I understand, like i said, that was the way that i understood it, but your explanation makes more sense. However, if the capacitor bank has to be charged more frequently, then would the result be the same? What if the capacitor bank isn't fully recharged when you need to slam down on the "d" on the "b" string and the power just isn't there? The only reason i ask this is because i too have noticed lack of low end with the markbass stuff with different cabs, basses and strings in many different situations. I say this because i have an sd800 and owned a ul502 too for a short time, and the low end response on the (IMO and the opinions of the other people who were there) epifani was better even with the lows flat on the epi and boosted on the sd800 (side-by-side comparison).
A couple things here. First... hello!
Regarding the 502, I have one also, and it is BIG down low... too big in some cases. So, I hear what you are saying there.
However, switching power supplies have come a long way, and I don't think that's the issue here.
I owned the SD800 for a while, and my feeling is that head has a bit of a hole in the lower mids, which makes the low end seem a bit 'loose' with some cabs. It's kind of an oxymoron of 'huge low end' that can sound 'weak and blurry' in some situations. I'm not sure why this is with that particular head (which sounds KILLER with a more mid oriented cab like the Berg AE410).
I don't experience ANY of that with the LMII, SA450 and F1 (OK, I kind of like this MB stuff

). While the LMII, etc. doesn't have the headroom or deep low end response of the SD800, it is voiced more evenly, and results in a more punchy low end that 'seems' louder, clearer, and cleaner (again, with some cabs) than the SD800 (I'll credit Tom Bowlus with identifying this issue first... I couldn't figure it out for a while).
The 502 is a real love/hate thing with me. The low end is just SO good, but there is just something wrong with the mid voicing and EQ of those heads. In a 'perfect' room, they sound great. In a less than perfect room, I can't seem to dial out the suck. I don't have this problem with most other heads.
K