Characteristics – Colorless, transparent, neutral, articulate, clear, fuzz-free, clean, natural, high resolution, great mid-range, solid bass. These are words and phrases commonly used by both customers and reviewers to describe the LDRx passive preamplifier sound.
Compared To Other Types of Passives – The consensus of customers and reviewers is you can expect performance that is superior to conventional passive preamps utilizing even the best audiophile grade potentiometers, stepped resistive attenuators or even most transformer based volume controls.
Compared To Active Preamps – Independent reviewers have found that the Tortuga passive preamps match the performance of even the finest high-end preamps costing many thousands of dollars more.
Key Features Under The Hood
Optically Isolated Passive Attenuation – The LDR3.V2 is a true passive preamp insofar as 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: The LDR3.V2 is built with our 3rd generation LDR3x.V2 preamp controller which employs microprocessor controlled analog light dependent resistors to provide audio attenuation and input switching with unparalleled audio quality.
Auto Calibration: Similar to tubes, LDRs are analog devices subject to aging and drifting over time. Unlike tubes, the LDRx & LDRxB employ self-contained auto-calibration to keep the unit in precise calibration. This provides added assurance that the preamp will hold its value over the long haul.
LDRs For Input Switching: The LDR3.V2 also uses LDRs for audio input switching in lieu of relays. Auto Calibration does employ relays but these are physically disconnected from the audio signal path during normal operation.
Software Updates via USB: If warranted, software can be easily updated by the customer via a USB port located on the rear panel. Software updates can downloaded from our website and uploaded into the LDRx from a laptop or desktop PC. Eventually, we hope to make the possible from a Mac as well.
Replaceable LDR Modules: While the useful life expectancy of LDRs are estimated to be upwards of 50,000 hours, just like tubes, some may fail earlier or go sufficiently out of spec over time to warrant replacement. And just like tubes, our LDR Modules are easily replaceable ensuring the lasting value of your passive preamp investment.
- Front Panel
- Clear silver anodized aluminum
- Black anodized aluminum
- Power Supply
- 120 VAC (domestic) – 12 VDC 0.5 amp linear regulated external “wall-wart” style power supply – 2.1mm pin (positive)
- 240 VAC (international) – 12 VDC 1.0 amp switching power supply “brick” with detachable IEC power cord with US AC plug – 2.1mm pin (positive)
- Preamplifier Type: Passive unity gain without buffer | attenuation via light dependent resistors (LDRs) in an LPad configuration
- Attenuation Range: -60 dB to 0 dB in a 70 step attenuation schedule (see impedance/attenuation diagram below)
- Compatible Amplifiers: Works best with tube or solid state amps having input impedance of 20k ohms or higher
- Impedance Characteristics: Adjustable input impedance with default 20k ohms (see impedance/attenuation diagram below)
- Control System: Software based 8 bit digital microcontroller driving 12 bit digital-to-analog volume control
- Software : Updateable via download from website and upload via USB cable from 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 if warranted
- Display: Dual numerical displays (blue) providing volume and status information
- Control Methods & Functions: Remotely controlled via the elegantly simple Apple Remote | Front panel control via rotary encoder with integral push button switch
- Power on/off
- Volume control
- Muting (with smooth ramp up/down of volume)
- Channel balance adjustment
- Input impedance adjustment
- Display brightness adjustment
- Display timeout adjustment
- Channel input select with adjustable max volume when new input selected
- Auto calibration start/stop
- Remote pairing (enabled via encoder bush button only)
- Input Switching: Audio signal switching done via LDRs - no electromechanical relays in the signal path
- Power Supply:
- US Domestic - 120 VAC Mains
- 12 VDC @ 0.5 amp low noise linear regulated external "wallwart"
- 2.1mm pin (positive) barrel plug
- 12 Volt Trigger Out: Heavy duty chrome plated through-hole threaded phone jack provide 12 volt signal when unit turned on
- USB Port: For updating control software if warranted.
- Point-to-point Wiring: All internal point-to-point wiring of power & audio I/O to PCB utilizes milspec teflon insulated silvered copper wire. Neotech UP-OCC solid silver wire available for hookup of the audio signal path.
- Inputs: 3 single-ended RCA inputs
- Outputs: 2 parallel single-ended RCA outputs
- Audio Connectors: Cardas GRFA-L rhodium over silver plated brass RCA jacks
- Robust black powder-coated uni-box extruded aluminum box
- 0.1 inch black anodized milled aluminum rear panel
- 0.25 inch black or silver anodized milled aluminum front panel
- Dark acrylic see-through front panel accent/inlay in front of display modules
- Heavy duty non-slip black polyurethane rubber feet | it stays where you put it
- Size (shipped package): Width - 8" | Depth - 12" | Height - 6"
- Size (unit): Width - 6.0" | Depth - 10.0" | Height - 3.5"
- Weight (shipped package): ~6.5 lb
- Weight (unit): [TBD]
- Items Included:
- Apple Remote
- External Power Supply
- USB Cord (for potential firmware upgrades)
- Typical Attenuation & Impedance - see example below for impedance adjusted to 10k