The ADL 600 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 600 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 600.
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 ADL600 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 600’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 600 is special because of its ease of use and flexibility. Each of the two input channels has separate mic, line, and instrument inputs, and you can select among four mic-input impedances, so the preamp works great with any type of microphone.
Most mic preamps have a fixed microphone-input impedance of between 1 and 2 kΩ. The ADL 600 provides variable microphone-input impedance, which can be set at 150, 300, 900, or 1500Ω.
As the impedance on the ADL 600 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.
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). In addition, some microphones are finicky about impedance; with variable impedance, you can make virtually any mic deliver its best performance.
Hearing is Believing
Technical explanations are well and nice but hearing is believing. Try the ADL 600 yourself and experience the thrill of using the world’s finest tube preamp.
I recently used the ADL 600 on Justin Timberlake's new album with Timbaland. It has a really cool 'Now Sound' to it. I also sometimes run my mixes through it. The ADL 600 is happening! I have one at my studio and at Timbaland's.
Atlantic Records and Timbaland
Great recordings require great pre’s, and the ADL 600 is incredible,” he enthuses. “It’s my favorite studio piece; I have thrown everything at this beast! From blistering metal guitars and pounding kicks to the sweetest acoustic, it just seems to understand where I want to go and speak with a big, warm airy tone. With the switch able impedance even your cheapest mic will sound great. And when it comes to vocals, let’s just say the ADL 600 is perfect.
Rhythm and Lead Guitarist
The ADL 600 is the workhorse of the studio! I’ve used it for bass, guitar, vocals and saxophone and the sound has stayed consistently clear and warm. Rarely do I have to EQ. You want to the vocalist to sound like the vocalist and this doesn’t add colors like other preamps. The ADL 600 is one of the greatest preamps to come on the scene in a long time.
Producer, Drummer, Engineer
The ADL600 has an amazingly open sound with a nice high end, great character in the midrange, and a low end that extends past the horizon. It's a very well rounded preamp that works well with vocals, percusive instruments, and especially guitar. I seem to find a new application for it every day.
President of GVE Records