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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => LAB: The Classic Live Audio Board => Topic started by: John Chevalier on August 15, 2012, 11:13:26 pm

Title: Which ISO transformers do you carry ?
Post by: John Chevalier on August 15, 2012, 11:13:26 pm
I have used  Masque Sound ISO transformers that have worked pefect for years. Recently the few I have have become lets just say lost. I cant seem to replace them anymore. Does anyone have a suggestion . I have used Switchcraft IL -19 's and Whirlwind ISO max in the past as well, I also have a few sea comm iso transformers. I use the barrel style just for ease of use but will consider something like Radial PRO-ISO Stereo boxes as a back up. I have had great luck with the masque sound version and do not see them for sale any more on there web site. I'm curious which one's you guys may use .
Title: Re: Which ISO transformers do you carry ?
Post by: Mac Kerr on August 15, 2012, 11:39:42 pm
I have used  Masque Sound ISO transformers that have worked pefect for years. Recently the few I have have become lets just say lost. I cant seem to replace them anymore. Does anyone have a suggestion . I have used Switchcraft IL -19 's and Whirlwind ISO max in the past as well, I also have a few sea comm iso transformers. I use the barrel style just for ease of use but will consider something like Radial PRO-ISO Stereo boxes as a back up. I have had great luck with the masque sound version and do not see them for sale any more on there web site. I'm curious which one's you guys may use .

It may be out of the price range at $210, but the Jensen Stereo Isolator (http://www.jensen-transformers.com/datashts/pi2xx.pdf) is as good as it gets. It can handle +20dBu levels at 20Hz, something none of the transformers you mentioned can do. Barrel type transformers, whether they're Masque, Sescom, or even Whirlwind, cannot handle low frequencies at high levels. they are best at mic levels, but they generally get used at line level. The Jensen is designed as a line level device.

If you want to build your own, the Jensen JT-11P1 (http://www.jensen-transformers.com/datashts/11p1.pdf) is about $70 but needs a box and connectors.

Mac
Title: Re: Which ISO transformers do you carry ?
Post by: Greg_Cameron on August 15, 2012, 11:55:57 pm
None of the small barrel style transformers will perform as well as the larger transformers when the signals get hotter and have low frequency content. I highly recommend the larger devices. I've been using the Whirlwind ISO1 transformers and they work well. I'm sure the Radials would be excellent.
Title: Which ISO transformers do you carry ?
Post by: Rob Spence on August 16, 2012, 12:06:04 am
I have a pair I built from Western Electric transformers. It was 25 years ago so I don't remember the details much. I think they were called repeater coils or some such. 600 ohm in and out. I mounted a project box on it and put male and female xlr on each side with a polarity switch and a pin 1 lift switch. They have worked well for me.


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Title: Which ISO transformers do you carry ?
Post by: Rob Spence on August 16, 2012, 12:06:45 am
I will see if I can post a picture.


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Title: Re: Which ISO transformers do you carry ?
Post by: Riley Casey on August 16, 2012, 10:15:27 am
I have built dozens of iso transfromers, both output ( 600:600 ) and input ( 10K:10K ) types over the years.  Most built with Jensen or Sescom transformers.  A good source for input transformers if one is up for cruising Ebay is octal socket balancing transformers that were sold by Altec, EV, Crown - all the major amplifier makers sold good quality input transformers for use with their amp.  I have always built them into Bud boxes with a female XLR and a TRS jack on the input side and originally a male XLR and pin one lift switch on the output side.  I have since decided it's simply more reliable to have two output connectors.  One with pin one thru and one with pin one open.  Why even bother with a pin one connection if the point of the transformer is isolation?  Because every once in a blue moon it's needed when you actually do want to balance an unbalanced output rather than simply isolate disparate grounds. 

There really is a difference between input transformers and output transformers btw.  If you're using generic iso's they are probably 600 ohm units and should be used to drive a line rather than receive a line.
Title: Re: Which ISO transformers do you carry ?
Post by: Mac Kerr on August 16, 2012, 10:35:46 am
There really is a difference between input transformers and output transformers btw.  If you're using generic iso's they are probably 600 ohm units and should be used to drive a line rather than receive a line.

However, the best place to put that transformer is at the input, so a line input transformer is probably a better bet if you are building your own. I too built lots of dual iso boxes with Altec octal plug transformers. I built them so the transformer stuck out of a hole in the Bud box so we could plug in the right transformer for the job.

Mac
Title: Re: Which ISO transformers do you carry ?
Post by: Curt Sorensen on August 16, 2012, 11:23:47 am
We've been using the Radial Twin-ISO fro line-level audio, but y'all should consider a few of these in your kit:

http://www.audiomanproducts.com/

If you read the product info, he mentions having transformers and caps on each leg of a pair.

While I can't vouch for the fidelity of the signal [as I'll use the Radials first] I use these mostly for connections between intercom systems that are noisy, or as a drier to remove voltage from com and IFB lines.
Hope that's not too much of a swerve.
Title: Re: Which ISO transformers do you carry ?
Post by: Keith Broughton on August 17, 2012, 07:43:35 am
Most of the applications I need iso for is not high level and extended low frequency response, so I find the Rapco ISOBLOX very handy and works just fine for pretty much anything I come across.
http://www.rapcohorizon.com/p-373-isoblox.aspx (http://www.rapcohorizon.com/p-373-isoblox.aspx)
It's always nice to have a couple of channels of Jensens though :)
Title: Re: Which ISO transformers do you carry ?
Post by: Tom Young on August 17, 2012, 09:25:02 am
We've been using the Radial Twin-ISO fro line-level audio, but y'all should consider a few of these in your kit:

http://www.audiomanproducts.com/

If you read the product info, he mentions having transformers and caps on each leg of a pair.

While I can't vouch for the fidelity of the signal [as I'll use the Radials first] I use these mostly for connections between intercom systems that are noisy, or as a drier to remove voltage from com and IFB lines.
Hope that's not too much of a swerve.

Nice looking box but why do they provide almost no spec's ?

DI's and other audio iso transformers need to be of certain (minimum) size in order to handle line-level signals (including cranked signals from active pickups, which approach line level) with response down to 40Hz and below. I think it was Mac who mentions this in an earlier post in this thread. Transformers designed to handle higher (line) levels simply do not fit into a XLR barrel type housing.

The transformers in this box look like they are small enough to fit into a barrel housing. This, and the missing spec's, are a big red flag for me.

FWIW
Title: Re: Which ISO transformers do you carry ?
Post by: Geoff Doane on August 17, 2012, 09:50:20 am

There really is a difference between input transformers and output transformers btw.  If you're using generic iso's they are probably 600 ohm units and should be used to drive a line rather than receive a line.

Input transformers usually have a Faraday shield, and in the case of at least one Jensen model, they should have very low capacitance on their secondary side (Jensen recommends about 3 feet of typical shielded pair cable, IIRC).

However, in a typical voltage transfer system, I don't see the disadvantage of using an "output" transformer at the receive end of a balanced line.  The wire resistance should add only marginally to the output impedance of the driving circuit, so what's the down side?

GTD
Title: Re: Which ISO transformers do you carry ?
Post by: Curt Sorensen on August 17, 2012, 11:22:04 am
When I went to look for the link, I saw that he had a new website. I thought he had published more specs previously, and I even remember thinking he might have provided too much info, as someone could build their own from it. It's not there now. There is some more info at:

http://www.steve1mac.blogspot.com/

There's a photo of the innards, a frequency response chart, but nothing regarding phase or the levels it can handle. At the price point and seeing the photo, I doubt that the transformers are stellar. But I've had a lot of luck using them with intercom connections where fidelity is not usually a topic, and I thought they might be worth adding to anyone's kit. I would use them for straight audio in a pinch, but then I have a pair of two-channel Radials for the critical paths to go to first.
It's my understanding that using two transformers makes it work for intercom, but I have to wonder if they're well matched enough to provide balanced audio that's, well, balanced.
And of course I have no connection other than being a satisfied customer.
Title: Re: Which ISO transformers do you carry ?
Post by: paul bell on August 17, 2012, 07:13:25 pm
I also carry a bunch of Rapco Isoblocks. They're my "magic box".