It's been awhile since we highlighted the LDR.V25 Preamp Controller as the core part of any DIY passive preamp or new/modified existing active preamp so here's to all of you DIY'ers out there...draw near and take heed!
Tortuga Audio's latest offering is the LDR.V25 Preamp Controller together with a 256x64 pixel white-on-black graphical OLED display module with encoder and apple remote. This is our 4th generation design. We use this same hardware in our commercial preamp product line.
The firmware is mature at this point with occasional minor bug fixes and/or tweaks but will remain proprietary hence we don't share the source code. The V25 runs on an ARM Cortex M3 microcontroller and is programmed in C. Updated hex code files can be downloaded from our website and uploaded into the controller by the end-user.
As a standalone passive preamp the V25 sounds great. You can also incorporate it into most any new or existing solid state or tube based active preamp with exceptional results.
Here are the highlights:
* 100 step volume control/attenuation over 60 dB range
* Muting with volume ramp-down and ramp-up
* Built-in self calibration of the LDRs - no LDR matching required
* LDRs are replaceable plug-in modules
* Can switch up to 6 stereo inputs with switching built into the board
* LDRs are also used for input switching in lieu of relays
* Mono/stereo mode controllable via remote
* Use a pair of V25 boards to handle balanced audio
* Fully remote controlled via any silver Apple remote with remote ID pairing (256 remote ID's possible)
* Adjustable input impedance between 1-99k ohms | up to 10 possible settings (#1 is 20k fixed default)
* Firmware can be updated via simple PC based bootloader program and USB cable
* Powered by most any DC source between 9 and 30 volts DC rated at 500 ma (actual demand is considerably less)
* 256 x 64 pixel graphical OLED display with interface board with mounted IR receiver module & encoder attachment point
* OLED attaches to the V25 board via a 14 pin ribbon cable which carries power, OLED, encoder and IR signals.
* Menu driven OLED display with numerous functions including
* Turn preamp off
* Control volume
* Adjust left/right channel balance
* Switch inputs
* Adjust display brightness
* Adjust display timeout (blanking)
* Change max initial volume on startup or input change
* Change units between steps & dB
* Show firmware version
* Adjust impedance & update calibration
* Reset (all impedance/calibration data)
When purchased together as a package, the LDR.V25 (equipped for 3 inputs) plus OLED display/encoder run $399.
With few exceptions, we ship most anywhere in the world. Here's a link to the LDR.V25: LDR V25 Preamp Controller | Tortuga Audio
This pic of the V25 shows the Rev A version. We are now on Rev C that looks almost identical has a few parts moved around. The Rev C board switched to SPI communication with the OLED rather than the earlier 8 line parallel method.
The control menu has changed slightly from the one shown below. The Impedance and Calibration items have been merged into a single Imped-Cal menu item since these are so inextricably linked functionally.