Product Documentation

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5.V2 Controller

Preamp Controller Board

The LDR3x.V2  board (the “V2”) was released on May 7th, 2014 with numerous improvements and new features as outlined below. 

The V2 is a preamp controller in the form of a populated 2.5 inch by 4.8 inch printed circuit board that forms the core of a passive preamp or as the attenuator/controller of an active preamp. The V2 builds on the experience and success of the V1 board.

ldr3x.v2 passive preamp controller board - top view

Insofar as the V2 lacks a power supply, controls or enclosure it is neither a complete finished audio premap nor is it a comprehensive kit.

Once connected to an external power source (not included), the V2 can accommodate one (1) single-ended audio input without any additional equipment and up to three (3) inputs when interfaced with an external input relay board (not included). 

The V2 is sold with an uninstalled infrared receiver module required for remote control. The IR receiver module can either solder to the V2 board, located external to the board, or mounted to the DM1 Display Module master board. 

The V2 can be controlled by the Apple Remote or Encoder or both. Neither are included with the V2 and must be purchased separately. Control inputs that are enumerated and explained in sections below.

The V2 is part of the Tortuga Audio family of LDR based passive preamps.

New Features 

The V2 introduces numerous new features many of which distinguish the Tortuga Audio LDR preamp controller from all other alternatives in the audio market. 

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 have an internal LED light source, 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 around $20? Done!

Increased Precision 

Whereas the V1 used 8 bit digital pots,  the V2 board employs both 12 bit DACs and ADCs. 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.

Better Power Supply

Version 2 replaces a linear voltage regulator with 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!

Software Updates via USB

The V2 uses an on-chip USB bootloader which allows software updates to be handled via a USB connection to a PC. Thus, software updates can downloaded from our website out and owners can upload the latest software into their V2 board from their laptop/desktop PC. 


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