In 1975 Bob
Orban came along with a single device, the Optimod-FM 8000, encompassing audio
processing, peak limiting and stereo generation, which permitted optimization and
matching of each component of an FM processing chain, from AGC to protective clipping
to stereo generation. It produced a louder signal with fewer artifacts while
maintaining superior stereo performance.
quest for FM perfection has continued, first in the analog domain and later
with algorithms and digital signal processing capable of greater precision and
stability. The field is quite competitive, with several manufacturers in the
U.S. and abroad offering many models of software-defined audio processors. On-air
processing continues to be a learning curve for manufacturer and broadcast
processor has personality of its own: a sound signature, a user interface that
may be more or less intuitive, greater or fewer tuning options, etc. Each GUI
is sufficiently different to require some familiarization with what the
settings really do sonically.
audio processors continuously adapt to the audio content as its texture changes
in real time. This makes it difficult to get the right sound for everything in
one sitting. Popular music recordings vary wildly in spectral content and studio
processing. In fact a lot of contemporary music has some distortion, which can
be magnified by even mildly aggressive processing.
have learned to fight back with clever solutions including speech detection,
separate voice processing settings and even distortion masking and repairing,
rounding off clipped audio coming in from the source material.
just keep getting better. Several years ago I standardized one of Saga
Communications’ clusters with three Optimod 8500s. Firmware varied from an
early version in the first box I bought to relatively newer firmware in the later
two. I found the most aggressive presets sounded too distorted for my taste on
most material. I always had to dial them down, to the chagrin of the PD, who
liked a lot of punch. I recently had the opportunity to upgrade the firmware in
my oldest 8500 and was pleasantly surprise to find it handling aggressive audio
The new Optimod-FM
8600 is a definite notch above Orban’s earlier products.
When I unpacked
this unit I noticed the striking glossy ebony paint of the front panel and rack
ears. The finish is as classy-looking as a grand piano’s. The rest of the
chassis is Orban’s usual zinc-plated steel, great for reducing interference
from magnetically-induced noise sources.
Orban Optimods are shown at work in the author’s
transmitter room. An Optimod-FM 8500 is visible in the middle rack, with the 8600
8600 was manufactured in Germany.Outsourcing manufacturing off of our shores seems to be a fact of life
these days. Orban tells Radio World that this demo unit was review stock, and that
U.S. buyers receive units made in the United States. German-made stock will be
sold to overseas buyers.
with two EIA power cords, one with North American blades, the other with a
European power source plug. The unit could default to 240 VAC, requiring you to
switch the AC input voltage selector to 120 VAC and change the line fuse to
twice the ampacity to compensate. This is common among audio processor hardware
manufacturers. The box arrives set for the highest AC voltage, so that a
purchaser who forgets to read the manual and plugs into a 240 V mains won’t
unit came set for North American power. I would have preferred a wide-range auto
voltage switching power supply to eliminate the danger of plugging it into the
wrong mains supply voltage.
bench-testing an 8600 with an exciter, I moved it up to the tower site of my FM
flamethrower and put it into the air chain.
to place my FM audio processor at the tower site to achieve best results.
Anything else between the composite output of a modern processor and the
exciter is a compromise, even if it is digital. Let the magic DSP-generated
composite signal created by your expensive box do the heavy lifting for FM
One of the
hot presets, called Impact, I could not use with my older 8500 because it
sounded too harsh. However, I was able to use the new Impact MX version with
the new 8600 as it sounded much cleaner.
new versions of some factory presets are labeled MX, which, according to Orban,
indicates MaXimum performance. These add an additional quarter-second processing
delay, which would not be viable for live on-the-air monitoring but is fine for
stations that have long given up live monitoring due to the eight-second
diversity delay required for the iBiquity HD Radio standard.
A lot of
new magic happens during that 270 millisecond delay. The processor uses a
lookahead audio buffer to give it time to study a larger sample of audio to better
decide how to tame it to prevent peak limiting distortion, especially with bass-heavy
material. This is not a subtle enhancement.
The 8600’s pre-emphasis limiter yields
less audible distortion while providing 2.5 dB more highs than its predecessor.
It is a departure from the 8500 as it uses psychoacoustic modeling to help
reduce distortion while improving transient response. This has enabled Orban to
achieve high-frequency response parity with source material in spite of the
pre-emphasis curve over-modulation protection requirement.
8600 Set-up Screen
include a two-band compressor structure that can be phase linear for audiophile
radio station formats. Diversity delay comes standard with up to 16 seconds
available to cope with newer IBOC gear requiring a delay greater than 8 seconds
to line up analog with digital audio.
a low-delay monitor output you can set up to provide a simulation of on-air
audio for your control room talent if your Optimod is at the studio. And there
is a novel new experimental mode for the stereo generator providing a single sideband
version of the 38 kHz L–R carrier, which results in even less interference with
SCAs while being transparent to most receivers’ multiplex decoders.
clocked at 64 kHz internally so that the output of the sample rate converters
can be safely used at 32 kHz through 48 kHz without worrying about overshoot.
introduced in the Optimod 8400, an improved DSP composite limiter uses Orban’s
patented half-cosine algorithm. It can be driven hard to get a little more
loudness, but with the inevitable tradeoff of more clipping distortion on some
The compressor/limiters of prior stages
do a superb job providing ample loudness. It is best to let those stages do the
heavy lifting and go light on composite limiting.
uses the same size color LCD display, joystick, spinner wheel and enter buttons
as the 8500. It is TCP/IP-centric and can be programmed and controlled remotely
via a network connection. It still comes with RS-232 serial port control, making
it compatible with earlier Optimod installations. If you have additional
subcarriers or RDS you can connect them to inputs on the 8600 where they’ll be
mixed with the composite output without requiring external BNC tees or
modify has three levels: Basic, Intermediate and Advanced. Many of the 8600’s
presets can be used as is, with the basic less/more control to adjust them to
taste. You needn’t be an expert off the bat. As time permits, you can delve
into the more advanced modes and play with, tweak and store your customized
can accept up to eight GPI contact closures for remote stereo mono control, to change
presets, turn off and on diversity audio delay or a host of other functions. In
addition it has two tally outputs that can be programmed to report if analog or
digital audio sources have gone silent. The 8600 will auto switch to an
alternate audio source if so desired.
is a digital device, care must be exercised in the peak analog audio level you
present to it. If you overdrive the analog-to-digital converter, you will cause
clipping distortion at the get-go. Unlike the old days of VU meters it is
important to observe the actual peak audio voltage levels rather than average
easy but may require you to watch the levels over many hours and many board
operators to be sure you’re maintaining sufficient headroom. Conversely, you
don’t want to set the incoming level too low as it will increase the noise from
the analog input stage and quantizing noise from the converter. There is a
sweet spot and the input bar graph makes it fairly easy to hit. The input level
control is well-named, “Clip Level” control.
incorporates a frequency-agile set-up tone generator. It can be used to
calibrate to your exciter’s input if you don’t mind putting tones on the air. I
usually use normal program material. If you set the pilot injection level to be
the same for either the 8500 or 8600, you can use it as a reference to match up
composite output levels.
The HD Radio
processing chain in the 8600 can be adjusted for independent compression and
equalization including a de-essing function to roll off high frequencies a tad,
if one desires, to prevent the HD side from sounding brittle.
golden ears you can independently flip the phase of the analog outputs and/or
the HD outputs. Thus you can compensate for phase reversals between your FM and
HD signals for better blending when an HD receiver switches between digital and
analog fall-back and also to correct for absolute phase difference in your air chain.
Some folks claim they can hear whether their speakers are pulling instead of
pushing on what should be an air compression of the original audio.
analog diversity delay adjustment menu item in the 8600 has three settings,
coarse, medium and fine, rather than only two. Having the medium dial rate
makes it much easier to tweak in the right amount of delay by ear. On a good
day I can get to within two AES samples without resorting to an HD modulation
monitor which might require up to a minute for each timing check.
might wonder why audio processor improvements are not applied to previous
models, perhaps offered as a software upgrade for a fee. The answer is simple. There
is only so much you can do with the horsepower under the hood.
Orban Optimod-FM 8600 Digital Audio Processor
+ Easy to set up with intelligent menus and excellent
+ Sounds even better than previous models, can play
louder, punchier and cleaner
+ Can be dropped in place of an 8500 as I/O is
- Increased latency
- Power supply requires voltage switch, room for
- Comes with two power cords, a waste of resources
Price: HD Digital - $13,990;
FM Digital - $10,990
For information, contact David Rusch at Orban in
Arizona at (480) 403-8300 or visit www.orban.com.
a huge amount of number-crunching power. As chips become faster and less power
hungry, the opportunity to add more coding tricks becomes more feasible.
power supply in the 8600 is identical to that in the 8500, but it runs a bit
cooler as the DSP board in the 8600 is more energy efficient.
the hood you will find the same dual architecture design as the 8500. One CPU
is dedicated to control and supervision, operates the LCD display, monitors the
switches, etc. The DSP board can run independently so audio processing, once
initiated, will continue to function even during a software upgrade. The
mission-critical DSP board soldiers on even if the control CPU falters.
8500’s DSP board used 12 Freescale 150 MHz chips while the new 8600 uses only
nine, more powerful, Freescale 250 MHz dual-core chips. The net result is
approximately three times the processing performance.
Orban’s cleanest Optimod yet. The final FM processing is better-sounding at
similar loudness levels than its previous flagship processor. The sound is a
bit more consistent with differing content.
that, like its predecessors, it is an easier box to set up and tune to your
audio pallet than other brands. And it does permit your FM to sound a bit more
like your HD audio.
achieves its goals with one drawback, increased latency, which makes it harder
for on-air personality to monitor actual air product. You also have to wonder
if the high cost of the product is worth the incremental improvement in an era
where the average listener accepts the limited quality of low-bitrate streaming
audio as perfectly acceptable.
For the few days I had the 8600 on the
air, my PD had a wide grin. He loved the sound. He was a little disappointed
when the day came to part with it.