Microphone Preamp

[Sonwatcher]

Does anyone use an external microphone preamp ? Not phantom power but a preamp. If so what does it add ?

Thanks

 

[WR0220]

I use an ART Studio V3 preamp with a Heil GM4 mic on my IC-7000. It matches the impedance between the mic and radio, adds (up to) 60dB gain and the 12AX7A tube adds a nice warm tone to my audio. I also like the 'OPL' circuitry that controls the peak of the output signal and prevents clipping.

 

[Robb]

gain, g a i n, Gain, GAin, GAIn, GAIN, G A I N!!!
Get enough transistors in a progressive series - with a source to be amplified - and gain must rise before it has a chance to square wave (distort) the input.

Oversimplification? Mebbe...

Recording studio preamps that I have used in the past were used to make all of the subtle audio nuances of any given mic 'pop out'. It makes them far more sensitive, and the recorded product has more depth, character, and 'drama' - for lack of a better word. The limited usable bandwidth of frequency response in CB/Amateur radios - of course - doesn't come close to 20-20khz average range of human hearing. It's more like 250-3khz. But it still can be improved with amping, and making transistors stepping up the gain by cascading them - can do that.

Matching the impedance between the mic and the input is also a necessary part of this process, which is done with a transformer and transistors. Actually, tube preamps are more desirable - because they amplify 'even' harmonics (2nd, 4th, etc harmonics) as opposed to solid-state/transistor devices. Solid-state devices tend to amplify the 'odd' harmonics (1st, 3rd, 5th, etc - harmonics). 'Even' number harmonics are more appealing to the ear, this is a major reason that the best recording studios still prefer tube preamps - BTW.

IMO - it is also the same reason that tube linears sound fuller and richer than solid state linears. But the downside to tubes is an overabundance of harmonics, whereas transistors lack the same amount of harmonic content. A 'cleaner' sound is not always the more desireable sound. And of course, the harmonics they do inject into the sound is the odd harmonics.

Oversimplification? Mebbe...

 

[WX2MIG]

Actually, tube preamps are more desirable - because they amplify 'even' harmonics (2nd, 4th, etc harmonics) as opposed to solid-state/transistor devices. Solid-state devices tend to amplify the 'odd' harmonics (1st, 3rd, 5th, etc - harmonics). 'Even' number harmonics are more appealing to the ear, this is a major reason that the best recording studios still prefer tube preamps.

And probably why the D-104 has that slight edgy bite to it's sound, the built-in pre-amp is transistor.

The warmth of a tube pre-amp is also effected by the tube used, the 12AX7 being the most popular pre-amp tube in both voice and instrument amplification, the actual tube used will have a bearing on the tonal quality it produces. The most dramatic difference would be heard between a vintage NOS RCA Black Plate, and a new production tube from China. The Svetlana tubes from Russia run hot and cold, some produce a nice tone, some run a little harsh.
If you get a tube pre-amp, shop around on eBay for New Old Stock 12AX7's from RCA, Phillips, Sylvania, GE, or even the old military JAN tubes as they were all made by one of the American electronics firms.
If your amp has twin tubes, look for matched pairs....

 

[Beetle]

Does anyone use an external microphone preamp ? Not phantom power but a preamp. If so what does it add ?

Thanks

Never used one; never needed one. Don't care if I don't sound "warm", only that you can understand me.

There seems to be a move to "broadcast-quality" audio which I don't understand. If you want to sound that "good" , get a job at a broadcast station. Ham radio is about communicating, not broadcasting.

 

[Sonwatcher]

Never used one; never needed one. Don't care if I don't sound "warm", only that you can understand me.

There seems to be a move to "broadcast-quality" audio which I don't understand. If you want to sound that "good" , get a job at a broadcast station. Ham radio is about communicating, not broadcasting.

Thanks for the negative post. I was just asking because I had read about some mics operating better with a preamp and wondered what they did . Sure it is about communicating and experimentation. I ask questions so I can learn . As far as the quality received by a preamp that was shared above I don't see anything wrong with trying to improve something. Yes, it can go overboard but there are improvements everyday in Ham radios. Doesn't make them bad . Just possibly doesn't appeal to everyone . The guys above may like better sounding audio. You don't . They're happy, you're happy. To degrade someone who's taste and appeals are different doesn't make them bad. It's life. Everybody's different . If you're working within the boundaries of the rules anyone can experiment .

 

[Robb]

The need to get better audio is out of the need to communicate better. A well-established modulation is far easier to hear - and vice-versa - to be heard. Also, it is because it is available and not so hard to understand or put together for anyone's station.

It is also the need for business to make some more money. Not denying that. But I think it is beneficial in the long run. Don't we appreciate our better radios with better audio character? A radio that receives well and can throw ultra-clear modulation is still most desirable to own and operate - isn't it? Isn't that thought "good radio"?

Many of the new Ham rigs coming out have all kinds of audio digital signal processing - "DSP". Some guys buy and use mixers for the parametric equalization they have - as well as being to amplify their mics. The 'phantom power' on board the better mixers also provide for high-end condenser mics to be used. A compressor is also a nice touch when on sideband, FM, or even AM for that matter. It all helps being more understood. Isn't that good in itself?

I appreciate talking to stations that sound great and are easier to understand. I want my station to do the same. The Icom IC-718 - that I recently bought - comes with a DSP unit installed. At least mine did when I bought it a few months ago.

I still have some great mics that I am going to try out on my HF rig - left over from my days back in a band. An Electro-Voice 757, an AKG D112, and even a Shure SM-57. Why not? Especially since I already have them - all I have to do is match them to the input impedance and give them an adjustable preamp. Should make my modest IC-718 sound as good as it can...

 

[Sonwatcher]

Thanks guys. It helps me understand a little bit what all the device does .I have read in different places where some mics need a preamp and my guess from what you shared that would be for the gain and impedance match.