Allen Avionics Audio Isolation Transformers page describes the typical ground loop problem situation with the following drawing:
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:
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:
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:
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.
70 Comments
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Audio isolation transformers Tomi Engdahl’s ePanorama blog
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tecmax says:
The Isolation Transformers are known to be the best options for conferring protection to the electrnonic devices. Thus these devices are considered to be vital for enhancing the endurance of the devices. Servo Stabilizer Manufacturers, Isolation Transformer Manufacturers
tecmax says:
The Isolation Transformers are known to be the best options for conferring protection to the electrnonic devices. Thus these devices are considered to be vital for enhancing the endurance of the devices.
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.
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/
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.
Tomi Engdahl says:
Inside an audio isolator transformer module
https://www.youtube.com/watch?v=fV_hsFK1MnA
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
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.
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.
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
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.
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.
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.
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.
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
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?
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
Tomi Engdahl says:
STOP hum and buzz in your amplifier projects !
https://www.youtube.com/watch?v=-DwXpAlIYnA
“Help! My audio amplifier project makes a buzzing noise when I turn it on.” This is the most common question I get. I decided to make a quick video to answer this question.
Tomi Engdahl says:
My method of eliminating ground loop noise in DIY battery powered Bluetooth Players
https://www.youtube.com/watch?v=b2Pb1KuVDS0
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.
Tomi Engdahl says:
Ground Loops – What they mean to DJs, and how to deal with them
https://www.youtube.com/watch?v=MIicl-UaUz4
Ground loops can be a real pain for DJs in the digital era, and something any working DJ should have an idea about, so they can work around it if they need to.
Tomi Engdahl says:
Noise Isolator / Handmade Ground Loop Breaker
https://www.youtube.com/watch?v=P5c7XIz0Kj8
Tomi Engdahl says:
DIY Ground Loop Isolator
http://freemansgarage.com/blog/?p=760
It is possible to make one if you have enough junk around the house
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JenNext Mentors says:
great post
Tomi Engdahl says:
https://www.electronicdesign.com/power-management/whitepaper/21140276/what-is-a-stepdown-transformer?utm_source=EG+ED+Analog+%26+Power+Source&utm_medium=email&utm_campaign=CPS200825022&o_eid=7211D2691390C9R&rdx.ident%5Bpull%5D=omeda%7C7211D2691390C9R&oly_enc_id=7211D2691390C9R
Tomi Engdahl says:
https://www.webstore.discodesign.fi/hairionpoisto-ja-erotus/maaerotin-hairionpoistaja-35mm/
Tomi Engdahl says:
Behringer HD400
https://www.thomann.de/fi/behringer_microhd_hd400.htm?glp=1&gclid=EAIaIQobChMI5-ab9cye8QIVAwDmCh0QXw9XEAQYBSABEgKSrPD_BwE
SubZero Hum Destroyer
https://www.gear4music.fi/fi/Nauhoitus-ja-tietokoneet/SubZero-Hum-Destroyer/27BH?origin=product-ads&gclid=EAIaIQobChMIkfjsis2e8QIVk9SyCh2FbAGxEAQYASABEgKlg_D_BwE
Tomi Engdahl says:
The Lundahl way!
https://www.youtube.com/watch?v=rz3BDgKacJA
We’ve made a movie to show you the work, the effort and the love we put into all our transformers.
Enjoy!
Viewer comments:
This is amazing. Like the video says, the process behind winding transformers is very manually intensive. I use a small hand winder, and it takes me about 4-5 hours to wind a 1 to 10 mic input. Shielding, soldering, testing, and potting takes another 1-2 hours.
Beautiful artistry
Tomi Engdahl says:
The making of a C-core
https://www.youtube.com/watch?v=byMggvy2ibY
Factory glimpse:
The making of a C-core.
Probably more steps than you expected…
C-core winding
https://www.youtube.com/watch?v=TsQ9TLLxBFw
Tomi Engdahl says:
Building Lundahl problem solver
https://www.youtube.com/watch?v=1tVEELkGvic
Factory glimpse:
The building of our problem solver (sorry, it only solves audio problems).
Tomi Engdahl says:
LL1538
https://www.youtube.com/watch?v=bGEGWhpaC30
The making of a LL1538
Focusrite // In harmony with Lundahl
https://www.youtube.com/watch?v=Vu_hEdgn8Pw
Lundahl Transformers and Focusrite
Since the first Focusrite ISA110 preamp modules were assembled in the late 1980s, the Lundahl LL1538 input transformer has been a major part of the Focusrite sound.
The LL1538 helps to provide the huge headroom and audible clarity that makes the sound of the Focusrite ISA range unmistakable, and has been manufactured in the same way by Lundahl in Sweden for 25 years. We show you round the Lundahl factory and find out why Focusrite still use the LL1538 to this day…
Tomi Engdahl says:
What Are Audio Transformers? Why Do They Sound So Good?
https://www.youtube.com/watch?v=1n-lXFTuMfI
Curious to know more about transformers and how they work?
Viewer comments:
This. Is. Incredible. Thank you so much for making this. Please continue to make more!
I have literally been looking for something like this for a long time. Clear, concise and covers the principles to then aid in personal research. When jumping into all these things it’s a lot of head knowledge and book learning on stuff that is all really useful but at the end of the day, someone who wants to know how it relates to audio feels a bit overwhelmed on both where to begin and what’s useful knowledge and whats a waste of time.
I would love to see more videos just like this on things like: tube, tape, transistors, the fundamentals of electronics and how to understand simple circuits
Tomi Engdahl says:
Audio Transformers
https://www.youtube.com/watch?v=ZTDTs4m7rbw
Tomi Engdahl says:
Building Audio Amplifier Transformers
https://www.youtube.com/watch?v=x82oZcY243Y
As an amateur, you will need Class B audio amplifier’s transformers but, unfortunately, they are obsolete nowadays and very rare to be found. Possible thru some Chinese websites but it is not guaranteed. Even if you find them, definitely, they will be of low quality and poor performance. So what if you can craft them yourself and with high quality also? This video will show you how to do that step by step. The following is a checklist action plan to accomplish that. Make sure you apply the instructions in each step before you move to the next. Explaining videos were added to facilitate the project. If something wrong happened, explain it to me in a comment and I will do my best to help.
Tomi Engdahl says:
How Cinemag Transformers Are Made
https://www.youtube.com/watch?v=TqOSfW5tqBA
CineMag transformers can be found in some of the best-sounding audio gear around, including guitar amplifiers, microphone preamplifiers, and more. What makes these custom transformers such a crucial sonic component, and how are these transformers made? Sweetwater heads to Simi Valley, California, to find out.
Tomi Engdahl says:
Audio line isolation transformer tests
https://www.youtube.com/watch?v=7ZzOJ6OPZS4