LDR3000P.V25 High Performance Passive Preamp


The LDR3000P.V25 is no longer being produced and has been replaced by the LDR3000x.V3 High Performance Preamp which is available with an updated V3 controller and is available configured as a passive preamp at a comparable price.
  • Remote controlled passive preamp
  • 3 XLR & 3 RCA inputs | XLR/RCA outputs
  • 100 step LDR attenuator
  • True unity gain passive with dead quiet background
  • Hi resolution OLED visual display

If you’re looking for high performance passive preamp we don’t believe you’ll find many passive preamps that sound better than the LDR3000P. Don’t take our word for it. Go ahead, buy one, and  you’ll have 30 days to try it at home in your own system. If you’re not happy with the LDR3000P you can return it within 30 days for a 100% refund less your cost for return shipping.

Out of stock

SKU: LDR3000P.V25 Category:
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A Flexible High Performance Passive Preamp

The LDR3000P is Tortuga Audio’s flagship passive preamp for the discerning audiophile who appreciates the best that a passive preamp has to offer.

LDR V25 Preamp Controller Board (Rev A)The LDR3000P is designed around our proven 4th generation remote controlled V25 volume/preamp controller that uses digitally controlled analog light dependent resistors (LDRs) to provide smooth 100 step volume control over a 60 dB range. Features include ramped muting/unmuting, channel balance adjustment, input switching, mono mode, plus our highly unique adjustable input impedance. Built-in calibration of the replaceable socketed LDRs ensures accurate attenuation, channel balance and optimal performance over the extended life of the preamp.

The LDR3000P is easy to operate via an intuitive interactive menu driven control interface designed around  the 7-button Apple remote and a bright easy to see 256 x 64 pixel white-on-black graphic OLED (Organic Light Emitting Diode) display.

The result is an outstanding audiophile grade passive preamp that combines advanced LDR (light dependent resistor) technology with a contemporary minimalist visual interface designed to satisfy the most demanding audio enthusiast.

Passive Preamp for both Single-Ended & Balanced Systems

Whether you have RCA gear, run with all balanced, or a mix of both, you don’t have to choose because the LDR3000P Passive Preamp handles both. There are 3 sets of RCA inputs and 3 sets of XLR inputs that you can use in any combination. The RCA and XLR outputs carry the same output signal regardless of the signal source type although the balanced output will only have one phase active (pin #2) if the input source is single-ended.

What To Expect from this Passive Preamp

If you haven’t tried a passive preamp before, or even if you’re already a fan of passive preamps, the LDR3000P will likely surprise and delight you.

The words people use to describe our LDR preamps include colorless, transparent, neutral, articulate, clear, fuzz-free, clean and natural. Paired with a high quality source component you can expect satisfying dynamics, a beautiful mid-range, and surprisingly solid bass. The 100 step attenuator is ultra-smooth with no clicks or pops and no mechanical contacts to corrode or wear out – you won’t even realize the preamp uses a stepped attenuator.

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 attenuators  and most transformer based volume controls.

When well matched with source components that have a robust output stage,  you’ll be hard pressed to find a better preamp anywhere regardless of price.

Passive Preamp Key Features

LDR Volume Control

Light Dependent Resistors (LDRs) are at the center of Tortuga Audio’s passive preamp technology. LDR based volume control deliver a clean, neutral yet satisfying sound that defies explanation but is nevertheless undeniable.  The result is a super smooth 100 step analog volume control complete with channel balance adjustment, muting and mono mode.

OLED Display & Remote Control

We’ve done away with all conventional buttons, dials and switches and replaced them with a single multi-function encoder control knob and a contemporary menu driven OLED display and a simple 7 button Apple remote. Audio gear for the 21st century.

Dead Quiet Signal Path

With no active signal amplification or buffering the LDR3000P is true unity gain preamp designed solely to provide passive volume control and input switching. The absence of actual signal amplification (gain) is rarely a drawback since nearly all source components have sufficient line stage output voltage to drive most amplifiers to ear splitting volume levels. Why amplify when you don’t need to. Go passive.

Built-in LDR Calibration

Just like tubes, LDRs are analog devices subject to aging and performance drifting over time. Unlike tubes,  our LDR preamps have built-in calibration that adapts to the LDRs as they age and to calibrate a new one if it requires replacement (all LDR modules are plug-in replaceable). This provides added assurance that your preamp investment will hold its value over the long haul.

No Relays In The Signal Path

LDRs are also used for smooth audio input switching thus eliminating the use of noisy electro-mechanical relays and their mechanical switching interface points.

Replaceable Plug-in LDR Modules

LDRs are estimated to have a useful life upwards of at least 50,000 hours. However, just like tubes, some may fail earlier or go sufficiently out of spec over time to warrant replacement. And just like tubes, our plug-in LDR Modules are easily replaceable ensuring the lasting value of your preamp investment.

Firmware Update via USB

Our software driven preamp controller can be easily updated by the customer via a pair of USB ports located on the rear panel. Software updates can downloaded from our website and uploaded into the preamp via a simple PC application.

Passive Preamp Specifications

These specifications reasonably reflect the current model but are subject to updating and modification without notification.

General Summary Remote controlled passive LDR preamplifier with visual OLED display and a 100 step LDR (light dependent resistor) attenuator with no gain stage or buffer, that handles 3 inputs balanced (XLR) inputs and 3 single-ended (RCA) inputs.
Audio SignalsInputs6 total inputs including 3 single-ended RCA stereo inputs and 3 balanced XLR balanced stereo inputs
Outputs1 RCA stereo output and 1 balanced XLR balanced stereo output
Mixed Signals* Output from single-ended inputs are available on one phase only (pin 2) of the balanced output.
* Only the output from one phase (pin 2) of balanced inputs are available on single-ended output
Input CouplingInput signals are direct coupled to the tube grid (no coupling capacitors)
Output CouplingOutput signals are AC coupled through coupling capacitors
Input SwitchingAll input signal switching is done via LDRs (light dependent resistors) with signal isolation in excess of 10 megaohms when turned off
Output IsolationOutput signal isolation (disconnection and/or grounding) is done by a combination of LDRs and miniature relays.
AttenuationTechnologyDigitally controlled, optically isolated, analog LDRs (light dependent photo-resistors) in a series/shunt L-Pad voltage divider configuration.
Steps100 steps of ~0.6 dB per step plus 1 additional muting step.
Range -60 dB to 0 dB
ChannelsFour (4) independent channels for handling stereo audio of both 2-channel single-ended and 4-channel balanced signal types with 2 LDR Modules per channel (total of 8 attenuation LDRs).
Channel BalanceLeft/right channel within 0.5 dB over full attenuation range with +/- 20 step channel balance adjustment at ~0.6 dB per step for a nominal max channel balance adjustment range of +/- 12 dB and
LDR ModulesEach individual LDR is packaged as a compact easily replaceable 4-pin socketed plug-in module that plugs into a 4 pin header. LDR modules are not mechanically keyed so attention must be paid to aligning white dot on module with corresponding white dot on printed circuit board when removing/replacing.
LDR Calibration The preamp includes a built-in software driven closed-loop measurement circuit that measures and calibrates each attenuation step of each LDR over the full attenuation range. Calibration compensates for any LDR performance changes over time or in the event an LDR needs to be replaced. During calibration the preamp operates "off line" and cannot play music. A calibration cycle typically lasts ~10 minutes.
Input/Gain StageTypeNone
GainNone (1x - unity)
Output/Buffer StageTypeNone
Output CapacitorNone
IsolationOutput signals are shunted to ground (effectively turned off) when preamp is powered down, muted, or running LDR calibration.
ImpedanceInput Default input impedance is 20k ohms with ability of user to configure up to 9 additional input impedance settings each between 1k and 99k that user can switch between to determine potential optimal input impedance for user's system.
OutputOutput impedance is fixed at ~100 ohms
PerformanceTotal Harmonic DistortionWhile not exhaustively measured is generally well below 0.5% under worst case scenarios.
Power Supply Mains InputIEC type socket with lighted switch and fuse drawer with external 0.5 A fuse plus spare | 120 to 240 AC
Type10W switching 12V DC rated at 0.85 A
ControlsControllerV25 Preamp Controller | Rev C | ARM M3 Cortex 32 bit microcontroller running at 72 MHz
Remote Silver 7-button Apple infrared remote (38 kHz NEC protocol)
Encoder Front panel control knob attached to a rotary stepped encoder with integral push button switch
Display 256x64 pixel white-on-black OLED display work in conjunction with software driven interactive menu driven control interface designed around the 7-button Apple remote. Please refer to online documentation for detailed explanation of the preamp controls.
Control Menu Control menu items - see online product documentation for control operation details

* Off (top menu item)
* Volume (default)
* Input
* Display
* Impedance/Cal
* No of Inputs
* Volume Units
* Volume Max
* Volume Display
* Version
* Reset

Mono Mode: User can switch between stereo and mono mode via the remote by pressing Center button twice in a row
Trigger OutRear panel mounted mono phone jack outputs a 12 V DC signal when unit is turned on. Signal can be used to turn other devices on/off that are equipped with a Trigger Input.
USB PortRear panel mounted dual type A USB port allows external PC based bootloader application to update controller's firmware | USB cable provided | firmware updating instructions can be found in online product documentation
EnclosureCaseHeavy wall extruded aluminum case with black powder coat finish
Front Panel0.25 inch thick brushed anodized aluminum with dark grey acrylic inlay in front of visual display attached via socket head screws
Rear Panel0.1 inch thick brushed anodized aluminum attached via socket head screws
FeetHudson Audio platinum silicone, non-skid, vibration absorbing, 1 inch hemispherical feet (four)
Other DesignPrinted Circuit BoardHigh quality nickel immersion gold solder printed circuit boards with blue solder mask
SolderLead free solder with 3% or higher silver content
ROHSCompliant or exempted
Ambient CriteriaPreamp must be operated in a stable, dry indoor environment only with stable ambient temperature within 60-90 degree F
Dimensions3.5 inches tall | 12.0 inches wide | 9.0 inches deep
Weight~ XX pounds | ~XX pounds as shipped
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