I thought "Lets find out" was a reasonable substitution for "Lets get started" considering the video`explicitly states "(Experiment)". Though we could have done without the "in this video".
First of all thank you for discovering such a problem. I've been suffered with this problem for a long time. Finally you revealed it. It was such a great demonstration with diagnosing & resolving. I think it's a prefect solution for those noises & it's pretty easy to solve it. Keep rocking Scott, stay creative 😉
The 1:1 transformer in between the audio did not work as the two grounds were still connected. If the 1:1 transformer was used two separate the grounds it would work, however, you of course can not do that with DC so you have to use a switching converter. This is precisely what the DCDC converter is; a transformer with switching power supply. I think it would have been good if you would have mentioned this in the video.
Correct me if im wrong but in the 1:1 isolation transformers grounds are not connected. Isolation transformers can filter out DC interference voltages. The interference that we saw in the osciloscope was actually an oscillation that via induction was created in the secondary winding of the transformers there.
Two notes from somebody who has used these little all-in-one isolated 1W or 2W power supply modules in projects before: -These devices are typically *unregulated* (including the specific one shown here), meaning that especially at very light loads, their output voltage can be substantially above the rated 5V and they will vary dramatically depending on the load current. -The power supplies usually have very high idle power consumption (5-20mA is typical) and also low conversion efficiency at low load. This makes them quite unsuitable for battery powered applications unless you can shut the converter off completely during idle times and your active circuit power is well above the idle consumption of the converter. Check the datasheets carefully before specifying one of these in a design - most of the graphs sneakily only show efficiency/regulation starting from 10%-20% of rated load, and their behaviour is *much* worse below those points! For light loads, this can be a big issue.
For some reason when using one of these its introduces somewhat a static hiss into my Bluetooth receiver and I do not know why? Any ideas ? Any help would be greatly appreciated.
@@rashad5286 a little late but put about 5k resistor in parallel to the isolated converter's output to create a light load, so the voltage is stable. Without this your bluetooth connection could break when no music is played due to the voltage unstabilities. Any other issue you're encountering such as hissing are due to your receiver itself and you can verify this by powering it with another battery.
Me three. If the spikes are caused by a current spike/drop the best thing might be to simply add a buffer cap. Not sure about the inductor though, at these low frequencies I have some doubts whether that would work, this is usually done for high frequency filtering.
@@danielegger6460 Inductor is for the back emf so just to create a local emi/c condition. Much like a diode or small value resistor before the converter to create a smaller loop area. any noise from the local supply is dropped to ground.
I built a mic and amp circuit from a salvaged electret mic from a cheap headset and a LM386 as an amp. 3 volt coin cell for the mic and 9v batt for the amp, with gain and volume controls. Whenever I turned the gain or vol up, terrible hum, like a horn. I could see the oscillation on the scope. Separating the grounds fixed the problem. Now I can use it to hear previously undetectable air leaks. THANK YOU for the solution to the problem !!
Two other areas you could look into are: a lower impedance ground between amp and receiver as well as better supply decoupling on the output of the 5v regulator. The decoupling network needs to take into consideration the frequency content of the receiver in order to decouple successfully.
Someone should create/sell a mod kit that mutes the speaker for like 2 seconds when it's powered on or something, tho a better solution probably exists
this video gave me the solution , that i was looking for over an year .. i am not an electrical expert , but i also did build my own music system and faced this problem .. and after a year later .. now.. i found the solution here THANKS
I powered my Samsung 10" tablet that I integrated in to my car by wiring directly to the car's cigarette lighter power feed, however, this created this same ground loop effect. I overcame that by buying a hefty 12v > 5v DC/DC isolating converter, but it was quite expensive, as I wanted it to be quite a high Amp rating in order to charge the tablet whilst using it. Great video!!
What about disconnecting the audio ground from one end (receiver) It's common that the main part of an audio system is the hub of all grounds, anything remote that is powered from the same supply uses the supply ground, with the audio ground disconnected, but in the case of a sceeened cable the screen is connected to the amplifier only
@@sparkyprojects this isnt a hum loop, its oscillating from feedback. What probably more likely happening is the power sugres in the audio amp are affecting the bluetooth ground, causing a feedback loop
@@researchandbuild1751 As far as I see it, there is no feedback, just big enough load-pulses from the bluetooth module to create a voltage shift on amp-ground vs bluetooth module-ground. The fix is probably isolation, or really good ground connection (like soldering the board directly to amp-ground without wires using a solid connection). Analog ground/differential inputs amplifier should also do the trick. Adding capacitors to power input of the bluetooth module itself may also help.
I had the same problem. And I tried the same methods and stayed at DC/DC converter, the best method. I really didn't realize what the problem is, if the amplifier and the bluetooth receiver have the same grounding, thanks for the explanation GreatScott xD
Excellent solution. You can also measure the voltage between the 5V negative rail of the receiver and the 3.5mm ground, when thereceiver is powered on. In my case (slight different receiver board) I measured a 3.3V difference between the 2 "grounds", that definitely means the receiver need a galvanic 5V separate source.
The ground loop isolator is used when your amp and source are on separate connections The point of it is to stop one device using the other as a ground. Additionally a ground loop is characterised by a 50 or 60 Hz continuous humm, the fact that it has a repetitive load (likely when the Bluetooth is transmitting it's beacon) shows it is not a ground loop
You know what i find most interesting in this video? Your amplifier. It uses an unbiased output stage where you're simply forcing the opamp to slew right over the required approx 1V bias voltage gap of the output transistors, and to somewhat smooth out the resulting switching atrocity, you have a feed forward resistor. This is actually kinda cool. According to my simulation, not quite hi-fi, but cool.
BT audio out GND joins the power ground of the amp board and creates a loop, also your daisy chain ground system is "no no" for audio / analog designs. Use a star ground configuration to a low impedance point like a main filter cap and interrupt the loop created by BT aout GND. Potentially I'd try to connect BT aout GND via 100n cap to non-inverting input of your amp ( pin3) to run the amp in differential mode. 12V/2 DC bias circuit should be bypassed by a cap and then brought to pin 3 via serial resistor eg 10k. Sure there are more options, but DC-DC isolation for such a basic circuit is an overkill.
@@AtlasReburdened This happens with direct current since the voltage is constant, but rember that an audio signal (and any type of signal) isn't constant. A capacitor put in series between a signal and an aplifier is actually used to remove offset voltage.
A lot of that noise can be removed by adding extra capacitance to the power supply rails for the bluetooth device, along with making it the common ground point for the project, so that the long cables to the input are not adding resistance to the ground path. 220uF 10V capacitor directly across the 5V pins into the unit will improve performance a lot, as the regulator output impedance rises with frequency, they are not good at reducing high frequency noise, you need low ESR capacitors near the load to do that.
Well I found a simpler solution that worked for me. A) Find the feed of the 12V to your amplifier and connect there. Don't use the PCB traces closest to the amplifier IC. Instead get closest to the power supply feed. B) Use thick wires to feed the LM7805 regulator! This makes all the difference. Don't use wire (single copper conductor). Use thick cable (many conductors). For me 16 AWG eliminates all the noise. After your linear regulator IC you can use smaller cable.
I have the same problem, and i really struggled to find a soloution for this. Thank you really much for explaining this problem and showing some soloutions! It kinda saved my day.
What he is doing here is prototyping, you don't manufacture PCB's for prototypes.... If he was making a finished design with an enclosure etc then you would make a PCB since you have a circuit you know works.
So wish l had your knowledge and Time as l'm getting a little old now going for 67 in couple of days. Still l enjoy to see you solve problems for so many , thank you for sharing.
This is a good answer, as the ground is common, there is no need to introduce a ground loop. It's also important to use buffer and filter capacitors near the consumer (in this case near the bt receiver AND near the amp).
I recently research on this problem . I found that there is problem in bluetooth receiver ground ( no proper thickness of track ) so it do not allow proper flow of current so i connect ic ground with a wire with main ground with additional wire. (very very very very cheap solution)
Thank you so much for making this video I was facing the same problem when I hooked up the receiver to my cars basic music system. Now I will be able to smack down the interference noises. Keep it up👍👌
Most interesting, many thanks, stopped me from chasing red herrings and focus on the simple fact that the noise comes from the power rail. This led me to a simple fix ... Starting with an existing power amp with a single rail 20V supply I used a 7905 to create a ground that is 5V below the positive rail. This creates a split supply to power my op amp based front end. The op amp doesn't care that the rails are asymmetric +5V and -15V. The Bluetooth audio module powered from the +5V rail produced a massive amount of noise but a 5mH inductor (a few windings on a toroid core,
You should give your completed schematics in the end of the video or the description, so if we ever want to attempt such a test we can see where exactly the change occured. Btw, YOU ARE AWESOME DUDE. I mean it.
Most of people who working in audio industries are in trouble due to interference noise in their audio system but your idea to isolate ground with DC to DC Converter is awesome
hey bro i noticed on cheap mouses that there are empty places on the pcb where there should be components but there arent. can you do a comparison to see if you complete the empty spots if it brings a difference or not.
thanx sir, tht mean in simple way if we use a battry charged bluetooth reciver 3.7 lithum cell bluetooth reciver then we ll not got the humming or distrbing sound while not playing the song. thnax plz rply
Add some bypass capacitors across R1,R2 to to decouple your amplifier's virtual ground (pin3) from supply fluctuations. If you use the isolation transformers then you can connect your input signal ground to this point as well.
@GreatScott! Man i bought the exact same Bluetooth module 2 years ago and never managed to get around this buzzing noise. I can now finally finish building my diy bluetooth speaker, thanks so much❤
Scott, you did the fix with the DC DC converter, but didn't explain the part or part number (handwriting looks like B05055 instead of S) and instead linked products in the description that weren't used, without linking any examples of what to actually use. I appreciate the help solving my problem! But you did all this work to still have viewers going down a rabbit hole of research to figure out what to buy!
I know that solution #1 (separate +5 volt power supply) and #4 (DC 5V/DC 5V) are the best. But, just for curiosity, was there a way to filter the +12 volt supply to the audio amplifier with one inductor in series? The rationale being: if you reduce the current for these short burst spike, then the ground side also gets less spike current. As explained as comment to another answer, you would put two capacitor on the +12 volt supply side of the inductor. One large electrolytic for near DC noise and a small 0.1 uF for the high frequency noise. And connect no capacitor at all on the +12 volt amplifier side on the inductor. The inductor has to be the kind that accept a constant DC current. The DC part reduce the active region margin of the inductor. For example, two coil rolled in opposite direction to cancel the DC magnetism, allowing the core to get it's full active region before saturating. Let's call that Solution #5 And one last idea that deserve attention: What about following the electrical engineering rule to designate one location as ground source and connect every ground to that location? That would be Solution #6
I was contemplating removing the logic from my Soundbar and replacing with my own setup similar to this (ideally retaining buttons and inputs). I may have to open it up and inspect it. It's a decent soundbar, but I don't like some of it's behavior (# of volume steps, auto-off delay, etc.).
@@Allocated_Brain Maybe I'm.just not getting the joke, but OP has tinnitus, a hearing issue which causes annoying fake tones to be heard when the sufferer is in silence.
It's being worked on. They've already figured a way to "reflow" the "pcb" to fix bad connections between components so right now it's just a matter of looking at the diagram to figure out where to point the inductive antenna. rTMS is a helluva thing, it's going to be BIG in the 2020's.
Hello sir nice video. Sir can u tell me about your blynk controlled RGB led lamp, if I want to use 50 watt LED chip instead of 10 watt then what should I change in your project circuit diagram. Does I change gain value or 1ohm resistor value. Plz reply sir waiting for your reply.
Boi i've been having the same problems, I tried to connect two different amps together to form a bigger amp with a separate line for smaller speakers. And i got a crazy buzzy noise. I just gave up on that project because there was nothing i can do. I will try the DC/DC converter method. I just hope its available here at my local stores. Thanks for making this video mate!
Hey Scott! I used this same technique in my creative desktop speaker pair a year earlier and it works great. Thanks for shedding some light on this matter. Nice job man! 👍
Was the noise from the 12 v supply? I didn't see you test it, but it has to come from somewhere. I didn't see or hear any mention of capacitors on the power supply lines - they would have helped remove induced noise. Typically you'd want caps on the each side of the 5 v regulator to ground (12 v and 5 v), but I'm guessing you probably know that.
As a point of clarification and question of uncertainty, the only reason the ground loop isolator didn't work for you is because the bluetooth transmitter and the amplifier shared power sources right (which means their shared ground was still connected through the PCB board and 5v regulator)? Considering at 05:12 when you built up a 2 mains power supply circuit to prove it solves the issue, then I wanted to be sure why the purchased ground loop isolator didnt work, considering it's designed to eliminate ground loop interference caused by 2 devices with separate power sources (or technically their own power adapters plugged into the same AC circuit), then it thus failed to remove the interference since interference was being caused from the ground shared on the PCB level and not through the shared ground introduced by the audio cable. I also wanted to clarify, since I'm not an expert on electricity or audio for that matter and am wanting to make sure I didn't just order a ground loop isolator for nothing (but will find out tomorrow I guess), if the DC to DC converter acting as a DC rail isolator only worked because it then separated the ground at the PCB level? Lastly, would the fact that at 07:42 when you tested the final solution, the audio could have been affected by the magnetism introduced by it's USB A end which was stuck to the magnetic ring of the speaker and would've magnetized the ground connection to the PCB or not really? Honestly asking to make sure I understand these concepts correctly since I'm trying to learn how it all works exactly.
Did you try adding some filtering ahead of the 5 Volt regulator perhaps a small R in series from 12 to the 5V regulator and a large C to ground at the input to the regulator (assuming a 7805 type regulator) or a large C after the 5V regulator if it is an LDO type? Just curious.
Could we also possibly use a capacitor to store the 5 volt charge to try and prevent the current spikes? I was looking at the schematic and thought that maybe it would work then again idk. Probably better to use the dc to dc converter but, if you can get back to me with an answer about this that would be awesome. Stay creative dude
Great video. Removes my wondering why the electronics side of the Roland Bridgecast mitigates sound using a ground loop isolator fine. Where as, with the input on a SP-404 MK II the inteference from ground is still present. It's in the circuitry that it can't be helped with the same solution.
I belive you used a little flyback, am I correct? Why didn't you use it to step down the voltage too? Also why wasn't it possible to couple and clamp the ground rails with a capacitor and two shottkey diodes?
I know this video is a year old but... If i were to use a powerbank pcb to power e. g. an Alexa, usb speakers or whatever and they have interference noise what am i supposed to do? I think the PCB from the powerbank doesn't filter the "amplification remains" so there is a slight buzzing. In this case there would be only the 5V and ground without a audio cable and you couldn't really seperate them (not like its shown in the video because its only one sound device instead of two). Would a (the right) Capacitor solve my problem or should i just use another powerbank pcb?
I'd have liked to learn about this DC to DC converter. Is it a buck converter, a LDO, something else? Does any DC/DC converter work? For instance a 7805 converts 12V into 5V... but it's not the same. The end of the video seems precipitated precisely because there's no info about this magical component.
Useful video. I am playing around with audio on an arduino which is staticky. I wonder if I have a separate 5v supply for my audio board (PAM 8403) that I will get rid of some of that.
I'm having this buzzing sound issue when connecting one Baseus Bluetooth adapter in a car phone charger and connecting it's 3,5mm output to my car audio. I'm thinking of getting a tiny usb extensio, cut it's cord and hooking a b0505s up. I would then use this usb cord with the dcdc converter to connect the Bluetooth adapter to the charger. Hoping it would solve my buzzing problems. Any thoughts if this would work?
I was thinking also at the DC/DC convertor but I would have removed the linear regulator. I didn't know about the ground loop isolator solution but at the same I didn't understand why there was still noise after using it. I mean the grounds were isolated from each other as shown in the schematic.
What if you use a diode between supply to the amplifier maybe that would flatten that waveform or find the time constant and figure out a rc value. Just a thought but that noise is very infectious to other circuits
I wanted to know if the 5V GND and the audio GND were actually connected together on the BT module. If the audio gnd were a virtual GND of say 2.5V, then connecting it to power GND was bound to cause problems. Also, how about short wires instead of a cable? Pretty massive ground loop there.
Common mode noise is a real bugger sometimes. DC isolation is the go to fix for it although sometimes it can be eliminated (or at least sufficiently attenuated) in the IF stage with ferrite beads or an RF choke coil. If you were dealing with radar frequencies even PCB foil trace placement and pathways are a solution.
funny that i did this experiment last year when adding BT OVCxxxx module to my car stereo's tape deck preamp output. Isolation transformers were a nogo but i remembered that i had some of those isolated DC-DC converters and it was perfect. I ended up using an ATtiny to monitor the tape deck motor outputs to simulate the encoder signals and give the bt module the ability to skip and prev songs using the OEM controls.
Hi Scott. I tried building a Bluetooth speaker from scrap and encountered the same problem. After testing the whole circuit with a multimeter, I discovered that the grounds in a tp4056 are separate and it solved the issue of ground loop. Have a look at it pls.
Sir, very nice video,, it's full of information.. Thank you so much,.. I have a question sir. I have the same bluetooth that you shown on your video thumpnil. When I played a song the bluetooth receiver giving cutting sound? What should I do?
I find with these ebay Bluetooth receiver boards marked AGND and GND are connected together. No isolation at all. Also, in most cases AGND (the audio input ground for left and right) and GND are the same on the amplifier.
Disconnect the audio ground from the amp input and use a thick, short piece of copper wire to link the BT and amp grounds together. Connecting BT power ground and BT Audio ground together creates a ground loop! Additionally add a lowpass filter with 22ohm resistor and 1000uF capacitor before the 5v regulator to dampen the current spikes.
I wish you had shown a clear view of the bottom of the isolator that you took apart so that we can see how it was made. We can guess how it was hooked up, but it's nice to be able to see how traces connected the components.
It kinda hurt when you clipped that 3.5mm's cable so close to the connector.
Ya
Ya
ikr
u can always reuse the jack if u get that plastic off but it would be simpler to just leave some wire
That was such a low en cable that you wouldnt want to use the connector anyway.
GreatScott: Doesn't say *Let's get started*
Me: WHO ARE YOU AND WHAT DID YOU DO WITH SCOTT?!
I am sorry :-( It just did not fit.
Lol
Actually, his name is Jeremy.
@@greatscottlab no problem xD
I thought "Lets find out" was a reasonable substitution for "Lets get started" considering the video`explicitly states "(Experiment)". Though we could have done without the "in this video".
First of all thank you for discovering such a problem. I've been suffered with this problem for a long time. Finally you revealed it. It was such a great demonstration with diagnosing & resolving. I think it's a prefect solution for those noises & it's pretty easy to solve it. Keep rocking Scott, stay creative 😉
The 1:1 transformer in between the audio did not work as the two grounds were still connected. If the 1:1 transformer was used two separate the grounds it would work, however, you of course can not do that with DC so you have to use a switching converter. This is precisely what the DCDC converter is; a transformer with switching power supply. I think it would have been good if you would have mentioned this in the video.
Correct me if im wrong but in the 1:1 isolation transformers grounds are not connected. Isolation transformers can filter out DC interference voltages. The interference that we saw in the osciloscope was actually an oscillation that via induction was created in the secondary winding of the transformers there.
If you ask me, biggest mistake in this video is that he forgot to mention "the" solution - proper star ground connection
Two notes from somebody who has used these little all-in-one isolated 1W or 2W power supply modules in projects before:
-These devices are typically *unregulated* (including the specific one shown here), meaning that especially at very light loads, their output voltage can be substantially above the rated 5V and they will vary dramatically depending on the load current.
-The power supplies usually have very high idle power consumption (5-20mA is typical) and also low conversion efficiency at low load. This makes them quite unsuitable for battery powered applications unless you can shut the converter off completely during idle times and your active circuit power is well above the idle consumption of the converter.
Check the datasheets carefully before specifying one of these in a design - most of the graphs sneakily only show efficiency/regulation starting from 10%-20% of rated load, and their behaviour is *much* worse below those points! For light loads, this can be a big issue.
For some reason when using one of these its introduces somewhat a static hiss into my Bluetooth receiver and I do not know why? Any ideas ? Any help would be greatly appreciated.
@@rashad5286 a little late but put about 5k resistor in parallel to the isolated converter's output to create a light load, so the voltage is stable. Without this your bluetooth connection could break when no music is played due to the voltage unstabilities.
Any other issue you're encountering such as hissing are due to your receiver itself and you can verify this by powering it with another battery.
What if you put some inductors in series to the power lines and some caps in parallel?
I though the same thing
Me three. If the spikes are caused by a current spike/drop the best thing might be to simply add a buffer cap. Not sure about the inductor though, at these low frequencies I have some doubts whether that would work, this is usually done for high frequency filtering.
I always do that back then.Just solder 2500 microfarad 16v capacitor parallel to the supply wires in the Bluetooth module.
@@danielegger6460 Inductor is for the back emf so just to create a local emi/c condition. Much like a diode or small value resistor before the converter to create a smaller loop area. any noise from the local supply is dropped to ground.
Have you tried it? Maybe lifting the ground from the BLE end shielding?
I built a mic and amp circuit from a salvaged electret mic from a cheap headset and a LM386 as an amp. 3 volt coin cell for the mic and 9v batt for the amp, with gain and volume controls. Whenever I turned the gain or vol up, terrible hum, like a horn. I could see the oscillation on the scope. Separating the grounds fixed the problem. Now I can use it to hear previously undetectable air leaks. THANK YOU for the solution to the problem !!
Two other areas you could look into are: a lower impedance ground between amp and receiver as well as better supply decoupling on the output of the 5v regulator. The decoupling network needs to take into consideration the frequency content of the receiver in order to decouple successfully.
I've thought that he will teatch how to remove the: "butu dewice ready to pail" sound when u turn on any speaker
Someone should create/sell a mod kit that mutes the speaker for like 2 seconds when it's powered on or something, tho a better solution probably exists
Exactly what i was thinking.. i was a bit disappointed lol
Lmao ikr i hate that fucking sound so much 😂
@@shutdahellup69420 They say its programmed via computers.
you forgot : 'the butu dewice iss connectedya succesffulaay"
this video gave me the solution , that i was looking for over an year ..
i am not an electrical expert , but i also did build my own music system and faced this problem .. and after a year later .. now.. i found the solution here
THANKS
Noise is the bane of audio projects, thanks my dude.
I powered my Samsung 10" tablet that I integrated in to my car by wiring directly to the car's cigarette lighter power feed, however, this created this same ground loop effect. I overcame that by buying a hefty 12v > 5v DC/DC isolating converter, but it was quite expensive, as I wanted it to be quite a high Amp rating in order to charge the tablet whilst using it. Great video!!
Oh man you’re a master, you produce videos of all the questions I used to have some years back and never had an answer to
Why didn't you say "let's get started"? You're not Scott, I need answers
I just did not fit this time. Sorry. Next time.
@@greatscottlab let's find out could have been replaced 😁
"Lets find out, in this video." 0:52
Scott but not Great
I was just making this as part of a college project and stumbled upon the same problem. Thanks a lot Great Scott, it's like you read my mind.
He is the best
Wow the exact same thing happened with my friend!
@@wasaybaig1519 XD
Lol
3:19 Scott: "So where do they come from?"
Me: _No._
My Brain: "Where did they go?! Where did they come from, Cotton-Eyed-Joe!"
Me: *NOOOO*
Go for the eyes boo!
Literal i need this 4 hours ago 😂
I love you baby marry me
Same here
I searched the whole internet for this before with no suitable results! Thanks!
What about disconnecting the audio ground from one end (receiver)
It's common that the main part of an audio system is the hub of all grounds, anything remote that is powered from the same supply uses the supply ground, with the audio ground disconnected, but in the case of a sceeened cable the screen is connected to the amplifier only
Power grounds would still be connected, so audio inputs would use that as audio ground.
Correct, but it's only one ground, not the 'hum loop' that i think is causing the problem
@@sparkyprojects this isnt a hum loop, its oscillating from feedback. What probably more likely happening is the power sugres in the audio amp are affecting the bluetooth ground, causing a feedback loop
@@researchandbuild1751 As far as I see it, there is no feedback, just big enough load-pulses from the bluetooth module to create a voltage shift on amp-ground vs bluetooth module-ground.
The fix is probably isolation, or really good ground connection (like soldering the board directly to amp-ground without wires using a solid connection). Analog ground/differential inputs amplifier should also do the trick.
Adding capacitors to power input of the bluetooth module itself may also help.
I had the same problem. And I tried the same methods and stayed at DC/DC converter, the best method. I really didn't realize what the problem is, if the amplifier and the bluetooth receiver have the same grounding, thanks for the explanation GreatScott xD
DC to DC isolator is the best of the best solution for diy amplifier projects. It helped me removing the buzz noise!
Excellent solution. You can also measure the voltage between the 5V negative rail of the receiver and the 3.5mm ground, when thereceiver is powered on. In my case (slight different receiver board) I measured a 3.3V difference between the 2 "grounds", that definitely means the receiver need a galvanic 5V separate source.
The ground loop isolator is used when your amp and source are on separate connections
The point of it is to stop one device using the other as a ground.
Additionally a ground loop is characterised by a 50 or 60 Hz continuous humm, the fact that it has a repetitive load (likely when the Bluetooth is transmitting it's beacon) shows it is not a ground loop
Great scott: I couldn't find the amp
Me: LOOK ON YOUR CEILING
You know what i find most interesting in this video? Your amplifier. It uses an unbiased output stage where you're simply forcing the opamp to slew right over the required approx 1V bias voltage gap of the output transistors, and to somewhat smooth out the resulting switching atrocity, you have a feed forward resistor. This is actually kinda cool. According to my simulation, not quite hi-fi, but cool.
BT audio out GND joins the power ground of the amp board and creates a loop, also your daisy chain ground system is "no no" for audio / analog designs. Use a star ground configuration to a low impedance point like a main filter cap and interrupt the loop created by BT aout GND. Potentially I'd try to connect BT aout GND via 100n cap to non-inverting input of your amp ( pin3) to run the amp in differential mode. 12V/2 DC bias circuit should be bypassed by a cap and then brought to pin 3 via serial resistor eg 10k. Sure there are more options, but DC-DC isolation for such a basic circuit is an overkill.
Cant you put a capacitor in paralell on the 5V line, so that it smoothes out the interfierance?
I tried by myself. doesn't work.
@@SyazwanSaidan Maybe some higher capacity capacitors.
If you added it in series you would form an open circuit as soon as it charged.
@@AtlasReburdened This happens with direct current since the voltage is constant, but rember that an audio signal (and any type of signal) isn't constant. A capacitor put in series between a signal and an aplifier is actually used to remove offset voltage.
@@AtlasReburdened Yeah i ment parralel
A lot of that noise can be removed by adding extra capacitance to the power supply rails for the bluetooth device, along with making it the common ground point for the project, so that the long cables to the input are not adding resistance to the ground path. 220uF 10V capacitor directly across the 5V pins into the unit will improve performance a lot, as the regulator output impedance rises with frequency, they are not good at reducing high frequency noise, you need low ESR capacitors near the load to do that.
Well I found a simpler solution that worked for me.
A) Find the feed of the 12V to your amplifier and connect there. Don't use the PCB traces closest to the amplifier IC. Instead get closest to the power supply feed.
B) Use thick wires to feed the LM7805 regulator! This makes all the difference. Don't use wire (single copper conductor). Use thick cable (many conductors). For me 16 AWG eliminates all the noise. After your linear regulator IC you can use smaller cable.
i love those tiny DC to DC modules, they are so freaking handy.
Yeah
But they waste energy
@@ProtoMan137 ist egal
this problem bust my ass for 7 years on every project and even electronic teachers tell me use two battery on adaptors thank you manso so much
I have the same problem, and i really struggled to find a soloution for this. Thank you really much for explaining this problem and showing some soloutions! It kinda saved my day.
Not to long ago I was looking for this exact solution but no video could resolve my issue, but I'm glad you have made a video about it.
Shows an ad for JLC PCB... *Doesn't use a pcb for doing this and uses something else*
Many promote VPN services but never use them on videos. It might have something to do with the target audience.
What he is doing here is prototyping, you don't manufacture PCB's for prototypes.... If he was making a finished design with an enclosure etc then you would make a PCB since you have a circuit you know works.
You can get sponsored and promote things without actually using them?
@@yeet1337 yeah... but what i said was a joke
@@yeet1337 I've understood the sponsors just send an email they'd be wishing to promote their product.
So wish l had your knowledge and Time as l'm getting a little old now going for 67 in couple of days.
Still l enjoy to see you solve problems for so many , thank you for sharing.
Usually i just solved this by disconnecting the audio ground. Quick and dirty but it worked.
Theres no noise if there is no audio!
This is a good answer, as the ground is common, there is no need to introduce a ground loop. It's also important to use buffer and filter capacitors near the consumer (in this case near the bt receiver AND near the amp).
Works well for the XS 3868 tbh
@@dusinnhht what capacity would you recommend?
I recently research on this problem . I found that there is problem in bluetooth receiver ground ( no proper thickness of track ) so it do not allow proper flow of current so i connect ic ground with a wire with main ground with additional wire. (very very very very cheap solution)
Hmmmm I did not try that.
@@greatscottlab pin this post!
Good to know. Will try it.
Tried adding an additional ground in my car and it did not work
It work
I enjoy even the way that Scott writes (left handed).
Thank you so much for making this video
I was facing the same problem when I hooked up the receiver to my cars basic music system. Now I will be able to smack down the interference noises.
Keep it up👍👌
I often do skip the intro music on channels but not yours. Love that music
Most interesting, many thanks, stopped me from chasing red herrings and focus on the simple fact that the noise comes from the power rail. This led me to a simple fix ... Starting with an existing power amp with a single rail 20V supply I used a 7905 to create a ground that is 5V below the positive rail. This creates a split supply to power my op amp based front end. The op amp doesn't care that the rails are asymmetric +5V and -15V. The Bluetooth audio module powered from the +5V rail produced a massive amount of noise but a 5mH inductor (a few windings on a toroid core,
Have you also tried to remove/modify the action sounds? Like “The bluetooth device is ready to pair” or “Phone connected”
Those are annoying as f
Every chinese device needs to speak, but WHY??????
@@fusseldieb Because chinese like "Fashion Sound"
Some times there is a programmed function to turn these off... like holding down the pair button or the play button or something.
@@adrigenvongarnerd i managed to reflash the flash ic to remove the sounds... as you can see in my video
Thank you greatt scott i learn a lot waching all your videos
Keep up the good work👍
You're welcome and thank you :-)
You should give your completed schematics in the end of the video or the description, so if we ever want to attempt such a test we can see where exactly the change occured.
Btw, YOU ARE AWESOME DUDE. I mean it.
Most of people who working in audio industries are in trouble due to interference noise in their audio system but your idea to isolate ground with DC to DC Converter is awesome
hey bro i noticed on cheap mouses that there are empty places on the pcb where there should be components but there arent. can you do a comparison to see if you complete the empty spots if it brings a difference or not.
thanx sir, tht mean in simple way if we use a battry charged bluetooth reciver 3.7 lithum cell bluetooth reciver then we ll not got the humming or distrbing sound while not playing the song. thnax plz rply
Add some bypass capacitors across R1,R2 to to decouple your amplifier's virtual ground (pin3) from supply fluctuations. If you use the isolation transformers then you can connect your input signal ground to this point as well.
As a person with electronics background I really enjoy you videos man. Keep up the good work!
This guy and diy perks complete each other
@GreatScott! Man i bought the exact same Bluetooth module 2 years ago and never managed to get around this buzzing noise. I can now finally finish building my diy bluetooth speaker, thanks so much❤
Scott, you did the fix with the DC DC converter, but didn't explain the part or part number (handwriting looks like B05055 instead of S) and instead linked products in the description that weren't used, without linking any examples of what to actually use. I appreciate the help solving my problem! But you did all this work to still have viewers going down a rabbit hole of research to figure out what to buy!
I know that solution #1 (separate +5 volt power supply) and #4 (DC 5V/DC 5V) are the best.
But, just for curiosity, was there a way to filter the +12 volt supply to the audio amplifier with one inductor in series? The rationale being: if you reduce the current for these short burst spike, then the ground side also gets less spike current. As explained as comment to another answer, you would put two capacitor on the +12 volt supply side of the inductor. One large electrolytic for near DC noise and a small 0.1 uF for the high frequency noise. And connect no capacitor at all on the +12 volt amplifier side on the inductor. The inductor has to be the kind that accept a constant DC current. The DC part reduce the active region margin of the inductor. For example, two coil rolled in opposite direction to cancel the DC magnetism, allowing the core to get it's full active region before saturating.
Let's call that Solution #5
And one last idea that deserve attention: What about following the electrical engineering rule to designate one location as ground source and connect every ground to that location? That would be Solution #6
I was contemplating removing the logic from my Soundbar and replacing with my own setup similar to this (ideally retaining buttons and inputs). I may have to open it up and inspect it. It's a decent soundbar, but I don't like some of it's behavior (# of volume steps, auto-off delay, etc.).
In a project i had the same problem as you and this solution comes to be the best one. Thanks a lot!!!
I wish I could isolate my grounds and remove my tinnitus :(
Is it already soldered in place? You could just scrap it and start over if your project is that botched.
@@Allocated_Brain Maybe I'm.just not getting the joke, but OP has tinnitus, a hearing issue which causes annoying fake tones to be heard when the sufferer is in silence.
@@aathish04 The joke is that OP as the 'project' is faulty at a fundamental level requiring a whole replacement unit.
It's 2020 and still no cure. It should be the future damn it!
It's being worked on. They've already figured a way to "reflow" the "pcb" to fix bad connections between components so right now it's just a matter of looking at the diagram to figure out where to point the inductive antenna.
rTMS is a helluva thing, it's going to be BIG in the 2020's.
Hello sir nice video. Sir can u tell me about your blynk controlled RGB led lamp, if I want to use 50 watt LED chip instead of 10 watt then what should I change in your project circuit diagram. Does I change gain value or 1ohm resistor value. Plz reply sir waiting for your reply.
I just searched for that and 3 days later GreatScott loaded up a video
Greatscott: let‘s find out in this video!
Me: huh ? Who are you
Great Scott: do you plan to try a bluetooth splitter ?
Boi i've been having the same problems, I tried to connect two different amps together to form a bigger amp with a separate line for smaller speakers. And i got a crazy buzzy noise. I just gave up on that project because there was nothing i can do. I will try the DC/DC converter method. I just hope its available here at my local stores. Thanks for making this video mate!
HERE IN NICARAGUA WE CANT DO IT EASY BUT I WILL thanks to the master Greats
Hey Scott! I used this same technique in my creative desktop speaker pair a year earlier and it works great. Thanks for shedding some light on this matter. Nice job man! 👍
Was the noise from the 12 v supply? I didn't see you test it, but it has to come from somewhere. I didn't see or hear any mention of capacitors on the power supply lines - they would have helped remove induced noise. Typically you'd want caps on the each side of the 5 v regulator to ground (12 v and 5 v), but I'm guessing you probably know that.
As a point of clarification and question of uncertainty, the only reason the ground loop isolator didn't work for you is because the bluetooth transmitter and the amplifier shared power sources right (which means their shared ground was still connected through the PCB board and 5v regulator)?
Considering at 05:12 when you built up a 2 mains power supply circuit to prove it solves the issue, then I wanted to be sure why the purchased ground loop isolator didnt work, considering it's designed to eliminate ground loop interference caused by 2 devices with separate power sources (or technically their own power adapters plugged into the same AC circuit), then it thus failed to remove the interference since interference was being caused from the ground shared on the PCB level and not through the shared ground introduced by the audio cable.
I also wanted to clarify, since I'm not an expert on electricity or audio for that matter and am wanting to make sure I didn't just order a ground loop isolator for nothing (but will find out tomorrow I guess), if the DC to DC converter acting as a DC rail isolator only worked because it then separated the ground at the PCB level?
Lastly, would the fact that at 07:42 when you tested the final solution, the audio could have been affected by the magnetism introduced by it's USB A end which was stuck to the magnetic ring of the speaker and would've magnetized the ground connection to the PCB or not really?
Honestly asking to make sure I understand these concepts correctly since I'm trying to learn how it all works exactly.
Did you try adding some filtering ahead of the 5 Volt regulator perhaps a small R in series from 12 to the 5V regulator and a large C to ground at the input to the regulator (assuming a 7805 type regulator) or a large C after the 5V regulator if it is an LDO type?
Just curious.
Could we also possibly use a capacitor to store the 5 volt charge to try and prevent the current spikes? I was looking at the schematic and thought that maybe it would work then again idk. Probably better to use the dc to dc converter but, if you can get back to me with an answer about this that would be awesome. Stay creative dude
Great video. Removes my wondering why the electronics side of the Roland Bridgecast mitigates sound using a ground loop isolator fine. Where as, with the input on a SP-404 MK II the inteference from ground is still present. It's in the circuitry that it can't be helped with the same solution.
I belive you used a little flyback, am I correct? Why didn't you use it to step down the voltage too?
Also why wasn't it possible to couple and clamp the ground rails with a capacitor and two shottkey diodes?
I know this video is a year old but...
If i were to use a powerbank pcb to power e. g. an Alexa, usb speakers or whatever and they have interference noise what am i supposed to do?
I think the PCB from the powerbank doesn't filter the "amplification remains" so there is a slight buzzing.
In this case there would be only the 5V and ground without a audio cable and you couldn't really seperate them
(not like its shown in the video because its only one sound device instead of two).
Would a (the right) Capacitor solve my problem or should i just use another powerbank pcb?
I'd have liked to learn about this DC to DC converter. Is it a buck converter, a LDO, something else? Does any DC/DC converter work? For instance a 7805 converts 12V into 5V... but it's not the same. The end of the video seems precipitated precisely because there's no info about this magical component.
I don't know if this has been mentioned yet, but perhaps a virtual ground with op-amps would work for isolation.
I believe the particular design is called an isolation amplifier
Useful video. I am playing around with audio on an arduino which is staticky. I wonder if I have a separate 5v supply for my audio board (PAM 8403) that I will get rid of some of that.
great i was looking for this type of video thankyou man
THANK YOU so much
and as always amazing video
You're welcome :-)
@@greatscottlab :-)
Have you tried to put a diode before the vin of the bluetooth module. If the noise is caused by a some voltage ripple may be that this can solve.
Thank you for going through all the effort of building up every possible solution just to educate us. Have a nice weekend.
I wonder if a bigger reservoir capacitor for the receiver and a inline inductor would have helped as well. That should help filter out the that noise.
can i use buck converter instead to isolate grounds?
I'm having this buzzing sound issue when connecting one Baseus Bluetooth adapter in a car phone charger and connecting it's 3,5mm output to my car audio. I'm thinking of getting a tiny usb extensio, cut it's cord and hooking a b0505s up. I would then use this usb cord with the dcdc converter to connect the Bluetooth adapter to the charger. Hoping it would solve my buzzing problems. Any thoughts if this would work?
I was thinking also at the DC/DC convertor but I would have removed the linear regulator. I didn't know about the ground loop isolator solution but at the same I didn't understand why there was still noise after using it. I mean the grounds were isolated from each other as shown in the schematic.
What if you use a diode between supply to the amplifier maybe that would flatten that waveform or find the time constant and figure out a rc value. Just a thought but that noise is very infectious to other circuits
Helpful information. I like your video
thank you for your project, but can you help us to show us how audio interface work. or help to diy it
I wanted to know if the 5V GND and the audio GND were actually connected together on the BT module.
If the audio gnd were a virtual GND of say 2.5V, then connecting it to power GND was bound to cause problems.
Also, how about short wires instead of a cable? Pretty massive ground loop there.
One can also use a 12v to 5v 1W DC-DC converter and eliminate the 5v regulator. The B1205S.
5:00 is it indicated that the output is mono
sometimes hum only appear if there's no input signal
Brilliant video ! If i only had it a couple of years ago ! had the same problem and ended up using 2 mains supplies.
Did you ever experiment with filtering the Bluetooth's supply rail ?
Common mode noise is a real bugger sometimes. DC isolation is the go to fix for it although sometimes it can be eliminated (or at least sufficiently attenuated) in the IF stage with ferrite beads or an RF choke coil. If you were dealing with radar frequencies even PCB foil trace placement and pathways are a solution.
funny that i did this experiment last year when adding BT OVCxxxx module to my car stereo's tape deck preamp output. Isolation transformers were a nogo but i remembered that i had some of those isolated DC-DC converters and it was perfect. I ended up using an ATtiny to monitor the tape deck motor outputs to simulate the encoder signals and give the bt module the ability to skip and prev songs using the OEM controls.
Hi Scott. I tried building a Bluetooth speaker from scrap and encountered the same problem. After testing the whole circuit with a multimeter, I discovered that the grounds in a tp4056 are separate and it solved the issue of ground loop. Have a look at it pls.
What about building an lc filtter to the power line of the Bluetooth receiver, this might also be a usable solution 🤔
Good topic for proff audio stuff. Ground is always important.
It was interesting that the ground loop isolation didn't work. I was wondering if possibly a series inductor filter could block out the noise?
Sir, very nice video,, it's full of information.. Thank you so much,..
I have a question sir. I have the same bluetooth that you shown on your video thumpnil. When I played a song the bluetooth receiver giving cutting sound? What should I do?
I find with these ebay Bluetooth receiver boards marked AGND and GND are connected together. No isolation at all.
Also, in most cases AGND (the audio input ground for left and right) and GND are the same on the amplifier.
Disconnect the audio ground from the amp input and use a thick, short piece of copper wire to link the BT and amp grounds together. Connecting BT power ground and BT Audio ground together creates a ground loop! Additionally add a lowpass filter with 22ohm resistor and 1000uF capacitor before the 5v regulator to dampen the current spikes.
You solved one of the reason's for the annoying white noise mate... 🍻
I wish you had shown a clear view of the bottom of the isolator that you took apart so that we can see how it was made. We can guess how it was hooked up, but it's nice to be able to see how traces connected the components.
so the result is add another pcb????