Audio isolation transformers

Allen Avionics Audio Isolation Transformers page describes the typical ground loop problem situation with the following drawing:

AGLfig1

If you want to do the ground loop elimination in audio path, you have to cut the galvanic connection but pass the whole audio range. The simplest and most common way to do the isolation is use audio transformer. High-quality audio transformers cover whole audio band with good response.

Usually when you install an audio galvanic isolation to almost any place in the audio cable connection is solves the ground loop caused humming problem nicely.

Xitel Ground Loop Isolator page gives a good example how to use a ground loop isolator (audio isolation transformer) to solve ground a typical ground loop problem:

groundloop_xitel

To make an audio isolator you have to get two audio transformers which have 1:1 transformation ratio and greater than 1 kohm impedance (prefererably many kilo-ohms for consumer line level applications). There are high quality audio transformers in the markes that meet those specs.

There are several ways how to wire an audio isolation transformer. Here is a basic wirings for isolation transformers for unbalanced and balanced lines:

rcaisolator

xlr_isolator

There are variations how ground are wired on different audio isolation transformers. There are various ways with their advantages and disadvantages. The followinf solution circuit diagram from Allen Avionics Audio Isolation Transformers page conbines all different variations to one device, so you can always easily select (with a switch) the one that works best on you specific application:

AGLfig4

The 3-position switch will eliminate the need to cut pin “1″ to lift the audio ground and the connection to the shield. Switch Positions:

1. Chassis shield connected. Audio ground not connected. Acts as a balanced line transformer to break ground loops. Eliminates hum and buzz.

2. Chassis shield and audio ground connected. Corrects balance on audio lines.

3. Chassis shield and audio ground not connected. Breaks ground loops. Provides audio isolation.

When selecting a transformer for your project keep in mind the quality. Cheapest transformers for audio use have some problems on the sound quality, typically distorted bass response and attenuating in high-frequency response. Basically a poor transformer slows down high frequencies more than low frequencies (because of transformer leakage inductance). This allows the low frequencies to pass first, creating what we perceive as a “fat/warm” tone. Inadequate frequency response on the low end (roll off at like 20Hz), causes low frequencies to be “slowed”, allowing the upper frequencies to be heard first, this is perceived as “barky/ brittle”.

When installing audio isolation transformer to an audio system HIFI people usually ask does that transformer affect the sound in some way and if it does something how much effect does it have. The truth is that the effect of adding an audio audio isolation transformer to a system that does not have ground loop problem could be anything from unnoticeable to normal listener to well noticeable. How much the transformer affects depends on the transformer quality and properties of the equipment between which the transformer is connected. So if there is no humming on the system, the transformer usually has some slightly negative effect on sound quality.

In case an audio transformer is installed to a system with ground loop humming, the effect of it will for sure be possible. The annoying ground loop humming will be heard by everybody. When the isolation transformer get rid of that, the would quality is very much improved at that moment (typically the negative effects of the transformer to sound are much smaller than the annoying humming is). It is a good idea to keep an audio isolation transformer on your tool box when you work with audio/video systems, and use it in you get ground loop problems.

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  12. tecmax says:

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  13. tecmax says:

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  15. Tomi Engdahl says:

    Inside an audio isolator transformer module
    https://www.youtube.com/watch?v=fV_hsFK1MnA

    A quick insight into use of an audio signal isolator.

    If you’ve ever been plagued by mains hum or electrical noise finding its way into your audio system, then this little toolbox essential can save a LOT of grief.

    Reply
  16. Tomi Engdahl says:

    Quick Press Mult Video Feed
    http://livesoundadvice.com/connections/quick-press-mult-video-feed/

    Here’s how to hook up one or more passive DI boxes to make a Quick Press Mult. This lets you send isolated audio to multiple video cameras without creating ground loop hum or a level mismatch.

    How to use passive DI boxes to feed audio to multiple video cameras. Allows you to make a Quick Press Mult for any last minute gigs.
    https://www.youtube.com/watch?v=gWpjVvPi4wQ

    Read more about it at http://livesoundadvice.com/connections/sound-advice-quick-press-mult/

    Reply
  17. Tomi Engdahl says:

    Inside an audio isolator transformer module.
    https://www.youtube.com/watch?v=fV_hsFK1MnA

    A quick insight into use of an audio signal isolator.

    If you’ve ever been plagued by mains hum or electrical noise finding its way into your audio system, then this little toolbox essential can save a LOT of grief.

    Reply
  18. Tomi Engdahl says:

    If you use UBS audio, check out possibility to do isolation in USB line:

    Do It Yourself Musician #4 – Fix USB Audio Noise with HifimeDIY USB Isolator
    https://www.youtube.com/watch?v=GbNyINuo-Uw

    use the HifimeDIY USB Isolator to solve a USB ground loop problem in my home recording setup. If you have a high pitched whining noise in your USB audio system, take a look at this video.

    https://www.amazon.com/gp/product/B00F4SCCR2/ref=as_li_qf_sp_asin_il_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=B00F4SCCR2&linkCode=as2&tag=internati0501-20&linkId=QPGZM62EU45K5D2K

    Reply
  19. Tomi Engdahl says:

    DIY Audio Isolator – STOP Ground Loops and Improve Your PC Recording.
    https://www.youtube.com/watch?v=TQJMGwKU6as

    Cheap commerically made isolation transformers often perform poorly , and professional grade units can cost a small fortune.

    My project today tries to strike a balance between the two , and it actually works very well.

    The HUM is gone.

    Reply
  20. Tomi Engdahl says:

    Using Ground Loop Isolator for home studio monitors
    https://www.youtube.com/watch?v=wnN31snqR9o

    How I eliminated my ground-loop to remove noise from my studio monitors. I used the RadioShack Ground-Loop Isolator and connected it to my usb sound card. Now I have no more hum or high pitch noise in my speakers.

    Reply
  21. Tomi Engdahl says:

    MPOW Ground Loop Noise Isolator Review
    https://www.youtube.com/watch?v=Djnfm-3NcL8

    This is a quick but effective review the the MPOW Ground Loop Noise Isolator. I hope it helps!

    Nice! Audio shop was going charge me $200 to fix the noise

    Reply
  22. Tomi Engdahl says:

    How To Get Rid Of Static/Squeaking Noises On A Desktop Computer Audio Card
    https://www.youtube.com/watch?v=hI11AgBo1Hc

    his problem is common with desktop computers due to the ground going to multiple devices all at once. The Mpow ground loop isolator helps make the computer audio clean.

    Reply
  23. Tomi Engdahl says:

    $10 FIX for Million Dollar Question | AUX Car Audio Interference Problem
    https://www.youtube.com/watch?v=CrKQU-BoVZg

    Auxiliary Interference – Discovering Ground Loop Isolators

    This quick video demonstrates the massive difference a ground loop isolator can make.

    Finally after years of searching I have found a solution for the obnoxious sounding feedback resulting from charging a smartphone and listening to music through the auxiliary cord at the same time. I have tried fixing this AUX interference problem by trying multiple cables, different aftermarket stereos, 4 vehicles and even an app which is supposed to remove the static sound from your phone.
    After trying all of these methods to find the culprit I resigned myself to the fact that I will just have to live with it. Luckily for me I stumbled across a comment at the bottom of a “How To” forum which suggested to try the ground loop isolator. Instantly after plugging the device into my Chevrolet Cobalt the problem was solved; all of my hard/ tedious work had finally paid off.

    Reply
  24. Tomi Engdahl says:

    Audio Ground Loop Isolators Comparison: Cheap = Good?
    https://www.youtube.com/watch?v=4t1H5TjQoyQ

    Today im testing some ground loop isolators if they degrade the sound quality. I noticed cheaper ones cut off the lower frequencies quite a bit.

    Reply
  25. Tomi Engdahl says:

    Buzz/Hum In Your Audio Recordings
    https://www.youtube.com/watch?v=dcQzzqFwRfM

    We cover a few tips to dealing with Ground Loop hum in audio recording systems.

    Reply
  26. Tomi Engdahl says:

    OBS Studio 116 – Audio Mixers vs. USB Interfaces – Which should you use? Is there a difference?
    https://www.youtube.com/watch?v=45pf0VoEwc4

    Reply
  27. Tomi Engdahl says:

    VinylVideo – Playing video from a 45rpm record
    https://www.youtube.com/watch?v=UtNGVb94TFE

    With a VinylVideo convertor you can play video from a vinyl record played on a standard record player. Curiosity, tech-demo or art?

    Reply
  28. Tomi Engdahl says:

    Forgotten Audio Formats: DCC & Elcaset
    https://www.youtube.com/watch?v=CkGMJBqZawA

    An affectionate look at two failed, but entertaining cassette formats.

    Fun with Forgotten Audio Formats – DCC & Elcaset
    http://www.techmoan.com/blog/2014/5/6/fun-with-forgotten-audio-formats-dcc-elcaset.html

    Reply

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