LDR V25 Preamp Controller Board (Rev A)

LDR V25 Preamp Controller Released

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Update: April 9, 2017 – The new V25 LDR Preamp Controller board  has been released to manufacture and we expect to begin shipping units later this month. The design of the V25 evolved rapidly to overtake our plans for a subsequent V3 thus making the V25 the new V3. Confused? Read on!

V25 Preamp Controller To Succeed the V21

February 9, 2017 – Today, Tortuga announced plans to release the LDR V25 preamp controller (the “V25”) as the successor to its popular V2/V2.1 model that has anchored its award winning line of passive preamps since first being introduced to the market back in May 2014.

The V25 is a software driven audio preamp controller, attenuator and source input selector. The V25 allows the audio hobbyist, professional designer or OEM to build exceptional high performance passive and active audio preamps that rival the best high end preamps available today regardless of price.

Like its predecessors (the V1, V2 and V2.1 preamp controller) the V25 utilizes light dependent resistors (LDRs) to control volume. Tortuga Audio’s LDR based volume control technology is now in its 4th generation and delivers a level of sound quality that once you experience it you won’t want to go back to conventional potentiometers, stepped attenuators or even transformer based volume controls.

The V25 preamp controller utilizes a software driven 32 bit digital processor to control multiple analog LDRs using multiple digital-to-analog converters (DACs). The V25’s power supply is used solely to power the processor, regulate the resistance level of the LDRs and handle the IR remote communications.

Notwithstanding that the LDRs are actively controlled, the V25 is fundamentally a passive attenuation device wherein the power supply is optically isolated from the the audio signal which only “sees” the LDRs as simple passive resistors.

The V25 is a unity gain attenuator and provides no amplification of the audio signal.

More info on the V25 can be found here.

The V25 is the New V3

Our original plan was for the V25 to be an interim successor to the V2/V21 while we continued to develop and refine the future V3. As work on the V25 progressed we realized that we could accomplish almost everything with the V25 hardware platform that we’d planned for the subsequent V3. Although not all of the planned capabilities for the V25 would be available from day one, it will only be a matter of time and subsequent firmware updates to get there. This led to some last minute changes to the V25 hardware which delayed shipping the V25 boards by 2-3 weeks but we felt the delay was well worth it. Consequently, we are standing down from any further work on V3 design because for all practical purposes the V25 is now the new V3!

The V25 – An Improved LDR Preamp Controller

The V25 is an updated preamp controller design with numerous improvements over it predecessors including:

Integrated Input Switching & Simplified Signal Path

The V25 has a simplified signal path that accommodates switching between up to 6 different sources within a single circuit board and no longer depends on an external switching board with multiple interface points.

LDRs Used As Switches

The V25 preamp controller uses LDRs in lieu of conventional electromechanical relays for all input source switching.

More Powerful Processor

The V25 employs a contemporary 32 bit ARM Cortex M3 processor which has plenty of speed and capacity to power the Tortuga Audio line of preamp controllers as they continue to evolve and improve.

Precision LDR Control via 8 DAC channels

The V25 has 3 separate 12 bit DAC chips that together employ 8 separate DAC channels for better control of the LDRs resulting in smoother, more granular and more accurate attenuation and channel balance.

Mono Mode

The V25 introduces the ability to switch between stereo and monaural listening modes.

Balanced Audio Phase Reversal

The V25 preamp controller enables the user to optionally reverse the signal phase of balanced audio sources as a means of optimizing playback of any piece of music.

A More Refined Attenuation Curve

The V25 has a more granular attenuation curve with 120 steps representing 0.5 dB per step over the 60 dB attenuation range.

Hands-off Self-Calibrating LDRs

The self-contained LDR calibration process introduced with the V2 model has been refined to operate entirely in the background in the V25 and requires no user interaction. This built-in self-calibration feature ensures the the LDRs remain calibrated and perform optimally at all times.

Improved Power Supply

Even though LDRs on the V25 are optically isolated from the audio signals they control, overall sound quality benefits from improved power supply quality with a lower noise floor.

Networking of Multiple Boards

Multiple V25 preamp controller boards can be networked in order to control more than just 2 stereo channels. Initially this will be limited to connecting a pair of V25 boards for balanced stereo audio. Further development of the firmware will enable additional boards to networked together.

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