Single-channel, high-voltage tube channel strip.
Riding on the popularity of the ADL 600 two-channel tube mic preamp, PreSonus delivers the ADL 700 single-channel tube channel strip. Featuring an award-winning boutique-quality preamp, the ADL 700 incorporates a custom-designed FET compressor; and a custom, four-band, semi-parametric EQ. With a broad frequency response from 10Hz all the way up to 45kHz, the ADL 700 has all of the features you expect from a high-end channel strip thanks to Robert Creel, the engineering mastermind behind many of PreSonus’ most beloved analog circuits, including the XMAX™ preamp.
Putting the AD in ADL 700
It all started with a single-channel version of the ADL 600 preamplifier, which was co-designed by PreSonus and famed tube-circuit designer Anthony DeMaria. The preamp employs a distinctive Class A discrete design that incorporates two 6922 and one 12AT7 vacuum tubes per channel, operating with ±300V power rails for maximum headroom and superb tone.
Power amplifiers are classified primarily by the design of the output stage and are designated Class A, B, AB, D, G, or H. In a Class A preamp, the output circuits are always on for the entire cycle of signal swing or the bias current flows at all times. As a result, Class A preamps have the most linear design, with no crossover distortion, and they deliver purer, clearer, and more musical results than the Class AB designs that are found in many preamps.
The dual-transformer design ensures low-noise operation, with maximum common-mode rejection. This resulted in an ultra-quiet tube preamp with a big, warm, smooth, clear, distinctive sound.
Beyond superb sound quality, the ADL 700’s preamp is special because of its ease of use and flexibility.
Among the hallmark features of ADL-series preamps are separate, balanced XLR mic, balanced XLR line, and ¼” TS instrument inputs and a single, balanced XLR output. An Input Source Select switch enables you to leave your signal sources connected at all times and choose among sources, patching the selected input through the signal chain and completely bypassing the other two inputs.
The preamp offers a choice of four mic-input impedances: 1500O, 900O, 300O, and 150O. Lowering or raising the ADL 700 mic-input impedance can create subtle coloring and filtering effects, enabling you to get a wider variety of tonalities without using the EQ.
In addition, the ADL 700 provides variable mic-input gain, employing an 8-position, military-grade, rotary switch that provides 35 dB of gain in stepped, 5 dB increments. A Trim potentiometer (±30 dB) allows you to make fine adjustments to the final preamp stage of the ADL 700 input.
The output stage is controlled by a fully variable attenuator that delivers ±10 dB of fine-tune trim adjustment, enabling you to dial in the perfect gain structure for any application.
A Tight Squeeze
The ADL 700’s FET (Field-Effect Transistor) compressor includes fully variable attack, release, threshold, ratio, makeup gain, and bypass controls. The compressors of two ADL 700s can be stereo linked allowing for more accurate stereo imaging. The ADL 700 compressor has a “soft knee” compression curve.
FET-based compressors such as the one in the ADL 700 use transistors to emulate a triode tube’s operation and sound. This type of compressor generally provides a faster attack time and better repeatability than the optical compressors that are more commonly found in channel strips in this price class.
The ADL 700’s 4-band semi-parametric EQ was designed to match the preamp and compressor, with musicality in mind. It combines isolated filters and optimized, per-band Q to provide subtle signal shaping without harsh artifacts. All bands have Gain (±16 dB) and Frequency controls, with overlapping frequency ranges and fixed Q (0.55). The low and high bands are switchable between shelving and peak.
Who’s on First?
Would you rather have the compressor before the EQ in the signal chain or put the EQ first? Placing the compressor before the EQ allows you to make dramatic changes to the EQ settings without needing to alter the compressor setting. However, if you place the EQ before the compressor, you can better control different frequencies, achieving a more natural response.
The ADL 700’s EQ>Comp switch provides the best of both worlds, allowing you the flexibility to chose which signal flow is right for your application at any given time. You also can independently bypass the compressor and the EQ using front-panel switches.
Of course, you get +48V phantom power, polarity inversion, and a 20dB pad, controlled by big, sturdy, military-grade switches. You also get a -12 dB/octave high-pass filter, the frequency threshold of which can be set at 20Hz, 40Hz, 80Hz, or 200Hz—or it can be turned off completely. It’s great for controlling room rumble and low-frequency noise.
Fast-acting, eight-segment LED meters accurately detect fast transients and peaks. Large, backlit, dual-mode analog VU metering enables monitoring of output and gain-reduction levels. A -6 dB switch offsets the meter for use with hot source signals. A master level control adjusts the overall output from -80 to +6 dB.
Double Your Pleasure
As much as you’ll enjoy having one 2-rackspace ADL 700, you will absolutely love having a pair of them. You can even stereo-link the two compressor sections: When the Threshold control is turned fully counterclockwise to the ST position, the onboard compressor controls are bypassed, and compression is controlled externally, via a Stereo Link connection to a second ADL 700.
With its extensive feature set, ultra-low noise (-100 dB S/N ratio), >73 dB gain, extended frequency response of 10 Hz to 45 kHz, and top-of-the-line sound, the ADL 700 is a superb creative tool for serious recording engineers and musicians