I’m afraid this is going to be a longer post. I have been thinking a lot about PSUs lately and the main reason is that want to change my modular case in the future, but am not really sure about what I should get. 9U is a bit too much for me, I’d like my modular to be more of a focused kind of instrument (even if I do have lots of modules) and one things I did wrong with my current case: it’s not great if you want to use it flat on the table (which is what I prefer), but I’m pretty happy with the Tip Top Zeus Studiobus PSU in there. It does seem to work well for me. At least I never had any issue so far, and I’ve been swapping a lot of modules in and out, and even had some not so well built DIY ones in there.
Power is a hairy topic, it’s probably the most complicated part of the modular, and the one which is more likely to create problems.
Though I think most of the time – and that’s something we tend to forget in these discussions – things do work even with not so great PSUs. What I mean is, there might be problems, but they might be hard to hear, so honestly who cares? I mean, I did use some plain Meanwell RT-50B (or RT-65B) power supplies wired directly to a busboard and in normal conditions I could not hear any noise, and didn’t have any other problems.
The noise&ripple values of these PSUs are much higher than what you get from most hybrid ones.
Most recent built-in PSUs like the one in the Make Noise skiff, the one in the Tip Top Mantis and the Intellijel ones all seem to have very decent specs to me (even if, as I said earlier, I find it a bit of a pity that the specs are always a bit on the thin side) and from what I could gather, work well from various points of view.
When reading about @ppqq’s concerns about ground problems I did some research, but could not find any real issues (just some minor things, which turned out to be “false positives”, or things that got solved quickly anyway) besides what has been already said, which does not seem to be a major drawback to me.
Still let’s not forget that you can have all sorts of annoying problems. I sure had a number of these over the years and some I were not able to troubleshoot (some I solved by changing PSU… but that’s far from being ideall). Problems can be that the output is noisy (hum, hiss, etc.) or that some – usually digital – modules go bonkers. I had them all, so I have become a bit more careful. The thing is also: you can have a nice working system and then at one point it starts to do weird shit. In these cases it’s hard to troubleshoot who the culprit is.
If I had to sum up what what my potential causes for PSU-related problems were in the past, I’d say:
- Using more than one case and patching them together, depending on the PSUs and how things are internally wired you can get that things get a bit noisy.
- As the Make Noise problem mentioned earlier shows, sometimes it’s down to how a certain module is designed. The issue can be a direct malfunction of a module, but what seems to also be very common (and I had some of that in the past as well) is crosstalk between modules, though that seems to be more of a busboard problem.
Since there’s no clear standards I guess we can’t really blame anybody for these hiccups, plus, on the other hand, the sheer number of different modules, each with their own way of working, makes it very hard to make the perfect PSU. It seems that a direct connection to protective earth (or earth ground) is a good idea, at least that’s what both Graham Hinton said multiple times and what the Rabid Elephant doc says. Less impedance between the ground connector on your modules and a real 0V (like the earth connection) seems to reduce the chances of noise getting into the system. So I guess having a class II brick that lacks the protective earth connector is probably a bad idea to start with?
- What I did in the past and what I would totally suggest to avoid to anybody: building your own case if you don’t know what you’re doing. It’s a really bad idea. If you’re lucky and you don’t electrocute yourself, you’re still likely to end up with a malfunctioning modular. Though it’s certainly a great learning experience.
- Using a switching brick that has a very high minimum load. One of the first cases I had, used a relatively expensive (for a switcher) Tracopower PSU, the minimum load was – I think – 400mA. Since it was a 3U case, it was often not drawing as much current and some of the digital modules in there (like the Vectr) would act all weird, failing to properly power on, with LEDs flickering etc. I guess this was because the ripple was really high so the voltages were all over the place.
- I didn’t hear most of the noises in an old case I had until I took it to a live performance. Once hooked up to the PA I got a really horrible hum and some buzzing sounds, which we found out were coming from my modular. After trying many things (like swapping modules) I am pretty sure it was the PSU, (and maybe the wiring)
- Noise can get into your system from other places as well so it’s not always the PSU or the busboards, it might get in from the modules themselves. It’s not unlikely that some modules pick up radio waves or other signals that “fload in the air”.
Btw. I have to correct myself about flying busboards. They do not seem to perform much worse than most busboards in lab tests. At least that’s what some measurements Genus Modu posted on facebook suggest. Which I am pretty surprised about, since I always thought that they must be worse.
I guess my main reason for wanting a good PSU is that I want to avoid some of the “bad case” scenarios, which might be uncommon, but are still very frustrating and complicated to deal with if they happen. Also I have come to believe that it’s probably a good idea to get a more “all inclusive” solution, by which I mean: I want to buy a case that comes with a PSU, possibly designed and built into the case by the same people who made the case.
Going 6U: both the Tip Top Mantis and the Intellijel cases have a couple of things I really like: great form factor, adjustable legs so you can keep them tilted on a table and – and here we get back to the topic – what appears to be a very decent PSU. I can’t think of many other alternatives to these but of course if anybody has a tip let me know!
