Making good sound - How to

[AB1GX]

-If you don't sound good no one's gonna listen-

What's the rules for using a dynamic mike?  Mine's about 450 Ohms.  Do I need to load it with a 450 Ohm resistor when connected to a high-impedance input?

How about an Anechoic booth? earphones?

I guess a little compression/equalization wouldn't hurt either, right?

[W1DAN]

Hi:

Now you ask the loaded question!

There will be many ideas on this subject.

Mine is:

Most mic preamps do not load the mic..they are high impedance and do not use a terminating resistor. Mic amp circuits are easy to build too.

Send that into an equalizer to make the mic sound the way you and others like it as well as to provide pre-emphasis to compensate for the average receiver's rolloff.

Send that to an audio limiter to prevent hitting more than -99% modulation.

Some people (like me) use an old broadcast multiband processor, others just use a D104. Both work well.

Now for other opinions......

73
Dan
W1DAN

[W1GFH]

-If you don't sound good no one's gonna listen-

This is somewhat true. But don't feel you'll be ostracized if you're not "hi fi".  Nothing wrong with a straight D-104 into a stock transmitter to produce respectable, hum-and-distortion-free audio, if that's your choice.

What's the rules for using a dynamic mike?  Mine's about 450 Ohms.  Do I need to load it with a 450 Ohm resistor when connected to a high-impedance input?

Most high impedance inputs require a higher signal level than is produced by a typical low impedance mic. Some people use a matching transformer in this case. Or they add a preamp to boost the input level.

How about an Anechoic booth?

If you have significant room echo (i.e. people tell you you sound like you're in a barrel) then adding some drapes and carpeting will help. Otherwise, soundproofing may not be worth worrying about.

earphones?

Some people enjoy wearing them all the time. Others only use them for critical tests.

I guess a little compression/equalization wouldn't hurt either, right?

Check out:

http://amfone.net/Amforum/index.php?board=51.0

[Bacon, WA3WDR]

It depends on the mic and the quality of the transformer (if used).  With a dynamic mike, a resistor load will reduce level and roll off the highs a little bit because of leakage inductance.  The right value resistor should be OK.  Once I had to put something like a 68K resistor in series with a capacitor (about 220 pF if I recall) across the hi-Z side of an input transformer to tame a 20 KHz peak in the transformer.  

Then again, a larger value capacitor there with no series resistor, and maybe a low-value resistor in series at the low-Z side, might produce a peak around 3 KHz that would improve clarity.  Experiment with it.

[steve_qix]

Sound Good - depends on your definition of "good".  It's VERY subjective.

I think good is 10Hz to about 6 or 7 kHz frequency response (for hi fi Amateur) with very low distortion and SOME, but not too much, compression/limiting/processing.

If the transmitter will modulate a 400Hz triangle wave CLEANLY, and also do a square wave of the same frequency, it's probably technically pretty good !  This is my ultimate transmitter test.  Every rig I own has to pass this test, along with the requsite frequency response test.  And, it has to modulate at least 150% in the positive direction.  But, again, this is one person's way of doing things.

Mics?  Large diaphram condenser mics rule the day (at least in my shack!).  A Behringer B1 is cheap and sounds AWESOME, and is directional - reduces any noise "behind" the mic.  Next would be a small-diaphram condenser mic.  Then the RE-20 broadcast dynamic.   The difference between the RE-20 and the Behringer is quite dramatic when heard over a very good transmitter and a good quality Modulation Monitor / headphone setup.   The RE-20 is GOOD, the Behringer is EXCELLENT.  The difference is the flatness of the frequency response, and the extended low end of the condenser.

More food for thought, I guess :-).  But, honestly, I would not bother with a cheapo dynamic.  Get a cheapo condenser.  Radio Shack sells (or I think they still sell) a condenser element for a few dollars, and it is QUITE good.  Used one for about 30 years until I finally bought the Behringer.  Most people cannot tell the difference between the 2 mics on the air.  Even in the headphones, they are close.  The condenser elements must be protected with a good pop filter !!!

Fun stuff

 

Steve

[WD8BIL]

Your station's sound is an extension of YOU.
Make it sound the way you want it to. This means, of course, a good off air monitor is required.
Many will tell you you need more this..... less that......
If what you hear in your monitor is what you want, leave it at that.

[flintstone mop]

I have heard excellent Tx audio from a modified Heathkit DX100 and a plain Jane D-104. No limiters, no expensive mics. It's your choice. A good way to adjust your station is to Tx into a dummy load and with a good audio recorder, record the the audio from the receiver. Make sure the Rx is in the wide position.
If you would list your equipment we can figger out how to turn it into a system. Your Class E Tx, if it follows designs from the folks on this forum will not be the limiting factor. And UNfortunately some folks have not trained their ears to hear subtle differences in audio. OR they are trying to adjust AM audio using the lower SSB audio from their transceiver.
There was a sound man at the Church I was attending that cut all bass off below 100 cycles on the audio board. To him bass was a rumbling sound that didn't belong in a music sound system. The sound system was supposed to "augment" the service NOT dominate. I was in between those two sound levels and loved those huge EV speakers and the 1 kilowatt bank of amps. It was a nice sounding room and the Pastor would always ask to turn it up on those Gospel songs.
OK enough about Church........sorry
Don't be toooo concerned about your station. We'll help out. And thanks for being aware of all the ways to make AM happen.
Fred