Bluetooth Ground Loop Isolation 

Word of warning: Those small monolithic isolated power supplies like the Murata one shown in the video are in general very poorly regulated, especially at light loads. The datasheet specifies a 10-15% variation in load regulation from 10% load to full load, meaning a "5V" supply could swing as much as 0.75V across its output range (generally just barely acceptable for USB devices). Worse still, they're almost always "unspecified" below 10% load, meaning the regulation is generally awful at very light loads. The Murata datasheet actually states output voltage can rise to as much as TWICE the rated value for loads below 5% (so 10V on that supply), which can easily kill a low-current device that's not expecting it - ask me how I know. Options for avoiding this include: 1. Ensuring you don't "oversize" the converter (make it just big enough for the load current of your bluetooth receiver, keeping in mind if your receiver has a low current "idle" mode when it's not connected to a device) and making sure you never unplug/replug the bluetooth receiver when the circuit is powered. 2. Adding a "dummy load" resistor to draw a bit of current all the time. The shown converter is rated to 200mA, so keeping it above 10% only requires a ~250 ohm resistor that will dissipate 0.1W, so a quarter-watt through-hole resistor would work fine here. 3. Putting in a Zener diode to shunt voltage if it rises above a certain point. A 5.6V or so Zener could do this, but Zeners aren't generally that "sharp" at low voltages like this so it might not regulate much better than the simple resistor, and is more expensive (you're also less likely to have one lying around). Also note that you might run into problems depending on what USB port you're using to power the receiver - if the data lines are connected to something else (like the vehicle), it could prevent you from breaking the ground loop depending on how the rest of the system is wired. Best to ensure you're using a cable or circuit that lacks the USB data lines completely (like the demonstration shown on a breadboard here) to avoid that issue entirely. Otherwise, this is a great alternative approach to an isolation transformer, as it will preserve the audio quality on the analog audio side of the circuit (audio transformers will typically negatively affect audio quality, especially on the high frequencies, at least a bit).

The beauty of this solution is that, unlike other devices that try to filter out the noise that is already there in the audio signal, this method stops the noise from being created in the first place!

Really helpful video! One of the best on youtube for getting rid of ground loop isolation. Keep making videos, your work is absolute perfection.

Finally I found your channel, that's explaining is what I needed... Thank you!

Thank you, your idea led me to my working 12v-solution with a Mornsun B1212S-2W, coupled with a 2.2uF cap, 12v bluetooth receiver. Be advised anyone reading that pin out is different compared to module in video. Glad I checked the datasheet!

This video is an absolute godsend to me because I have been frustratingly trying to solve the ground loop in my cars bluetooth module I added. I'm going to give this a shot.

THANK YOU! Did it as many people on YT without capacitor and a choke and it DID NOT WORK! Parts ordered. Cheers!

Nice video demonstration man. It is very good and 100% true. Most of the people never knows this thing.

Nice... i was avoiding this solution, but it is the bes one so far so... thank you!

Thanks, was really curious how this sounds - only heard about it up to now

Glad to found your video! Many thanks for sharing this useful educational info (and demo). I have build some amplifiers with bluetooth and all of them have this kind of ground-loop noise (but only with bluetooth). Using capacitors can reduce the noise but cannot eliminate it. I have one made and the noise is absolutly terrible, not useful but by seeing this I think I can revive the project. Many thanks!

Great. Thanks for your teaching and time.

Great solution. Thanks for taking the time to help others like me!

Worked! Thnx! I had 2 bt modules on the same power supply and when i separatet the power supplys the house disapiert 80%

In the case of using a common power supply to operate both modules... Remember, the bluetooth module generates an interesting step-function type noise (buzz) as the IC consumes current. These audible pulses occur in the power supply and will come through the audio channels in the case of poor grounding between the two. I suggest soldering one or more heavy and short straps between the amp and bluetooth module ground planes. I use solder wick braid for this.

this is helping me in 2021 ty brother

Thanks, very useful, i wanted to buy a 'integrated' Bluetooth amp for my diy boombox but now i see it's best to have separate amp and Bluetooth module. (It does get allot more expensive buying everything separate, gives me doubts) How come it's so expensive? Make me wonder about powering the bluetooth dongle separate (in case of having the batteries and things needed at hand), that would also do the job? I don't have the items yet so i can't test it.

Thank you for sharing this solution. This is more expensive than the bluetooth receiver itself. The hum is because the amp and BT receiver is sharing the same power supply. I hope i can find a fix for using this receiver in car without hum.

Hi, Thanks for your explaination. Do you know the same kind of solution for 9V to 5V and for 6V to 5V?

I will try this and let you know the results, though the pins you showed on the transformer were out of shot.

Finally, a solution, thanks for this.

I used this circuit diagram with my B1212S-2W but I didn't get the noise out of it... How to do it?

Thank you!

Please help me, I am currently building my diy portable speaker.I have 2 20w 4 ohms speakers connected to PAM8610 amplifier powered by 3S2P 18650 batteries which has an output of 12 volts. I want to connect the bluetooth receiver which only requires 5 volts to the same 12v source of the amplifier using a DC-DC step down module. And i heard a lot of people complaining about ground noise. In this case assuming that the voltage is stepped down to 5v, what capacitor and inductor should I use and where will I connect it? Please help me. I have the slightest knowledge about electronics since I’m in the medical field. And so far, your solution is the best. Please haaalp

I agree with your experiment using dc- dc isolator solves the problem.I have the same problem when I am supplying 3.7 volt from a common battery to both Bluetooth audio receiver & class d audio amplifier. So in your video you told that an LC filter at speaker output also solves the problem.Is it necessary in a filter less class d audio amplifier.Please comment.

Would you please tell me what size capacitor and inductor I need if I where to use a 12-12 isolator. Note. It will be for my car so it will be power by a car battery 12v

I have a couple of questions. 1st- Does it matter if the capacitor is polarized or not? 2nd - is there a direction for the inductor? This is my first Bluetooth project

Very interesting explanation. I don't know a lot about electronics but I was able to follow along. I'm assuming the reason I'm hearing ground loop interference from the Bluetooth transmitter in my car is because it is powered and grounded along with the factory car amplifier. How would I go about getting rid of interference in that case aside from powering the transmitter with its own battery?

Hi, What kind of inductor should I use ? 1/4W , 1/2W or 1W ? Thanks for this useful video !

Is this ground loop the same for amp? I have PAM8403 module with 2x5w 4 ohm speaker connected to pc via USB(5vpower) + 3.5mm jack(input)? They do work properly about 20% of volume but more than that the speaker started popping. How come other premade pc speaker that are also powered by only PC usb don't have ground loops?

Hi, I have a similar setup, but it is entirely 12v, Is this the right kind of part? MeanWell (D/S)PU01M-12 Should I use different rated capacitor and inductor for 12v?

I hooked it up per your instructions and it hums even louder. Now if I put my hand close to the isolation converter and touch it it hums really loud. I noticed that you used a USB port to connect the Bluetooth. Would it make a difference that I removed the female port that was on the bluetooth and directly soldered the dc 5v + and - to the module?

I have a TPA3118 mono module. I modded it, decreased to 20db gain. I added a potentiometer for volume adjustment. The pot when full and zero level no noise but at middle levels i m hearing noise. How can i eleminate this problem?

Thanks for sharing! It took me over a year to find this solution. Great tutorial and audio example! Do you know how really cheap bluetooth speakers fix this problem?

I ordered the components, If this works I owe you a beer or three.....

Hello NizzyAmps CSIMC YX48D05-10 isolator, but cant find the capacitor or inductor needed, I tried to find the datasheet but no sucess, If you can advice that be great! thanks in advance for great video I was searching from long time.

Great work! This is the answer I have been looking for. I am a newbie to electronics, do you know what value inductor and capacitor to use for a 12v dc to 12v dc isolator? Help would be greatly appreciated

What is replaced part for this?coz in Indonesia there is No part Murata. Thx.

wow! definitely going to ckech this out. has anybody tried to cut the ground loop by ereasing some ground traces on the pcb itself?

Hi, Is there any cheapest method available for eliminating ground loop noise?Like you told by filtering it can be eliminated. I have seen most bluetooth speaker uses differential input amplifier to eliminate the ground loop noise. But in my bluetooth speaker configuration I am using single ended class d amplifier so I am not able to eliminate the ground loop noise. I mean other than DC to dc converter is any other method available . Thanks .

Hi, great work man. Have you ever done any work with the noise/ground loop on a tda7492 Bluetooth amp?

thanks king 🎼🎼🎼🎼

Can i get source from the voltage regulator to connect to the isolated dc dc regulator?

Hey there! Great video.. I'm wondering if an isolation transformer on the output of the bluetooth will do the same job? Why do you think the power supply isolation is better? Thanks!!

Hey great explanations. I have used 5v to 5v DC-Dc isolating module in my DIY bluetooth speaker I stil have ground loop. Here's how i connected the converter, The 5v power input to the amplifier and i removed the sheath a little from both +ve and negative wires and connected the DC-Dc isolating converter there and connected it to the USB Bluetooth module. Is that type of connection ok? I use PAM8403 with two 3 w 4 ohm speakers. and 1 more thing there's a slight hear beat like thump from the speakers as well. Can you suggest me the inductors and capacitors of the right value so that i solve this issue?

Assim, para parar a respiração ofegante é apenas adicionando outra fonte de alimentação para o módulo Bluetooth?

Nice job! I've been looking for a solution like this since long time ago.... Could you please share capacitor and inductor specs?

Can anybody help me out, what should be the inductance for a NKE1212SC? I have one of those all in one 12v bluetooth modules.

Hi! Good job! But i have a question about the ground of BT receiver. This is not connected to common ground of amplifier and power supply? Or the BT receiver output ground is floating and not connected to ground input? Thanks!

Thnk, this was an issue I came across. Works for me! By the way, I am suffering from low volume output of my Bluetooth receiver module (KRC86B). I think I need to combine it with a pre-amp board. Do you have any suggestion which to use?

Hi. I am using these for a a few things now they are brilliant but they die very easy if you make mistakes. But I never used the inductor or cap before. I think without it sounds fine. what are they for?

Help, I'm trying to use a Bluetooth board and a small amp like yours but I can't get rid of the noise. The only difference is I'm using an electrolytic capacitor. I did get rid of the noise by hooking the amp and Bluetooth to separate batteries. Any input would be greatly appreciated.

It looks like you are using an isolator followed by a filter. Isn't this redundant? Can you explain the difference? Sorry if I missed it.

I really need your help... I bought a bluetooth module for my car. And it have that buzz noise...I connected the Bluetooth wires to the cigarette supply.

What does the inductor do in this circuit?

can you please explain how to connect R+,R- and L+,L- audio outputs to R,L,GND connector

How much Amper the dc-dc give? I need something the clean the ground loop noise form chromecast audio that share the power with the amplifier

How much is the value of resistor to use?

I just saw your video, and what you accomplished is exactly what I'm trying to do. I've got a bluetooth amp module powered by a 12v rechargable battery. The voltage is boosted by a boost converter for the bt module. The module also has a aux in jack. I wired the parts (the murata nke1212sc, a 47uh inductor, and a 4.7uh cap.) Between the battery and the rest of the circuit. Nothing rrally happened. Noise was similar, couldn't get music to play, then the Murata module smoked and stopped working. I checked my connections and were all fine. Any suggestions?

can you post a parts list and where to order from. I'm fairly new to mini amps and this would solve my only real problem with my builds.

Q: If the component truly isolates its 2 sides, why are the support component necessary? Doesn't 'no connection' inherently mean that no ripple is passed on at all? Why the extra filtering if there isn't anything there to be filtered? (In other words, I already have the B0505S-1W isolated converter, and may or may not have the inductor and capacitor, but I'm way too lazy to look for them if I don't really need them! lol)

Do you know any transformer for 3.7v-4.2v or will the 5v work? I wanna use a lipo batt without booster.

I tried your solution for my system but the MEV3 stops working after a couple of minutes. I power the amplifier directly and the other components (two controllers) with the MEV3, having a load around 60 mA to 150 mA. I measured 0.06 A to 0.07 A at the input of MEV3 when running. Could you please help me to find the reason of this problem? My configuration: - MEV3S0505SC - 4.7 uF capacitor (Tantalum) - 10 uH inductor (09HCP)

How much power does your BT receiver need? I want to do the same thing you're doing, but use a chromecast audio. However I don't think 200mA from the isolator will be enough.

What is the model number for the amplifier you're using?

Nice video, but where have you been?

would you still need that component if you used a 5v power supply for the amp and another 5v powrt supply for the bluetooth?

I followed your schematic using a NMH1205SC (12v in, 5v out) as suggested in your list. It's a 5 pin converter (instead of 4 pins). Testing the output voltage across pins 4/6 (as labeled by Murata) produces apprx 14v. If I test the voltage across pins 4/5 or 5/6, I get apprx 7v. Funny thing is pin 5 is supposed to be 0v. I've confirmed this on two separate converters. Any ideas?

Excellent video. I have a problem with my system. Basically it's a small arcade cabinet. There is one 5 volts power supply that feed a raspberry pi, a screen and a PAM8403 amp. I think I get noise because the amp is sharing the power supply with the other component. Do you think that if I add this kind of isolation tranformer between my power supply and my amp I would get rid of the noise? Also what wattage do I need knowing that my speakers are 2 times 3 watts (4ohm impedance). Thanks a lot.

Great idea. Just built one. One question, my capacitor gets hot right away, without even any load on it ( 25V 4.7UF). Does that make sense?

My converter gives more output than input supplied, is it normal? Like i gave 4.8volts and output is 5.2 volts.

I have a bluetooth module that is 6v at the lowest allowable voltage what would I need to use to do this?

For me it works without the capacitor and resistor

Hi, can I use only the DC-DC isolator without using capacitor and inductor? Thank you.

hi there thanks for sharing,.. I have a question though.. will it be the same effect (eliminate ground loop) if I'm using buck converter lm2596s instead of dc-dc murata isolation? thanks

i have this issue in my bluetooth speakers. i am no engineer at all so don't know anything about it. can you please tell what can i do to remove hiss/high pitch annoying sound?

DC isolator is perfect, but the cheapest way is to add a capacitor with a value of at least 2200uf.

What is the function of the 47 Ohm resistor, limit current?

hi, I'm new in electronics, so I have a little doubt. I have a project with an amplifier and a bluetooth module, both 12v so I have a 12v battery and the noise was horrible until I put a dc dc isolated 12v converter, but without a capacitor and an inductor. the capacitor must be at 16v? and the inductor make de voltage lower? Uf? uh? helps please! thanks man!

I have the adaptor and the noise it's on using the earphones. No ground loop. The conclusion is that noise it's not generated in any way from any ever ground loop. Even powered by external usb pack. How to solve this? This setup it's clear it will not help.

Can I skip the capacitor ? Can I replace 47uH with 22uH?

do you have any alternative from the murata chips?

can i use Inductor: 22uH instead of 47uH?

Another way? I don't have isolators

Yep. I just use a battery..

Its expensive 5 dollar each =(

no, this doesn't work.