RapcoHorizon BLOX Series Inline XLR Isolator 1-channel Line Isolator Reviews

This product was a simple solution to a pesky hum issue. Excellent service from Sweetwater as well.

These did just what I needed them to! We had a buzz in our speaker system and these eliminated it!

Every so often we have had issues with buzzing in our speakers. I never used these before, but after playing a gig where we used our board and the sound company's speaker's we had a buzz. They used something similar to the Rapco ISOBLOX, and it helped. So I purchased a couple of them, Ive only had to use them a few time's but they really work!!! Great investment!

Product and customer suppor are Excellent!!!!!

It does what it's supposed to do: Isolates one ground from another. Audio quality is good. Transformer inside isn't a Jensen, or Radial, but it's good, smooth, and broad. And, very cost effective when you need a solution. It's small enough that a couple tossed in a gig bag don't eat up too much space, Robust enough you can take it on the road. Easy enough to deploy, that it can be your go-to. For Broadcast, when setting up phone systems, which can be a nest of buzzes, ground loop hums, and assorted noises, the perfect quick solution when you're under the gun to get the broadcast on the air. Live shows, in a venue where regular Edison can be iffy, Problem solved. Keep a couple in your pocket. Again, not the perfect transformer. Rupert Neve wouldn't be integrating them into his designs. But, for fast, quality, reliable solutions...put it into your kit. Several of them.

A very basic part of any audio toolbox, I bought it mainly to isolate a ribbon mic from phantom power on a mixer with phantom switchable only across all inputs. It does the job effectively with no loss in quality.

Does what it's supposed to do. One of those things where's it's gonna work or it's not and that's about it. Used this to isolate an old mains system that had a nasty ground loop after the snake return but before the driverack. Took the unit apart real quick and it's simply Neutriks connectors connected to a small transformer inside a metal tube. If you think you can do better for $30, go ahead, but it works if applied right and is a quick fix. It's basically a cheap XLR to XLR DI, so test the connection you want to troubleshoot with a DI first, and if that works, this is likely the product for you. This will NOT fix noise/interference picked up in a guitar cable.

This Isoblox transformer does the job fine, to isolate an XLR signal between components with different power sources or supplies. It does not have a "Jensen" transformer, which are pretty pricey, but neither does the Radial Ice Cube (which I also have). It performs the same as the Ice Cube but lacks the ground lift switch which the Ice Cube has - but the Ice Cube costs double. When the Ice Cube DOESN'T work, the Isoblox doesn't either. (There are clearly buzzes that these won't fix, don't be surprised! - might have to treat the AC power in those cases.) When the Isoblox and Ice Cube both work, they are interchangeable (so far, only one weekend's gigs to report, but I A-B'd them). I have not found the ground lift switch (missing on the Isoblox) to be significant yet but it is clear that it MIGHT be under some conditions, but for half the price of the Ice Cube, I can build my own ground lift switch, which is just a toggle switch and two jacks in a cigar box, not rocket science.

For folks looking at this, there are THREE useful devices to put in an XLR line between any two devices which have different power supplies (mixers, speakers etc, which may all have potential ground voltage differences), and my new practice is to put all three of these functions in any line level XLR cable. (Mic cables are not an issue for me.) The Isoblox under review has only ONE of these three functions. The missing functions are the ground lift and the polarity reversal switch. These are included in the more expensive two-channel isolation boxes from Radial that cost up to 3 bills, but to save that money you can DIY them, because they are as easy as a light switch. To accompany the Ice Cube I built a polarity switch. I plan a new DIY cigar box polarity switch for the Isoblox with a ground lift switch just to have it available in case.

In other words, the XLR line optimally should have a transformer (the Isoblox) and two switches, polarity (reversing Pins 2 and 3) and ground lift (cutting the signal from Pin 1 entirely), which should be routinely turned to both positions to just see which sounds better. It was a surprise to me to find out that the polarity reverse switch can sometimes significantly improve the sound, and this has nothing to do with ground isolation or buzz problems. Some two-channel transformers have the polarity switch on only ONE channel -- in my opinion this could be an error. Sometimes a single channel will sound better just by reversing the polarity, so it is not just a phase issue between two separate signals but an issue with the signal itself or a difference in processing between the two devices.

I should mention that I built a two-channel cigar-box polarity switch box and despite apparently clean wiring it generated a buzz, which the same wiring in two different boxes did not - a gremlin (electronics is not my bag). My research on XLR line transformers indicates that sometimes they may work better when closer to the receive than to the send, and this suggests that single-channel transformers like this Isoblox may be preferable to two-channel ones unless it is a stereo signal going between stereo devices. All this is a grey area but with any buzz problem it's good to try every possible experiment with the signal path.

At SW we are buying service and accumulated knowledge, and every SW client is assigned a sales rep who is a knowledgable musician and when you find out that he has your back in a pinch then you'll know what gratitude is. Trying to give a little back here. :)

I have reviewed both these devices. I use them both routinely in similar positions to isolate my battery pedal board from AC-powered external devices; I have two balanced outs from the pedal board via a mini-mixer. There was a bad buzz in the FOH speakers, and muting my guitar's input channel on the mixer made it go away. Putting the Isoblox in the (balanced xlr) line from the pedal board to the mixer input slightly reduced it, but the Ice Cube cut it entirely. I have not found any situation in which the reverse was true. The Ice Cube, although more expensive, appears to be a better device. That's the report!

I've yet to benefit from the unit as I can tell. I hoped it would help isolate some of the ground noise I was getting... an actual radio station bleeding in on the ground line, ever so faintly, but it's still there. Anyway, I keep it in-line, just in case at any other venue, it would be of more help.