LDR Pre is an ultimate, high-end analog stereo audio volume controller (passive preamp) that will amaze you with unmatched transparency and detail. Audio signal is attenuated with Light Dependent Resistors (LDRs) from Advanced Photonix, accurately driven by Atmel microcontroller. Programmed attenuation curve follows standard logarithmic response of a human ear, which delivers a listening impression of a perfectly linear volume attenuation. The absence of sliding contacts and moving parts, as well as any active components in the signal path paints a truly unique and faithful sound image.
LDR Pre is an ultimate, high-end analog stereo audio volume controller (passive preamp) that will amaze you with unmatched transparency and detail. Audio signal is attenuated with Light Dependent Resistors (LDRs) from Advanced Photonix, accurately driven by Atmel microcontroller. Programmed attenuation curve follows standard logarithmic response of a human ear, which delivers a listening impression of a perfectly linear volume attenuation. The absence of sliding contacts and moving parts, as well as any active components in the signal path paints a truly unique and faithful sound image.
Volume level, active input and output, and other information is displayed on an TruBlack OLED screen with 180 degrees viewing angle and exceptional contrast. LDR Pre can be controlled either by included IR remote or with volume knob with push button switch on the front panel. Volume control and menu navigation uses rotary encoder which, unlike traditional volume pots, has a "bumpy" feel when turned. This is not to everyone's taste - if you prefer buttery smooth feeling under your fingertips, you can choose GlideX version on checkout.
Volume level, active input and output, and other information is displayed on an TruBlack OLED screen with 180 degrees viewing angle and exceptional contrast. LDR Pre can be controlled either by included IR remote or with volume knob with push button switch on the front panel. Volume control and menu navigation uses rotary encoder which, unlike traditional volume pots, has a "bumpy" feel when turned. This is not to everyone's taste - if you prefer buttery smooth feeling under your fingertips, you can choose GlideX version on checkout.
On the rear, there are four independent stereo gold plated RCA analog inputs and two independent stereo outputs. As an optional upgrade, I can offer CMC high-end gold plated RCA connectors. Input and output switching is done with ubiquitous small signal NAIS, FUJITSU or OMRON relays with sliver-palladium (AgN) contacts, which ensure untouched signal purity and total isolation from digital signals. Device is housed in solid all-aluminium box with 8mm thick front panel. All components are soldered on manually routed and optimised dual-sided PCB.
On the rear, there are four independent stereo gold plated RCA analog inputs and two independent stereo outputs. As an optional upgrade, I can offer CMC high-end gold plated RCA connectors. Input and output switching is done with ubiquitous small signal NAIS, FUJITSU or OMRON relays with sliver-palladium (AgN) contacts, which ensure untouched signal purity and total isolation from digital signals. Device is housed in solid all-aluminium box with 8mm thick front panel. All components are soldered on manually routed and optimised dual-sided PCB.
There are some DIY solutions around that use Arduino Nano with Mega328P which has only 8-bit DACs, causing uneven volume transitions and audible "bumps". In this device, LDRs and input switching are operated by upgraded MCU version MEGA328PB, cutting edge 16MHz 8-bit micro-controller running four independent ultra-fast 16-bit DAC channels (one for each LDR) for an unprecedented volume precision and smoothness. This translates to 65536 possible resistance values for each LDR instead of 256!
There are some DIY solutions around that use Arduino Nano with Mega328P which has only 8-bit DACs, causing uneven volume transitions and audible "bumps". In this device, LDRs and input switching are operated by upgraded MCU version MEGA328PB, cutting edge 16MHz 8-bit micro-controller running four independent ultra-fast 16-bit DAC channels (one for each LDR) for an unprecedented volume precision and smoothness. This translates to 65536 possible resistance values for each LDR instead of 256!
Latest firmware allows user to customise each device with his own welcome message and input/output names limited to 7 characters each, simply by navigating through the setup menu. Default calibrated impedance of the volume controller is 10KOhms, but it's possible to change it to any value from 5K to 50K. You can also easily setup and calibrate the LDRs to match the input impedance of your downstream power amplifier. LDR Pre settings are saved automatically to EEPROM on power down, but running code is smart enough to not save the volume above 50% (configurable threshold) to save you from unpleasant surprise on the next power up and protect your downstream equipment.
Latest firmware allows user to customise each device with his own welcome message and input/output names limited to 7 characters each, simply by navigating through the setup menu. Default calibrated impedance of the volume controller is 10KOhms, but it's possible to change it to any value from 5K to 50K. You can also easily setup and calibrate the LDRs to match the input impedance of your downstream power amplifier. LDR Pre settings are saved automatically to EEPROM on power down, but running code is smart enough to not save the volume above 50% (configurable threshold) to save you from unpleasant surprise on the next power up and protect your downstream equipment.
Firmware highlights:
Firmware highlights:
sleep timer - device will go to sleep after configurable timeout, up to 255 minutes
child lock - possibility to disable encoder and use remote only
screen saver - configurable timeout after which the screen is turned off
safe volume level - configurable maximum volume level to be saved in memory for the next power on
fast A/B switching - switch between two last used inputs for A/B source comparison
custom input and output names, with possibility to reset to defaults
There are four inputs and two outputs. Two outputs can be toggled to run independently or simultaneously. Each input and output name can be customized from the setup menu. OLED can be configured to turn off completely after configured number of seconds.
There are four inputs and two outputs. Two outputs can be toggled to run independently or simultaneously. Each input and output name can be customized from the setup menu. OLED can be configured to turn off completely after configured number of seconds.
It usually takes one week to complete each device as they are built on order, however we do usually stock one fully completed unit that can ship immediately.
It usually takes one week to complete each device as they are built on order, however we do usually stock one fully completed unit that can ship immediately.
This is the most transparent audio pre (attenuator) you could possibly find. It sounds better, has more functions and is much cheaper than similar offerings from competitors. This is the (real) letter from one of the buyers:
This is the most transparent audio pre (attenuator) you could possibly find. It sounds better, has more functions and is much cheaper than similar offerings from competitors. This is the (real) letter from one of the buyers:
"Both my friend and myself are enjoying the pre very much, you have something very good indeed on your hands. Beautifully built to a VERY HIGH STANDARD, rare to find an even handed and so transparent /neutral preamp, especially at the price you are selling them at. I am waiting as S***** C***** is determined to out do your model having told him about how good your version is. He is sending out a new board with mods. I will make a review of comparison once I have tried that. Thank you for a great product, now all you need is a professional review."
"Both my friend and myself are enjoying the pre very much, you have something very good indeed on your hands. Beautifully built to a VERY HIGH STANDARD, rare to find an even handed and so transparent /neutral preamp, especially at the price you are selling them at. I am waiting as S***** C***** is determined to out do your model having told him about how good your version is. He is sending out a new board with mods. I will make a review of comparison once I have tried that. Thank you for a great product, now all you need is a professional review."
User review at Stereo.net.au: https://www.stereo.net.au/forums/topic/313385-dacgear-ldr-pre-mk2/
Dimensions: W172mm x H60mm x D250mm. Warranty: 1 year.
LDR Pre MkII User ManualFor ordering see eBay page: https://www.befr.ebay.be/itm/134474115148