LDRxB.V25 Balanced Passive Preamp
Price: $2,695
This is a legacy product and is no longer produced or sold by Tortuga Audio.
| This model was eventually replaced by the LDR3000P.V25 High Performance Passive Preamp. |
A high performance balanced passive preamp combining LDR attenuation technology with elegant contemporary styling. The LDRxB.V25 accommodates up to 3 balanced XLR inputs and a single unbalanced RCA input, with dual (parallel) balanced XLR outputs plus a single RCA output.
| If you’re looking for the original, pre-V25 model, see the LDRxB. |
A really nice balanced passive preamp
The LDRxB.V25 is an update to the original LDRxB, using the V25 preamp controller board along with an updated graphical OLED display. The result delivers clear, articulate, honest sound with a dead-quiet background, satisfying dynamics, and surprisingly powerful bass.
Key features
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LDR volume control — LDRs sit at the center of Tortuga Audio’s passive preamp technology, delivering a super smooth 100-step analog volume control complete with channel balance adjustment, muting, and mono mode.
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OLED display & remote control — a single multi-function encoder knob, a menu-driven OLED display, and a simple 7-button Apple remote.
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Unity gain — no amplification — a true unity-gain preamp providing passive volume control and input switching only.
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Built-in LDR calibration — adapts to the LDRs as they age, and calibrates a replacement if one is needed (all LDR modules are plug-in replaceable).
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No relays in the signal path — LDRs handle audio input switching too.
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Firmware update via USB — updateable by the customer via a pair of rear-panel USB ports.
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High quality stylish enclosure — eco-friendly renewable bamboo together with black-anodized brushed aluminum panels milled from high grade stock.
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Neotech point-to-point signal wiring — all signal wire connections hand-wired point-to-point using 24 AWG Neotech UP-OCC solid copper hookup wire.
Specifications
Attenuation type |
Passive series/shunt (L-Pad) voltage divider using two LDRs per channel — 4 attenuation LDRs for single-ended attenuation, 8 for balanced |
Attenuation range |
-60 dB to 0 dB in 99 steps of ~0.5 dB, plus 1 additional muting step |
LDR modules |
All LDRs are easily replaceable plug-in modules |
Gain |
Unity (1x) gain — no amplification, processing, or active manipulation of the audio signal; audio signal optically isolated from the control system |
Buffering |
No input or output stage buffering |
Self calibration |
Built-in algorithm calibrates the four attenuation LDRs at each of the 99 attenuation steps to compensate for drift, aging, or LDR replacement. Pre-matched LDRs not required. |
Adjustable impedance |
Nominal 20k by default; up to 9 additional configurable settings between 1k and 99k, switchable with live music to optimize input impedance for the system |
Number of channels |
2 channel stereo |
Channel balance adjustment |
+/- 10 dB in 0.6 dB increments |
Channel balance accuracy |
Within 0.5 dB over the full attenuation range |
Channel isolation |
Each channel signal is 100% isolated and independent from the other; audio signal grounds are tied to a common star ground point |
Audio inputs |
Balanced: 3 pair Neutrik XLR. Single-ended: 1 pair Cardas RCA. |
Audio outputs |
Balanced: 2 pair Neutrik XLR wired in parallel. Single-ended: 1 pair Cardas RCA from a single phase of the balanced output. |
Input switching |
Via LDRs — typical 50 ohm resistance when on, in excess of 5 megaohms when off; no relays in the signal path; 6 LDRs used for input switching |
Output isolation |
Output signal is switched off and isolated during auto-calibration via LDRs (no relays in signal path); isolation in excess of 10 megaohms when switched off; 2 LDRs used for output isolation |
Total harmonic distortion |
Typically ~0.2% under normal operating conditions |
Power supply |
US: nominal 12 VDC linear regulated "wall wart," 0.5 A. International: nominal 12 VDC switching "wall wart," 1.0 A |
Power regulation |
2-stage regulation — 5V first stage via low-noise switch-mode regulator, followed by 3.3V low-noise second-stage linear regulator |
Processor |
ARM M3 Cortex 32-bit microcontroller running at 72 MHz |
Display |
Interactive menu-driven 256x64 pixel white graphic OLED display |
Mono mode |
Switch between stereo and mono via the remote (LDR switch) |
Firmware updates |
Via PC-based HID bootloader application (no Mac option); bootloader and firmware files downloadable from the company website |
USB port |
Type A female, for firmware updates via the PC bootloader application; cable provided |
Trigger out |
Outputs 12 VDC when the unit is powered on |
Enclosure |
Milled anodized aluminum front panel with acrylic inlay lens; anodized aluminum rear panel; powder coated top panel; lacquer-finished 3-ply bamboo side panels; 4 non-skid bamboo feet |
Printed circuit board |
High quality nickel immersion gold solder PCBs with blue solder mask |
Solder |
Lead-free solder with 3% or higher silver content |
RoHS |
Compliant or exempted |
Fuses |
No internal or external fuses |
Ambient requirements |
Stable, dry indoor environment only, ambient temperature within 60-90 degrees F |
Dimensions |
~3.75" tall, ~12.5" wide, ~10.5" deep |
Weight |
~8 lbs as shipped |
Items included |
Preamplifier, Apple Remote, external power supply, USB cable |