Abacus LDR3 V2 Passive LDR Preamplifier

Passive preamplifier based on the latest Tortuga Audio LDR3xV.2 board with Auto Calibration, replaceable LDR's, and USB port for software updates. It uses pairs of microchip controlled Silonex LDR's to achieve the best in signal attenuation with perfect balance.

Preamplifier has 3 inputs and one pair of outputs. All functions can be controlled via front panel rotary encoder or remote control: on/off, volume, input selection, mute, balance.
Preamplifier also has 12V trigger output.

Highest quality copper RCA connectors, Teflon silver wire, aluminum chassis, aluminum feet.

USB port is used for controller software updates which also allows for choosing different impedance curves via different software packages downloadable from Tortuga website. Preamp will ship with the latest software package available.

On a personal note I must say that this version of LDR3X sounds absolutely amazing in front of my 300b amp. I have built and used many other LDR preamps and this one seems to be the best yet.

For more information on LDR3xV2 board please visit Tortuga Audio website.

Listing also includes 12V power supply.

Shipping in CONUS $14.00 PayPal add 3%

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The LDR3x.V2 – What Is It?

The LDR3x.V2 is an a passive preamp controller designed around light dependent resistors (LDRs) that allows the DIY’er to build a passive or active preamp with exceptional audio performance that can be controlled with a remote.

Digitally controlled, analog audio preamp controller in the form of a populated 2.5 inches wide by 4.7 inches long printed circuit board
Controllable via the Apple Remote (not supplied) or comes with an optional Tortuga Audio handheld IR remote
Allows the DIY audio enthusiast to build their own exceptionally transparent and articulate balanced or unbalanced audio preamplifer
Rivals the performance of even the best high end preamp costing 10-100 times more than the LDR3x.V2
By itself is an unrivaled passive preamp/controller but can also be incorporated into any DIY active preamp design
Utilizes light dependent resistors (“LDR”) in lieu of conventional potentiometers or stepped resistive attenuators for volume control
Precision control of the LDRs and all other functionality of the LDR3x.V2 is done via a software driven on-board microcontroller (microprocessor)

Auto Calibration - Version 2 will no longer be dependent on specialized external test equipment and software tools for initial calibration and tuning of the LDRs. All of that is now self-contained in the board itself. In the event one or more LDRs age differently and drift out of calibration, the LDR3x.V2 can adjust each LDR’s attenuation table to bring the unit back into precise calibration. This also mitigates dependence on having to use matched sets of LDRs in each build. Also, owners are no longer dependent on us for storing and maintaining their calibration data should updates be needed in the future.

Replaceable LDR Modules - LDRs are similar to tubes insofar as they are nonlinear analog devices, they light up inside, they don’t behave exactly the same from one to the next even if the same make/model, their performance characteristics can change over time, some fail early on, and they eventually age and die (although 50,000 hours is a long life). Wouldn’t it be nice to just yank a bad one out, and stick in a nice new one for less than $20? Done!

Increased Precision - Whereas Version 1 used 8 bit digital pots, Version 2 employs 12 bit DACs. This gives the LDR3x.V2 16 times greater precision in adjusting the resistance values of the LDRs. This means more precise channel matching over the full attenuation range and that translates directly into improved stereo imaging and sound stage.

Quieter Power Supply - Version 2 replaces a linear voltage regulator for a precision low noise switching power supply module with superior ripple rejection. The result is a darker background between the notes and improved articulation and expression of sound. What does this mean? It now sounds even better!!

Separate Channel Grounds - Left/right channel grounds are kept separate leaving the option of grounding them at the attenuator or elsewhere in the audio signal pathway. The net benefit it to make it easier to isolate grounds and avoid the audible hum inherent in ground loops.

Software Updates via USB - Version 2 uses an on-chip USB bootloader which allows software updates to be handled via a USB connection to a PC. Thus, software updates can be emailed out and owners can download the updates to the LDR3x board from their laptop/desktop PC. Eventually this will also be doable from a Mac as well.