No Compromises—Our Finest Channel Strip!
Stunning high-end sound and incredible versatility are hallmarks of this top-of-the-line, tube-driven channel strip, which integrates an award-winning, boutique-quality preamp; a custom-designed FET compressor; and a custom, four-band, semi-parametric EQ.
We created the ADL 700 because you insisted! The PreSonus ADL 600 two-channel tube mic preamp was such a hit with customers—including such top artists, engineers, and producers as Chuck Ainlay, Jimmy Douglass, Mark Mancina, Demetric Collins, and Victor Wooten—that we were inundated with requests for a single-channel version in a channel strip, with a compressor and EQ that would be up to the preamp’s high standards.
You were right—it was a great idea—so we gave the design job to Robert Creel, the engineering mastermind behind many of PreSonus’ most beloved analog circuits, including the XMAX™ preamp. It took years of hard work but he delivered big-time. The ADL 700 channel strip is everything we—and you—hoped it would be!
Our premium channel strip boasts frequency response from 10 Hz all the way up to 45 kHz and offers all of the features you’d want in a high-end device. And the ADL 700 is a great value — as you expect from PreSonus!
Putting the AD in ADL 700
We 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 delivers maximum headroom and superb tone.
Ride the Rails
The ADL’s Class A preamp incorporates two 6922 and one 12AT7 vacuum tubes per channel, operating with ±300V power rails, delivering maximum headroom and superb tone. 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.
"This is a very linear, modern-sounding valve preamp—the way I think good valve preamps should be," says Hugh Rabjohn (Sound on Sound, August 2013).
The Word is Out About This Special Preamp
Indeed, the reviewers are raving about the ADL 700's sound. “For a tube design, the ADL 700 has an incredible signal-to-noise ratio and a huge dynamic range,” notes George Schilling (Resolution, March 2013).“The preamp sounded great,” agrees Chris Grainger (Mix, January 2013). "A stellar mic amp,” confirms Rob Tavaglione (Pro Audio Review, February 2013).
Top artists and producer are equally enthusiastic. "The ADL 700 makes acoustic guitars sound smooth and sweet and vocals are big and clear,” says three-time Grammy Award-winner Keb' Mo. Legendary producer Teddy Riley is positively giddy: “The ADL 700 is an INCREDIBLE mic-pre!! Next level of anything I’ve ever used!! Very quiet and warm sounding. I’ve recorded several vocal sessions while using the ADL 700, and I’ve only had GREAT results!!”
A Deeper Look at the Preamp Design.
As mentioned earlier, the ADL-series preamplifier runs on power rails of ±300V. Most off-the-shelf, op-amp-based designs run on power rails of 10V to 18V. Higher-voltage power rails deliver more headroom, deeper lows, smoother highs, and a richer overall sound.
We only use genuine transistors, resistors, and capacitors in the ADL 700 because this provides ultra-low noise and transparency. Op-amps add noise, coloration, and harshness to a signal. You won’t find them in the ADL 700.
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 ADL 700 employs large, high quality, custom-wound, shielded input and output transformers. Among other things, these securely decouple the preamp from the outside world (the mic and the A/D or following devices), which is very important in a high-voltage tube design such as this one.
The ADL 700’s Cinemag input transformer sets the stage for the preamp’s nearly ruler-flat/linear and detailed sound; the rest of the preamp amplifies what the Cinemag delivers. No other input transformer sounds like the Cinemag does—and we tried others.
The nickel/iron-core, large-scale output transformer delivers high headroom. It will begin to saturate in a pleasing (some would say “creamy”) manner at very high levels. This adds the bit of finish to the sound.
Beyond superb sound quality, the ADL 700’s preamp is special because of its ease of use and flexibility.
Rob Tavaglione (Pro Audio Review, February 2013) states, “The ADL 700 is a fine sounding unit that excels with versatility and flexibility.” Eric Tischler (Tape Op, January-February 2013) adds, “I arrived at these settings quickly, and by feel.... If you’re looking for an incredibly adaptable mic preamp—one that you could use on anything—I’d recommend checking this unit out.” (That’s easily done: Just visit your PreSonus Signature Dealer.)
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.
Variable Impedance Removes Impediments
Most mic preamps have a fixed microphone-input impedance of between 1 and 2 kΩ. The ADL 700 provides variable microphone-input impedance, which can be set at 150, 300, 900, or 1500Ω.
As the impedance on the ADL 700 preamp is lowered, a resistive load is put on the microphone. This will not damage the microphone but lowering or raising the impedance can create subtle coloring and filtering effects, enabling you to get a wider variety of sounds without using the EQ.
In general, a lower input impedance can add color to the mic to produce effects that simulate a “darker,” or more “closed-in” tone, or that change the mic’s apparent sensitivity. This effect is easier to notice on passive microphones (ribbon or moving coil) than on active microphones (condensers or active ribbons/dynamics).
Variable Levels Enable a Perfect Gain Structure
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 full-featured FET compressor in the ADL 700 was custom-designed to work with the ADL tube preamp and the new ADL 700 EQ.
The ADL 700’s FET (Field-Effect Transistor) compressor includes fully variable attack, release, threshold, ratio, makeup gain, and bypass controls. You can even stereo-link the compressors of two ADL 700s for more accurate stereo imaging.
When FET is Your Best Bet
Broadly speaking, there are four types of analog compressor designs: those that use opto-isolators (optical), Field-Effect Transistors (FETs), voltage-controlled amplifiers (VCAs; an example is the PreSonus Studio Channel compressor), and variable-gain compressors. Each has its uses, but we’re going to focus on the two types you’re most likely to find on today’s high-end channel strips: optical and FET.
The majority of today’s high-end channel strips utilize optical compressor circuits. In general, the response time of the optical circuits in these compressors tend to soften the attack and release, which can smooth out uneven volume fluctuations. They often have a distinctive sonic signature, so they can be as much an effect as a gain-control device.
FET compressors use a special transistor to vary gain, emulating a triode tube’s operation and sound. Inherently high-impedance devices, FET compressors tend be very clean and reliable and provide a faster attack time and better repeatability than the optical compressors that are more commonly found in channel strips in this price class. "At lower ratios (such as 1.25:1, my favorite on the ADL 700), users can… get an invisible, balanced, and full sound that really compliments the musical mic pre,” states Rob Tavaglione (Pro Audio Review, February 2013). "The compressor is accurate and responsive, and very good for managing the normal dynamic excursions of most vocal performers, subtly but firmly" adds Hugh Rabjohn (Sound on Sound, August 2013).
To some extent, which you prefer is a matter of taste. You might want the sound of an optical compressor for one application but prefer a FET-based compressor for another application.
However, aside from having a distinctive sound, optical compressors have drawbacks. Most notably, when the components in an optical compressor heat up or cool down, the resulting attack and release times can change considerably. That means you might not get consistent results—even on, say, multiple snare hits in the same song.
Unlike optical compressors, FET compressors such as the one in the ADL 700 are not susceptible to temperature fluctuations, so they provide consistent, repeatable results.
There’s also an environmental issue with optical compressors. Optical circuits contain a small amount of cadmium, a metal that is banned in new electronic equipment under the European Restrictions of Hazardous Substance (RoHS) Directive. Unlike optical compressors and certain professional athletes, the FET compressor in the ADL 700 uses no banned substances. We’re just sayin’….
On Your Knees
The ADL 700 compressor features a soft-knee compression curve. The term “knee” refers to the way the compression curve bends at the threshold point when represented graphically.
With hard-knee compression, the gain reduction applied to the signal occurs as soon as the signal exceeds the level set by the threshold.
With soft-knee compression, the onset of gain reduction occurs gradually after the signal has exceeded the threshold, producing a more musical response (to some folks).
The ADL 700’s 4-band semi-parametric EQ was designed to match the preamp and compressor. It combines isolated filters and optimized, per-band Q to provide subtle signal-shaping without harsh artifacts.
“The EQ was designed with musicality in mind,” comments Chris Grainger (Mix, January 2013). Resolution magazine's George Shilling (March 2013 issue) found that, "The EQ is smooth and refined.... [It] is more than powerful enough for general use but is pretty forgiving, and the low end can be huge (without wooliness) in Peak mode."
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.
Work the Way You Want
We've given the ADL 700 all the features you expect in a high-end professional channel strip, with flexible features that let you work the way you want to.
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.
“The ADL 700 is a serious, versatile channel strip and a great addition to our studios," state Bass Monsters Victor Wooten and Steve Bailey. "With a smooth compressor and impressive EQ, it’s perfect for our basses, vocals, and anything else we plug into it. Now we are using it on all of our projects. We love it!”
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 20 dB 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 20 Hz, 40 Hz, 80 Hz, or 200 Hz—or it can be turned off completely. It’s great for controlling room rumble and low-frequency noise. “The high pass filter is especially helpful with its sweepability,” comments Rob Tavaglione (Pro Audio Review, February 2013).
We didn’t skimp on metering either. 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 PleasureAs much as you’ll enjoy having one 2-rackspace ADL 700, you will absolutely love having a pair of them. Or more! “I’d love to have four or five of ‘em,” raves Eric Tischler (Tape Op, January-February 2013). 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.
The Reviewers Get The Final Say
"This is a very grown-up product, and I enjoyed working with it very much,"
concludes Hugh Rabjohn (Sound on Sound, August 2013).
“It’s solidly built, yet thoroughly refined and should prove a terrific all-rounder in any studio setup,”
declares George Schilling (Resolution, March 2013).
“It features performance that approaches the best of the best, though at half to two-thirds the cost of the competition,”
insists Rob Tavaglione (Pro Audio Review, February 2013).