Elegantly Simple Signal Path

The single greatest challenge for any line stage preamp is to remain true to the source material while delivering the attenuated audio signal to the amplifier honestly and without editorializing.  The LDR300 achieves this by combining Tortuga Audio’s proven LDR volume controller with a simple yet highly effective solid-state junction field effect transistor (JFET) current amplifier (output buffer) while eliminating the unnecessary voltage amplifier (gain stage) in between.

A 2 stage regulated split voltage power supply mitigates the need for any input coupling capacitor with the output operating a near zero volts DC offset.

This elegantly simple design keeps the signal path short and simple without compromising performance. So you can hear more of the music and less of the hardware.

V25 LDR Preamp Controller

The LDR300 is designed around our 4th generation remote controlled V25 preamp controller that uses digitally controlled analog light dependent resistors (LDRs) to provide smooth 100 step volume control over a 60 dB range. Features include ramped muting, channel balance adjustment, input switching, both  stereo and mono modes plus adjustable input impedance. Built-in calibration of the replaceable socketed LDRs ensures accurate attenuation, channel balance and optimal performance over the extended life of the preamp.

The LDR300 is easy to operate via an intuitive interactive menu driven control interface designed around  the 7-button Apple remote and a bright easy to see 256 x 64 pixel white-on-black graphic OLED (Organic Light Emitting Diode) display.

No Gain Stage

The reality with most of today’s line stage source components (DACs, CD transports, phono preamp etc. ) is you simply do not need your preamp to boost the signal voltage  in order to achieve acceptable volume levels. The LDR300 takes advantage of this by avoiding the complexity, noise and cost of a gain stage. The result is a better sounding preamp with less processing and manipulation of the audio signal.

Solid State Buffered Output

The proprietary Class A output stage is a robust current amplifier (buffer) designed around the highly respected  ultra low noise LSK170 junction field effect transistor (JFET).  The direct coupled JFET operates in combination with a constant current source between a split voltage power supply. The result is natural sounding audio with robust dynamics without the dryness often associated with solid state equipment. Impedance matching is never an issue so you can use longer interconnect cables without concern and feed both a main amp and a subwoofer from the same output.

Low Noise Split Voltage Power Supply

The LDR300 employs an inherently low-noise split voltage power supply topology that places the buffer’s JFET transistor almost exactly in between the positive and negative power rails where it operates near zero volts DC (minimal offset).

Just as the middle of a stretched rubber band remains nearly motionless when either end are vibrated randomly,  the majority of any noise present on the split voltage power rails will cancel out and have minimal impact on the output of the buffer that operates near zero volts DC. This results in a very high power supply rejection ration (PSRR) and a sound stage with an exceptionally deep and dark background.

In addition to the already inherently high PSRR, the independent positive and negative power supply rails each utilize 2 separate voltage regulators in series with a combined 100+ dB ripple rejection. Both the left and right channels each have their own separate filter/bypass capacitors at each rail. Premium components are used throughout including Vishay/Dale resistors, Elna Silmic II (silk) electrolytic filter capacitors, and Vishay polypropylene coupling capacitors in the signal path.

Optional Output Coupling Capacitor Upgrade

A good yet modest stock polypropylene output coupling capacitor can be upgraded to an excellent high performance V-Cap oil impregnated metallized polypropylene capacitor. More info on the V-Caps can be found here.

Specifications

These specifications reasonably reflect the current model but are subject to updating and modification without notification.