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Innovations: Lectrosonics’ DPR Digital Plug-On Transmitter

Since the mid-1980s, the plug-on transmitter has been a cornerstone of Lectrosonics’ wireless offerings. Karl Winkler, vice president of sales and service, recounts the history and highlights how that effort has led to the company’s new offering, the DPR Digital Plug-On Transmitter.

Lectrosonics’ DPR Digital Plug-On Transmitter
Lectrosonics’ DPR Digital Plug-On Transmitter

Since the mid-1980s, a cornerstone of the Lectrosonics wireless microphone line has been the plug-on transmitter. The company’s first product in this form factor was the M33 belt-pack unit with a special machined XLR mount (it also had an RCA connector on the side!) The XLR connector itself relied on the normal Switchcraft locking mechanism which was fine for cables and stationary applications, but didn’t fare so well for interview microphones and the like. The plastic housing of the M33 didn’t inspire much confidence, either. And, without a portable, camera-mount receiver, the M33 didn’t end up to be a big seller.

The next product to come along, though, started the trend we still see today for rugged, plug-on transmitters that can turn just about any microphone into a wireless unit. H175DC already had many of the features associated with Lectrosonics products: an all-metal housing, locking XLR connector, an easy-to-use but secure battery door, and very good sound quality for the time. The successor, the H185, was the one that really caught the market wave in the late 1980s, with its companion CR185 receiver. The 185 saw the addition of the now-famous quick attach and release locking connector for the XLR. Many of these systems are still operational today.

The analog UH190, UH195 and UH200 (the first one with 48 volt phantom power) plug-on units set the standard for their day in the 1990s with rock-solid RF performance, dual-band audio companding and well-known Lectrosonics ruggedness. These were followed by the UH400, UH400A, HM, and HMa Digital Hybrid Wireless units in the 2000s. A special version of the UH400, dubbed the “TM,” extended the low-frequency response by an extra octave and has become the standard plug-on transmitter for PA system alignment, since it does not compand the audio signal and thus avoids interfering with the dynamics and linearity of the PA test signals and musical source material. The TM400 system has been used by most major touring companies, speaker companies and freelance system tuners for the past 15 years.

This latest generation plug-on transmitter from Lectrosonics, the DPR, now has pure digital modulation, a proprietary codec, extremely low latency of 1.4 ms and flat frequency response from 25 Hz to 20 kHz. The new transmitter is part of the D Squared family of digital wireless microphone products, is fully compatible with the DSQD receiver and features an RF tuning range of 470 to 608 MHz (470 to 614 MHz for the export version). Analog to digital conversion is handled at a 48 kHz sample rate and 24 bit depth. The new transmitter includes specially developed, high-efficiency circuitry for extended operating time on two AA batteries, and offers RF power selections at 25 and 50 mW, which is comparable in range to 60 and 125 mW with an analog or hybrid wireless system.

Lectrosonics Debuts New D Squared Wireless Transmitter and Receiver

An extra feature in the DPR not found in any of the previous Lectrosonics plug-on units is that the unit can be configured as either a transmitter or a recorder, with files stored on microSD card memory in the industry standard Broadcast Wave .wav (BWF) format at the native 24 bit depth and 48 kHz sample rate. A 3.5 mm TRS jack on the side of the unit allows jam sync with timecode, making audio file alignment quick and easy in post-production. The microSD memory card can also be used to update the unit’s firmware in the field.

Phantom power is selectable to off, 5v, 15v or 48v to accommodate a wide range of microphone types, from dynamic to studio condensers, shotguns and measurement microphones. Studio-quality audio performance is assured by high-quality components in the preamp, wide-range input gain adjustment and DSP-controlled analog limiting. Input gain is adjustable over a 55 dB range in 1 dB steps to allow an exact match to the input signal level, or calibrated noise signal, maximizing audio dynamic range and signal to noise ratio. The two-way IR port ensures quick setup with associated receivers and allows for encryption key transfer and other data sharing between units. The DPR responds to remote “dweedle tone” commands, available via third party apps such as New Endian’s LectroRM, allowing users to change settings including frequency, audio level, record start/stop and lock/unlock, without physically touching the transmitter.

The extremely durable DPR housing is machined from aluminum alloy billet material and plated with an electroless process to increase hardness while maintaining conductivity. The unit is the same size and shape as the previous generation plug-on units, including the HM and HMa, so that standard accessories are compatible with the new unit, including the PHTRAN3 pouch with clip, and the HMCVR weather-resistant silicone cover. The input wiring is also the same as previous generations, allowing the use of existing cable and barrel adapter accessories, including the MCA5X lav mic adapter and MCAM30 for use with Earthworks M30-type measurement microphones. The DPR is powered by two AA batteries.

With an audio frequency response of 25 Hz to 20 kHz +0.0, – 3dB, a dynamic range of 110 dB before limiting and a flat in-band phase response, the DPR is ideal for use as a wireless test and measurement link with calibrated microphones for audio system alignment and monitoring.

The DPR, like all product members of the D Squared digital wireless family, supports encryption in a 256 bit AES, CTR mode format for robust security, meeting FIPS 197 and 140-2 standards. Three different key management modes can be employed, including Universal, where all units in the D Squared family share the same key; Shared, where a unique key is created and can be shared between transmitters and between transmitters and receivers; and Standard, where a unique key is created but cannot be shared between transmitters or from transmitters to receivers. By including the Universal mode, all units work together, right out of the box, without having to generate a unique key. The Shared mode is likely to fit well into sports broadcasting, where several receivers, including stationary units and camera-mount systems, may need to pick up the signal from a signal transmitter. For higher-level security concerns, the Standard key policy is the correct one, where only one receiver can pick up and decode the signals from one or more transmitters.

Since the final measurement of any wireless microphone system is the sound quality, the DPR was designed with special care in this regard. Special shielding prevents stray signals from causing internal interference or noise, and high quality components ensure excellent audio integrity. The DPR is available worldwide via authorized Lectrosonics dealers.

Karl Winkler is VP of Sales and Service at Lectrosonics.

Lectrosonics •