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Several years ago, Anthony DeMaria, President of Anthony DeMaria Labs and Jim Odom President of PreSonus met at an AES show in New York. Jim noticed a prototype microphone preamplifier lurking in the back of the ADL booth and was intrigued. After chatting with Anthony about the design – three tubes per channel, dual input/output transformers, 600 volt power rails – he had to hear it. Totally floored by the mammoth sound and complete absence of noise, Jim was convinced this was a match made in sonic nirvana. Designed by Anthony DeMaria Labs, engineered and manufactured by PreSonus in the USA, the ADL 600 is a microphone preamplifier that has a sonic character like no other.

The ADL 600 is an original high voltage two-channel microphone preamplifier designed by world-renown analog tube circuit designer Anthony DeMaria. The ADL 600 utilizes a unique high voltage, Class A discrete design with three vacuum tubes per channel for maximum headroom and tonality. The ADL 600 is built by hand in the USA by PreSonus and utilizes the finest components in the world including switched attenuators, military-grade vacuum tubes, analog VU and LED meters, custom-designed proprietary transformers, and the list goes on. No expenses are spared with the ADL 600 down to the last polypropylene film capacitor. The ADL 600 is big, warm, smooth, and clear; a sound like no other.

Control and Flexlibility
The ADL 600 is designed for ulitimate sonic performance, however its ease of use and flexibility allowing for many types of input sources further sets it above all other preamplifiers. The input selector allows for selection between Hi-Z instrument input, line input and four different microphone impedances for a wide variety of sounds and applications. The High Pass Filter is a rotory switch with three filter settings (40Hz, 80Hz, and 120Hz @ 6dB per octave) for passiively and unobtrosivly controlling room rumble and low frequency noise. The input gain attenuator is a military-grade rotory switch delivering 5dB step increments and a total preamplifer gain of over 72dB. The output stage is contolled by a fully variable conductive plastic attenuator delivering +/-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 both controlled by big sturdy military grade switches.

Under the Hood
The ADL 600 is built with the finest components available in the world. The ADL 600 is a fully discrete transformer input and output Class A design incorporating three military-grade vacuum tubes per channel operating at voltages of +/-300V power rails for maximum tube tonality and headroom. There are no op-amps or integrated circuits (IC's) in the signal path to ensure the purest sound possible. The dual tranformer design also ensures ultral low noise operation with maximum common mode rejection.

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

Breathtaking
The ADL 600 sets a new standard in tonatily for tube preamplifiers. Vocals become big, smooth and articulate, bass guitars are deep and tight, and mixes become richer than ever. The ADL 600 is breathtaking both in terms of appearance and in sound performance. The ADL 600 delivers a sound like no other.

For an In-Depth Look at the ADL 600 click here
 
FEATURES INCLUDE

• Class A High Headroom Transformer Coupled Microphone Preamplifier
• High-Voltage Class A Dual Transformer Design
• >73dB Gain
• Selectable Microphone Input Impedance
• Switched Gain and Variable Fine Trim Controls

PHOTO GALLERY

• Microphone, Instrument and Line Inputs
• Ultra Low Noise (-100dB S/N ratio)
• Variable High Pass Filter, 48V, -20dB Pad, Polarity Invert
• Analog VU and Fast-Acting LED Metering
• Price: $2,295

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• All tube design (no IC's or chips)
• All parts are designed based on the original Fairchild 670
• All capacitors and resisters match values as per original
• XLR input / output
• Handbuilt in the USA
• Heavy-Duty Chassis
• Handles located on front and sides
• Great for analog & digital recording, tracking, mastering, as well as live

• One Year limited warranty
• Vents on front and sides for maximum air flow
• Two 24 volt fans (voltage set at 20 volts for silent operation)
• One Bottom PCB (Hinged Standoff)
• One Top PCB (Hinged Standoff)
• Two Back PCB's

• Remote Power Supply
• One PCB
• Detachable AC Cable
• Front Power Switch
• Keep All Vents Clear of Obstructions
• R-313 - This pot sets B+ voltage, must be set at 240 volts
• Remote Power Umbilical Cable - 18-gage 600 volt multi pin five foot cable
• Rear Tube Fan - power to fan set at 20 volts for silent operation

• Front Blue Grill Lamp - indicates power to fan, if this lamp is off must check all three fans, 1-installed in power chassis and two in main unit. If unchecked may cause serious overheating
• Fuse - 5 amp S/B 5x20mm
• Tube compliment - (1) 6084, (1) 5651, (1) EL 34, (1) GZ 34
• Power Requirements - 120 volts, 50-60 cycles
• Rack Space - 3-U High, 14" Depth
• Shipping Weight - 42 lbs.

ADL has developed a non-tube proprietary discrete design. This new power supply is versatile enough to be used with either the ADL Mono 660, Stereo 670, or the original 670 Fairchild. ADL has started to integrate this new power supply with the original 670 units too.

• Remote Power Supply eliminating any transformer magnetic noise
• 6 foot umbilical custom cable between power supply and main unit
• 3 U High chassis

• 6386 Heaters 6.3-VDC
• Remaining Four tube heaters 6.3-VDC, plus meter lamp
• Ventilation Fans
• 6386 bias voltage negative 6.2-VDC
• 6386 Q point voltage negative 19.9-VDC
• 6973 grid voltage negative 14.6-VDC

Additional High Voltages Include

• 442-VDC
• 242-VDC
• 160-VDC

TRANSFORMERS.......................................2
SHIPPING WEIGHT....................................31 Lb
POWER CONSUMTION.............................47.5 WATTS
120-VAC FUSE............................................2-A S/B 5x20mm
230-VAC FUSE............................................1/2-A S/B 5x20mm

6386 BIAS VOLTAGE NEGATIVE 6.2-VDC
This voltage feeds both cathodes (pin-2, 8) of each half of the 6386, allowing the tube to operate at its' peak performance. As elevtrons befin to gather near the filament, they need a slight push toward the plate and because the grid is slightly more negative then the filament the electrons are pushed away from the grid and towards the plate.

6386 Q POINT VOLTAGE NEGATIVE 19.9-VDC
This voltage connects into the A-26 audio transformer which then feeds both grids (pins-3, 7) of each half of the 6386. Its' purpose is to set the operating or quiescent point. Because this voltage is negative relative to the cathode, it will draw electrons away from the filament and toward the plate which is considered positive in respect to the grid. Every tube has an operating window or region in which the tube operates at its' best performance. According the 6386, a negative voltage of 19.9-VDC will allow the tube to operate at its' peak performance facilitating proper electron flow from the filament to the grid.

6973 GRID VOLTAGE NEGATIVE 14.6-VDC
This voltage connect to the grid (Pin-3). As described before, this voltage sets the operating zone or window allowing the tube to operate at its' peak performance.