LDR1B.V2 Balanced Passive Preamp

LDR1B.V2 Balanced Passive Preamp

Price: $1,895

This is a legacy product and is no longer produced or sold by Tortuga Audio.

This model was eventually replaced by the updated LDR1B.V25.
A LDR1B.V2K kit version of this preamp was also available.

A fully balanced audiophile grade passive (unity gain) preamp with a single input and dual parallel outputs, designed around Tortuga Audio’s third generation LDR technology — a balanced, single-input counterpart to the LDR3.V2. The LDR1B.V2 comes in silver or black anodized, and lacquered bamboo, front panels, with Neutrik XLR signal jacks on the rear panel.

Eliminating input switching hardware entirely gives the LDR1B.V2 true balanced attenuation with a straight in/out signal path — Tortuga Audio considered it among its best sounding LDR preamps at the time.

Subjective performance

Descriptive words and phrases commonly used by both customers and reviewers to describe the sound include: colorless, transparent, neutral, articulate, clear, fuzz-free, clean, natural, high resolution, great mid-range, solid bass.

The consensus is performance superior to conventional passive preamps using even the best audiophile grade potentiometers, stepped resistive attenuators, or most transformer-based volume controls — and matching even the finest high-end active preamps costing many thousands of dollars more.

Key features under the hood

  • Optically isolated passive attenuation — there’s no amplification or buffering of the audio signal notwithstanding the presence of a power supply. Audio signals are optically isolated from both the power supply and the LDR control circuitry.

  • 3rd generation LDR technology — built with the LDR3x (V2.1) preamp controller, using microprocessor-controlled analog LDRs for both audio attenuation and input switching.

  • Auto calibration — self-contained auto-calibration keeps the unit precisely calibrated as the LDRs age.

  • Firmware updates via USB — updateable by the customer via a rear-panel USB port, downloaded from the Tortuga Audio website and uploaded from a PC (Mac support was never completed).

  • Replaceable LDR modules — LDRs have an estimated useful life upwards of 50,000 hours, but just like tubes, our LDR modules are easily replaceable.

Available options

  • Front panel: clear silver anodized aluminum, black anodized aluminum, or bamboo

  • Power supply: US domestic 120 VAC — 12 VDC 0.5A linear regulated "wall-wart," 2.1mm positive pin. International 100/240 VAC — 12 VDC 1.0A switching "brick" with detachable IEC cord and US AC plug, 2.1mm positive pin

Specifications

  • Preamplifier type: passive unity gain without buffer; attenuation via LDRs in an L-Pad configuration

  • Attenuation range: -60 dB to 0 dB in a 70-step attenuation schedule

  • Compatible amplifiers: works best with tube or solid state amps having input impedance of 20k ohms or higher

  • Impedance characteristics: 20k ohms nominal, configurable between 1k and 100k per channel

  • Control system: software-based 8-bit digital microcontroller driving 12-bit digital-to-analog volume control

  • Software: updateable via download from the website, uploaded via USB cable from a PC

  • Auto calibration: user enabled/disabled, self-contained auto-calibration of LDRs to correct for drift/aging

  • Replaceable LDR modules: similar to tubes, LDR modules can be easily unplugged and replaced

  • Display: dual numerical displays (blue) providing volume and status information

  • Control methods & functions: remote via the Apple Remote, or front-panel rotary encoder with integral push-button switch — power on/off, volume raise/lower, mute/unmute with smooth ramping, channel balance adjust & reset, display brightness raise/lower, channel input select, auto-calibration start/stop, remote pairing (via encoder push-button only)

  • Power supply: 115 VAC in / 12 VDC 0.5A out external "wall-wart," 5mm barrel plug, 2.1mm pin; 240 VAC in / 12 VDC 1.0A out external switch-mode "brick," 5mm barrel plug, 2.1mm pin, detachable IEC cord. Low noise/ripple, max +/- 20 mV

  • 12V trigger out: heavy duty chrome-plated through-hole threaded phone jack, 12V signal when the unit is on

  • USB port: dual Type A, for control software updates

  • Point-to-point wiring: milspec teflon-insulated silvered copper wire for power & audio I/O to PCB; optional Neotech UP-OCC solid copper wire for the audio signal path

  • Inputs/outputs: 1 balanced XLR input; 2 parallel balanced XLR outputs

  • Audio connectors: standard black Neutrik brass/bronze XLR connectors

  • Enclosure: robust black powder-coated extruded aluminum box; 0.1" black anodized milled aluminum rear panel; 0.25" anodized milled aluminum or 0.375" 3-ply bamboo front panel; dark acrylic see-through front panel accent/inlay in front of the display; non-slip black polyurethane rubber feet

  • Size (shipped package): 8" W x 12" L x 6" H

  • Size (unit): 6" W x 8" D x 3.5" H

  • Weight (shipped package): ~7 lbs

  • Weight (unit): ~4 lbs

  • Items included: preamplifier, Apple Remote, external power supply, USB cord