Prismatic Ray - bus sync vs RCA

I just bought a demo PR from Perfect Circuit for $325. Even at that steep discount, I assumed it would be one of the last couple runs with the RCA jacks for sync, but it is from 2017 with the bus sync. They likely swapped their display model with the newer model.

I could always send it back, and may do so as I’m going to have to have to rearrange it so its on the same power bus as my VC. But the price was right, so…

Are there any big problems with sync being on the power bus? I would guess the major driver for moving to RCA sync is not having to share the power bus, but maybe there’s more. Noise? I guess the Castle VCO uses the bus for sync as well, so it can’t be too bad. Or can it?

So they use RCA sync now? That would be excellent. I have a bunch of PRs running off the power bus sync signals, sharing with a load of other modules. No problems with noise, even on a secondary Malekko PSU using the sync-bus cable to link it to the primary Malekko PSU. (Primary because that one has the VC on it.) YMMV with another PSU.

1 Like

Ya, starting in 2018 they moved to RCA sync. I would prefer that, but it’s not a show stopper. I guess sync frequencies are fairly low, so are probably more tolerant than other signals.

I’m currently using some cast off HEKs with flying bus cables, but I’m invested enough in video modules that I need a more solid case.

Noise will depend on the quality of the PSU. I prefer the Melekko PSU but I also use the 4ms Row Power 40 modules and their flying power bus. Noise has never been a problem for me. Panel space, however, is an issue. One RP40 per row of modules works well but eats up more panel space than I’m comfortable with, so I’m heavily attracted to the Vessel case.

1 Like

If you’re careful and the cable is not too long (this one is about 12-18 inches, you can make a jumper for sync to whatever bus you need


There shouldn’t be a quality difference at all, it’s more about standardizing sync on all products moving forward to being RCA I/O only rather than pseudo-standards or the bus ribbon.


I had nothing but problems w/ my Row Power’s. Noisy & were likely the culprit of several borked modules. Burnt power regs or something IIRC

Yes, I’ve read about other people having some problems with a later batch. Perhaps I was just lucky to get 4 good ones, but I’m wary of anecdotal evidence. Still, I’ve been very impressed with the 2 Malekko PSUs I have here. I’m seriously considering a Vessel for my next case/psu expansion.


Seems to work fine with a TIpTop uZeus

I read somewhere there was a problem with the power bricks 4MS recommend, so it may have been a bad batch. That was a year or maybe two ago, so it might not apply now. I don’t know. I don’t know who does know. After all, anyone buying a product can only really comment on that single example. Unfortunately, we tend to generalise from single cases, so I’m very wary of any anecdotal evidence.

I know people who will still say negative things about a product, even generalising to entire companies, based on a single negative experience from years ago. Sometimes the thing they’re complaining about was an early version of one of a comany’s first modules, and long since fixed, which seems grossly unfair to me.

However, sometimes a negative experience results from a real problem in a product. This might be such a case, but for all I know, it might not be.

Without manufacturers posting their lab tested specs on ripple/noise floor at full load, it’s hard to know sometimes. I understand the reluctance, since some modules are the culprits, injecting noise back into the EuroRack rails.

As of about 1.5 years ago (there are some new options now), we tested just about everything available for EuroRack. Most of the switching topology supplies perform horribly with analog video systems.
There’s a list of recommended power supply options here which includes everything that we found acceptable to get what we’d deem as acceptable performance from our modules:

Out of respect for other manufacturers, and that we wanted to make sure to give room for revisions and improvement, we don’t have a “bad egg list.” (But we did test everything mentioned in this thread.) We strongly recommend if you want the modules to function as they are supposed to, to limit your power supply configurations to those on the above list. Clean power and performance are much more important than the perfect skiff case or most budget friendly option.

The practical concern is switching noise bleed. This will show up as diagonal scrolling jaggies on the edges of any high gain process or hard keyer, but be present in everything. If you see a clean image with no diagonal scrolling jaggies that looks good to your eyes, then I wouldn’t be too worried.

If you are seeing something like that, you may be very surprised at how much better your modular will look if you replace the power supply.


Are there more Vessel cases on the horizon? I don’t see them on the schedule.

1 Like

We’re building more in March, hopefully.