This vacuum tube preamp was in my home studio. It has a few scratches on top but the front panel has no noticeable wear except at the screw holes (which will be hidden when put in a rack). I no longer have my studio so I brought this to a pro audio tech and he tested it for me and gave it a clean bill of health with no issues.

The dbx 586 is a 2-channel vacuum tube microphone preamplifier released in the late 1990s, designed to add analog warmth and classic tube character to digital and analog recordings. 

Key Specifications

• Tube Complement: Hand-selected 12AU7 vacuum tubes operating at a true high-voltage 230V rail rather than a "starved plate" design.
• Input Gain Range: +10 dB to +60 dB via the 'Drive' knob.
• Frequency Response: <10 Hz to >200 kHz (+0/-3 dB).
• Equivalent Input Noise (EIN): Typically -126 dBu (150 Ω source, unweighted, 20 Hz – 20 kHz).
• THD + Noise: 0.04% typical at +0 dBu out. [1, 2, 3, 4, 5]

Signal Path & Processing

• EQ Section: 3-band EQ with sweepable mids (100 Hz to 8 kHz). Includes a switchable Q-factor (Narrow 0.5 octave or Wide 1.5 octaves) for the midrange band and shelving Low/High bands at 80 Hz and 12 kHz.
• Limiter: Features a proprietary two-stage PeakPlus limiter with an adjustable threshold from 0 dBu to +22 dBu.
• Inserts: Individual 1/4'' send and return jacks per channel for integrating external processors (post-tube, pre-EQ). [1, 2, 3, 4]

Connectivity & Hardware

• Inputs/Outputs: Balanced/unbalanced XLR and 1/4'' connectors, featuring gold-plated Neutrik jacks.
• Phantom Power: Switchable +48V phantom power.
• Digital Output Option: Historically offered an optional digital output module utilizing dbx Type IV Conversion System (AES/EBU or S/PDIF at 16 or 20-bit).
• Dimensions: 3.5'' H x 19'' W x 8'' D (2U rackmount size).
• Weight: 10 lbs