Looking for a V4 DIY bundle?

Check out our V4 bundle option that includes the V4, LDR module, remote, plus OLED display assembly both with and without the optional solid state buffer module.

V4 series LDR attenuator & preamp controller

The V4 is the successor product to Tortuga Audio's popular V3 model preamp controller. The V4 series represents Tortuga Audio's 5th generation audio attenuation technology designed around light dependent resistors (LDRs) since initial introduction in 2012.

The V4 series LDR attenuator & preamp controller is a 2-channel, 100 step stereo volume/preamp controller with integrated input switching for switching between up to 4 different audio sources. The V4 comes with an infrared remote control plus local control via a rotary encoder (with integral pushbutton), together with a sporty high contrast OLED display with a menu driven interactive user interface.

V4 preamp controller LDR module install diagram — V4 board shown with socketed plug-in quad LDR module removed

The V4 stepped attenuator and preamp controller board is available to the DIY audio enthusiast, professional designers and OEMs. Tortuga Audio may from time to time also offer finished preamps built around the V4 series preamp controller technology.

Technology

The V4 is an analog device at heart but has a fully digital brain. The V4 is run by a 32 bit ARM microcontroller. Despite its digital nature, the V4 performs no digital signal processing on the audio signal, there's no signal amplification (no gain), and the power supply present never touches the audio signal.

Under the hood, the V4 utilizes filtered high resolution pulse-width-modulation together with precision differential op amps to accurately achieve target LDR current/resistance levels. Refined over 15 years of development, Tortuga Audio employs LDRs to smoothly attenuate audio over a 60 decibel range using 100 discrete steps with no sonic artifacts and no mechanical components.

To be useful, the relationship between LDR control current and LDR resistance level must be known. Since this performance curve is unique to each LDR and will likely change slightly over time, Tortuga Audio employs a proprietary algorithm that literally measures and records current vs. resistance at each of the 100 attenuation steps. This calibration process takes place with the preamp "offline" and typically less than 10 minutes and can be performed at any time to keep the preamp optimally tuned. This unique feature is literally built into the hardware and software of the V4.

Performance

The V4 offers a subtle yet pleasant improvement in subjective performance over conventional methods of volume control due to the use of LDRs. Words like clean, organic, natural, involving, dynamic with strong bass are commonly heard from customers and reviewers of our LDR preamp attenuator/controllers.

Tortuga Audio has been building LDR based preamps since 2012. Over the years we have received feedback from customers and reviewers from diverse backgrounds who have owned or experienced all types of audio equipment, some costing as much as a house. With rare exception, audiophiles consistently prefer the subjective "voicing" of our LDR attenuator/preamps.

To put it in simple bottom line terms, Tortuga Audio LDR preamps make listening to your music more fun.

A passive preamp

In its default configuration, the V4 is a passive preamp. We define a "passive preamp" as one where the audio signal is not acted upon by some other signal or power source. There is no amplification (no gain) and there is no active buffering of the audio inputs or outputs. Each audio channel sees only 2 LDRs arranged in the typical series/shunt fashion of an LPAD attenuator. Acting in convert, the series/shunt LDRs control volume by reducing the voltage of the incoming audio signal. By this definition the V4 is inherently a passive volume controller.

Optional active preamp | solid state buffer board

The V4 can be converted into a high performance active preamp by adding a plug-in SSPB.V4 Solid State Buffer Board. The buffer board is a direct coupled device with no input or output coupling capacitors. The input stage employs an op amp with optional gain and an output stage consisting of a constant current JFET buffer. The buffer board generates its own +/- 12 volt split supply off of the same 5 volt supply that powers the primary V4 board.

V4 preamp board with solid state buffer module - right side view — V4 board with optional plug-in SSPB.V4 solid state buffer board attached

Performance of the V4 equipped with a buffer board is dynamic and robust. The buffer board does not change the neutral organic voicing of the V4, it just gives it some more muscle for those systems that are not the best match for a passive attenuator.

What's included?

The following items are included with each V4 board:

A fully functional V4 board that has been calibrated and tested
J5 female socket with wire - a 2 pin wired socket that plugs into the J5 pin header for powering the board
4 threaded hex standoffs with screws for mounting the V4

What's NOT included that you'll need?

The following items are not provided but are typically required to have a fully functioning V4 system:

A plug-in quad LDR module if not purchased together with the V4 board
An OLED display assembly if not purchased together with the V4 board
RCA and/or XLR audio jacks and sockets for connecting audio signals to the V4 board
A 5 volt power supply rated at least 1 amp. You can probably get away with a 0.5 amp power supply but we recommend 1 amp.
Some type of enclosure or plinth to which you can mount all the V4 hardware

V4 manuals

The online product documentation system ("Docs") has 2 manuals for the V4; an operations and control manual and a hardware manual. Each are discussed briefly below.

This manual describes the how to operate the V4 via infrared remote, local rotary encoder, together with its menu driven OLED display .

This manual describes the design basis, hardware features and interfaces of the ePot.V4 Max ("V4" or "Max" ) LDR stepped attenuator & preamp controller.

Standard service charge

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