Long story short, I am using a nice sounding car amp for mini HT system. Not planning on hauling a 12v SLA battery into the TV room! So I got a 200w Meanwell SMPS, medical grade PF correction. It works ok, but a little noisy compared to the battery.
I can hear the buzz at least 2' from speakers drivers. Grounding the metal cage helps but does not completely eliminate the noise. It's not a ground loop because I am using an iphone for source of sound! Only the Meanwell is connected to "Earth"
So how can I get this SMPS to have a quiet output? A bunch of caps on the 12vdc outputs?
Advice would be appreciated!
I can hear the buzz at least 2' from speakers drivers. Grounding the metal cage helps but does not completely eliminate the noise. It's not a ground loop because I am using an iphone for source of sound! Only the Meanwell is connected to "Earth"
So how can I get this SMPS to have a quiet output? A bunch of caps on the 12vdc outputs?
Advice would be appreciated!
If you really think the noise is coming from the PSU rails (and I'm not 100% convinced) then the usual method is an C/L/C filter with an appropriately sized inductor.
Sticking large caps on the output of an SMPS is definitely not advisable and in any case would probably be ineffective.
I would have thought the Meanwell would have a pretty clean output tbh (noise/ripple should be in the data sheet) and so ideally you should look with a scope at the rails and identify any problem before trying to guess at possible solutions.
Sticking large caps on the output of an SMPS is definitely not advisable and in any case would probably be ineffective.
I would have thought the Meanwell would have a pretty clean output tbh (noise/ripple should be in the data sheet) and so ideally you should look with a scope at the rails and identify any problem before trying to guess at possible solutions.
You would have to use trial and error because without a scope you can not see the problem you are trying to fix.
The caps need only be fairly small but must be of low E.S.R. say 220uF. The coil will probably be in the 5 to 10uH region but it must be able to handle the current and also have very low DC resistance.
Have a look at post #543 and 544 here.
Amp Camp Amp Kit 1.6/1.8
The caps need only be fairly small but must be of low E.S.R. say 220uF. The coil will probably be in the 5 to 10uH region but it must be able to handle the current and also have very low DC resistance.
Have a look at post #543 and 544 here.
Amp Camp Amp Kit 1.6/1.8
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It;s not the SMPS on its own; its the fact you now have a common-mode loop (likely for EMC compliance reasons) between the SMPS mains connection, and the TV/HT equip you have the amp connected it to.
First thing - plug the SMPS into the wall as close as possible to the equipment from which the amp it powers, receives a signal; same duplex if possible. try that, see waht happens.
First thing - plug the SMPS into the wall as close as possible to the equipment from which the amp it powers, receives a signal; same duplex if possible. try that, see waht happens.
This is getting stranger. I must must be doing something wrong. TV and Meanwell PS are plugged into the same power strip. The Meanwell is powering the amp and the Meanwell cage is grounded to the same power strip.
I am getting a pretty loud hum from the speakers.
Should I connect the the amp ground to the power strip as well? Currently it's only connected to the Meanwell PS via V+ and V-. Not to the ground.
I am getting a pretty loud hum from the speakers.
Should I connect the the amp ground to the power strip as well? Currently it's only connected to the Meanwell PS via V+ and V-. Not to the ground.
You will just have to be logical and build it up and see where the problem occurs.
In post #1 it sounded like you had just the amp and PSU coupled up together with a 'floating' signal source.
If you have the amp physically coupled to the TV then that is a whole different set up.
Try a different PSU if you have it (the SLA battery) to be sure. If it is OK then try connecting the ground of the audio (is that battery negative?) to your power strip mains ground and see if the problem now occurs with battery or not.
But BE VERY CAREFUL. It is impossible to give exact advice without seeing the whole set up.
In post #1 it sounded like you had just the amp and PSU coupled up together with a 'floating' signal source.
If you have the amp physically coupled to the TV then that is a whole different set up.
Try a different PSU if you have it (the SLA battery) to be sure. If it is OK then try connecting the ground of the audio (is that battery negative?) to your power strip mains ground and see if the problem now occurs with battery or not.
But BE VERY CAREFUL. It is impossible to give exact advice without seeing the whole set up.
Hi ! may i ask which one ?
i am about to do something similar with my desk stereo system
However i wonder if the smps cage must be grounded to the mains ground
Thanks a lot, gino
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What is the idle current of your car amp? It may be the ßMPS is into skip mode due to a little too low of a load.
Easy test for that is place a load in parallel with amplifier. A 12V light bulb of about 50watts would be perfect. (Such bulbs get HOT!)
If the noise goes away with the extra load your problem is that tha SMPS is skipping at an audiable frequency.
Easy test for that is place a load in parallel with amplifier. A 12V light bulb of about 50watts would be perfect. (Such bulbs get HOT!)
If the noise goes away with the extra load your problem is that tha SMPS is skipping at an audiable frequency.
Hi thank you very much indeed. I have seen some pics of car audio amps and the look is very impressive. Maybe they sound also good.
I will try some soon. The second hand market is flooded with used units. Very difficult to spot the good and the bad without testing them.
Hi ! may i ask to elaborate a little more ? you mean that the ground on the smps must be connected to the mains ground ?
Moreover as i am about to use a Xbox psu that does not have a ground terminal ... will i be safe ?
thanks a lot, gino
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Please provide a model number for the Meanwell so that we can look up its datasheet.
The last one I looked at had an internal Y2 capacitor connnected between output COM and the earth terminal. No more than wiring up mains PE to earth terminal and connecting shield to output COM should be required in this case. Higher-power units may have different mains filtering setups, however, and may at least be problematic if used floating. Hopefully you don't get to choose between a rock and hard place.
The last one I looked at had an internal Y2 capacitor connnected between output COM and the earth terminal. No more than wiring up mains PE to earth terminal and connecting shield to output COM should be required in this case. Higher-power units may have different mains filtering setups, however, and may at least be problematic if used floating. Hopefully you don't get to choose between a rock and hard place.
Hi ! i do not own a Meanwell smps ... yet. Actually i would be very grateful to get a recommendation of a specific unit to buy. I guess a 20A unit would be fine ? i will be testing only small power amps.
or even bigger no problem. It will be an investment.
I have only a great respect for the brand. I have seen Meanwell smps inside professional equipment of a certain level of quality of price and for me this is more than enough.
So i am open to suggestions of a specific model or from other brands as well.
that one would be great i guess. Do you remember the exact model maybe ?
Thank you very much indeed.
I use a Meanwell 5V/10A SMPS to power my 24x7 server that also provides power for the USB soundcard running net radio.
And my main music transport, using a Meanwell 24/200W fanless supply.
I've also run Class A amplifiers using the same LRS-200 supplies. I don't use any Class D amps. Yet I'm happy to use Meanwell switching supplies. I run 3x LRS-200-24, LRS-50-5, LRS-200-12 and LRS-75-12 for a variety of applications, mostly audio and PC audio-related.
I have zero, repeat zero noise on any amplifier or transport or DAC. They are dead silent. And these are the cheapest supplies they make. It's not that they don't have ripple, they do but it's pretty high frequency and well-controlled. Hum is created from 50 and 60Hz components, even the most trashy switching supplies have that problem.
As has been advised, look elsewhere. A good first step is to check the noise with a shorted input (for some Class D amplifiers, there are some caveats).
The PSU needs to be grounded at its terminal and at its case. This means a metal enclosure with a dedicated screw for the mains earth in, and a wire to the supply from this junction. This keeps the case at ground potential externally, and provides a return path for the Y-caps between output and ground to prevent output ripple floating above earth potential.
If this earthing arrangement is not adhered to, you will get some pretty nasty currents through the equipment.
And my main music transport, using a Meanwell 24/200W fanless supply.
I've also run Class A amplifiers using the same LRS-200 supplies. I don't use any Class D amps. Yet I'm happy to use Meanwell switching supplies. I run 3x LRS-200-24, LRS-50-5, LRS-200-12 and LRS-75-12 for a variety of applications, mostly audio and PC audio-related.
I have zero, repeat zero noise on any amplifier or transport or DAC. They are dead silent. And these are the cheapest supplies they make. It's not that they don't have ripple, they do but it's pretty high frequency and well-controlled. Hum is created from 50 and 60Hz components, even the most trashy switching supplies have that problem.
As has been advised, look elsewhere. A good first step is to check the noise with a shorted input (for some Class D amplifiers, there are some caveats).
The PSU needs to be grounded at its terminal and at its case. This means a metal enclosure with a dedicated screw for the mains earth in, and a wire to the supply from this junction. This keeps the case at ground potential externally, and provides a return path for the Y-caps between output and ground to prevent output ripple floating above earth potential.
If this earthing arrangement is not adhered to, you will get some pretty nasty currents through the equipment.
Thank you very much indeed for these kind and precious advice. I will look for a LRS-200-12 unit then. I guess i will have to add a screw on the metallic enclosure and connect it to the earth mains in and done with that ? Great !
thank you very much again.
P.S. i see a declared MTBF of about 39 years !!! a really good investment for the years to come
thank you very much again.
P.S. i see a declared MTBF of about 39 years !!!
a really good investment for the years to come
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