Can anyone school me and tell me the different traits (pros/cons) of each of these emitters? I have been absent from the site for a while and I’m not familiar with any of these.
I see Simon is offering all of them in the Convoy M21B 21700 as well as the XHP70.2
4000-4500k is the temp range I’d be looking at.
Gt-fc40 will have the best output with great tint. I think that Simon can replace the XHP70.2 for xhp70.3hi if you ask. But I’m not sure about the bins offered. Output would be even better than gt-fc40.
IMHO and based strictly on the lights I have. Hope this helps.
GT-FC40 in M21B, E, and F all 4500k:
Overall: Offered in M21B (rear switch), but also more importantly in E and F which have USB-C integral charging and side switch. Throw is roughly 280m (M21B) to 330m (M21E). Orange peel reflector. I have just also bought the 5500k version and preliminary verdict is that it is also fantastic with CRI 98.
Color rendition: The CRI and R9 is absolute world class. This LED in actual use (vs beamshot) has an uncanny resemblance to 219b 4500k, in fact more like 219b than any other LED except Nichia’s own E21a. I call this the Nichia imitator because of this reason.
This LED is at this time the only medium thrower with top notch color rendition on market. These Convoy lights in my mind are the prototype every-day all-around light and THE gift light I buy for friends and relatives. All 3 recommended without reservation.
519a 4500k in S21D:
Overall: I have the S21D version (rear switch), quad LED, TIR optic. The CCT tends to be lower than spec, 4500k actually measures about 4000k, partially explaining why this LED is more golden/yellow than expected.
Color Rendition: World class CRI and beautiful golden/yellow beam color, with tint that is more neutral/closer to BBL and NOT rosy or magenta. It is not a thrower like my GT-FC40. I love this light also because it gives a very different beam color from the legendary Nichia 219b 4500k (the king of rosy tint and color rendition), while still having excellent CRI. Like having different types of wine. If I have to pick one, I would still go for Nichia 219b 4500k though.
This LED and the GT-FC40 are not competitors of each other in the sense that they are in my mind different classes of LED/light. 519a is floody light, better for more close up work and not outdoor exploration/”safety” light for example, IMO.
B35AM in M21B 4500k:
Overall: I just bought this one because the pedigree is extremely intriguing - supposed to be equivalence of four Nichia E21a’s grouped together in one LED. The comparison between this light and GT-FC40 in same host would be fascinating. Unfortunately it is offered only in M21B and not E and F. Not sure about output and throw vs GT-FC40 in same host.
Color Rendition: World class CRI, but what does it look like? Curiously I do have E21a and know that it is very magenta/rosy like 219b 4500k, but from youtube review of the B35AM I can’t tell for sure. I will just have to find out for myself. OCD 
white wall beamshots coming as soon as light gets here.
I would vote to hold off on XHP 70.3 until you could see more reviews with beamshots and how good Simon’s bin is. I had Thrunite T2 with XHP70.2 “Neutral White” and it has tremendous output but also is the worst green hell I’ve seen. I found one review of XHP70.3 https://thelitereview.com/flashlights/cyansky-p25-v2-0-review-xhp-70-3-led/ and that particular LED looks like that green monster is still there. Let others go first on this one.
I agree with cannga.
Pretty good overall assessment by cannga.
519A should be the most efficient and therefore offer the longest runtime (still pretty short, don’t expect long runtime from any of them). It’s the only one without the magenta-rosy tint that some enthusiasts love but many people (myself included) can’t stand.
I would disagree that the 519A (domed) and GT-FC40 are “rosy”. They are are both relatively neutral in tint, which for most LED use cases is desirable. The 519A is generally very close to the BBL in either direction. The GT-FC is fairly close to the BBL, but seems to have a larger range of DUV in samples. They will be “rosy” if you compare them to many other modern LED emitters that have positive DUV, but they don’t have an extreme magenta tint/negative DUV like the 219B. Obviously if you dedome a 519A it will be “rosy”.
I never said 519A is rosy, quite the opposite.
I could be reading it wrong, and in isolation, the 519A is probably more efficient than the B35AM, but according to L.R.O. reviews of the S21B 519A and the S21A B35AM the B35AM with the boost driver ends up being a more efficient system than the 519A with linear driver. I think.
ETA: Obviously, that’s not to say that there couldn’t be a more efficient 3V driver for a 519A. But from convoy, I like the B35AM.
In terms of efficiency at mid output, it is:
519A < B35AM <= GT FC40
Are you sure you used those symbols as intended?
Comparing one with a Boost Driver and the other with a Linear Driver is a bit apples to grapefruit in terms of a comparison.
My B35AM in a Convoy M21B produces a lovely beam. However, I generally prefer the 519A beams. Whether one is more or less efficient than the other is really open to debate because both are close to each other when driven the same. I tend to think the 519A is more flexible in terms of power profiles and emitter output.
Good review with measurements [Review] Convoy S21A B35AM high CRI EDC flashlight . Outstanding CRI and R9 numbers, but 1100 lm is only low side vs GT-FC40. I have this light coming and will compare head to head with my GT-FC40 in same host M21B. I am excited about my B35AM light in MAO finish :+1: but if throw and brightness are what you’re interested in, from reading reviews I don’t believe it will match GT-FC40.
It seems CRI of XHP70.3 4000k per Simon is 70. And it’s a Cree (very high green hell potential). I would vote to pass or at least let other people be the guinea pig :innocent: on this one.
I carry and use flashlights, not loose LEDs, so the performance of the entire system matters. If the 519a is more efficient on paper, but commercially available flashlights with B35AMs get longer runtimes than flashlights with the same battery and a 519A, then that’s what counts to me.
Thanks for the replies. Not sure I’m really all that clear why you’d buy one over another still.
Not sure runtime efficiency really matters all that much. Not if using 18650 or 21700 cells.
Don’t suppose anyone has a side by side picture of the different LEDs showing their relative sizes?
Of course it won’t match the FC-40, B35AM uses 2x less power.
[quote=cannga]
There are some XHP70.3 with a CRI of 80 and 90 out there! 70 is the lowest I have seen and that tends to be on the very cool emitters.
I have a couple I'm working on from Simon, an L6 and M21F.
Which one of those would throw the most? 519a with dome one or B35AM?
Currently have a Convoy M21B GT-FC40 in 4500k which I love, but I would like something just a little more throwy, yet still high cri and warm tint. With the M21B MAO being available, I am thinking maybe getting another one of those, but would a B35AM be throwier than the GT-FC40?
In terms of throw in the same host, I will say throw will be 519A>B35AM>GT-FC40.
I don’t know, B35AM with it fairly compact domeless form factor and higher brightness may thow at least equally good.
Maybe just get the M21A or E?