LDR Stepped Attenuator | ePot.V4 Max

$275.00

Now accepting Pre-Orders | Only $50 deposit required now
We will invoice you the balance due when the product is released and ready for shipment which is expected before the end of 2024. Secure your spot in the queue now!
The ePot.V4 is a software driven electronic stepped attenuator and preamp controller, that when equipped with appropriate power supply and OLED display module can function as a  full featured, remote controlled passive preamplifier, and when equipped with an optional solid state buffer board, can functions as an active preamplifier. Like all Tortuga Audio preamp controllers, the V4 employs light dependent resistors (LDRs) as the sole means for for audio attenuation (volume control). No mechanical potentiometers or switched mechanical attenuators are used. The V4 represents the 5th generation of Tortuga Audio LDR based passive preamp attenuator and controller and builds on work that began over 15 years ago.

Available on backorder

Required V4 add-ons

All these items are required but the V4 can be purchased without them if you already have them

  • OLED display assembly front view with cabling and encoder
  • quad ldr module2 - top view
  • Apple remote alternative | the "Function" remote

Product total

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Grand total

Pay a deposit of $50.00 per item
SKU: epot.v4.max Category:

An LDR stepped attenuator | preamp controller

The ePot.V4 Max (the “V4”) is a chassis mounted electronic LDR (light dependent resistor) stepped attenuator and preamp controller board for the DIYer, designer and OEM.

The V4 Max is a 2-channel, 100 step stereo volume/preamp controller with input switching for up to 4 sources, remote infrared control plus local control via rotary encoder, together with a sporty high contrast OLED display with a menu driven interactive user interface.

V4 preamp controller board with detached LDR module

The V4 offers a subtle yet pleasant improvement in subjective sonic 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.

The V4 is run by a 32 bit ARM microcontroller but is inherently an analog device with no digital processing of and audio signal. Analog audio signals passing through the V4 are also optically isolated from any power source. There is no active gain stage and there is no active buffering of the audio inputs or outputs. Each audio channel sees only 2 light dependent resistors (LDRs). The LDRs control volume by reducing the voltage of the incoming audio signal. By this definition the V4 is inherently a passive volume controller.

By itself, the V4 can be used as a passive preamp. However, when mated with the optional buffer board or any third party downstream buffer/gain stage the ePot.V4 becomes a high performance active preamp.

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.

Specifications

TopicDescription
Preamp type Passive preamp (no no active manipulation of the audio signal by a power supply)
Application 2-channel single-ended or balanced audio (balanced audio requires additional expansion board)
Attenuation methodL-pad resistive voltage divider network using light dependent resistors (LDRs) in lieu of potentiometer or fixed discrete resistors
Attenuation perceptionSmooth, quiet, continuous transitions with no sonic artifacts between each discrete attenuation step
Attenuation range 100 discrete attenuation steps of ~0.6 dB per step over a 0 to 60 dB range.
Attenuation controlPrecision closed loop LDR current control with 16 bit resolution pulse width modulated command signal
Attenuation moduleReplaceable plug-in LDR attenuation module each with 4 LDRs (2 LDRs per channel).
Volume mutingFully muted output at step 0 using dedicated muting relay
Volume ramping User selectable volume ramping behavior (down and up) during muting/unmuting
LDR calibration User-initiated calibration of each LDR against a 100 step resistance schedule that varies with impedance setting with results stored in an EEPROM memory. Measuerment during calibration uses 16 bit ADC resolution.
GainUnity (1x) gain passive - no amplification
Input coupling Direct coupling with no passive coupling capacitors or active buffering
Input switching Switching between 4 input devices using miniature electro-mechanical relays
Input impedance 50k default input impedance with up to 9 other impedance settings each adjustable between 1k and 99k and the ability switch between impedance levels with live music to optimize input impedance for their system
Signal interconnectionPin header or individual solder lugs for connecting inputs, outputs and signal ground
Signal groundAudio signal grounds are isolated from power ground within controller, however, audio signal ground must share common ground with power supply via an external star ground point in order for LDR calibration feature to function properly
Remote controlFully controlled via inputs from 2 different handheld infrared remotes.
Encoder controlPartially controlled via inputs from a rotary encoder with integral pushbutton
OLED display 8 bit grayscale high contrast white-on-black 256x64 pixel graphic OLED display with an intuitive, easy to use, menu based control scheme. OLED display assembly integrates the display, an infrared receiver and an encoder into a single assembly with single 14 pin ribbon connection to the V4 board.
Auxilliary controlsOptional (via customized firmware) monitoring and control interfaces including trigger out, status LED, serial UART, serial I2C, and 4 digital/analog GPIO pins.
Total harmonic distortionTypically less than 0.5% | essentially inaudible
MicrocontrollerARM based STM32G4 32 bit microcontroller running at 144 MHz
FirmwareObject oriented C++ firmware running under a lean real time operating system (FreeRTOS). Firmware updating via USB connection using a vendor based updating application that runs on a PC, Mac, or Linux machine
Printed circuit board2 layer FR4 board with high quality gold plated nickel immersion solder pads
Optional buffer boardCustom designed plug-in daughter buffer board converts the passive V4 into an active preamp with adjustable gain
Optional power supplyCustom linear power supply provides a very low noise source of primary 5 volt power plus split +/- 12 volts for the optional buffer board
Channel balanceAdjustable channel balance up to 20 steps (12 dB) left or right while maintaining overall volume level
Signal isolationAll audio signals are optically isolated from control power
Power requirementsPower draw with ~5 volts DC supply | Off - 50 milliamps, On Without Buffer - 160 milliamps, On With Buffer - 200 milliamps

V4 manuals

Tortuga Audio’s online product documentation system (“Docs”) for the V4 includes both a hardware manual and an operations and control manual.

We highly recommend that you explore these 2 manuals via the links below.

V4 preamp controller board with detached LDR module

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

V4 Operations & Control Manual

(button link does not work yet)

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

What’s included?

The following items are included by default with each V4.

  • The ePot.V3 board itself with a 90 degree 12 pin J4 audio signal pin header installed
  • Power supply plug with 4-6 inches of wiring for connecting 5 volt power to the V3 board
  • Female faston lug for connecting power ground to the faston ground tab

What’s not included that you also need?

The following items are required for a complete V4 based system. They can be purchased as add-on options at the same time you purchase the V4 or they can each be purchased separately.

LDR module | V3 & V4

$49.00

The plug-in LDR attenuation module is an essential part of the V4 LDR attenuator & preamp controller and contains 2 pairs of LDRs used as voltage dividers for controlling volume. An LDR attenuation module is usually purchased as an add-on item at the same time as the V4 board itself but can also be purchased here separately.

OLED display assembly

$175.00

The OLED display assembly is a high contrast 256 x 64 pixel white-on-black graphic OLED (Organic Light Emitting Diode) display for use with Tortuga Audio’s V25, V3 and V4 series preamp attenuator/controllers and related Tortuga Audio preamps. The OLED display assembly provides an easy and intuitive user control experience through an interactive menu driven control interface designed around  the 7-button Apple remote. The display assembly includes a custom adapter board with installed infrared (IR) receiver module and a header for connecting an encoder module. All cabling is included. The unit is fully tested and ready to go and requires no…

Function remote control

$40.00

The Function remote was designed as an alternative infrared remote for the Apple TV streamer and other TV brands. Tortuga Audio has adopted the Function remote to replace the silver Apple remote that is no longer in production. In the event the Function remote interferes with your Apple or non-Apple equipment, it can easily be re-configured to use a different non-interfering configuration. The Function remote is easy to use, is well constructed, has a high quality feel, and is very responsive. The Function remote works only with the V4 but not the V3 or any earlier preamp controllers.

Other required items but which are not sold by Tortuga Audio include:

  • Nominal 5 volt DC power supply rated at 0.5 amp or greater.
  • Audio signal input/output jacks
  • Preamp enclosure

Optional items

The following optional items are offered by Tortuga Audio for the V4 for those who want to explore an active preamp and/or the benefits of a low noise linear power supply

Solid state preamp buffer | SSPB.V4

$224.00

The SSPB.V4 Solid State Preamp Buffer is an optional add-on daughter board for the ePot.V4 LDR preamp attenuator/controller board that turns the passive V4 into an active preamp with adjustable gain. The buffer board gives the V4 more sonic authority via a robust current drive while the adjustable gain provides the option of boosting the loudness of the unity gain passive V4. The SSPB plugs into the V4 using the same sockets normally occupied by the plug-in LDR module. The LDR module plug plugs into the SSPB instead such that we end up with a 3-layer cake of printed circuit…

Available on backorder

Pay a deposit of $50.00 per item
  • An optional low noise linear power supply gives the V4 board plus optional buffer board raises the performance bar for V4
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