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Jensen Transformers CI-1RR

ISO-MAX Single-Channel Audio Input Ground Isolator / Hum Eliminator

Made in the USA
Jensen Transformers CI-1RR ISO-MAX Single-Channel Audio Ground Isolator

Jensen Transformers CI-1RR ISO-MAX Single-Channel Audio Input Ground Isolator

Designed for use in the finest home theater and audio systems, this audiophile-quality isolator is equipped with high-grade nickel-iron-molybdenum alloy cores, ensuring extremely low distortion and ruler-flat frequency response.

RF interference rejection is maximized by Faraday shielded windings.  High quality gold-plated connectors provide high performance connections and maintain long term reliability. 

The CI-1RR not only eliminates hum and buzz but also enhances audio quality by reducing spectral contamination due to ultrasonic and RF interference.

The CI-1RR is housed is a sturdy metal enclosure, measuring 4.32" W x 2.6" D x 1.45" H., including the flanges. The flanges have mounting holes, which are handy for permanent installations.

If you're not sure which model to choose, please check out our Jensen Transformers Application Guide.

Please do not confuse the CI-1RR with similar (but inferior) products. Jensen Transformers' ISO-MAX Studio-Quality Audio Isolators provide the ultimate signal interface solutions.  They solve the fundamental problems associated with ground loops, without degrading signal quality.

With inferior products coming from all over the world, we think it is a genuine treasure to find a company like Jensen Transformers, actually designing and manufacturing some of the finest products in the world, right here in the USA, and we are proud to be able to offer their products.  The CI-1RR is made in the USA, is backed by the manufacturer's comprehensive one-year warranty, and has a remarkable 20-year warranty on the transformer device itself.

Ground Loops?

(or why the best planned systems sometimes sound bad)

It is a subject that is seldom discussed in manufacturers publications, or even in magazines of the trade, but ground loops can happen even in the most carefully planned A/V system.  When ground loops happen, the result is unwanted hum and buzz.

Ground loops are often the result of the fact that in a complex A/V system, some components may be powered by a different electrical branch circuit than the rest of the A/V system. The result is that the neutral or groundside of the two circuits can be at a slightly different potential.  It can be because one of the circuits is loaded more heavily than the other, or because one run is longer than the other, or any number of other reasons that are beyond the scope of this article.

Ideally, ground loops would be prevented at the design level, but if you are working with an existing room, it is not always possible or practical.

Ground loops can occur in mobile installations as well, because all of the amplifiers in the system have their own internal power supplies, and voltage drop percentages in a 12-volt system can be even more challenging than in a home system.

The Solution

The Jensen Transformers CI-1RR is elegant in its simplicity.  Just insert it in the audio line and it immediately provides these benefits:

  • Eliminates the inherent ground noise coupling mechanism
  • Common-mode ground noise rejection of 95 dB at 60 Hz
  • Wide bandwidth:  -3dB at 0.25 Hz and 25 KHz
  • Handles signals up to 7 volts at 20 Hz or 11 volts at 30 Hz
  • Input impedances are 49 kOhm when driving typical 47 kOhm inputs

Immediately, the effects of the ground loop become a non-issue.  Problem solved.  There are not too many things that one can install in an audio system that can do so much with so little effort.

Don't Forget the Cables!

Good cables are very important in the fight against hum and noise. You will need at least one short patch cable in order to insert the CI-1RR into your signal path, and you may want to consider upgrading your existing cable(s) as well.  To avoid excessive high frequency losses, no more than 3 feet of cable should be used on its output.  The CI-1RR does not include any cables, but if you need them, we have some excellent audio interconnect cables available.  Please click here to see them!

Jensen Transformers' Description


Single Channel Audio Input Isolator

Ideal for use with Sub-Woofers and Mono-Block Amplifiers where use of a stereo unit would be impractical


  • Ruler flat frequency response preserves "Audiophile Quality" signals
  • High-Grade Nickel-Iron-Molybdenum alloy cores for extremely low distortion
  • Faraday shielded windings for maximum R.F. interference rejection
  • High quality gold plated connectors for long term reliability


Jensen Transformers CI-1RR ISO-MAX Single-Channel Audio Ground Isolator, right-front

Here is another angle.

Jensen Transformers CI-1RR ISO-MAX Single-Channel Audio Ground Isolator, front panel

In this photo you can see the gold-plated RCA type input and output jacks.

Jensen Transformers CI-1RR, open

Here is a peek inside the device.

Jensen Transformers CI-1RR product box

This is the product box.

Jensen Transformers CI-1RR User Manual - click to download PDF

Here is the datasheet in PDF format.

Add to Cart to see your discounted pricing!
Product Description SKU MSRP Your Price Quantity
ISO-MAX Single-Channel Audio Input Ground Isolator CI-1RR $175.99 $159.99
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