will require.

Wiring it up right will be found in the pinout of the radio's mic plug. You will need to go to CB tricks and look up your radio then find out where each pin goes.

Should work well if you can get all of your ducks in a row . . .

**EDIT**
http://www.worldwidedx.com/installa...-mic-sound-your-cb-export-radio-part-1-a.html

 

[Captain Kilowatt]

Should work well if you can get all of your ducks in a row . . .

And THAT is the crux of it all. The output from the computer is typically a line level output and will cream the microphone input amp in the radio. You need a way to reduce the level out and simply turning the sound card level will not do it as there will be too much HISSSSS or HUMMMMMM by the time you get it low enough. You need a pot or fixed attenuator. As for the transformer, year Radio Shack may have one but it is far from optimal but you can try it and see. IIRC the RS transformer is only a 1Kohm to 8 ohm ratio. Typically you would want 10K ohms to 500 ohms or thereabouts with the 10K side on the computer. Experiment and don't blow anything up.

 

[Robb]

And THAT is the curx of it all. The output from the computer is typically a line level output and will cream the microphone input amp in the radio. You need a way to reduce the level out and simply turning the sound card level will not do it as there will be too much HISSSSS or HUMMMMMM by the time you get it low enough. You need a pot or fixed attenuator. As for the transformer, year Radio Shack may have one but it is far from optimal but you can try it and see. IIRC the RS transformer is only a 1Kohm to 8 ohm ratio. Typically you would want 10K ohms to 500 ohms or thereabouts with the 10K side on the computer. Experiment and don't blow anything up.

Perhaps that is Canadian for 'crux'.

In any event; this is so. But not outside of the realm for any radio hobbyist to accomplish. It is relatively simple to do so long as a small dose of patience is used. The Jensen xformer is the preferred part; but I imagine that the computer's 'line out' into to a suitable impedance xformer can now be had at Guitar Center. Or even online if one looks for one, since computer audio oriented gear is far more commonplace now.

 

[cjruger]

Thanks guys, although this is sounding a little over my head, ill give it some thought

 

[Captain Kilowatt]

Perhaps that is Canadian for 'crux'.

In any event; this is so. But not outside of the realm for any radio hobbyist to accomplish. It is relatively simple to do so long as a small dose of patience is used. The Jensen xformer is the preferred part; but I imagine that the computer's 'line out' into to a suitable impedance xformer can now be had at Guitar Center. Or even online if one looks for one, since computer audio oriented gear is far more commonplace now.

I fixed the typo before I even saw your comment above about it. I hate fat fingers and a small touchscreen on the phone. New bifocals don't help matters either.As for doing it sure it's easy to those that know how. There are also two ways to do it. Make it work and make it work while following the rules of level and impedance matching hence my mention of the transformer from Radio Shack. Unless they have a different xmfr that 1K:8 ohm unit is far from ideal. It will work but why not do it better if you can. In my years in broadcasting I saw a LOT of audio stuff that "worked" but would make any professional in the business cringe. I am not saying we need to be professional just that there is a better way to skin a cat.

 

[Robb]

Lo and behold there it is . . .

Whirlwind ISOXL Line-Level Isolation TransformerISOXL B&H Photo

http://www.jensen-transformers.com/ln_out.html

 

[cjruger]

So if i were to look online or ebay what would i search for? That is the only step im not really sure about

 

[cjruger]

Beat me to it. So that has an audio jack on the
Back side that the computer feeds and what goes into the pinned side?

 

[cjruger]

If i were to do this, how improvement over a d104 desk mic would i see if any?

 

[Captain Kilowatt]

Lo and behold there it is . . .

Whirlwind ISOXL Line-Level Isolation TransformerISOXL B&H Photo

JENSEN TRANSFORMERS, INC. - LINE OUTPUT TRANSFORMERS

Those look half decent even to my critical standards.

I would use them myself. Jensen is well known in audio circles and is not bad. Myself I still have a stash of Hammond audio transformers of various impedances, some nridging transformers and some impedance matching. I also still have some Radio Design Labs modules for impedance bridging and level adjustments. They run off a wall wart and are super clean. Even have a mike amp or two as well from RDL and a couple balanced to unbalanced modules mounted on an XLR connector and nased om the TL072 opamp. One of these days I should get everything together and do something worth while with them.

 

[Captain Kilowatt]

If i were to do this, how improvement over a d104 desk mic would i see if any?

It depends what you want to do. There is nothing wrong nor great aboit a D104. A D104 is just another amplified mike ( some versions ate not amplified) that has earned a reputation beyond reality. Kind of like the Bird meter. At one time I actually used a D104 with processing gear. It sounded GREAT.

 

[psycho]

Nothing like making CB radio complicated. Buy a nice radio and tune it up properly.....find a good sounding mic and be happy.
If Buford T Justice and the Bandit could have so much fun with crappy radios/antennas, it isn't that tough.

 

[cjruger]

Im getting bored and nothing is ever good enough for me. I always need more... More power, more radio, more antenna, more AUDIO. Its not like i fire up the base unit to have deep and meaningful conversations with people i dont know

 

[KM3F]

What you need to know about your project is the radio will only pass an audio band width just so wide so there is a limit to frequency level balancing you can do.
For example if the low frequency 'roll off' is at 300 hertz you can't force 100 hertz through to pick up more bass as if there was no roll off.
Same on the high end.
Most radios have a band pass filter in the audio stage at some point that sets this band limit up by design.
Also the mike you use has to have a somewhat flat response across the band width or the radio has to be able to pass the processed added boost in the sections where you want it to occur.
If you don't pay attention to these parameters you won't get all that could be gotten out of the effort.
Be aware that on air opinions will range all over the spectrum as to what sounds good and what does not except for some setting that results in distortion or excess in some part of the spectrum.
Some of the reason is how well the other stations receiver reproduces your audio. It may be through a tiny little 3" speaker that cannot reproduce very much bass fidelity so the report is you need more bass when he just cannot hear what you all ready have.
So that's one reason you will get differing opinions
CB channels being 10 kHz wide will suffer from enhanced audio if you widen out the band width. It's bad enough now with just amplified mikes turned up to high, and no other mods. It's called bleedover!
There is a lot more to it but lets stop here.
Good luck.