Presonus ADL600 Twin Channel High Voltage Valve Preamp

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Class A Preamp designed by Anthony DeMaria

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Manufacturer: Presonus

Category: Recording & Playback

*Note that the price is based on when we previously had this product in stock. When placing an order for an item temporarily out of stock, in most cases the price will remain the same, however occasionally the price may be subject to change. If this is the case then we'll tell you straight away and offer a refund.



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.

The ADL 600’s high-pass filter employs a rotary switch with three filter settings (40 Hz, 80 Hz, and 120 Hz at 6 dB/octave) for controlling room rumble and low-frequency noise.

The input-gain attenuator is a military-grade rotary switch that provides eight 5 dB stepped increments and a total preamplifier gain of over 73 dB. 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. And of course, you get +48V phantom power, polarity inversion, and a 20 dB pad, controlled by big, sturdy, military-grade switches.

2 input channels, each with:

  • Mic, line, and instrument inputs
  • High-voltage, Class A, dual-transformer, vacuum-tube preamp
  • 3 military-grade vacuum tubes
  • Input-source select
  • Variable mic-input impedance (150, 300, 900, 1,500Ω)
  • Variable high-pass filter (40, 80, 120 Hz)
  • 8-position Gain switch
  • Variable Trim adjustment for final stage
  • 48V phantom power
  • -20 dB pad
  • Polarity-reverse switch
  • Backlit VU meter (output level) with -6 dB switch (for metering hot signals)
  • > 73 dB of gain


  • 2 unbalanced ¼” instrument inputs (front panel)
  • 2 transformer-balanced XLR line inputs
  • 2 transformer-balanced XLR mic inputs
  • 2 transformer-balanced XLR line outputs


  • 2U 19” rack-mountable, rugged steel chassis
  • Internal power supply with standard IEC connector
  • Chassis-ground link connectors (lift chassis ground)

Additional Info

Additional Info


Input Impedance

  • Microphone Selectable, 150/300/900/1500Ω
  • Balanced Line 2 kΩ
  • Instrument 100 kΩ

Maximum Input Level

  • Microphone (1500Ω, +20 dB Pad out) +5 dBu
  • Microphone (1500Ω, +20 dB Pad in) +25 dBu
  • Balanced Line +30 dBu
  • Instrument +30 dBu

Gain Range

  • Microphone (1500Ω, +20 dB Pad out) 18 dB to 72 dB
  • Balanced Line -12 dB to 40 dB
  • Instrument -5 dB to 42 dB


  • Noise Floor (all inputs, minimum gain) -95 dBu (A-weighted)
  • Microphone Equivalent Input Noise (EIN) -125 dBu (A-weighted)
  • Frequency Response 10 Hz to 45 kHz ±1 dB
  • Maximum Output Level +23 dBu (@ 0.5%THD+N)
  • Output Impedance 600Ω
  • Tube Complement (per channel) 1-12AT7A, 2-6922


  • Internal supply, standard IEC connector 115 or 230 VAC / 100W


  • Dimensions 2U rackmount
  • Height 3.5” (88.9 mm)
  • Depth 17" (431.8 mm)
  • Width 19” (482.6 mm)
  • Weight 28 lb. (12.7 kg)