A name familiar to many in broadcast radio engineering is Jim Wood, probably best known for his work at Inovonics.
Wood has spent decades developing practical, high-performance products that have found their way into broadcast facilities worldwide.
Through his semi-retirement venture, The Schlockwood Laboratory, he has continued that tradition by designing equipment that delivers professional capability while remaining accessible to smaller broadcasters, hobbyists and amateur radio operators.
Schlockwood Laboratory’s first offering, the SW200 multiband audio processor, quickly earned a loyal following among FCC Part 15-compliant broadcasters and the amateur radio community.
Its combination of effective multiband processing, straightforward operation and affordable price made it a popular choice for operators seeking professional-sounding audio without the complexity or cost of traditional broadcast processors.
The product line later expanded with the SW300 AM Modulation Monitor and Field Strength Meter, giving low-power broadcasters access to modulation monitoring capabilities that had previously been available primarily through professional broadcast instrumentation.
Rather than simply continuing to produce a successful design, Wood revisited the original processor to expand its capabilities while preserving the attributes that made the SW200 so well regarded.
The result is the Schlockwood Laboratory SW210, an analog triband audio processor that significantly broadens the platform’s flexibility while retaining its straightforward, low-latency design philosophy.
According to the company website, the unit is sold factory direct for $580.
Checking it out
At first glance, the most noticeable change is the move to a professional 1RU rack-mount enclosure. Beyond providing a more polished appearance, the new chassis allows the SW210 to integrate naturally into conventional broadcast equipment racks while accommodating a substantial increase in front-panel controls and metering.
Expanded LED indicators now provide detailed visual feedback for both the Automatic Gain Control (AGC) and triband processing sections, making setup considerably easier than on the original SW200. Familiar controls — including input gain, pre-emphasis, processor drive, equalization, peak control, positive peak modulation and output level — remain, while several new adjustments significantly expand the processor’s versatility.
Internally, the SW210 continues the practical design philosophy established by its predecessor. Through-hole construction and readily available components make field servicing feasible for users with electronics troubleshooting experience, a refreshing departure from today’s increasingly common surface-mount-only designs.
The processor also retains many of the core technologies introduced in the SW200, including subsonic input filtering, gated AGC, colorless PWM gain control and a zero-latency analog signal path. Together, these design choices reflect Wood’s emphasis on creating a processor that is not only capable, but also maintainable and built for long-term service.
Processing architecture
While the SW200 established itself as a capable analog processor, the SW210 introduces a number of thoughtful refinements that enhance its flexibility without sacrificing the straightforward operation of its predecessor.
The Automatic Gain Control (AGC) has been enhanced to respond not only to average program level but also to peak program content. In practice, this produces more consistent loudness while avoiding excessive gain riding on short-duration transients. Front-panel AGC metering has likewise received a significant upgrade, replacing the original pair of tri-colored LEDs with a multi-segment display that provides far more useful visual feedback during setup and day-to-day operation.
Among the most notable additions is the new Articulation control. Rather than acting as a conventional equalizer, it adjusts the processor’s emphasis on speech presence, allowing operators to optimize audio for applications where intelligibility is paramount.
Travelers’ Information Stations, amateur radio and talk-oriented programming all benefit from the additional “talk power,” while music-based formats can be tailored for a more balanced presentation.
Equalization remains familiar to users of the SW200, with ±8 dB of adjustment available for both low- and high-frequency response. Complementing these controls is a new variable bass turnover adjustment that allows the operator to tailor low-frequency processing characteristics to suit different programming formats.
Whether the goal is a warm, full-bodied music presentation or tighter, more controlled bass for spoken-word programming, the additional flexibility makes it easier to establish a distinctive on-air sound.
The triband processing section also receives meaningful attention. Rather than relying on a single processing indicator, the SW210 provides individual multi-segment LED displays for each processing band across a 15 dB range. This expanded metering makes setup much easier to balance processing activity and confirm that each band is contributing appropriately to the overall sound.
Output processing has likewise been expanded. A continuously variable Peak Control allows the operator to select any point between predominantly limiting and predominantly clipping, enabling the operator to tailor the processor’s character for maximum loudness or cleaner, more natural audio.
The continuously adjustable output low-pass filter spans 3 kHz to 12.5 kHz, allowing the SW210 to adapt to a range of operating environments, including licensed AM broadcasting, FCC Part 15 installations, Travelers’ Information Stations, shortwave broadcasting and amateur AM operation.
Perhaps the most significant enhancement is the increase in available positive peak capability. Whereas the SW200 supported positive modulation levels of up to +135 percent, the SW210 extends that capability to +200 percent without requiring forced negative clipping.
To further support asymmetrical modulation, Schlockwood has incorporated a defeatable automatic polarity-correction circuit that monitors program polarity and automatically rotates the waveform orientation to maximize positive modulation while minimizing distortion.
Recognizing that the processor may be used with both professional broadcast equipment and consumer-grade hardware, Schlockwood has equipped the SW210 with balanced XLR connections as well as 3.5 mm input and output jacks. This thoughtful approach eliminates the need for external interface adapters in many installations and reflects the processor’s broad appeal across licensed broadcast facilities, low-power AM stations and amateur radio applications.
Several installation options remain user-configurable through rear-panel jumpers, including defeat of the automatic polarity correction, AGC and pre-emphasis circuits. These provisions allow experienced users to tailor the processor’s operation for specialized applications while maintaining the straightforward setup that made the original SW200 so popular.
Evaluation on the air
Our temporary workshop presented an initial challenge: elevated AM-band noise that complicated early listening tests. Once the interference issue was resolved, the SW210 was paired with our Hamilton Rangemaster AM1000, an FCC Part 15-certified AM transmitter, for over-the-air evaluation.
Testing included both the balanced XLR and 3.5 mm inputs using professional and consumer program sources. In each case, the SW210 interfaced seamlessly, requiring no special level matching or external adapters.
Initial setup was intentionally conservative to establish a neutral baseline before making subjective adjustments. Starting settings included 0 dB input gain, Articulation disabled, 10 kHz pre-emphasis, Processor Drive at 0, Bass Split at 60 Hz, bass and treble equalization centered, Peak Control set midway between limiting and clipping, positive peaks limited to 100 percent, a 10 kHz output cutoff and output level adjusted to -10 dB.
With music feeding the processor, the improvements over the original SW200 quickly became apparent. The addition of an input-confidence LED immediately confirms the presence of program audio, while the expanded AGC metering provides significantly more insight into the processor’s operation during setup.
Adjusting input level until the AGC operated within its intended range was straightforward, after which Processor Drive was increased until each triband section averaged approximately 5 dB of gain reduction. The output level was then raised until the Rangemaster approached 100 percent modulation, as verified with the Schlockwood SW300 modulation monitor.
The familiar equalization controls behaved much as they did on the SW200, but the new Bass Split control introduced an additional degree of flexibility. Rather than simply boosting or attenuating low frequencies, it allows the operator to control how bass energy is presented to the processor, making it easier to tailor the overall audio character across different programming formats.
Perhaps the most impressive addition was the new Articulation control. Switching from music to spoken-word programming immediately demonstrated its effectiveness. Voice reproduction became noticeably more intelligible and forward without sounding harsh or unnatural, allowing announcements to cut through background music with considerably greater presence.
Operators using the SW210 for Travelers’ Information Stations, amateur AM operation, or other speech-intensive services will likely find this feature especially valuable, though limited and judicious application remains equally useful for stations that mix music and voice programming.
The variable output cutoff control also exceeded expectations. As bandwidth was progressively reduced, the processor maintained clean, natural-sounding audio rather than producing the muffled or overly aggressive sound often associated with narrow-band operation.
This flexibility makes it practical to optimize audio for a wide range of applications, from full-fidelity Part 15 broadcasting to narrower amateur radio or shortwave operating conditions.
Automatic polarity correction performed as intended, maximizing positive modulation while avoiding the need for excessive negative clipping and the distortion that often accompanies it. Operators who prefer manual control — or who find themselves particularly sensitive to program polarity while monitoring with headphones — can disable the automatic polarity circuit, along with the AGC and pre-emphasis functions, via rear-panel configuration jumpers.
Throughout testing, the processor exhibited an exceptionally low noise floor, with no audible hiss or artifacts introduced by the processing itself.
Refreshing
Having worked with a variety of analog AM processors over the years — from early CRL and Inovonics designs to more recent DSP-based processors — I found the SW210 refreshingly straightforward.
It avoids chasing excessive loudness in favor of clean, controlled audio tailored to the application. The analog signal path also means there is effectively no processing latency, an advantage for applications such as live announcing and amateur AM operation.
Broadcast engineers with experience maintaining legacy AM air chains may find the SW210’s automatic polarity correction familiar. The concept dates back to processors such as the CBS Laboratories Volumax series, in which maintaining the correct audio polarity enabled transmitters capable of asymmetrical modulation to achieve higher positive peaks without increasing distortion.
Schlockwood brings that same philosophy into a modern analog processor, automatically and noiselessly selecting the waveform polarity that best supports positive modulation while allowing the function to be defeated when desired.
Despite the increased number of controls, setup never became intimidating. The expanded metering made it easy to understand exactly what each adjustment was doing, allowing changes to be made confidently rather than by trial and error
The SW210 fills a niche not only for experienced hobby broadcasters looking to achieve more professional on-air audio, but it would also be right at home for licensed broadcasters, shortwave broadcasting and amateur radio enthusiasts.
Instead of cobbling together a mix of consumer or pro-sumer gear or going with legacy broadcaster equipment, which may require rehabilitation beyond the knowledge of an appliance-operator Part 15 enthusiast, the SW210 is a modern-day broadcast processor that delivers excellent results without leaving less experienced users bewildered.
This processor is not only reasonably priced, but its performance makes it a worthy contender against the products of larger audio processor manufacturers. Not only does the successor to the SW200 build upon the attributes of the former, but it also produces excellent audio that can be gentle and articulate or, for those seeking loudness, make your signal heard in deep fringe coverage.
While flexible, the SW210 does require some initial familiarity to fully take advantage of its processing structure, as inexperienced operators may find themselves overmodulating, especially if they lack access to a SW300 modulation monitor or a similar off-air monitoring receiver.
The SW210’s design reflects a series of deliberate engineering trade-offs rather than cost-cutting for its own sake. At first glance, some broadcast engineers may question the molded plastic enclosure and external AC power supply, features that can create an initial impression more commonly associated with consumer equipment than professional broadcast hardware.
The plastic enclosure also provides less inherent RF shielding than a conventional metal chassis. For the Part 15, amateur radio and Travelers’ Information Station environments for which the processor is primarily intended, however, this is unlikely to present a practical concern.
Should the SW210 find its way into a high-RF commercial broadcast facility, careful equipment placement and sound RF management practices would be prudent, as they are with any sensitive audio equipment.
Once placed into service, those initial impressions quickly give way to the processor’s actual capabilities. Throughout our evaluation, the SW210 consistently delivered clean, well-controlled modulation that could be tailored from smooth and transparent to highly competitive, while its through-hole construction and the use of readily available electronic components provide a level of long-term serviceability that has become increasingly uncommon in modern broadcast equipment.
In the end, Schlockwood Laboratory appears to have invested where it matters most: the engineering inside the chassis rather than the cosmetics surrounding it.
Verdict
The Schlockwood SW210 is not only a capable analog processor for AM broadcasting — whether FCC Part 15-compliant or licensed — but is equally well suited to amateur radio, Travelers’ Information Stations and shortwave broadcasting.
Much of that versatility stems from the addition of the Articulation and variable Cutoff controls, which allow the processor to be optimized for a wide range of operating conditions.
Rather than reinventing an already successful processor, Jim Wood has refined the original design with practical improvements that enhance both flexibility and day-to-day usability without compromising its straightforward analog operating philosophy.
While the controls are straightforward enough for the novice broadcast enthusiast, a knowledgeable broadcast engineer can dial in a station’s sonic signature in short order.
Find product information at the Schlockwood Laboratory website.
Sidebar: Why Positive Peaks Matter
Many AM transmitters are capable of positive modulation levels greater than 100 percent, yet remain limited to 100 percent negative modulation.
Modern audio processors take advantage of this characteristic by maintaining waveform polarity that favors positive modulation, increasing loudness and improving perceived coverage without introducing the distortion associated with excessive negative modulation.
The SW210’s automatic polarity correction simplifies this process by continuously selecting the waveform orientation that maximizes positive peak performance.
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