I’m learning PCB analog circuit design, and trying to master the LM386 before I move on to the big boys. This was exactly the issue I had with my first board, and bodging a 2.2k resistor from line in to ground fixed it. I also built the prototype while referencing your other LM386 videos. Can’t thank you enough!
@thehudlessfarmer7 жыл бұрын
Thank you, you have just saved me a lot of time and frustration. I can turn up my LM4780 to max now and with my ear pressed right against the speaker I can only hear the faintest hint of a hum :)
@JohnAudioTech7 жыл бұрын
Hey everyone! Thanks for the views. My first video with over 1K views in under 20 hours. Also, a big thanks to those who answered questions left here in the comments. I can't do it all myself.
@Drdozzer7 жыл бұрын
I really enjoy your videos! Thanks for sparking my interest for building amps, it's a very rewarding hobby! :D Keep up the good work!
@edrickmendez79787 жыл бұрын
JohnAudioTech Hi ..I'm a new subscriber love your videos man..so my question its I'm going to build a custom boombox with a TDA amplifier its says 100w x 2 do you have some video where I can learn how to do this?
@josephkingston92526 жыл бұрын
John I purchased a 750 watt ever start inverter, I hooked it to a marine battery, whenever I plug my guitar amplifier and pa system into the inver, a lot of static hum starts, but when I pick my guitar up, quite a bit of the hum leaves but is still there, without getting technical please tell me what I can do to fix it.
@carlosmaestre5 жыл бұрын
Hi, just saw this page: antiqueradio.org/recap.htm and wanted to question: is it possible to wire an electrolytic backward and have this kind of "hum" in modern sound systems?
@ahmeterden73374 жыл бұрын
Hi all. I used 100ohm resistors with my good old Creative SBS A220 speakers and succeeded. Noise is gone. Also that did not make any adverse effects on sound quality when I connected my phone to my speakers. Also thank you very much John for this video.
@sutharpiyush714 жыл бұрын
Hey, Did you connect a single resistor? In between ground of input or input channel? 🤔
@chinhchinh62657 ай бұрын
No it does not work. It just lower you hum and audio signal. But still buzz
@captainjim10105 жыл бұрын
Thank you for this! I had to put a 2 resistors, one to ground + left and one to ground + right in order to get both channels silenced... got rid of buzzing by 90%
@paulsagoe95824 жыл бұрын
Please help me out. +233570306 on WhatsApp
@sutharpiyush714 жыл бұрын
How exactly you add resistor with channel + ground? 🤔
@KausikKumaar4 жыл бұрын
It works but audio quality/volume get reduced
@captainjim10104 жыл бұрын
@@KausikKumaar in my case audio quality got better
@KausikKumaar4 жыл бұрын
@@captainjim1010 ok maybe i am using low resistance will try increasing to 10k
@chuckmaddison2924 Жыл бұрын
I have just had a look at my crap system in sunroom. Had bad hum the cheap player had no bass and no controls. So I plugged in a scrap amp , got the tone but also got hum . Now put 1k across both inputs and fixed. I was looking for a hum loop. Many thanks.
@stark_energy2 жыл бұрын
Commonly, there are two kind of noise in computer PC: ground loop noise (only if you have different grounds connected) and picking up noise signal from audio cable. For ground loop suppression, just buy ground loop suppressor (basically just using transformer). For noise picked from audio cable, you can shield/wrap your audio cable with aluminium foil and connect that aluminium to ground, works for me.
@pianokeyjoe Жыл бұрын
Yeah my little wall mount amp will be used for PC and Casio keyboard audio(it is essentially a PC speaker system without the PC speakers , so just the internal amp mounted on a decora faceplate in a switch wall box). I have all the connections ready but there is a 3 pin input terminal that does LEFT, RIGHT and GRD. I have shielded twisted pair Cat5e cable.. no pro audio cables at all. So what is your suggestion to keep possible PA amp hum at bay there?(this also has a mic input just like in a PA pager system).
@rodrigobarrera2666 Жыл бұрын
Hello, I was wondering if cable lengh matter and were to pick the shield if using 3.5 mm audio jack? Regards
@chinhchinh62657 ай бұрын
What if it is just noise? I dont connected to any cable but it still noise, buzz
@markb19112 ай бұрын
@@chinhchinh6265 An amplifier “looks” for a signal on its inputs, and amplifies them from a power source. But if the power that the amp is supplied with changes and is unstable, it can be amplified because even if there’s no input signal the amp sees a change in voltage level and differences in voltage level are also what an input signal is. Basically you can hear the amps power source or other things interfering with it because they are not supposed to be there and affect the amp like an input signal would.
@Schjoenz Жыл бұрын
When you say "across amplifier input", does that mean, i connect both ends of the resistor to the negative and positive of the input? So if I have a stereo input, then I should put on both channels? Connecting the left channel to the ground, and right channel to the ground as well? Like this: L-(1Kohm)-G-(1Kohm)-R
@ryantoomey6117 жыл бұрын
Another way is to use an isolation transformer on the audio or use a larger filter capacitor on the power supply.
@diypasstime77854 жыл бұрын
Where should the audio transformer be placed? In the audio input or output?
@jiroyamada11393 жыл бұрын
@@diypasstime7785 Input.
@endall396 жыл бұрын
Just to clarify, you might show what that install looks like on a typical amp board (e.g., parts express) with stereo input. Very helpful video. Thx!
@oldschooljohnny5 жыл бұрын
Great video... we need more like this to help the average techie! Good work
@LeoGerritsen6 жыл бұрын
Use a small board with the BA3121 it will cancel out lots of distortion caused by ground loop. It uses CMR characteristics of the opamp.
@XaFFaX7 жыл бұрын
This works because you are shorting part of the input into ground through resistor, which makes you amplify less noise. However you also amplify less input, what means that you just lowered the volume. If this was a "simple and no-loss solution" each and every datasheet for an amplifier would included this input resistor as a default part. This obviously is not the case. What you can do as a "lossless" solution is to use special input jacks, which when there is nothing connected to the input short inputs to ground. This causes no hum when nothing is connected and no loss when you actually connect something. You can easily check there is no hum for almost any amp when you connect input connection to ground. Many guitar amp input connectors have this, this is why when you do not connect a cable to the input there is no hum and when you connect one without a guitar at the other end the hum is there and effect is the same as in the video. There are also other factors like cable shielding (especially with very high gain amps), how ground is laid out in the amp circuit, filtering etc. Overall I would not recommend this, since you are removing hum, by lowering the volume, which does not make much sense...
@lunarchsbrain21257 жыл бұрын
XaFFaX.tk I don't notice any difference between the input with or without resistor, even if I put it while playing. However I have to use a 200ohm resistor to remove the noise, could that damage the input? With an higher resistance the noise remain the same
@codebeat41926 жыл бұрын
I don't understand the thumbs ups. Maybe you have to dive into the depth of electrons, electrons flow to the path with the lowest resistance. I think you did it wrong by placing the resistor in serie and not parallel, in serie you are right (lower the input by resistance), in parallel you are wrong. The resistor in parallel avoids a floating state (not connected) and acts actually as a pull-down resistor, it simulate something is connected. In fact it stabalize the floating state and suppress noise. 10k is very common because there are also 10k pots. When you connect a source with only a resistance, lets say 300 ohms, the electrons take that route. I think you connect it the wrong way.
@redakaysoumi32776 жыл бұрын
yes you're right it's just a pull-down resistor and it'll work for most cases to avoid a floating state
@researchandbuild17516 жыл бұрын
His solution is 100% valid. If you use a high value resistor like 1meg ohm, it actually can help "short" EM interference to ground by forming a non-floating state. Meaning the amplifier will stop picking up "RF" EM noise. And in fact it is a recommended practice to never leave high gain inputs floating. Since the resistor is a high value, it will have little effect on any normal input signal since those signals are much larger than the noise EM signal. This video is perfectly accurate and is a valid solution. It's not going to cut the gain down hardly at all.
@rich10514146 жыл бұрын
This pulls down the floating voltage. It isn't just reducing the volume. The noise is of MUCH less current than the actual input, and this works to filter off the low current voltage overlapping the signal. That isn't the same as lowering the volume. On the other side of the input is a buffer which will compensate for your resistor to ground. There is nothing compensating for the noise getting dumped to ground.
@TheOneWhoMightBe5 жыл бұрын
This was a nice, simple demonstration of how to potentially kill the ground loop noise in the AUX input in my car. Have to try it out this weekend before I buy a more expensive option.
@sutharpiyush714 жыл бұрын
Did it worked for you bro?
@kratomleaf89377 ай бұрын
wow that shrieking sound is awesome tho, i might want that to be a pedal effect for my guitar
@saikrishnamethuku78924 жыл бұрын
Resistor across input ? Power input or audio input ?
@nithinpb70424 жыл бұрын
@davinder singh how to connect? Can u share a connection diagram?
@nithinpb70424 жыл бұрын
@davinder singh I should attach a resistor on both L and R channel?
@coffee_quaffer3 ай бұрын
Audio input
@shutdahellup694205 жыл бұрын
1:18 How Dubstep beat drop be like...
@trei2unu7 жыл бұрын
love your videos sir! amplifiers are one of my hobbies so all of this is very interesting and teaching
@nickthevoice5 жыл бұрын
I builded lots of amplifier with Lm4780 / lm3886 / tda7293 and many class A with always the same humm noise trouble ! I try your tips about 1K resistor between the gnd and signal input that help to reduce but not gone at 100% do you have another tips for build a truly silent amplifier ? thanks in advance ! :)
@jimparsons6803 Жыл бұрын
Liked the clip. I would have thought to use a T-Filter. Didn't think to use a low value resistor. Thanks.
@KolfMAKER2 жыл бұрын
This is a great video, great explanation! Thanks @JohnAudioT. I have an issue with an active speaker (B&O BeoLab 8000 with built-in amp). It has an RCA plug for line-in that I want to use. And it has an auto stand-by function which means: the amp & speaker switch on when audio signal is coming in, and it (normally) switches off within 3 minutes after the audio signal has ended. I have a kind of distortion that causes buzzing noise. The noise is too loud for the amp to switch to off permanently. It does try to switch off, but then immediately switches back on again. This process repeats continuously. This happens both when I have no external audio source connected to the RCA connector for line-in. As well as when I have an external audio source connected to the line-in. Though the buzz is a little bit less when I plug an iPhone as audio source to the RCA line-in connector. But even with a source connected to the RCA, there still is a lot of sensitivity. Because when I touch the cable that connects the RCA to the AMP, it immediately switches on again. Next I connected a 10K resistor across signal input & ground input. Without an audio source connected, it even increased the buzzing noise. With an audio source connected, the resistor makes no difference. Any ideas/suggestions?
@JohnAudioTech2 жыл бұрын
When you say nothing is connected to the RCA line in, you mean the cable is unplugged at the speaker side, right? If so, this could mean an internal issue with the amplifier. If it goes quiet, you are picking up noise along the cable. I'd guess the cable is pretty long.
@KolfMAKER2 жыл бұрын
@@JohnAudioTech Thanks John! Correct, there is no external audio source connected to the RCA line-in plug. The RCA plug of course is connected internally to the amplifier. This RCA connector sits on a small PCB and is connected via a 4-pin cable to the amplifier and a circuitry that detects audio signal and switches the power between Stand-by/Off and On. This 4-pin cable is about 15 cm long. If I touch that cable, the amp immediately switches on and the buzz is present. If the amp is on and I then touch the 4-pin cable the buzz gets louder. Also when I touch the RCA connector on the back at the signal tip (so not ground), the buzzing gets louder and there is cracking noise. Same happens when I touch with a screw driver (I hold the plastic part of the screw driver, not the metal). I have another BeoLab 8000 speaker; it doesn't have these issues. Question: do you have any suggestion what next step I should make?
@JohnAudioTech2 жыл бұрын
@@KolfMAKER Sounds like an open ground or shield ground. Check continuity with a multimeter if you have one.
@praveenramachandran94454 жыл бұрын
Awesome fix! It worked in eliminating the irritating hum from my DIY subwoofer amp. As I built the normal stereo power amp first, and then this subwoofer amp, I will have to do the same on the stereo inputs on the main amp? Can this be reduced to one single resistor on the initial input, which is the headphone out from my computer instead of three resistors, one for subwoofer amp's mono-fied input, and the two separate left/right inputs on the main amp board? :/
@rhenry742 жыл бұрын
Dang, wish I had seen this 2 months ago. It would have saved me hair pulling on my DIY build.
@YX4zf3 Жыл бұрын
Why does putting a resistor across the inputs work?
@1marcelfilms7 жыл бұрын
i got a long 5 meter headphone extension cable but it is next to power wire and it hums a lot and when i plug in headphones it pops loud.
@jVonHausen7 жыл бұрын
Did adding the resister also shunt the feedback when touching the capacitor?
@dozyproductionss2 жыл бұрын
So how can we do this with the class D aliexpress amps? Not sure where to look on where to put the resistor over the input.
@zedbaswedan4766 Жыл бұрын
How are you, Mr. John, I hope you are always healthy. I am your fan. Resistors are installed before or after the Tone control ' I'm Waiting for Your Reply, Thank You Very Much 🤗🤗🤗
@hendritresnahadi41462 жыл бұрын
How about the volume, it would be decrese or go down right? Tx u sir 🙏
@AdikMusicOfficialTM6 жыл бұрын
How Dubstep was Discovered XD 1:18
@Rainbow__cookie5 жыл бұрын
Lol
@jacksace84057 жыл бұрын
which input wire you connect the resistor?left and gnd?right and gnd? or right and left?
@MathewPanicker10103 жыл бұрын
Look at 4:39
@Anglynn747 жыл бұрын
Your video is the only one so far that has the same EXACT buzzing that I'm hearing coming out of my speakers that I hooked up to my television. They can be used on a tv or computer they used to be on my computer & worked fine. Hooked them up to my tv & the audio works but there is the buzzing (same exact sound in your video here). For the past 3 days have tried all kinds of fixes, all kinds of wires, went to the store & bought different wires, etc. nothing works, constant buzzing. I've heard of something called a ground loop isolator, not sure if that would work but the buzzing is driving me nuts. I can hear audio just fine but during quiet scenes in a show the buzzing is there, I can also hear the same thing you did when I tap my fingers against the end of the prong (the end of the plug)....it did not buzz when it was hooked up to my computer, only when hooked to my tv. Not sure if a ground loop isolator would work, it's my last resort, if the isolator won't work I'm disconnecting them & Putting the speakers back on my tv but I cannot for the life of me figure out how to stop the buzzing, been 3 days now & tried everything I possibly could to no avail.
@Anglynn747 жыл бұрын
also I don't have cable television so there's no coaxial cable causing interference or causing the buzzing. I'm clueless at this point.
@JohnAudioTech7 жыл бұрын
It could be a ground loop issue if you tried the remedies in the video. If the amp can be powered with a battery as a test (mains isolation) that could narrow it down.
@RijuChatterjee6 жыл бұрын
Try turning off all switched mode power supplies in the vicinity (phone chargers, laptop adaptors, computer power supplies, all electronics that plug into the wall).
@core2duo26027 жыл бұрын
Incredible results with so simple trick. How many ohms do I need for the resistor?
@JohnAudioTech7 жыл бұрын
Depends on your audio source. For a headphone type music player/phone, 470 to 1k would work. For a line level device, 2.2k to 4.7k would work. Too high of resistor value and the less they will shunt the noise. Too low and source signal can be diminished or bass rolled off.
@summersong886 жыл бұрын
John, what value to use for a laptop that goes to a DAC? Thanks very much.
@roosar20015 жыл бұрын
Twisted pair wont shield unless you're using a proper differential input. Just FYI.
@GarryGri Жыл бұрын
I have a mini arcade cabinet box with a PI, LCD screen, joystick driver, and small mono amp in it. The speaker is giving this type of hum and is also picking up interference from the pi. The audio cable from the PI to the AMP is already shielded. Would a simple resistor solution work for this, or do i need to shield ether the PI, the AMP or both? It running retro pi in the case, and apart from the audio buzz it's all running quite well. Apart from the buzz the sound level range from the AMP is fine.
@bobhurley43695 жыл бұрын
Hi, could you explain exactly what the resistor is actually doing, that causes such an improvement in the sound ?
@JohnAudioTech5 жыл бұрын
It lowers the impedance of the input so when the source signal is off or disconnected, the amplifier is less likely to pick up hum or buzz on its input. It doesn't really have an affect to the sound in normal use.
@RexxSchneider2 жыл бұрын
@@JohnAudioTech To be a little more precise: the audio source shown was designed to drive headphones, perhaps a 32 ohm load. You have a source with a relatively low output impedance, so lowering the input impedance of the next stage down to 1K doesn't reduce the audio signal, but it does significantly reduce the voltage generated by the magnetically induced hum _current_ by a simple application of Ohms law. Most headphone amps would be happy driving 100 ohms, so you could use an even lower value resistor if you still have some hum to get rid of.
@manusudha42693 жыл бұрын
I was looking for something like this ...I will try your trick . Thanks !
@pianokeyjoe Жыл бұрын
You put the 1k resistor across what 2 pins of the input though? There are 3 wires on my input side, LEFT, RIGHT and GROUND. Are you putting the resistor across the LEFT and RIGHT pins? Or across LEFT and GROUND or RIGHT and GROUND?
@JohnAudioTech Жыл бұрын
Your last sentence is correct.
@danielm.43595 жыл бұрын
I'm having a stranger problem, i have this kind of noise only if I connect an input signal. I've tried everything but it just still here. With 270ohm resistor to ground it goes quiter but on higher volumes very annoying. Anyone any experience about that?
@dom38277 жыл бұрын
can you explain me what exactly happens than? Why is the humming noise shorted out but the audio signal still present? I want to understand it, im a noob :) Thanks
@RijuChatterjee6 жыл бұрын
The noise is basically a voltage induced due to stray em waves from neighboring electronic devices and stuff and it has no ENERGY behind it, only voltage. Voltage without current is just a big mouth, all talk no action so the moment you say, here, sustain your potential difference across this conductor by inducing a current and therefore power dissipation in it the noise voltage just taps out and is like nah but the low impedance input from your audio player goes ahead and says meh I'll give you a little more current my man no problem but then of course if you connect a microphone or piezo then it's the same as the noise because yeah you don't have much ENERGY coming out of those either.
@ItsDextrin6 жыл бұрын
I like your explanation.
@rich10514145 жыл бұрын
The hum doesn't have a lot of current backing it, while the actual signal does, therefore, it is effected to a MUCH greater degree than the actual signal you want. The hum is basically floating voltage, and the resistor biases the input to 0v. You must use a source that has adequate current to strong arm through that biasing though. Some 'line level' sources have quite the high output impedance, and a mod like this will significantly lower the volume.
@sciexp5 жыл бұрын
Hello, thanks for sharing this video. I have an lm386 guitar amp. The noise comes with nothing connected. I have connected the 1 k resistor as you suggest here, and the noise goes out, like in the video, but with the guitar, affects the volume. So, I have two questions: Does it happen the same attenuation to you, with your earphones out? Have you checked this? And when you talk about shielding, do you mean to use a shielded guitar cable, shield the electronics of the guitar, or both things
@JohnAudioTech5 жыл бұрын
Guitars need high impedance inputs, so the 1k resistor will shunt too much of its signal to ground. You should try a higher value. Shielding the cable and electronics as much as possible can reduce noise.
@sciexp5 жыл бұрын
@@JohnAudioTech I have tried with a 104 capacitor and it reduces noise volume as well. It seems that the volume of the signal for a guitar does not decrease too much. And it is more clean...
@stevenjones5226 Жыл бұрын
How much power can this filter? Say I have a 3,000 home amp on some custom 20 speaker 10" towers
@melissa39203 жыл бұрын
Thanks. I was making a circuit for a guitar on a breadboard. Turns out, I just needed to shorten the antenna. I mean shorten the leads to the output jack. Problem solved.
@scorpion18loco4 жыл бұрын
Thanks , it help me a lot, I was tired of shitty noise :)
@lee26carl Жыл бұрын
John, good day. Mine has problem like someone is coking. Its on and off though.
@1970Landei7 жыл бұрын
So just that I'm not wrong. A resistor between the input (+) and GND for each channel?
@Jandejongjong6 жыл бұрын
Same question i had;)
@FacundoAguilera6 жыл бұрын
@@Jandejongjong yes
@joseveliz69796 жыл бұрын
Looks like a resistor between the left and right channel (trs) to me and the ground is yellow. Just my visual observation. Please correct me if wrong.
@FacundoAguilera6 жыл бұрын
@@joseveliz6979 No, yellow is the other channel.
@BlackyZE6 жыл бұрын
@@FacundoAguilera in that case we would hear noise from other chanell that's not resistor crossed ...
@carlangelomacapagal52284 жыл бұрын
On guitar have only 2 wire . (Mono) . Main input and the ground . If you put a resistor on it . Where you put the one end of resistor . . On the video was . 3 wire L-R-G so the resistor put on left input and right input . Where to put on Mone with only two wire.
@carlangelomacapagal52284 жыл бұрын
*Where to put on Mono with only two wire.
@FM_PERON20224 жыл бұрын
Nice, and this applies to microphones?
@RexxSchneider2 жыл бұрын
No. Microphones really need a proper preamp to match impedances and provide a line-level signal suitable for power amps.
@waynepryce343 жыл бұрын
If I don't have a board like that, can I solder in between the wires somewhere
@ognjencolic72087 жыл бұрын
WOW i have build a few amps in past month (just for fun) and i thought that only way to get rid of that input noise is to go ham on shielding input cable. Its really simple solution and it does work. I have one question and i think that you could help me with (if you have time to reply of course). I have Samsung TV with great panel but it surprisingly lacks any sound output but i can disassemble it ant tap some female RCA connectors on speaker but since i need line out not amp out will a few resistors in series do the job or i would have to do some voltage divider to bring the voltage to line level input,on my amp it says Sensitivity : 150mV and Impedance: 50kiloOhms . Thanks in advance
@ognjencolic72087 жыл бұрын
Thanks for the reply appreciate it. That is the problem its a single board design and size of the board is 10x10cm and its multi layer boars,its one of those pesky SOC,single chip with heat sink on it and some memory and some transistors. I found some AMP out to line level converters online so i will try to copy that design from net. All in all thanks and if you have some more elegant solutions please speak your mind :D Cheers
@fraaggl3 жыл бұрын
ok cool but i have female jack connector on my amp, so i have absolutely no clue on where to put the Resistor... I've tried randomly but no effect.
@mashilmy3 жыл бұрын
hey can you make something like single coil guitar pickup hum canceller, like musicman active silent circuit? umm i hope you'll know what guitarist problem. there's the US patent diagram on google, but they (musicman) kept the resistor value confidential. btw, nice channel..very informative.. just subscribed to you
@R2_Audio_11 ай бұрын
Hi! Where should i put my resistor? Left and right audio input? If yes, then it didn't work for me, the buzz is still present.
@Sokercandy10 ай бұрын
Change the value.signal input+ ground.or use a buffer amp
@LousyPainter3 жыл бұрын
Should the resistor across the input be equal to the input impedance of the amplifier?
@RexxSchneider2 жыл бұрын
No. The problem occurs because the input impedance of the amplifier is a lot higher than it it needs to be, which makes the induced hum current produce a higher hum voltage at the amp input. You need to lower the input impedance of the amplifier as much as is practical to reduce the hum voltage by adding a resistor across that input. The lowest value of resistor will be determined by the lowest impedance that the audio source can drive - for headphone outputs, that's often around 32 ohms.
@prolensphotography38234 жыл бұрын
what resistor value I'm going to use if guitar to amp? any suggestion value of ohms
@amosmantyla68984 жыл бұрын
Thank you for narrating. Truly.
@marto16713 жыл бұрын
Hi! I have a TPA3118 60w mono class D amp, wirh a 12v 1,5a power source from a dtv tv deco, connected to a 12v chinese bluetooth/radio/usb module, i wann hook up a volume potenciometer (i have a 10k and a 100k). Sounds loud and cool, the thing is that i get a lot of noise, i maybe put a B1212S, just guesing, and i dont know wich of the volume potenciometer put either, recomendation for the noise and the potenciometer? (first speaker project, and sorry for my english) Best regards from Argentina!!
@randomtube82265 жыл бұрын
That sound when he touched the capacitor 😂
@C40V155 жыл бұрын
that's a cover. someone?
@tallnrough684 жыл бұрын
Across the L & R input ? Not the ground at all ?
@99hari557 жыл бұрын
So my 5.1 amp Stereo is 7294 ic dual sub irfp150mosfet surround is tda2030 4 ic centere is tda 2030 2 ic ....i have this small noise issue....Which resisters use to reduce noice? ...i am also use shielded cables for all inputs to volume control and amplifier ...
@amosou79234 жыл бұрын
They have 75 hms to 600 hms impedance plug(3.5mm). May I know which one should I use for my v8 sound card? The wire is about 30 meters long
@seandelong88186 жыл бұрын
I'm working on a project in my truck. I bought a 12v 100 watt amp and hooked everything up and it sounded great with my truck off. Once I started the truck the input voltage would raise when I gave it gas (due to the the engine giving a higher rpm generating more "power") and thus began an ear peircing hum and backround noise. How would I fix a problem like this?
@JohnAudioTech6 жыл бұрын
Sounds like a ground loop issue. Google ground loop automotive audio. you should be able to find good info.
@seandelong88186 жыл бұрын
@@JohnAudioTech alright I'll take a look at that and let you know.
@robertneill3057 Жыл бұрын
Also the truck's alternator needs checking to see if it has a suppression capacitor fitted to the output. A 3uF 250v polyester/polypropylene film capacitor should suffice.
@GotaSir9113 жыл бұрын
Solutions- Use DC-DC isolator Avoid ground loop Dont make your audio Jack an antenna Use 2 power supplys if you use bluetooth
@AniketBasak3 жыл бұрын
AMOGUS
@RexxSchneider2 жыл бұрын
Main solutions for hum: shield the input wires and keep impedances as low as possible.
@pentacle97837 жыл бұрын
Hi John. Great Vid. I get the same hum albeit Louder off my Adcom as soon as I turn it on. I did accidentally drop the unit within a box on its side 3ft off the ground. Do you think I may have damaged the caps or need to resolder some points which may have come loose?
@dispersemedia3 жыл бұрын
What if the hum is caused by the power supply? Will replacing the filter caps solve the problem?
@strangebreed38322 жыл бұрын
Ground outside ring of RCA at the amplifier you're using to rid the hum. If it buzzez a little loop the output power supply cables a time or two like a roller coaster works for any AC ripple bleed through
@abhishekmusic903 жыл бұрын
Hello..im sitar player ..i also play electric sitar....i have a same problem.....can send me a circuit diagram to stop humming and which component use in the circuit please help me
@kirankesav76084 жыл бұрын
Hey john, can we use this at each stages, like before preamp, before poweramp etc.
@terencekaye99487 жыл бұрын
Hi John,, Thanks for the great video,, I was wondering what amplifier chip your using in the video and what current and voltage your supplying the chip with,, Sounds Great.. I Still haven't received my PAM8403's from china yet,, boy it sure take a long time,,
@mikejok4793 жыл бұрын
Damgoo audio boards have been good for me get the 5 knobber built in xover
@zapz21014 жыл бұрын
ok, im confused. you gotte bridge the positive and negative leads? wont that short the signal?
@oshaulen2 жыл бұрын
Nice Video ! Truly fix the noise mostly.
@easygeorge31613 жыл бұрын
I get a lot of humming while using my phone through the mixer ,, what device ,, which way is the best way around .. which isolator is the best one to use .. (inexpensive
@DanubioRodriguez7 жыл бұрын
what cap can add to remove noise from an atx fan? in my tda7377?
@DanubioRodriguez7 жыл бұрын
in high freq listen noise
@rudyserlet89594 жыл бұрын
Where can i find that little sony player ??? Whats the name or number of it ?? Thank you
@Rhythm.Studio Жыл бұрын
Value of resistor ? And can use a capacitor ? If yes, how much value for guitar to cut noise for grounding loop and RF to install at output jack
@yvonnemcclain6524 жыл бұрын
Help! I have in my RV a Jensen AWM970 stereo/DVD player. It has a loud humming/buzzing noise while playing the DVD on the tv. It also has a ghost line that travels upward & the more interior lights I turn on the louder the hum/buzz gets. Any helpful ideas to fix these issues?
@JohnAudioTech4 жыл бұрын
Are you running off a power inverter? These devices can be quite electrically noisy. A quality filtered power strip may help but don't expect miracles.
@vinodhvarma6075 Жыл бұрын
nice explanation sir, can you please share the circuit diagram ?
@Grunchy0053 жыл бұрын
"Where is the resistor connected in the circuit?" I think I figured it out. His 1/8" plug has 3 wires coming off, all twisted together. One larger yellow wire, two smaller wires red & green. I think the yellow wire is the ground and the red & green would be right & left headphone signals. It looks to me like he put the 1kohm resistor between red & green.
@-bru-NO2 жыл бұрын
I guess if you tried it, you must have realized you were wrong 9 months ago. The yellow wire isn't connected to anything, since it is one of the two audio channels. He's connecting the resistor between (for example) L and GND. That would be tip and sleeve in a TRS jack. He's doing it on mono, not stereo.
@siggi51991 Жыл бұрын
The last images in the end was like the berry on the top of icecream :D
@nickybbchannel99874 жыл бұрын
i have a peavey pa amp head how would i quieting it itss a little hum and alot of wind its 260 watts...great hope u can help me thx alot
@Eliastaye65 жыл бұрын
HELLO i have a question did you put the resistor in between the GND? or did you connect it to the left and right source
@PDinNM5 жыл бұрын
between the input and ground on each channel. i.e. two resistors
@Eliastaye65 жыл бұрын
Thank you sir it worked. Am still in disbelief wow...thank you again lets keep the community growing!
@Albanez394 жыл бұрын
Hoping you are someone responds to this: Can I put a resistor on the output? I'm trying to use a small 5V amp for my car, because connecting my phone through AUX emits audio at the lowest possible volume. I NEED an amp to use the car speakers (unless I go and wire them directly to the amp) through a 3.5mm jack. Hence, I'm giving speaker-level input to the car stereo, which demands line-level input. I tried using a bluetooth amps as well, but it produced a lot more noise. So...can I use a resistor on the 3.5mm jack that outputs the audio to the car stereo???
@RexxSchneider2 жыл бұрын
If your phone is giving insufficient output for the car's AUX input, then you need a small amount of preamplification. For that, you want a preamp, not a power amp. Something like an NE5532 preamp kit with a volume control would fit the bill. John designed just such a stereo preamp for the same sort of reasons as you and he has a project video documenting it at kzbin.info/www/bejne/ZoDWaYCujZtgmbM .
@rileysheldon85356 ай бұрын
Whenever I connect my speakers to my amp it just doesn’t work and makes this noise through the speakers as soon as they are connected
@mohangabhale55552 жыл бұрын
Can i use for 5v amplifier board like pam8403
@gumbung3 жыл бұрын
Automatic subscribe to this channels, a lot of experience here... Thanks
@evergreatest76444 жыл бұрын
can I add a resistor in the input if I want to amplify a mic level signal from a microphone. I bought a cheap PA system which outputs too much noise, even when using the wireless mic or when connected to bluetooth as a bluetooth speaker
@neodiy4 жыл бұрын
You should use mini transformer and coupled inductor at the input and output to remove the noise 99%
@ardenbook3 жыл бұрын
more details? any picture?
@ChudGippity3 жыл бұрын
I have hiss like that when I turn on the av reseaver. And when I give volume to 0 the speakers scream. But no audio intput is jacked in. On every input it is hissing. Please help
@amosou79234 жыл бұрын
Hello, Boss I saw impedance plug on amazon, will it useful to reduce hum noise? What hms should I choose? Thanks a lot.
@rubikfan14 жыл бұрын
I cant open my current speaker set up(atleast not without breaking it). Are there thing i can to the 3,5mm to improve it? Like an adapter or something
@logotrikes4 жыл бұрын
That was especially worthwhile John....
@paraggiri59854 жыл бұрын
Simple solution yet effective, thanks.
@danielm.43596 жыл бұрын
Hi! And what if my TDa2030a kit dont have any buzz without volume control but have buzz with it. What can i do? (I tried other potmeters aswell) Thanks for you answer! Great videos by the way!
@GaganDeep-uw3vo5 жыл бұрын
I am facing same problem
@sanathnakulugamuwa72564 жыл бұрын
My amp 200 watts wich resistance is good
@adam2011927 жыл бұрын
At the start of your video you show a pre-made amp, i have purchased an almost identical one of these very recently and need to reduce the noise. It has the same 3pin input as yours showed with L R and Ground. What would be the best method of inserting a 1K resistor on the input in this instance ?
@JohnAudioTech7 жыл бұрын
The resistors don't need to be on the board. You can place them at another location, such as the input jacks if you are using them. This might be an easier way to place them.
@kevinlivingston95637 жыл бұрын
adam201192 did you solve your problem? I'm using a 50k potentiometer but I still get the noise. Not sure if it's too high value or not grounded properly.
@adam2011927 жыл бұрын
Kevin Livingston sorry I've only just seen this. It didn't solve the problem at all. I'm using the same amp as described in this video but I think that the audio/mp3/bluetooth module unit I'm using is causing a load of feedback noise.
@amitghosh69664 жыл бұрын
Why in some audio amplifier boards the value of capacitor at the ripple rejection pin is reduced than specified in the datasheet of that audio IC ? What will be the effect of it on the amplifier ?
@JohnAudioTech4 жыл бұрын
A lower value capacitor would mean lower ripple rejection. However, if the circuit is powered from a battery or a well filtered supply, lower ripple rejection may not be an issue.
@Mr.Engine9933 жыл бұрын
It works but at the cost of ruining sound quality. The bass is almost entirely filtered out and the treble sounds a little bit weird
@RexxSchneider2 жыл бұрын
That depends entirely on the characteristics of the audio source and the wires you are using. If you are losing bass by lowering the amplifier's input impedance to 1K, then your source has a lot of inductance. This is not a suitable fix for hum coming from guitar pickups, for example. To fix those sort of problems, you have to have a preamp/buffer very close to the guitar.
@Mr.Engine9932 жыл бұрын
@@RexxSchneider thanks for replying. I wasn't making a guitar amplifier, just a big sound system for my computer. Way later than I posted the comment, I found our that my DIY 3-band equalizer, which was before the amplifier, picked up a lot of EMFs which led to all this hum and noise. I built a second version which was on a protoboard and the noise was gone so this solution wasn't needed in the end.
@RexxSchneider2 жыл бұрын
@@Mr.Engine993 I'm glad you found the solution. Hopefully, other folks with similar problems will benefit from seeing how you solved yours.
@PunakiviAddikti4 жыл бұрын
I've had some cheap amplifier boards cause noise by themselves. Literally powered them from batteries to eliminate any power supply buzz, but nope the issue persists. Sometimes it's just the amplifier itself it seems.
@RexxSchneider2 жыл бұрын
Make sure you still put supply decoupling capacitors close to the amplifier. Batteries can sometimes have a noticeable internal resistance at frequencies above dc and they are part of the signal path, since we assume the supply rails are at ac ground when designing. If the buzz or hum is not coming from the power supply, then it's being picked up or induced into your circuit. You might try putting aluminium foil inside a box and grounding it, then put your amplifier inside the box, making sure you're not shorting anything out. If it fixes the problem, then you just have mount your amplifiers in earthed metal boxes. If not, then you need to look at how your circuit is grounded. There should ideally be a single point that every ground is earthed to directly. That eliminates earth-loops. Otherwise, chances are that your inputs are picking up the hum/buzz. You need shielded wires for all non-power audio wires, and again the shielding should go to a single earth point. If all of that fails, then you really do have crappy amplifier boards.
@junjungebutan8433 жыл бұрын
Wer the resistor put?is it the left right or ground??
@Mt-xw2lh3 жыл бұрын
One in left + ground and one in right + ground. I think so
@crazyexperiments48156 жыл бұрын
So I have a TPA3116D2 Dual Channel class D amplifier board and I'm using it with a separate Bluetooth amplifier and when Bluetooth is turned it makes like a 5k hz noise but when I'm using aux through the Bluetooth amplifier it doesn't make any sound. And I've tried the Bluetooth amplifier on another amplifier but it doesn't make any sound when Bluetooth is connected, what could be wrong?