Well, it would behoove you to look into that mystery. Not trying to bust your balls here, but if somebody asks you about battery life with some battery they are using--let's say, for grins, a lantern battery--you ought to know the current draw at that voltage. Right now, your answer is 104mA, which is about 0.6W. But if they use a 12V battery, it's 115mA, for 1.4W? Does not make sense.
BTW, the earlier tests do not have the 48V converter running. i.e. switchboard not connected yet.
Okay, I've been working on this mystery this afternoon. I decided to repeat the test using a Bench Power Supply. So if the Tek battery has some weirdness to it due to it's built in converter, I'd remove that equation from the test. So here I am using a linear HP regulated PSU, plugged into the wall.
Set it to 12.01 VDC output.
Feed the voltage to the DC jack of the preamp. Get my 'expensive' Fluke and inserted it in between, to measure the current before going into the preamp.
With both PP switches off, I get a reading of 125.7 mA
Turning on one of the PP switch, without any mic connected, I get a reading of 130mA
Turning on both the PP switch, without any mics connected, I get a reading of 133.9mA
Loaded one channel with my power hungry mic... both channels PP ON, I get a reading of 143.8mA
Okay, still with me so far?..... The theory is if we lower the voltage, current consumption should go up. Right?
Without changing the preamp/mic/phantom power setup, I slowly turn the dial on my HP regulated PSU down to 6.0 Volts...
12Volts = 144mA
10Volts = 145mA
09Volts = 147mA
08Volts = 150mA
07Volts = 147mA
06Volts = 137mA
Current did go up as voltage went down to 8Volts... then from 8Volts down to 6Volts, the current consumption got reduced.
In all voltage settings, the mic pre and the attached mic was still working.
If not, you have a massive loss in your converter circuit at higher supply voltages. I doubt that is the case, because that would be one hot puppy. But it's worth nailing down.
There's probably some efficiency loss. I'm not claiming close to 100% efficiency, or even above 90+% efficiency. But right now, the converters run cool to the touch and have no problem powering the preamp.
I've been monitoring closely if either the split or the 48V converters get hot since day 1. But they don't even get warm. Defnitely, not hot. And I've been running this on and off for several hours straight.
Thanks for your inputs! Much appreciated! I'll tackle the PP one of these days.