LDR attenuation module
The ePot.V3 series Max and Mini preamp attenuator/controllers both require the use of the same V3/V4 series plug-in LDR attenuation module. The LDR Module is usually purchased at the same time as a V3 Max or Mini controller but can also be purchased separately here.
The V3 series LDR attenuation module is shown below removed from, and located next to, an ePot.V3 Mini. Below that image is an ePot.V3 Max with the same LDR attenuation module installed.
Each V3/V4 series LDR module has 4 embedded LDRs plus an EEPROM memory chip. The memory chip contains the attenuation/calibration data tables for each LDR at one or more impedance settings. The LDR module provides 100 steps of attenuation between -60 to 0 dB. Each channel uses 2 LDRs in a series/shunt configuration. Each LDR is individually controlled by a microcontroller, located on the Max or Mini, which uses stored calibration data to achieve the resistance values needed for each of the 100 volume steps. Tortuga Audio does not pre-match LDRs because the calibration process normalizes the behavior of each LDR around 100 targeted sets of resistance values.
When used in an ePot.V3 Max, an LDR attenuation module can be re-calibrated as needed and can be re-configured for any impedance setting from 1k to 99k with 20k being the typical fixed default impedance level for setting #1.
Only the ePot.V3 Max is capable of calibrating an LDR attenuation module. The Mini does not have built-in LDR calibration. Therefor, you must specify the fixed impedance of the LDR attenuation module when purchasing one for an ePot.V3 Mini.
Hardware, operation and control manuals
A more comprehensive description of the epot.V3 Mini and Max hardware, installation, operation, and controls can be found in the following online documentation: