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Blue Jeans Cable Audio Isolation Transformer/Ground Loop Hum Eliminator for Subwoofer or Full-Range Audio

4.4 (8) Write Review
Free shipping on orders over $29.99

$49.95

$ 25 .99 $25.99

In Stock

About this item

  • Comes with instruction sheet to help guide you to the solution to an audio hum problem -- even if it's not a ground loop
  • New improved design
  • Assembled in our shop in Seattle, Washington


Product Description

BJC isolation transformer

Subwoofer Isolation Transformer -- the solution to the most common hum issue

Blue Jeans Cable Subwoofer Isolation Transformer / Subwoofer Hum Eliminator

A good subwoofer can transform the home theater experience by adding a movie-theater feel to your surround sound system. But a powered subwoofer, built to amplify low-frequency sounds and effects, is also susceptible to one of the most vexing home theater problems: hum.

Troubleshooting Subwoofer Hum:

There are a few possible causes of subwoofer hum: (1) internal noise from the power supply, (2) induced hum in the subwoofer cable, (3) hum getting into the signal path prior to the subwoofer cable, and (4) "ground loop" hum from a difference in ground potential at the source and the sub. This transformer will eliminate (4), the most common cause of subwoofer hum, but will not resolve the others.

Specific troubleshooting tips:

- Cause (1), a bad subwoofer power supply, can be checked by simply unplugging the input cable from the sub and seeing if hums with no input.

- Cause (2), induced hum in the subwoofer cable, is normally caused by the cable being too close to power cords -- check cable spacing. If this is the cause, the problem will likely vary in intensity as you increase or decrease the spacing between signal and power cables. The strength of this interference is inverse to the square of the distance, so small amounts of adjustment can make large differences!

- Cause (3), hum getting into the signal path prior to the sub cable, is harder to diagnose, but usually the way to proceed is to test what happens when you switch or disconnect individual sources from your amp. Unplug them from power, too, if possible, as this will prevent upstream ground loops from being a factor. If the problem is specific to a source, then most likely either the source is generating the hum or there is a ground loop issue between that source and your amp.

If the more common ground-loop issue between receiver and sub, (4) above, is your only problem, this transformer will resolve it. This isolation transformer is a quality, US-made audio transformer which eliminates the need for a straight-through ground/ground connection between your receiver and your powered subwoofer. With the grounds on both sides isolated from one another, ground current won't flow down the shield; the result is elimination of ground loop hum. We recommend it be used with Blue Jeans Cable LC-1 subwoofer cables, which are heavily shielded to reduce induced noise, for a truly quiet, low-noise-floor subwoofer.


William S.
2025-06-18 13:43:46
I purchased a new powered subwoofer recently and hooked it to my existing receiver. When the receiver was powered on without audio content, and the subwoofer was in standby mode (no detectable audio content), the subwoofer was silent. And everything functioned well when playing music. However, when the receiver was turned off, and the subwoofer was in standby mode, it emitted an annoying hum. Various rearrangements of the power and audio cables failed to get rid of the hum. I also tried some alternative cables with the same result. When I removed the audio cable from the subwoofer, the hum went away. Various sources suggested this behavior was a symptom of a ground loop. I ordered a Blue Jeans Cable SWT1 which was delivered very quickly. I simply inserted it between the subwoofer and the receiver using quality audio cables with RCA-type connectors and the hum disappeared. I am not an audiophile, but I could not detect any adverse impact on the music played through the subwoofer. This product delivers when it comes to eliminating hum caused by ground loops. The device has the appearance of quality construction.The packaging also includes useful background information about various causes of hum, acknowledging that the SWT1 is designed specifically to eliminate hums from ground loops; but it will not necessarily eliminate hums from other sources. The packaging indicates the seller will take back the product and give you a refund if it does not solve your problem, so this eliminates risks to the buyer. Return labels are included and no return authorization is required. In terms of solving my problem, and the policy regarding returns, I give this product five stars.
Trevor Suarez
2025-06-09 15:35:24
I'm always skeptical of these kinds of products, and this one wasn't cheap, but I didn't want to buy one that was meant for a stereo signal and awkwardly only use half of the connections, and I certainly didn't want to buy a super cheap one that would just degrade the signal, so I found this, saw the reviews, saw the FANTASTIC return policy (if it doesn't work, you just return it, no questions asked... it COMES with a return shipping label in the package!), and bought it.When it arrived I recreated the hum conditions, nervously plugged it inline with my sub signal, and BOOM! No more hum! And there's absolutely 0 perceptible signal quality loss!This product PERFECTLY fixed my issue!Also, again, the return policy is fantastic and the included information sheet was incredibly informative! I don't write reviews often, but I just had to share how fantastic this whole product experience has been!Yay! No more hum when my CPU or GPU is under load! Woot!
LoveMachine
2025-04-24 17:45:29
My subwoofer was generating lots of grinding static noise due to a poor power supply design on a home theater PC. Anytime the PC was connected by HDMI to the AVR, scratching/grinding noise. I tried all the standard tricks (all gadgets on the same outlet, Fiber HDMI cable, heavy duty short shielded RCA cable, etc.) to no avail. This little guy arrived, plugged it inline with the existing cheap RCA cable from the LFE output of the AVR to the sub input. PERFECT. No static/hum/grinding noise, just Boom-Boom. Sure, there's a huge markup on a few bucks worth of components, but totally worth it to avoid the frustration.
Nicklas R. Johnson
2025-04-17 18:53:20
If you're unable to plug your subwoofer into the same outlet as the rest of your home theater system like I am, but your hum problem goes away if you do, chances are you have a ground loop hum that is likely to be solved using these isolation transformers. What's happening is a tiny amount of current is finding an alternative path back to ground through your speaker cable because the voltage at your subwoofer is not exactly the same as the voltage at your home theater system; due to the potential difference, a very small amount of current flows, and the amplifier in your subwoofer amplifies this as sound.Unfortunately if your subwoofer has three connections- one LFE and two Speaker level inputs- you probably need to isolate all three channels. In that case, you need three transformers. That gets expensive pretty quickly at a $50 price-point, though it's also the case that transformers which work at frequencies down to 20 Hz are a bit of a specialty item, thus the cost.Incidentally, if you DO need to isolate speaker connections, get yourself a pack of these RCA/phono to gated screw terminal adapters: https://www.amazon.com/gp/product/B01C5YGXB8 . The specs on these transformers allow for an input signal of up to about 12v, which is pretty dang loud; they should be able to handle most home theater applications that require speaker-level isolation.These solved my problem, though after about 4 months, one of them started decoding AM broadcast signals unexpectedly, which unfortunately is a thing that can happen if you have a nearby AM station and some component in the unit starts behaving like a diode- this can be a bad solder joint, a capacitor that goes bad, or even a bad winding in the transformer. I haven't tried to solve the problem any further; simply swapping the transformer made the problem go away, but if I'm feeling adventurous, I might try to peek inside and see what exactly went wrong.I'm giving 4 stars instead of 5 because of the high price point and because I had one go bad after just 4 months. Of the ones that work, however, they work very well and solved a vexing problem for me.
Mike Wilson
2025-03-05 11:33:11
I had a subwoofer hum that I did everything trying to remove, bought new shielded rca cables, separated all cables from each other, and made sure everything was grounded…….still had the hum. Bought this fantastic little box and hum is completely gone. Thank You Blue Jeans Cables!!! A++++++
Chuck2017
2025-01-26 11:35:50
This is some kind of filter NOT a isolation transformer! Removed all the bass. Has loose connection in it, it kept going in and out of bass. Yes I have very good cables! Going to try another. This is very expensive for not working properly! Would never buy from Blue Jeans again!
Jay W.
2025-01-23 12:23:50
solved 90% of the buzzing so it's tolerable now. Nice quick solution
KMac
2024-11-23 09:40:08
I had higher hopes for this product. It does reduce some low end hum noise, but I still get a fair bit when the system shuts down.