LDR3000P.V25 High Performance Passive Preamp
Price: $1,995
This is a legacy product and is no longer produced or sold by Tortuga Audio.
| The LDR3000P.V25 was eventually replaced by the LDR3000x.V3, available configured as a passive preamp at a comparable price. |
Remote controlled passive preamp with 3 XLR and 3 RCA inputs, XLR/RCA outputs, a 100-step LDR attenuator, true unity-gain passive operation with a dead-quiet background, and a high resolution OLED visual display.
A flexible high performance passive preamp
The LDR3000P was Tortuga Audio’s flagship passive preamp, built around the V25 preamp controller — digitally controlled analog LDRs providing smooth 100-step volume control over a 60 dB range, with ramped muting/unmuting, channel balance adjustment, input switching, mono mode, and adjustable input impedance. Built-in calibration of the replaceable, socketed LDRs keeps attenuation and channel balance accurate over the preamp’s life.
It’s operated via an intuitive menu-driven interface built around the 7-button Apple remote and a bright, easy-to-see 256x64 pixel white-on-black OLED display.
Passive preamp for both single-ended & balanced systems
Whether the source is RCA, XLR, or a mix of both, the LDR3000P handles it — 3 sets of RCA inputs and 3 sets of XLR inputs usable in any combination. The RCA and XLR outputs carry the same signal regardless of source type, though the balanced output has only one phase active (pin #2) when the source is single-ended.
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 — no conventional buttons, dials, or switches: a single multi-function encoder knob, a menu-driven OLED display, and a simple 7-button Apple remote.
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Dead quiet signal path — with no active signal amplification or buffering, the LDR3000P is a true unity-gain preamp, providing passive volume control and input switching only.
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Built-in LDR calibration — adapts to 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, eliminating noisy electro-mechanical relays.
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Firmware update via USB — updateable by the customer via a pair of rear-panel USB ports.
Specifications
Category |
Criteria |
Description |
General |
Summary |
Remote controlled passive LDR preamplifier with OLED display and a 100-step LDR attenuator with no gain stage or buffer, handling 3 balanced (XLR) and 3 single-ended (RCA) inputs. |
Audio Signals |
Inputs |
6 total: 3 single-ended RCA stereo inputs, 3 balanced XLR stereo inputs |
Outputs |
1 RCA stereo output, 1 balanced XLR stereo output |
|
Mixed signals |
Output from single-ended inputs is available on one phase only (pin 2) of the balanced output; only one phase (pin 2) of balanced inputs is available on the single-ended output |
|
Input switching |
Via LDRs, with signal isolation in excess of 10 megaohms when off |
|
Output isolation |
Via a combination of LDRs and miniature relays |
|
Attenuation |
Technology |
Digitally controlled, optically isolated, analog LDRs in a series/shunt L-Pad voltage divider configuration |
Steps |
100 steps of ~0.6 dB per step, plus 1 additional muting step |
|
Range |
-60 dB to 0 dB |
|
Channels |
4 independent channels handling both 2-channel single-ended and 4-channel balanced signals, with 2 LDR modules per channel (8 attenuation LDRs total) |
|
Channel balance |
Left/right within 0.5 dB over the full attenuation range; /- 20 step channel balance adjustment at ~0.6 dB per step (~/- 12 dB max) |
|
LDR modules |
Each LDR is a compact, easily replaceable 4-pin socketed plug-in module |
|
LDR calibration |
Built-in software-driven closed-loop measurement circuit calibrates each attenuation step of each LDR over the full range. During calibration (~10 minutes) the preamp is offline and cannot play music. |
|
Input/gain stage |
Type |
None (no gain or input stage — pure passive attenuation) |
Output/buffer stage |
Type |
None — output signals shunted to ground when powered down, muted, or during LDR calibration |
Impedance |
Input |
Default 20k ohms; up to 9 additional configurable settings between 1k and 99k |
Output |
Fixed at ~100 ohms |
|
Performance |
Total harmonic distortion |
Generally well below 0.5% under worst-case scenarios (not exhaustively measured) |
Power Supply |
Mains input |
IEC socket with lighted switch and fuse drawer, external 0.5A fuse plus spare; 120-240 VAC |
Type |
10W switching, 12V DC rated at 0.85A |
|
Controls |
Controller |
V25 Preamp Controller Rev C — ARM M3 Cortex 32-bit microcontroller at 72 MHz |
Remote |
Silver 7-button Apple infrared remote (38 kHz NEC protocol) |
|
Encoder |
Front panel control knob on a rotary stepped encoder with integral push-button switch |
|
Display |
256x64 pixel white-on-black OLED, driven by an interactive menu-driven control interface |
|
Trigger out |
Rear panel mono phone jack, outputs 12 VDC when the unit is on |
|
USB port |
Rear panel dual Type A USB, for PC-based bootloader firmware updates |
|
Enclosure |
Case |
Heavy wall extruded aluminum case, black powder coat finish |
Front panel |
0.25" brushed anodized aluminum with dark grey acrylic inlay in front of the display |
|
Rear panel |
0.1" brushed anodized aluminum |
|
Feet |
Hudson Audio platinum silicone, non-skid, vibration-absorbing, 1" hemispherical (four) |
|
Other Design |
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 |
|
Ambient criteria |
Stable, dry indoor environment only, ambient temperature within 60-90 degrees F |
|
Dimensions |
3.5" tall, 12.0" wide, 9.0" deep |