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PreSonus ADL 600 Stereo High Voltage Tube Microphone Preamp

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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 p... Click To Read More About This Product

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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.

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.

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.


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
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

Power (factory-configured): 115 or 230V AC/100 watts
Dimensions: 19"W x 3-1/2"H x 17"D
Weight: 28 lbs.
Pro Coverage
One year parts and labor warranty.

  • Customer Reviews

Review Snapshot

by PowerReviews
PreSonusADL 600 Stereo High Voltage Tube Microphone Preamp

(based on 2 reviews)

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Reviewed by 2 customers

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(11 of 12 customers found this review helpful)


Want Fat guitars? ADL600 Baby!!

By B.K.

from Aurora, CO.

Comments about PreSonus ADL 600 Stereo High Voltage Tube Microphone Preamp:

The ADL 600 is designed by botique pre-amp designer, Anthony DeMaria. Anthony DeMaria Labs makes several models of preamps and compressors. This particular model was picked up by Presonus who builds and markets it. Construction is solid with beefy metal knobs and military grade switches. The tone is what floors me. It's a fat sounding tube preamp that is clean and warm. It also has a nice smooth high end that's clearer than anything on the market. I've been running my guitar mics through this and into the Apogee Ensemble and it sounds phenomenal. Best guitar tones I've gotten yet! Move over Avalon, the ADL600 is here!! I've gotten to borrow one for an extended period of time, and can't wait to actually buy one.

(2 of 2 customers found this review helpful)


PreSonus ADL 600 - the final touch on your soundscape.

By Brian Holt

from LA, California

Comments about PreSonus ADL 600 Stereo High Voltage Tube Microphone Preamp:

I took the plunge on the PreSonus ADL 600 and so far am very happy with the results. I figured that to make a real difference you get what you pay for. This seems to have been the right logic, because the minute I put this device into the signal path things sounded better. My testing included several vintage analog synths, a modern analog synth, a late 90's analog modeling synth, a clone-wheel organ, and a very popular workstation synth, all running through a modest 12 channel mixer, which feeds the ADL 600 to its XLR Line ins. Out the ADL 600, to a Crown xTi2000, then to Yamaha SM15v club speakers. Settings on the ADL 600 are for simple line level application. I'm driving the preamp to just below the red line on the VUs. Nothing crazy, not looking for a pricey distortion box here. Result: instant gratification. I don�ۡ���t have any science to state here so I have to resort to subjective terms, but all the things I was looking for were present: warm, round, smooth, detailed, better balanced, and surprisingly, at high volume there was a noticeable reduction of harsh tones. Later this week I will be testing it with an older amp (Carver PM600), which I anticipate will further improve the way this preamp defines the sound. The cool thing was that I liked the sound of my rig so much that I played for about 5 hours non-stop! Could not tear myself away from it. I would add that the freshness of the soundscape inspired some new bits and pieces of music �ۡ���� that�ۡ���s what we are really looking for in equipment: Inspiration. Great piece of gear! Worth every penny. I can't wait to lay some tracks down and hear what this does in the recording environment. Thanks PreSonus!

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