Inovonics 222

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kc2ifr:
Wondering if anyone has used this AM processor and what did ya think?
Thanks in advance.

Bill

W2XR:
Hi Bill,

I have this processor, and I find that it is superb for use with conventional plate modulated AM transmitters. It is user-adjustable in terms of allowing for symetrical or asymetrical modulation; asymetrical modulation in the positive direction is adjustable to 125% or better. It is a very clean sounding unit, and really increases the density (loudness or average level) of the modulation, largely due to the carefully controlled compression ratio between the audio input and limited audio output. Older limiters, particularly of the tube variety, do not exhibit the same level of control of the audio as the Inovonics, with the result that occasional peaks will slip through and overmodulate the transmitter.

As such, the 222 also provides very tight control of the negative-going peaks.

It also provides user-selectable NRSC preemphasis, so you can provide the same HF boost as mandated by the FCC for commercial AM broadcast stations. If you don't like the NRSC EQ, defeat it by the front-panel switch and use your own EQ curve from an external equalizer.

Note that I also have an Orban Optimod-AM 9100A multi-band processor. This is one of the best processors ever made for modern AM transmitters, and it employs a sophisticated clipping scheme to maximize the control and density of the modulation without the clipping sounding offensive, in addition to a superb AGC/limiting function. However, many plate modulated rigs cannot easily pass the clipped output waveform of the Orban, due to the ringing and overshoot that is created by the inherent complex non-linear impedances within the input and driver transformers, modulation transformer, modulation reactor and DC blocking capacitor, power supply LC filter network, power supply bounce issues, etc. This is apparent in use by difficulty in keeping the transmitter from exceeding the baseline during modulation with complex (i.e. speech) waveforms, while attempting to maintain the positive-going peaks at or above 100%. Frequently, in order to keep the negative going peaks from exceeding the baseline, positive going peaks have to be held down to about 80% or so with the Orban, when used in conjunction with a plate modulated rig. This is not the case with the 222.

I think the Orban is ideal for state-of-the-art AM rigs employing Class-E modulation schemes, etc., but one must be careful when using it with a plate modulated rig. Orban themselves clearly state this within the operating/installation manual for their processors.

Another processor that I have good success with, when used with a plate modulated rig, is the Dorrough DAP-310. It is also a multiband device, but devoid of the complex clipping scheme used in the Orban equipment. It does employ clipping in the output, but the clipping is really intended to capture any negative-going peaks that could overmodulate the transmitter, and normally the DAP-310 is set up so the clipper is rarely, if ever, actuated. These units are quite plentiful, but almost always require a lot of work nowadays to get going properly. I replaced nearly 40 electrolytics in mine, plus two FETS, and several other electrical parts as well when I first obtained it, and this is not at all unusual for solid-state broadcast gear run 24/7 over the 15 to 20 year lifetime of the equipment. Obviously, that's a lot of operating hours.

For these reasons, I recommend the 222 for use with plate modulated transmitters. They can be had very reasonably priced on e-Bay, and brand-new I think they can be purchased from the broadcast supply dealers for around $650.00. I paid $100.00 for mine from a local AM station, where it was on the shelf for years as a back-up/spare of last resort, and it was in pristine condition when I obtained it. Additionally, the 222 has been in continous production since the late 1980s, and Inovonics provides excellent support of their products. It is a great $$$ value insofar as broadcast-quality audio processors go.

Buy it; I think you'll be happy with the result. And no, I am not affilated with Inovonics in any way.

73,

Bruce

W1DAN:
Hi Bill:

Bruce is correct on the above. I have owned a 9100A and really liked it (wish I had one again). I now use a Gregg Labs 2540, which is simelar to the 9100a. I added homebrew negative clipper and brick wall 6.5kc LPF filter. I have used many other processors and have studied the 222. It is a very good limiter.

That being said....

Limiters are limiters and affect the sound by restricting the natural dynamic excursions of your peaks. I believe you run a BL40 Modulimiter and it sounds very good on your station. If you add the 222, you'd get tighter peak control with more limiting and clipping (for what it is worth going through a tube rig with it's frequency and phase response non-linearities causing overshoot). You would also get the NRSC bandwidth limiting. Note Inovonics sells resistor kits to change the LPF values for even tighter bandwidth control...I like about 6.5kc myself.

I have determined that a very small amount of compressor overshoot clipping is helpful. More than that (and having owned an Optimod 9105A HF that is a real buzz saw to the audio..BTW, I'm looking for one cheep) the listener will notice the grunge.

With the Inovonics 222 after a compressor system (which I feel is most advantageous) you will get louder, but a bit less natural sounding.

Hope this helps!

Dan
W1DAN

kc2ifr:
Hi guys,
I have the 222 installed and will respond later. Unfortunately my 500 pooped the bed and that is the xmitter I am using it on!!!!
More to come.........................................................
Bill

W2XR:
Quote from: kc2ifr on July 30, 2008, 07:04:52 PM

Hi guys,
I have the 222 installed and will respond later. Unfortunately my 500 pooped the bed and that is the xmitter I am using it on!!!!
More to come.........................................................
Bill


Hi Bill,

Good to hear that you acquired a 222. Yes, please let Dan and me know as to your thoughts and experience with this limiter.

73,

Bruce

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