I have bought a Skytec Pro 240 amplifier and I am having trouble with noises from the power grid. The main problem is the elevator here in the building, which produces unpleasant noise when someone is using it.
There are four 1000 uF filtration capacitors in this amplifier. Would it be enough to install 10000 uF capacitors instead or do I need to do something else with the power supply? I am not an expert, any help would be appreciated.
There are four 1000 uF filtration capacitors in this amplifier. Would it be enough to install 10000 uF capacitors instead or do I need to do something else with the power supply? I am not an expert, any help would be appreciated.
Sounds like the Skytec's EMC immunity isn't the required level. These days when designing products you have to expect the worse caqse EMC problems.
In the UK, BT Vision have a exemption from certain aspects of the CE requirements beacuase it is based on EMI, adding high frequency mush to the mains, which all other equipement will have to filter out.
In the UK, BT Vision have a exemption from certain aspects of the CE requirements beacuase it is based on EMI, adding high frequency mush to the mains, which all other equipement will have to filter out.
The mains noise could be attenuated by fitting a filter at the mains input socket of the equipment. Does your equipment have a mains filter?
These are sold as ready made assemblies that bolt to the chassis and provide an IEC socket on the outside face for connecting to the mains.
Is the interference air borne?
Is the signal input filtered?
Again an RF filter can be added. This is a simple DIY modification.
Is the output filtered?
Not quite so easy to do DIY, but certainly possible and not costly.
These are sold as ready made assemblies that bolt to the chassis and provide an IEC socket on the outside face for connecting to the mains.
Is the interference air borne?
Is the signal input filtered?
Again an RF filter can be added. This is a simple DIY modification.
Is the output filtered?
Not quite so easy to do DIY, but certainly possible and not costly.
Thanks for the replies! The interference is definitely conducted, it is caused by the elevator running. I opened the door and I could confirm that the buzzing starts just as the elevator starts moving and stops when it stops. It is also dependent on the output level - when I turn the amplifier up, the interference sounds get louder as well. The walls here are reinforced concrete so I think it is quite unlikely for airborne interference to get through those walls all the way from the top of the elevator shaft.
The only airborne interference sources were mobile phones and I removed them from the room.
There is actually a lot of room in the amplifier chassis, I could install some filtering device inside, without the need of another box.
I did not get any documentation with this amplifier, how can I verify if it has a mains filter? The only thing that seems to be able to filter anything are those four capacitors I mentioned, but that is only my uneducated guess.
What do you suggest?
The only airborne interference sources were mobile phones and I removed them from the room.
There is actually a lot of room in the amplifier chassis, I could install some filtering device inside, without the need of another box.
I did not get any documentation with this amplifier, how can I verify if it has a mains filter? The only thing that seems to be able to filter anything are those four capacitors I mentioned, but that is only my uneducated guess.
What do you suggest?
RF goes through concrete, so radiated interference is certainly possible. As it gets worse at higher volume settings, it is getting in at the beginning. Does it still occur wth no inputs plugged in, or only on some inputs?
The capacitors are for smoothing, not filtering interference. They may have some limited filtering function too, but this is a side-effect of smoothing.
The capacitors are for smoothing, not filtering interference. They may have some limited filtering function too, but this is a side-effect of smoothing.
Thanks for the suggestions!
I tried it without input connected and the noise was not there. I had this connected to an integrated sound card (a temporary measure) so I tried connecting it to a portable mp3 player. The noise was not there. However, when I connected it to the integrated sound card again, the noise returned.
So the problem seems not to be in the amplifier or cables, it is in that integrated soundcard!
However, I plan to use this with a different computer and a stand-alone, higher-quality sound card. Do you think that the interference will be present even on the new PC with a better, stand-alone soundcard? The new PC will also have a better power supply so maybe if the interference is conducted, the problem will not be there. But if it is airborne, the new PC might have the same problem.
Is there any way I can verify whether the interference is conducted or airborne? Would installing an RF filter on the amplifier input help in this case? Does the filter affect sound quality?
I tried it without input connected and the noise was not there. I had this connected to an integrated sound card (a temporary measure) so I tried connecting it to a portable mp3 player. The noise was not there. However, when I connected it to the integrated sound card again, the noise returned.
So the problem seems not to be in the amplifier or cables, it is in that integrated soundcard!
However, I plan to use this with a different computer and a stand-alone, higher-quality sound card. Do you think that the interference will be present even on the new PC with a better, stand-alone soundcard? The new PC will also have a better power supply so maybe if the interference is conducted, the problem will not be there. But if it is airborne, the new PC might have the same problem.
Is there any way I can verify whether the interference is conducted or airborne? Would installing an RF filter on the amplifier input help in this case? Does the filter affect sound quality?
PC power supplies often omit mains filtering components. This saves the manufacturer a few pence. The locations for them are left in place on the PCB, so if anyone complains he can say they were omitted by accident.
Does the noise occur in a battery powered AM radio? If so, it is radiated. On the other hand, it could be poor filtering and bad grounding in the PC power supply - they are not usually designed for high sound quality.
Does the noise occur in a battery powered AM radio? If so, it is radiated. On the other hand, it could be poor filtering and bad grounding in the PC power supply - they are not usually designed for high sound quality.
I had a similar issue with my laptop PC external switching power supply. The PS was injecting noise on the ground and getting to the amp on the ground. When the PS was unplugged, laptop running on battery, no noise. I initially used a "cheater plug" to eliminate the PS ground. The proper fix in my case was to isolate circuit ground from chassis ground in my amplifier with an RC filter.
I tried examining the noise further, as you suggested and I found out that the interference from the elevator was really conducted. It affects only that one machine so it probably has a low quality PSU. It does not affect my laptop when it is running on AC without a battery.
However, it seems that computers generate lots of airborne interference by themselves.
I never thought that input could be influenced by interference this much, I had assumed that the amplifier is the most sensitive component.
My laptop (which has a plastic chassis) seems to be the worst when it comes to generating interference. Putting it directly on the amplifier creates terrible sounds.
Since I found out that the problem is not in the amplifier's power supply, I should probably check the "PC Based" part of this forum for more information about this kind of interference and possible solutions... maybe use better shielded cables or buy an external soundcard with its own power supply and move it away from the PC...
Thanks for all the help!
However, it seems that computers generate lots of airborne interference by themselves.
I never thought that input could be influenced by interference this much, I had assumed that the amplifier is the most sensitive component.
My laptop (which has a plastic chassis) seems to be the worst when it comes to generating interference. Putting it directly on the amplifier creates terrible sounds.
Since I found out that the problem is not in the amplifier's power supply, I should probably check the "PC Based" part of this forum for more information about this kind of interference and possible solutions... maybe use better shielded cables or buy an external soundcard with its own power supply and move it away from the PC...
Thanks for all the help!
How old is the building your in? if it's relatively new, then the lift motors will be controlled by inverters.
These are renowned for polluting the the mains,also the building will be supplied with a 3 phase and neutral power supply,the supply to your office will be supplied from one of these phases and neutral.Another problem could be the cable supplying your office sockets will be run in trunking along with many other cables,thus causing induction.
So just try a good quality mains filter,many are on the market a varying prices.
Before buying,try your bit of kit at home,see if that makes a difference.
These are renowned for polluting the the mains,also the building will be supplied with a 3 phase and neutral power supply,the supply to your office will be supplied from one of these phases and neutral.Another problem could be the cable supplying your office sockets will be run in trunking along with many other cables,thus causing induction.
So just try a good quality mains filter,many are on the market a varying prices.
Before buying,try your bit of kit at home,see if that makes a difference.
The building is quite old but the elevators here are relatively new (I think they are less than 10 years old). It is not an office building, I live here. I will try a mains filter as you suggest.
I will probably also need to solve the issue with air interference from the computers... I have ordered a cable long enough for connecting the amplifier to the computer I actually plan to use for playing music and I will see if it is generating interference too.
I will try a mains filter as you suggest.I will probably also need to solve the issue with air interference from the computers... I have ordered a cable long enough for connecting the amplifier to the computer I actually plan to use for playing music and I will see if it is generating interference too.
Good luck on getting the building fixed. Ha! I had a little trouble from buzzing from a lamp dimmer, a flourescent light, and interference from CB radios driving down the street While the commercial RF filter device shown will work, I'm cash short and junk rich. The preamp was in a grounded steel box, that is the first requirement. Second I moved the power transformer out of the box- used a wall transformer. Third, I put RF chokes on the DC entry to the steel box. I wound the RF chokes by stripping the transformer wiring from a PCAT switcher supply toroid, and leaving 20 turns on it. I put one of these on both DC inputs to my steel box. No more RF problems. Oh, my mains frequency filter, the xxxx uf electrolytic cap, I paralleled it with a .1 uf ceramic cap of the same voltage rating.
Thanks for the suggestion! I will make an extra filter for the amplifier like you suggested.
And to solve my problems with PC noise, I am buying a digital/analog converter (it should have occurred to me sooner...) and I will connect it to the PC's optical audio connector. So hopefully all interference problems will be gone soon!
And to solve my problems with PC noise, I am buying a digital/analog converter (it should have occurred to me sooner...) and I will connect it to the PC's optical audio connector. So hopefully all interference problems will be gone soon!
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