The ADL-600 was designed by Anthony DeMaria with a no-holds-barred signal path.

The PreSonus ADL 600 is a high-voltage, 2-channel microphone preamp designed by world-renowned analog tube circuit designer Anthony DeMaria. It utilizes a Class A discrete design with 3 vacuum tubes per channel for maximum headroom and tonality.

Control and Flexibility
The ADL 600 is designed for supreme sonic performance and flexibility with XLR microphone/line inputs and 1/4" instrument inputs. The input selector allows for selection between Hi-Z instrument input, line input, and 4 different mic impedances for a number of applications. The rotary High Pass Filter switch has 3 settings (40Hz, 80Hz, and 120Hz @ 6dB per octave) for controlling room rumble and low-frequency noise. The input gain attenuator delivers 5dB-step increments and a total gain of over 72dB. The output stage is controlled by a variable conductive plastic attenuator that delivers +/-10dB of fine tune trim adjustment to dial-in the perfect gain structure for the application at hand. The ADL 600 also includes 48V phantom power and a -20dB pad.

Under the Hood
There are no op-amps or integrated circuits (IC's) in the signal path to ensure the purest sound possible. The dual-transformer design guarantees ultralow-noise operation with maximum common mode rejection.

Metering
The ADL 600 is loaded with both fast-acting 8-segment LED meters for accurately detecting fast transients and peaks, as well as large analog VU meters for metering output level.

Components
The overall approach to the ADL 600's design was to keep the signal path as simple as possible by keeping the component count to a minimum. The few components that are in the signal path were chosen for their sonic qualities: custom audio transformers, polyfilm pulse capacitors, 1% metal film resistors, and conductive plastic potentiometers. Also, rotary switches and fixed 1% metal film resistors are used in the preamp gain circuit to keep noise to a minimum and to prevent any coloration that may be caused by a potentiometer.

The custom-designed input transformer is fully encased in a Mumetal enclosure, yielding excellent noise characteristics and magnetic shielding. The transformer interfaces the balanced mic/line inputs to the tube preamp circuits. On the primary side of the transformer are circuits for +48V phantom power, microphone impedance, 20dB pad, and line input. All of these are switched by sealed relays for reliability. Also, the relays are located at the point where the switching is required. This minimizes the signal path length and helps to keep noise low.

The combination of a 12AT7A tube and a 6922 tube form the principle gain stage, giving the ADL 600 its open and airy sound. This is primarily due to the circuit topology and the wide power supply rails applied to this stage-+/-320VDC. A high endurance Grayhill rotary switch and 1% metal film resistors are used to set the gain in 5dB steps. Polyfilm pulse capacitors are used for interstage coupling to maintain stunning clarity. The preamp stage drives the High Pass filter circuit and the Output trim. The High Pass filter can be bypassed or set to 40Hz, 80Hz, or 120Hz. Polyfilm capacitors are used for the filters, which are first-order and provide 6dB/octave roll-off. The Output trim potentiometer feeds the input to the second 6922 tube, which drives the Mumetal shielded output transformer. A DPDT relay allows for output phase reversal at the primary side of the output transformer.

PreSonus ADL 600 Stereo High Voltage Tube Microphone Preamp Features:

• High-voltage Class A dual-transformer design
• >73dB gain
• Selectable microphone input impedance
• Switched gain and variable fine trim controls
• Microphone (XLR), instrument (1/4"), and line (XLR) inputs
• Ultralow noise (-100dB S/N ratio)
• Variable high-pass filter, 48V, -20dB pad, polarity invert
• Analog VU and fast-acting LED metering

Make your mixes richer than ever. Order the ADL 600 today!

PreSonus ADL 600 Stereo High Voltage Tube Microphone Preamp Specifications:

• Input impedence:
• Microphone: Selectable, 150/300/900/1500 ohm
• Balanced line: 2k ohm
• Instrument: 100k ohm
  
  Maximum input level:
• Microphone (1500 ohm, +20dB pad out): +5dBu
• Microphone (1500 ohm, +20dB pad in): +25dBu
• Balanced line: +30dBu
• Instrument: +30dBu
  
  Gain range:
• Microphone (1500 ohm, +20dB pad out): +5dBu
• Balanced line: -12dB to 40dB
• Instrument: -5dB to 42dB
• Noise floor (all inputs, minimum gain): -95dBu (A-weighted)
• Microphone equivalent input noise (EIN): -125dBu (A-weighted)
• Frequency response: 10Hz to 45kHz ±1dB
• Maximum output level: +23dBu @ 0.5% THD+N
• Output impedance: 600 ohm
• Tube complement (per channel): 1 - 12AT7A, 2 - 6922
  
  General:
• Power (factory-configured): 115 or 230V AC/100 watts
• Dimensions: 19"W x 3-1/2"H x 17"D
• Weight: 28 lbs.

PreSonus ADL 600 Stereo High Voltage Tube Microphone Preamp

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Average of 4 User Ratings

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Customer Reviews

Overall

Quality

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Solid and buttery.

Posted by CBA from VA on Oct 4, 2008

Experience w/product: I own it

Reviewer's Background: Recording Engineer

Reviewer's Play Style: N/A

I own this and it's a great solid FULL preamp. No apologies. It's quiet and the high end is ridiculously smooth like butter. Great for everything but classical tracking. I'd use it to master a classical track though...

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Quality

Features

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Hand-Built and sounds like it

Posted by Kennedynamics from San Francisco on Jul 31, 2008

Experience w/product: I own it

Reviewer's Background: Home Recording

Reviewer's Play Style: Punk Funk

The ADL-600 isn't just the kind of pre-amp that makes mediocre mics great, it's the kind of rack mount device that borders on art just in it's build. It reminds me of a Ferrari, where you can see the 12-cylinders through the mid-engined plexiglass. Anyone who can see the tubes and clean layout through the top grill (and you'll need both hands to lift it!), plus the super-cool dual-analog needles, high quality chrome aircraft switches and graduated knobs can feel the quality of this beast. With Anthony Demaria's artful design and Presonus' ongoing dedication to building affordable and great sounding gear (I own the FP10 8-channel Firewire interface, and the pre-amps on that are still better than most dedicated mixers), i think the ADL-600 is one of those rack devices that will make you sound great and provide tons of options like switchable impedence, pole inversion, and of course, the presonus blue 'on' light that looks super cool.

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Features

Value

Best Preamp For Me So Far

Posted by Gordy from Richmond, VA on Feb 24, 2007

Experience w/product: I own it

Reviewer's Background: Active musician and songwriter

Reviewer's Play Style: Several

I've tried MP20, DBX, a few others, all less than $600, but laid out the 2 grand for this one and it was worth the money. Super sound, excellent noise control, and after two years it's still working like new...I have'nt tried them all, and maybe there's a better one, but so far, this is the best preamp I have found...

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Quality

Features

Value

Pretty good!

Posted by Casey from Winter Park, FL on Dec 4, 2005

Experience w/product: I have used it

Reviewer's Background: Recording Engineer

Reviewer's Play Style: Rock, Alternative

I used this in a vocal overdub session with a Blue Kiwi mic we got a very clean signal. We went straight off the mic panel to this pre-amp and then straight to pro tools. We bypassed the console completely so it was not in the signal path. It sounded great!

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PreSonus ADL 600 Stereo High Voltage Tube Microphone Preamp

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