can I please have a reply on what can I expect as skew betwen the LR channel with the Tortuga LDR ? (db or %)
The LDR calibration algorithm is coded for a 0.2% accuracy of each resistance level of each LDR at each of the 70 attenuation steps which covers a resistance range from 100 ohms to 100,000 ohms.
The formula for dB = 20 * Log (Rshunt/(Rshunt + Rseries))
If both the shunt and series LDR are equally off by 0.2% then you still get the exact dB you're targeting because we're dealing with ratios. So let's instead assume that the Rshunt is off by +0.2% and the Rseries is off by -0.2%. If we crank that through the dB formula you get 0.035 dB error from the target. Let's further assume that the other channel is just the opposite so you now have a 0.07 dB channel-to-channel dB error.
All fine and good but we all know the real world introduces additional errors. So let's assume the REAL error in the calibrated resistance levels is actually 5 times worse or 1%. Now we get a 0.174 dB error from the target dB schedule and up to 0.348 dB difference between left and right channel.
Reality is likely somewhere in between on average over the full attenuation range.