ABOUT Compressors - Xmit Audio Chain

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WBear2GCR:
About Compressors -

The way that almost all compressors work is somewhat counter-intuitive unless it's been explained first.

Imho, given a choice a "soft knee" peak limiter is preferable to a compressor for Ham xmit audio...

The compressor works by first boosting gain while sitting around, then reducing it when presented with an input signal! So, if the compression ratio is set high, the effect is to turn the mic gain all the way up!! When you talk, it turns the "mic gain" back down in proportion to the input signal's level...

It tries to keep the level constant, and high.

The higher the compression ratio and level the more it tries to keep everything at the same level (also time constants play a role here too...but we can ignore them for now).

IF you use heavy compression, it should in fact keep you from overmodulating - but the resulting audio probably won't be pleasing.

OTOH, a peak limiter does nothing until presented with a signal near a threshold. Once passing that threshold, it reduces gain sharply to keep the output signal from going beyond a proscribed maximum. Usually it will permit ~3dB of output change for an input change (above the threshold) of several 10s of dBs...

In summary:

- Light compression can keep your average modulated levels up and if you move around on the mic, keep the variation in level less.

- Peak Limiting will prevent overmodulation no matter what, but have very little effect otherwise.

Many of the commercial products for pro audio and broadcast audio perform both functions, compression and peak limiting. However not all compressors have peak limiters. Some do and some do not have adjustable thresholds (and other parameters) for the limiter section. Caveat Emptor.

          _-_-WBear2GCR

David, K3TUE:
Based on all I have heard and read I anticipate a need for the following in my audio chain:

Microphonium
Phantom Power (for condensor mic potential)
Mixer
Limiter (this seems essential)

And the addition of the following would be nice:

EQ
Compressor

I was looking at the behringer UB-802 Mixer with a Behringer VX-2000 a while back.  The VX-2000 seems to have been replaced by the VX-2496.  But now I see that the Behringer MDX-2600 has 2 channels AND a limiter, which would make it an all-in-one solution for the above list of needs, except it does seem to be missing 48V phantom power).

QUESTIONS:
1) Does anyone see some essential audio-chain component I forgot?
2) Does anyone have any experience with the MDX-2600?
3) Am I just totally off base and should be looking at something else.

I ask all of this because I would like to make sure I get something decent, keep my conponent count low, and make sure I have not missed anything.

Thanks.

WA3VJB:
David,

Is there something that says you have to have a condenser microphone?

Lots of good dynamics out there. Let me know price range and I can make some suggestions.

David, K3TUE:
Quote from: WA3VJB on May 09, 2006, 07:20:43 PM

Is there something that says you have to have a condenser microphone?

Lots of good dynamics out there. Let me know price range and I can make some suggestions.



Nope, the point was just to keep my price down and my options open.


I have considered condensor mics based on what I have heard and read (much on eHam) and the number of nice mikes at affordable prices ($200 or less) that are also condensor:

   Marshall MXL-990 Mic
      This seems to be noted on eHam as perhaps one of the best cost:performance condensor mics in this price range
   Behringer B-1
      Behringer is much maligned in the music community, but I am not making music, and many seem to like this, and I have heard quite a few which sound quite nice
   Studio Projects C1 Microphone
      I have heard recording, but none on the air, but it sounds nice to my ears


Of course, I would not ignore any of the following, which I hear come highly recommended, but seem to cost a bit more (around $350):

   Sennheiser MD-421 II
      Many have said they like this, but not as many seem to keep it
   Shure SM-7B
      I think W2DTC uses this, and he has a good sound
   Electro Voice RE-27 N/D
      I have heard so much about the RE-20, and then started reading that the RE-27 N/D, while not a successor to the RE-20, is even more suited amateir AM use


I have a couple of mics that will get me going just fine (I hope):

   Astatic D-104
      Too popular to not be worth trying, and many I have heard sound fine
   Turner 22X
      I just liked the way it looked, but don't have a clue what it sounds like

WA3VJB:
OK David, I should have also asked you what kind of transmitter this is coming together with. The choice of microphone is the EASIEST to avoid its being the weak link in the chain, but past a certain point you might not hear much difference.

SO, do tell what you're going to be running there, OM, over over

(Oh, and since you're a neighbor I can probably arrange some loaners)

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