Legrand C2G 3.5MM Isolation Transformer (21-Inch Audio Jack Extension Cable)

What buyers think

Buyer-review evidence is mixed but informative. Several reports describe noticeably reduced speaker noise after placing the 3.5mm isolation transformer in-line between an audio source (such as a TV, computer, or auxiliary device) and the rest of the audio path. Others mention that it can help when the hum is triggered by using multiple connections at once. A smaller portion of feedback flags possible tradeoffs, including interference pickup (such as picking up a local radio station) and one account of audio temporarily dropping out when reconnecting the 3.5mm cable.

Overall, the recurring theme is that it can solve ground-loop hum when the problem is truly related to shared grounding, but results depend on your specific setup and where the device sits in the cable run.

What this 3.5mm isolation transformer actually does

An isolation transformer is meant to interrupt the electrical ground path between components while still allowing audio to pass. In practice, this targets the classic symptom of ground loops: a persistent hum (often described as 60Hz hum or buzzing) that appears when devices are powered through different outlets or circuit paths.

This model is an in-line 3.5mm auxiliary transformer intended for stereo audio signals. It includes a 21-inch cable, which is useful when you need enough slack to insert the isolator somewhere convenient between the source and your speaker or receiver.

How to use it for best results

To get the noise benefit, placement matters. A common approach is to start with the component that was connected when the hum first appeared, then insert the transformer at one end of the audio run. If the hum persists, you typically try moving the isolator to the other side of the problematic cable path (for example, swapping which end the transformer sits between).

If your setup is creating noise only when you connect multiple cables or adapters at once, consider whether your audio connection is sharing ground through that combined path. In those cases, inserting the isolator in the audio line can be the targeted fix.

Pros and cons for real-world buyers

It’s a good fit if you hear ground-loop hum in a 3.5mm setup

If your system produces buzzing or humming from speakers when connecting a TV, computer, or other auxiliary audio source through 3.5mm, this category of device is designed for that exact symptom. Review feedback frequently points to hum reduction once inserted in-line.

It may be frustrating if the noise is interference-related

Some buyers report the transformer can pick up unwanted radio or create another kind of noise. That does not mean it will happen in every installation, but it is a reminder that not every “hum” problem is purely a ground-loop problem, and extra troubleshooting may be required.

You should also plan for basic troubleshooting

If audio drops out after reseating a connection, or if you need to adjust placement to eliminate hum, the isolator is still workable, but it is not always a “plug it in and forget it” device for every scenario.

Legrand C2G 3.5MM isolation transformer specs at a glance

• Connector type: 3.5mm auxiliary (male-to-male)
• Length: 21 inches
• Signal type: supports stereo audio signals
• Intended use: break ground path for ground-loop isolation in audio chains
• Model: 40000

Is the Legrand C2G 3.5MM isolation transformer worth it?

It’s worth considering if you have a true ground-loop hum issue in a 3.5mm audio chain and you want an in-line, relatively simple hardware solution that targets the ground path. It can also be a practical option when the noise appears only with certain combined connections.

However, if your noise is more like high-pitched switching interference that requires a different filter strategy, or if your install is sensitive to added pickup, you may need to experiment with placement or consider a different type of isolation approach.

Alternatives to consider (based on your problem)

• If the issue is ground-loop hum in 3.5mm audio: an isolation transformer like this is one of the most direct categories to try.
• If the issue is interference or signal-level imbalance: you may need a different solution than ground-path isolation (for example, a different filtering or audio interface approach), because ground-loop tools may not resolve non-ground sources.
• If you need a more flexible connectivity solution: look for isolation options that match your specific connector types and cable layout, since some setups require adapters or different end genders to route cleanly.

Price and availability

Price can change frequently. If you’re shopping for this specific 21-inch 3.5mm in-line isolation transformer, check the current listing for the most up-to-date cost and stock status.

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FAQs

Will this 3.5mm isolation transformer remove ground-loop hum?

It is designed to reduce hum caused by ground loops by breaking the ground path between audio components. Many buyers report improved or eliminated speaker noise after inserting it in-line, but results depend on the specific source of the noise.

Where should I place the isolation transformer in my audio cable run?

Start by placing it in-line between the audio source and the device producing the hum. If the noise remains, try placing it at the other end of the audio run, since different setups require different insertion points.

Can the transformer introduce other noise?

Yes, some buyers report interference pickup in certain environments, such as radio noise. If you notice a new tone or interference after installing, adjusting placement or using additional shielding and grounding steps may help.

Does it affect audio quality?

Buyer feedback generally describes no obvious audio-quality loss when the transformer is working as intended for isolation. That said, any audio inline device can behave differently depending on your exact chain and signal levels.

Is this transformer only for TVs and speakers?

It’s intended for audio/video system use where a 3.5mm auxiliary connection is involved, including setups like TV to sound system, computer audio to speakers, and other stereo auxiliary chains experiencing ground-loop noise.

Is it suitable for stereo audio?

Yes. This model is intended to support stereo audio signals while isolating the ground path.

What if my hum is not caused by a ground loop?

If the noise originates from a different cause, such as a non-ground electrical interference source or an incompatible audio chain behavior, an isolation transformer may not fully solve it. In those cases, you may need a different type of troubleshooting or solution.

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