Total posts : 45366
Well, This begins to answer my own question concerning advantage of having a 222. I can’t pretend to understand exactly what it is an Inovonics 222 specifically does, I think a little inkling of comprehension is wriggling to the surface…
Although the following (from which I selected these excerpts) is considerably over my head, it did help to (just barely) begin to get a grasp on the advantages of having the 222… and thought maybe someone else might be interested in it as well…..
The following excerpts from http://www.nu9n.com/am.html
The Percentage of Modulation Used
This is a major issue with the AM mode. Since AM is inherently an Amplitude Modulated mode by design, the carrier modulation will be directly proportional to the “Loudness” of the perceived audio relative to the carrier strength……
….If the carrier is under-modulated, the resulting audio will be light and subdued. On the other hand, if the carrier is over-modulated (above 100% negative peaks), distortion will quickly set in. If the negative modulation peaks can be limited to under 100%, then the positive peaks could be above 100% without distortion!…
…This is where “Asymmetrical Peak Limiting” built into modern AM processing comes in handy! Again, the average male voice is asymmetric in nature. This means that when examined on an audio spectral analyzer, the amplitude peaks will be slightly higher on one side of the plot as opposed to the other. This is why proper “Phasing” of the audio is critical! We always want the positive peaks to be higher than the negative peaks in amplitude since the negative peaks cause distortion when modulated above 100% at the transmitter….
…With modern AM processing where built in asymmetrical peak limiting is employed, we can manage the negative peaks at about 95% while letting the positive peaks travel well above 100% while still satisfying the transmitter with clean output. It’s like having your cake and eating it too! Of course, like anything else, there are some purity issues and tradeoff when using real aggressive peak-limiting. There will always be a fine balance between low distortion and aggressive peak limiting. The trick is finding the balance that will satisfy both sides of the equation – Loudness vs. Cleanness. A little bit of peak limiting will go a long way, so don’t get too carried away!
Inovonics 222 Processor
For those on a tight budget like me, I personally like the Inovonics Model 222 AM processor. This AM processor has a pre-emphasis network, a low-pass filter (either at 9.7kHz or 5kHz), a tight asymmetrical peak limiter, and filter overshoot compensation. Also, the “Positive Peaks” control can be adjusted for a maximum of 130% positive peak modulation relative to the negative peaks! All features are bypass switchable You can find the 222 at Broadcast Supply Worldwide (BSW) for around $550.00….
…If you cant afford an AM processor with built-in pre-emphasis but you would still like to simulate an NRSC 75µs Pre-Emphasis Curve (seen below in red) using a 1/3 octave EQ, you an achieve this by examining the following graphs and simulated EQ settings that I have provided below in Figures 7 and 8: (graphs shown at http://www.nu9n.com/am.html ).. The EQ values used (above) will simulate 75µs NRSC pre-emphasis very nicely!
I suppose you need a expensive scope to simulate a NRSC pre emphasis curve as shown there.. and have a clue to start with. Nevertheless I found the article to be interesting. Hope someone else did too.