The Optimod 8000A – Changing Audio Processing
[March 2025] In between the studio and the transmitter is a very important piece of gear – the audio processor. While a station can operate without one, the results will be inferior and likely a big turnoff to the listeners, especially if a newer engineer is constantly turning the pot up and down. Something was needed to process the audio and give the operator faster and less obvious control.
The long road from the early days to today’s complex digitally-operated processors includes more than a few innovative products. A very few were actually disruptors, in that they accomplished a major jump in audio processing.
In the “Good ‘Ole Days” audio processing for broadcast was very personal – the station operator literally had his hand on the potentiometer, trying to guess when peaks were coming so he could prevent overloading the transmitter – and going off the air. (Transmitter logs of the 1920s and 1930s were full of comments like ‘transmitter failure due to modulation peak.’)
Initially, the response was to keep average modulation low, to leave room for peaks; some stations might have averaged around 10% or so. Engineers began devising ways to both limit the largest peaks so to increase average modulation. Audio processors lifted average modulation to the 30% range. Innovation, using tubes and, later, solid state integrated circuits, brought average modulation to 85% in the 1970s. Then the race really was on to get as loud as possible.
But that was AM.
THE FM CHALLENGE
In some important ways, FM audio was handled differently.
The pre-emphasis applied to FM audio is one issue. Designed to reduce “noise” for listeners, it added another task for the audio processor. Level compressors and peak limiters had to function differently. The stereo generator was yet another component in the chain.
As with AM, research brought improvements and higher average levels of modulation. But, the additional steps, added a new issue that limiters could not solve.
Then Bob Orban achieved a breakthrough that made almost all other audio processors obsolete.
THE FM SOLUTION
It was 50 years ago -1975 – when the Orban Optimod 8000A hit the market. As a special treat for NAB attendees, to celebrate its 50th anniversary, a still-operational, 50-year-old Orban 8000A processor will be on display at the Spring Show.
Reflecting on the 5 decades of audio processing the 8000A kicked off, we contacted Bob, and in discussing what this meant for broadcasters, he explained exactly why the 8000A was so revolutionary.
BDR: Bob, first of all: Congrats on a product that some still see not only as the breakthrough that is was, but is something that is still possible to be used make a station sound good. As you look back on the 8000A, how would you like it (and you) to be remembered?
Bob Orban: The 8000A should be remembered as an example of a truly disruptive product in an industry that was used to a conventional paradigm: the idea that compressors, limiters, and stereo generators should be separate boxes with transformer coupling and should require users to set up each box separately.
The 8000A resulted from practical experience I had developing some one-off audio processing and then observing that modulation was not consistently controlled. It was the late Arno Meyer of Belar who gave me the insight that “the lowpass filters in the stereo generator were ringing and overshooting.”
From there, I realized that I had to address the overshoot issue, and I couldn’t do it without control of the entire compressor/limiter/stereo generator interface, as the transformers were also causing tilt issues. Additionally, I was able to create a much cleaner signal path with an order of magnitude less harmonic distortion than the conventional boxes used at the time.
A WARM RECEPTION
BDR: Combining the multiple stages in one box was definitely good idea, and a different direction than the industry was using at the time. But were you ever worried it would not “sell” in the marketplace?
Bob Orban: I thought that the 8000 was likely to sell well because of Eric Small’s enthusiasm for the product and excellent results with early on-air trials of the engineering prototype. It was shown to increase loudness by 3 dB compared to Audimax/Volumax/TX stereo generator, which was a big deal.
Eric, who was appointed to market the unit and who consulted on RF-proofing and FCC relations, was of course an experienced consulting engineer with many contacts in major markets, so he had a great deal of credibility.
BDR: As we know, the 8000A did sell well – and in markets of all sizes. Whether it was the idea of just one box doing the work of three or the immediate “bump” in modulation, it seems everyone who understood the concept wanted one.
I found it interesting to note that even your competitors saw the value of the Optimod 8000A. For example, Frank Foti told me: “The dawn of the Optimod changed the landscape for audio processing mainly due to Bob Orban inventing low pass filters that – effectively – did not overshoot. This changed the game by 3 dB or more, in on-air loudness. At the time, that was a huge step forward.
“Additionally, the HF limiting method was a novel approach, as it basically was/is a differential pre-emphasis network. As we know, these methods worked extremely well.”
And, Greg Ogonowski recalled meeting you at the 1974 NAB Show. He said: “I went by the Belar booth, since we were using Belar AM monitors at KLIF. I also remember seeing a sign on the corner of the booth for a new FM audio processor, and immediately thinking, ‘let’s see what this is all about, as more than likely, I’ll end up at an FM station soon.’ The reason why Bob was in the Belar booth was because it the late Arno Meyer who pointed out to Bob that the low pass filters in stereo generators were creating massive peak overshoot and over-modulation. Bob was the first to address this problem in Optimod 8000. As a result, it could hold your modulation meter to 100! Much better than 11! Optimods of that era were oftentimes as much as 6 to 7 dB louder than their competition. This changed everything for FM broadcasting.”
A PERSONAL FAVORITE
BDR: As audio processing moved from analog to digital, and with the ability to process multiple bands for higher and higher modulation, with less intermod products, I would like to know which model of the Optimod is your personal favorite and why?
Bob Orban: My favorite Optimod models are the 1600PCn software-based Optimod and XPN-AM.
These are the ones where I coded all of the DSP myself and was able to make further improvements to many of their modules compared to our older DSP-based design.
By coding the DSP myself, I was able to streamline the standard modify/listen/modify-again workflow that experienced processor designers use when developing processing – I didn’t need to wait for
one of our DSP engineers to make changes based on my feedback.
OPTIMOD AT HOME
BDR: I think many of us who saw the 1600PCn at the NAB Show were impressed by the power you were able to build into the application. So then, being able to choose any Optimod version you wanted, is this the version you use at home? And, would visitors be surprised to see that?
Bob Orban: Yes. One of the things I do at home is produce music, and I use the 1600PCn for mastering. (Before the 1600PCn existed, I used the 6200 and then the 6300 for this purpose.) I would probably use an Optimod-TV 8685 to watch TV if it supported HDMI with HDCP copy protection, but its SDI I/O precludes its use in the consumer space.
I don’t think that visitors would be surprised to see a 1600PCn (which is, after all, just another app on my PC), but I imagine if I could use the 8685, it would create more of a stir!
BDR: Thank you, Bob, for all your contributions to the industry, and your willingness to share your thoughts.
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For a great series of articles on Audio Processing by the late Jim Somich, click here.
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