The E21A can’t handle as much current as other options, so the KR4 with these emitters is limited to 5Amps (no FET), which produces about 1200 lumens (for the 5000K version). Other emitters that can run with a FET to current output can produce 3000-4000 lumens in the KR4.
The first sample of the KR4 that went out for review with E21A’s in it had visible tint shift with the stock optic. A frost optic mostly fixes this, although makes the beam wider and less throwy.
The efficiency of the E21A emitters is good for such a high CRI emitter. However, a low CRI emitter is capable of something like 30% higher output.
Ordered Kr4 e21a,will order Ti Kr4 e21a(hopefully Ti body with copper head design) as soon it become available.Thanks for your time answering our questions.
I'm just getting deeper into this topic, so please excuse me if this is a FAQ:
I'm trying to wrap my head around the whole "no FET" business. If understand this correctly, a common driver design is using a combination of linear regulators for better efficiency on lower brightness levels and a FET to switch a pseudo direct-drive straight from the battery for the top end. So when you're referring to "no FET" does this mean that linear regulators are used all the way up to the brightest output level? Are there physically no FETs populated on the PCB or are they bypassed in firmware?
Are there schematics available for the driver used in the KR4 or similar designs? I want to understand this!