Tortuga Audio LDR1 Operating instructions

Brand: Tortuga Audio

Model: LDR1

Type: Operating instructions

LDR1 & LDR6 Operating Manual – Rev 1

Tortuga Audio

Operating Manual

LDR1 & LDR6 Passive Preamplifier

January 2013

LDR1 & LDR6 Operating Manual – Rev 1

Tortuga Audio

Contents

Terminology .................................................................................................................................................. 1

LDRx: When features and operation are common to both the LDR1 and LDR6 reference will be made

to the LDRx. ............................................................................................................................................... 1

Overview ....................................................................................................................................................... 1

Passive Preamp ......................................................................................................................................... 1

Audio Taper: .............................................................................................................................................. 1

Light Dependent Resistors (“LDR’s”):........................................................................................................ 2

Power Supply: ........................................................................................................................................... 2

Inputs: ....................................................................................................................................................... 2

Outputs: .................................................................................................................................................... 3

Encoder & Remote: ................................................................................................................................... 3

Front Panel: ................................................................................................................................................... 3

Rear Panel: .................................................................................................................................................... 3

Status LED: .................................................................................................................................................... 4

Off: ............................................................................................................................................................ 4

On: ............................................................................................................................................................. 4

On-Blinking-Slowly: ................................................................................................................................... 4

On-Blinking-Rapidly:.................................................................................................................................. 4

Flashing Briefly: ......................................................................................................................................... 4

Remote Functions: ........................................................................................................................................ 4

Power: ....................................................................................................................................................... 4

Raise: ......................................................................................................................................................... 4

Lower: ....................................................................................................................................................... 4

Mute: ......................................................................................................................................................... 4

LDR6 Only - Input Select Keys: .................................................................................................................. 5

Balance: ..................................................................................................................................................... 5

Reset: ........................................................................................................................................................ 5

Infrared Protocol and Codes ..................................................................................................................... 5

Encoder Switch: ............................................................................................................................................ 6

Power On: ................................................................................................................................................. 6

Power Off: ................................................................................................................................................. 6

LDR1 & LDR6 Operating Manual – Rev 1

Tortuga Audio

Mute: ......................................................................................................................................................... 6

Un-Mute: ................................................................................................................................................... 6

LDR6 Only - Input Select: .......................................................................................................................... 6

Balance Adjust: ......................................................................................................................................... 6

Balance Reset: ........................................................................................................................................... 6

Encoder: ........................................................................................................................................................ 6

Volume: ..................................................................................................................................................... 6

Un-Mute: ................................................................................................................................................... 6

Input Select: .............................................................................................................................................. 7

Balance Adjust: ......................................................................................................................................... 7

Plugging It In ................................................................................................................................................. 7

LDR1 & LDR6 Operating Manual – Rev 1

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Terminology

LDRx: When features and operation are common to both the LDR1 and LDR6

reference will be made to the LDRx.

Overview

Passive Preamp: The LDRx Passive Preamplifier is a unity gain (i.e. passive – no

amplification) attenuator.

The LDR6 has 6 selectable unbalanced RCA stereo line stage inputs and a single

unbalanced RCA stereo output.

The LDR1 has a single unbalanced RCA stereo line stage input and dual unbalanced

RCA stereo outputs.

The LDRx can be operated via the rotary encoder/pushbutton switch on the front

panel and via an infrared remote.

Unless explicitly noted, either control has

identical functionality.

Why call it a “preamplifier” if it doesn’t amplify? It’s a matter of convention as much

as anything. Historically, a “preamp” is the device upstream of the amplifier which

allows for selecting the input source (CD, DAC, Phono etc.), adjusting volume, and in

some cases adjusting channel balance and tone control. Most preamplifiers also

provides some degree of active amplification or buffering between the source

device and the amplifier. A truly passive preamplifier neither amplifies nor buffers.

The LDRx Passive Preamplifier is passive in the truest sense. Perfectly manifested,

the perfect preamplifier does nothing to the audio signal other than to attenuate its

strength (i.e. control volume). No coloration. No added anything. And ideally,

nothing removed either. Getting out of the way to let the music through the way it

was recorded - the perfect preamp.

Audio Taper: The LDRx is a stepped attenuator with 70 discrete steps between 0 db

and -60db where step 0 triggers full muting of the incoming signal. The LDRx

emulates a ~100k potentiometer using the conventional L-Pad configuration. The

audio taper of the LDRx is logarithmic as shown in the graphic below.

Note that approximately the last 10 dB of attenuation leading up to full volume

follow a more granular increments than the previous 50 dB. This feature smooths

out the incremental volume increases as you approach max volume where even a 1

dB steps can

result in very noticeable increases in sound pressure levels.

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Digital Control Unit: The LDRx is an analog

device that’s controlled by a

microprocessor based digital control unit (“DCU”). The DCU and related control

circuitry are optically and electrically isolated from the audio signal. The DCU uses

proprietary techniques to ensure that the LDR6 delivers matched and balanced

stereo output. The secondary function of the DCU is to mange communications with

the Encoder on the front panel and the infrared Remote.

Light Dependent Resistors (“LDR’s”): Unlike most preamplifiers, the LDRx does not

use a conventional analog potentiometer (or stepped attenuator with discrete

resistors

) for volume control. Volume is controlled via four (4) analog light

dependent resistors (2 per channel) whose light intensities (and thus resistance

level) are controlled by the DCU.

Power Supply: The power supply is a high quality, high reliability, high efficiency 90-

264 volt AC input, 12 volt DC (1 Amp) output, regulated switching power unit. It has

built-in overload, short circuit and thermal protection and a built-in EMI filter. It’s

Energy Star and CeC compliant with a level V efficiency rating. As “wallwarts” go,

it’s a decent power supply.

The audio signal is both optically and electrically isolated from the power supply.

The power supply powers the DCU, the infrared remote receiver and also provides a

switched 12 volt trigger output for external components.

Inputs: The LDR6 can accommodate up to six (6) different selectable stereo line

stage inputs via single ended (unbalanced) RCA connectors on the rear panel. The

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LDR1 accommodate a single unbalanced RCA input. All inputs share a common

audio ground. The audio ground is electrically isolated from the power supply

ground.

Outputs: The LDR6 has a single unbalanced RCA output. The LDR1 has dual

unbalanced RCA outputs.

Encoder & Remote: The LDRx is fully controllable via the black knurled rotary

encoder/pushbutton knob located on the right hand side of the front panel. The

same control functions are also available via the Remote.

Unless explicitly stated, the Encoder and Remote have the same functionality. The

Remote is clearly labeled and is far more intuitive to use than the Encoder.

However, for normal volume control, the Encoder operates just like any other

volume control knob (turning it clockwise increases v

olume, counter clockwise

decreases volume).

The LDR1 uses the same remote as the LDR6 even though some of its buttons are

irrelevant to the LDR1 such as the Input select buttons.

Front Panel: LDRx: The LDRx Front Panel has a single multi-function black/knurled Encoder Knob

on the right hand side and a circular Infrared Lens cover on the left hand side.

There is also a blue Status LED (light) to the immediate left of the Encoder Knob.

See Encoder Switch, Encoder and Status LED below for operational details.

LDR6 Only: The LDR6 has 6 additional blue Input LEDs (lights) located between the

Status LED and the Infrared Lens. The Input LEDs are labeled and indicate which

Input is currently selected.

Rear Panel:

LDRx: The LDRx rear panel has a 12 VDC power supply input jack, and a 12 VDC

Trigger Output jack.

LDR6 Only: The LDR6 rear panel has 7 pairs of single ended line stage RCA jacks.

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Going from left to right, the first pair are the outputs and remaining 6 pair are

inputs labeled Aux, DVD, TV, Phono, DAC and CD. Please note that the Phono input

is a line stage level input only and is not equipped to handle low level signals

directly from a turntable.

LDR1 Only: The LDR1 rear panel has 3 pairs of single ended line stage RCA jacks.

Going from left to right there are 2 pairs of outputs and a single pair of inputs.

Status LED: The LDRx Status LED is the right-most LED on the Front Panel located immediately

to the left the Encoder Knob. The Status LED conveys the following information:

Off: The LDRx unit is off.

On: The LDRx unit is on, Un-Muted and in Volume Adjust Mode (default)

On-Blinking-Slowly: The LDRx unit is on and is either Muted or at maximum

Volume.

On-Blinking-Rapidly: The LDRx unit is on and is in Balance Adjust Mode (see

Adjusting The Balance).

Flashing Briefly: Indicates acceptance of new Input or new Balance Adjustment.

Remote

Functions:

The LDRx Remote is a 15 key infrared remote transmitter with the following actions:

Power: Turns the power on/off

Raise: Raises the volume. When the Volume is at maximum the Status LED will blink

slowly.

Lower: Lowers the volume. When the Volume is at zero, the unit will Mute and the

Status LED will blink slowly.

Mute: Mutes and Un-Mutes the unit. When the unit is Muted the Status LED will

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blink slowly. While Muting and Un-Muting the Volume will

ramp down and ramp up respectively.

LDR6 Only - Input Select Keys: Press CD, DAC, Phono, TV,

DVD or Aux to select the desired Input. Doing so will

immediately Mute the unit and the Status LED will blink

slowly. Once the desired Input has been selected, pressing

the Enter key will lock in the selection, the Status LED will

flash briefly and the unit will Un-Mute and ramp up to the

same Volume setting as before but will now be connected

to the newly selected Input.

Balance: Press the Balance key to put the unit into Balance

Adjust Mode. The Status LED will blink rapidly indicated the

unit is in Balance Adjust Mode.

Left/Right (Balance Adjust Mode): When in Balance

Adjust Mode, pressing the Left key will incrementally shift

the Balance towards the left channel while pressing the

Right key will shift the Balance towards the Right channel.

The Status LED will continue to blink rapidly. Once the

desired Balance has been achieved, pressing the Enter key

will lock in the Balance adjustment and the Status LED will

flash briefly indicating the unit is now back in normal

Volume Adjust Mode. Note that the Raise/Lower Volume

keys remain operational during Balance Adjust Mode.

Reset: Press the Reset key to return the Balance to zero. The Status LED will flash

briefly.

Infrared Protocol and Codes: The Remote uses the NEC infrared protocol. The

Remote codes can be easily programmed into most programmable remotes using

the following system address and command codes.

Decimal

Hexadecimal

System Code [110] [6E]

Key Command Code

Balance

00h

Power 3 02h

Reset

03h

Raise 8 07h

Mute

08h

Left

09h

Enter 11 0Ah

Right

0Bh

Lower 14 0Dh

0Fh

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DAC

10h

Phono

11h

TV 19 12h

DVD

13h

Aux 21 14h

Encoder Switch: The Encode Knob has a pushbutton switch function that is activated by gently

pushing the Encoder Knob inwards towards the panel.

Power On: When off, a momentary push/release will turn the unit on.

Power Off: A push/hold for between 2-5 seconds followed by release will shut the

unit off.

Mute: When Un-Muted a momentary push/release will Mute the unit.

Un-Mute: When Muted, a momentary push/release will Un-Mute the unit.

LDR6 Only - Input Select: A push/hold while also turning (left or right) will put the

unit in Input Select Mode and allow selection of the desired input by turning the

encoder. The selected input (the selected LED will be lit) will take effect upon

release as indicated by a brief flashing of the Status LED.

Balance Adjust: A push/hold of between 5-10 seconds followed by release will

place the unit into Balance Adjust Mode and allow adjusting the left-right channel

balance by rotating the encoder in the desired direction. Once you’ve adjusted the

balance, a brief push/release will lock in the new balance setting and return the unit

to normal Volume Control Mode.

Balance Reset: A push/hold for greater than 10 seconds followed by release will

reset the Balance to zero upon release.

Encoder:

The Encoder Knob is a rotary switch. Unlike a conventional potentiometer, the

encoder has no hard stops (rotational limits). It will turn an infinite number of times

in either direction. The encoder sends switch pulses to the DCU. Going from zero to

full volume will take [approximately 2 full rotations of the Encoder Knob. It’s

possible to spin the Encoder Knob faster than the DCU is capable of detecting.

Continuing to turn the encoder in the same direction once the LDR6 has reached

minimum or maximum volume serves no useful purpose.

The Encoder’s rotary functions are only active when the unit is turned on.

Volume: In Volume Control Mode (the default mode), turning the encoder

clockwise will raise the volume, turning the encoder counter-clockwise will lower

the volume.

Un-Mute: When the unit is Muted (Status LED blinking slowly), turning the Encoder

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will Un-Mute the unit.

Input Select: In Input Select Mode, turning the encoder will select the next

adjacent input corresponding to the direction of the turn.

Balance Adjust: In Balance Adjust Mode, turning the Encoder clockwise will shift the

balance weighting towards the right channel while turning it counter-clockwise will

bias the balance towards the left channel.

Plugging It In The power supply has a 5 foot cord that terminates at a 2.5 mm female barrel plug.

Plug the “wallwart” head into any nominal AC outlet and insert the barrel plug into

the “12 VDC” jack in the rear panel of the LDR6.

Each time the AC power supply unit is plugged in or energized while plugged into

the LRDx, the LED’s on the front panel of the LDRx will flash briefly and then go dark

indicating the unit has power and is ready to be used (although the unit will remain

turned off until turned on).

There is no power supply on/off switch on the LDRx. The LDRx is continuously

powered. When the LDRx unit is turned off, the power draw is de diminimis and the

DCU reverts to a low power standby mode.

Turning The Unit

Encoder Knob: When the unit is off (panel LEDs are all off) the unit can be turned

on by momentarily pressing in and releasing the front panel Encoder Knob. Upon

powering up all the LEDs will briefly flash leaving the Status LEDs lit at all times. On

the LDR6 the LED corresponding to the currently selected input will also bit lit.

Remote: The unit can also be turned on via the remote by momentarily pressing the

red Power button on the remote.

Turning The Unit

Off

Encoder Knob: When the unit is on, the unit can be turned off by pressing and

holding in the Encoder Knob for more than 2 seconds but less than 5 seconds before

releasing. All the LEDs on the front panel will briefly flash and then go dark

indicating the unit is now off.

Remote: The unit can also be turned off via the remote by momentarily pressing the

red Power button on the remote. As with the Encoder Knob, all the LEDs on the

front panel will briefly flash and then go dark indicating the unit is now off.

Controlling

Volume

Volume is ad

justed via the Encoder Knob or via the Raise/Lower buttons on the

Remote.

When volume is adjusted down to minimum level (step 0) the unit is fully Muted

(the input signal is effectively disconnected) and the Status LED blinks slowly.

Similarly, the Status LED will also blink slowly when the volume is at 100% (step 70).

There is no external counter or display indicating which step you are at between

minimum (step 0) and maximum (step 70).

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When the unit if turned on, the volume level will ramp up to the same level it was at

when it was last turned off but in no event will it automatically return to a level

greater than step 30 or less than step 10.

Muting the

Output

Encoder Knob: The unit can be muted at any time by momentarily

pressing/releasing the Encoder Knob. The volume will ramp down to zero, enter

Mute mode and the Status LED will blink slowly. Once muted, the unit can be un-

muted by either again momentarily pressing/releasing the Encoder Knob or by

slightly rotating the Encoder Knob in either direction. Upon un-muting, the volume

will ramp up to the same volume setting prior to being muted, however, in the case

where the Encoder Knob was turned to un-mute the unit, the volume setting will

have adjusted accordingly at the end of the ramp up.

Remote: The unit can also be muted by pressing the Mute key on the Remote. Once

muted, the unit can be un-muted by pressing the Mute key again or by pressing

either the Raise or Lower keys.

Selecting the

Input

LDR6 Only - Encoder Knob: The desired input channel can be selected by

simultaneously pressing in and turning the Encoder Knob. Doing so will Mute the

current input and the Status LED will blink slowly. Turning the Encoder Knob while

it’s pressed in will switch the inputs as evidenced by which input channel LED on the

front panel is currently lit. Once the desired input has been selected, releasing the

Encoder Switch will lock in the input selection, un-Mute the unit and the volume will

ramp back up to the same level prior to being Muted.

LDR6 Only - Remote: The desired input can also be selected via the Remote by

pressing any one of the six input select buttons CD, DAC, Phono, TV, DVD or Aux.

Selecting a new input will immediately Mute the unit. Once you’ve selected your

desired input, pressing the Enter button will lock in your selection and un-Mute the

unit.

Adjusting the

Balance

Encoder Knob: The left-right stereo balance can be adjusted by pressing in the

Encoder Knob for at least 5 seconds but no more than 10 seconds. Upon releasing

the Encoder Knob, the unit will enter into Balance Adjust Mode as evidenced by the

rapidly flashing Status LED. You can now adjust the balance by rotating the Encoder

Knob to achieve the desired left-right channel balance. Once the desired balance

has been achieved, momentarily pressing/releasing the Encoder Knob will lock in

the current balance as evidenced by the Status LED briefly pulsing and then

remaining lit.

The current Balance setting can be automatically reset (no left or right bias) by

holding in the Encoder Knob for at least 10 seconds. Upon releasing the Encoder

Knob the Balance will return to zero as evidenced by the Status LED briefly pulsing

and then remaining lit.

Remote: The balance can also be adjusted by pressing the Balance key on the

Remote. Doing so will cause the unit to enter into Balance Adjust Mode as

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evidenced by the rapidly flashing Status LED. The Balance can then be adjusted via

the Left and Right keys on the Remote. Once you’ve set the desired Balance,

pressing the Enter key will lock in the new Balance settings. Note that with the

Remote you can still raise and lower the Volume while the unit is in Balance Adjust

Mode.

The current Balance setting can be automatically reset (no left or right bias) by

pressing the Reset key on the Remote. Doing so will return the Balance settings to

zero as evidenced by the Status LED briefly pulsing and then remaining lit.

12 Volt Trigger

Output

When the unit is turned on, 12 volts DC will be present on the Trigger Output jack

on the lower right of the Rear Panel. This trigger signal can be used to turn on other

components equipped with 12 VDC trigger inputs; amplifiers being the most

common component. The Trigger Output will revert to 0 volts when the unit is

turned off.

The Trigger Output requires the use of a conventional 1/8th inch (3.5mm) mono

phone plug.

Tortuga Audio LDR1 Operating instructions

Brand: Tortuga Audio

Model: LDR1

Type: Operating instructions

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Tortuga Audio LDR1 Operating instructions

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