Line level Isolation

Jay Barracato

Graduate Student
Jan 11, 2011
1,528
4
38
Solomons MD
What is your preference for products that provide line level transformer isolation?

About the only ones I am really familiar with are the Whirlwind Iso's.
 
Re: Line level Isolation

I have a few EbTech "Hum Eliminators" and a couple of "Line Level Shifters" that have sufficed well enough.
 
Re: Line level Isolation

Jay,

I use Radial's Twin Iso... same form factor as the JDI or J48 you're used to, dual Jensen transformers inside, ground lift, polarity reverse... if that won't fix it, you'd better get out the screwdriver.

twin-iso-34-l-280.jpg
 
Re: Line level Isolation

What is your preference for products that provide line level transformer isolation?

About the only ones I am really familiar with are the Whirlwind Iso's.

Horizon/rapco make the Isoline 2, which is a 1:1 line transformer. It has TRS on one side and Mxlr on the other so it may not work for all applications
 
Re: Line level Isolation

The Art DTI has XLR + TRS + RCA in and out :) . I'd like a 1/8" stereo too but that would tie the grounds together so I can understand why they chose not to include that. A $1 dual RCA to 1/8" stereo cord fixes that for cheap anyways :) .
 
Re: Line level Isolation

One of the bands I work for has a couple of art microphone splitters. They are already on the replace as soon as possible list. I don't think I will be looking at anything else from them soon. The radials are the level I am looking at. I will also check the specs on the rapco. I have used a lot of rapco cables but never any of their black boxes.
 
Re: Line level Isolation

I use Altec (or Peerless) 15335A transformers for this job. They tend to cost less than the Jensen equivalent and sound just as good (to my ears). They are on an octal base so you got to put them in a box (Hammond/Eddystone/whatever).
M
 
Re: Line level Isolation

I have a couple of home built units made with Western Electric transformers from the 70s. Even though the phone system was limited bandwidth, many of the components were wide band. I have a headphone amp I made with a speakerphone op amp back in 1972. There was a design note for the chip that defined the add on caps and resisters that opened it up to 20hZ-18kHz.
 
Re: Line level Isolation

I use the Whirlwind Iso's and have been super happy with them. I have a few now in my workbox and they get used all the time... I don't think you can ever have enough of these on-hand when doing corporate work :lol:

If you keep a sharp eye on eBay... you can usually pick them up for $30-40 a pop, although the 1x3 can go for a bit more. I have yet to spend over $50 for one.... they are built like tanks too, considering how little there is going on inside.
 
Re: Line level Isolation

Great timing - I got bit by hum last week, with nothing on-hand. One acoustic guitar with amp plugged in via output XLR. Same guitar would hum in a different amp that was clean with a second guitar. If the guitarist touched the 1/4 out, problem went away. 1/4 swapped - still noise. Plugging guitar into DI and then into LowZ in the amp actually made it worse (ground lifted or not...) Disconnecting from the board solved the problem. Since it was localized to his guitar, I suggested a trip to the luthier. He had some problems before (not always) but the luthier could not find anything.

Ah, but that is another issue. Isolation between the board and amp would have solved it.

I was looking at the WW ISO1, ISO2,and the inline ISOXL. I do like the Radial products - the question is why not to use the Whirlwind.

I got this note back from Whirlwind comparing their products:
Hello from Whirlwind,


The ISOXL does have a smaller transformer and its frequency response will not be as low as the larger TRSP600L used in the larger box type ISOs. The frequency response spec at 100 Hz, 0 dBu is -0.13 dBu. That's not bad as long as you don't drive it really hard.

The spec on the TRSP600L @ is 20 - 20k Hz, +/- 0.57 dBu but at +20 dBu.

So the ISOXL becomes a handy and relatively inexpensive problem solver. In fact, they're used all the time to isolate mixers from amplifiers in PA systems.

The ISO1 uses the same TRSP600L transformer as the Line Balancer but only has the single channel of isolation without the splitting capability but it's a bit less expensive.


I guess my other my other question is when do these different specs become audible?

frank
 
Re: Line level Isolation

Briefly, it comes down to the amount of iron you have in the transformer. Smaller transformers (like those that fit in the barrel of an XLR) will have a tendency of saturating easily when driven hard, particularly in the low frequencies. I wouldn't put a small cheapie iso transformer on the line outs of your mixing console if you're doing full range audio (considering that levels on the output of a mixing console can exceed +20 dBu). If it's just a talking head event, you should be fine with a smaller transformer.
 
Re: Line level Isolation

I have a few of the older Rapco units that are pretty nice. These were made in the USA. When I wanted to expand my collection, I tried finding any that were listed as Made in the USA and sadly my search turned up empty. Ended up buying some Whirlwinds. Dirt cheap, but they do the job.
 
Re: Line level Isolation

Any opinions on this: http://www.audiopile.net/products/Electronics/MST-103_mic_splitter/MST-103_cutsheet.shtml

I've used one to prevent hum when I am splitting my output to 2 amps on different circuits. It's cheap but seems OK, but I have to wonder if I am degrading my sound quality. Still, a little distortion, if even audible, is better than a hum, I guess. What do you think?

Seems like it's more appropriate for microphone level splitting than line level isolation. Big difference in the voltages used.