Amplifier hum when connected to Online UPS

[Miany]

Hi All,

Amplifier - Sugden Masterclass IA-4
Power source - APC 1kva online UPS

Recently i have noted a very slight GRAINY NOISE\HUM coming from the amp (audible only if i place my ear on the top plate). If i connect directly to the mains, the amp is DEAD SILENT.. I suspected a faulty UPS and tried with another one (same model). The noise is still there..

- Should i suspect the batteries?
- UPS is having four "5A" output sockets. Should the class A amplifier needs a higher current socket? Could this be the issue?

I dont want the gear to be directly connected to mains with the chance of voltage fluctuations and power outages.

What could be wrong here? Should i look at some other solution other than online UPS?

Thanks,
Miany

 

[newlash09]

Hi All,

Amplifier - Sugden Masterclass IA-4
Power source - APC 1kva online UPS

Recently i have noted a very slight GRAINY NOISE\HUM coming from the amp (audible only if i place my ear on the top plate). If i connect directly to the mains, the amp is DEAD SILENT.. I suspected a faulty UPS and tried with another one (same model). The noise is still there..

- Should i suspect the batteries?
- UPS is having four "5A" output sockets. Should the class A amplifier needs a higher current socket? Could this be the issue?

I dont want the gear to be directly connected to mains with the chance of voltage fluctuations and power outages.

What could be wrong here? Should i look at some other solution other than online UPS?

Thanks,
Miany

Hi miany

As I understand, there is no hum coming from the speaker drivers . It is only coming from the amplifier. Which mainly denotes a humming transformer. I've had some real world hum issues in the past. And I've found 2 reasons for it in my room :

1. DC on mains AC supply. If you can borrow or buy a DC blocker, you can find out if this is the case.

2. But the most probable reason is improper ground plain, which means the entire chain is not connected to the same ups. And some components with a ground pin are running off some other wall plug. If that is not the case, then one of the component running off the ups does not have a ground plug, and is only a 2 pin plug. Shift this 2 pin plug equipment to a separate wall plug and try. All the best.

 

[Miany]

Hi miany

As I understand, there is no hum coming from the speaker drivers . It is only coming from the amplifier. Which mainly denotes a humming transformer. I've had some real world hum issues in the past. And I've found 2 reasons for it in my room :

1. DC on mains AC supply. If you can borrow or buy a DC blocker, you can find out if this is the case.

Thanks for the response! If i connect the amp directly to mains, there is no hum.. it is dead silent... so there is no DC on mains AC...Is there any chance of DC presence in the AC generated by Online UPS??? Also, please suggest some DC filters.. I can try to get that and rule out this possibility.

2. But the most probable reason is improper ground plain, which means the entire chain is not connected to the same ups. And some components with a ground pin are running off some other wall plug. If that is not the case, then one of the component running off the ups does not have a ground plug, and is only a 2 pin plug. Shift this 2 pin plug equipment to a separate wall plug and try. All the best.

I tried removing everything else from the UPS and connected the amp directly to the UPS, still there was HUM. So we can rule out other equipment as well.

On contacting APC, they are suggesting to check for proper earthing. They are saying the purity of AC generated has got a lot to do with the earth connection.. I need to check this now.. Will check and update..

 

[newlash09]

Hi Miany

I tried to see if any DC blockers were available on Amazon India. But sadly couldn't find any. Some folks on naim forum, seem to be using balanced transformers to avoid these issues. But using balanced transformers is not ideally suggested on gear not designed to work on balanced designs. Will still check if I can find medical grade transformers, as these are usually of the balanced design to give the purest current possible for sensitive medical diagnostic equipment.

 

[Dev.R]

Your Sugden may require more current then the one supplied by your online UPS. Moreover the UPS does not guarantee safety for the equipments ( you may stop charging the UPS while listening to music , that way the voltage fluctuations will not affect your valuable equipments)
Cheers.

 

[OM_2K19]

Hi All,

Amplifier - Sugden Masterclass IA-4
Power source - APC 1kva online UPS

Recently i have noted a very slight GRAINY NOISE\HUM coming from the amp (audible only if i place my ear on the top plate). If i connect directly to the mains, the amp is DEAD SILENT.. I suspected a faulty UPS and tried with another one (same model). The noise is still there..

- Should i suspect the batteries?
- UPS is having four "5A" output sockets. Should the class A amplifier needs a higher current socket? Could this be the issue?

I dont want the gear to be directly connected to mains with the chance of voltage fluctuations and power outages.

What could be wrong here? Should i look at some other solution other than online UPS?

Thanks,
Miany

This UPS is baed on Double Conversion so the output is always 100% clean sinewave. Most probably, it's a grounding issue. If possible hook your UPS to a different Socket and check if the issue persists.

 

[Miany]

Hi Miany

I tried to see if any DC blockers were available on Amazon India. But sadly couldn't find any. Some folks on naim forum, seem to be using balanced transformers to avoid these issues. But using balanced transformers is not ideally suggested on gear not designed to work on balanced designs. Will still check if I can find medical grade transformers, as these are usually of the balanced design to give the purest current possible for sensitive medical diagnostic equipment.

Yes.. I too did the same in Amazon.. could not find any.. the only available option seem to be Emotiva CMX-2... but doubt if that will be available in India....

 

[Miany]

This UPS is baed on Double Conversion so the output is always 100% clean sinewave. Most probably, it's a grounding issue. If possible hook your UPS to a different Socket and check if the issue persists.

Yes.. It seems like there is a minor issue with earthing.. Need to fix that and check if the issue is going away...

 

[Miany]

Your Sugden may require more current then the one supplied by your online UPS. Moreover the UPS does not guarantee safety for the equipments ( you may stop charging the UPS while listening to music , that way the voltage fluctuations will not affect your valuable equipments)
Cheers.

Yes.. I too doubt the current taken by Sugden here... But for online UPS, the input voltage fluctuations wont affect the output AC (atleast theoritically!)... There is a minor issue with earthing, which i need to fix and check again...

 

[arj]

efficiency of a pure class A is 10-20% so multiply your amps rated power output by 10 ..as long as the Online UPS is around double that ( so its not fully loaded), the power rating is enough. since the amp is 33W , your UPS is just about that ( if you assume higher than worst case efficiency of 10%)
Since the input power taken by a pure class A is the same irrespective of the speaker load unlike a Class AB, it may not be a power issue.

But if there is a Hum using your UPS which does not exist in a direct connection, I would take it off the UPS ..it is an expensive amp and anyway you do not need it for an amp (in my experience an amp is best direct to the wall socket)

 

[Miany]

efficiency of a pure class A is 10-20% so multiply your amps rated power output by 10 ..as long as the Online UPS is around double that ( so its not fully loaded), the power rating is enough. since the amp is 33W , your UPS is just about that ( if you assume higher than worst case efficiency of 10%)
Since the input power taken by a pure class A is the same irrespective of the speaker load unlike a Class AB, it may not be a power issue.

But if there is a Hum using your UPS which does not exist in a direct connection, I would take it off the UPS ..it is an expensive amp and anyway you do not need it for an amp (in my experience an amp is best direct to the wall socket)

Thanks for the response! In fact, the load indicator of the UPS is also not indicating anything critical.. its very well within the limits only... Do i need to take into account the current drawn too? The UPS has got only 5A output sockets.. Does this matter?

Yes.. i have disconnected the UPS now.. dont want to take any risk now... Though power outages are not that common in my area, it is still there once in a while... I hate to see the entire system getting turned off without any notice, in a power outage.. Apart from the claimed clean power, that is something that i looked at when i went for the online UPS.

 

[renjith lal]

I had some voltage issues while I was in Bangalore and some one recommended Vertex servo stabilizers. I used it and find it reliable.

 

[arj]

Thanks for the response! In fact, the load indicator of the UPS is also not indicating anything critical.. its very well within the limits only... Do i need to take into account the current drawn too? The UPS has got only 5A output sockets.. Does this matter?

Yes.. i have disconnected the UPS now.. dont want to take any risk now... Though power outages are not that common in my area, it is still there once in a while... I hate to see the entire system getting turned off without any notice, in a power outage.. Apart from the claimed clean power, that is something that i looked at when i went for the online UPS.

Yes you could try connect it with a 15A socket via an adaptor to see the effect , although I dont remember my Electrical engineering fundamentals but I doubt if it is due to current or power..more to do with magnetic fields

Anyway as long as you dont have a solution or root cause, better to plug in directly. you dont lose much in sound quality in well designed amps since all amps anyway have power supplies inside ! its Dacs/Transports and to some extent preamps that I have seen gain the most with pure sine waves.

Amplifiers do not get affected by power outages and only by Spikes and for that as long as the grounding is right and you have the right Circuit breakers, thats enough.

 

[raghupb]

Yes you could try connect it with a 15A socket via an adaptor to see the effect , although I dont remember my Electrical engineering fundamentals but I doubt if it is due to current or power..more to do with magnetic fields

Anyway as long as you dont have a solution or root cause, better to plug in directly. you dont lose much in sound quality in well designed amps since all amps anyway have power supplies inside ! its Dacs/Transports and to some extent preamps that I have seen gain the most with pure sine waves.

Amplifiers do not get affected by power outages and only by Spikes and for that as long as the grounding is right and you have the right Circuit breakers, thats enough.

If trying this, just make sure a geyser or AC is not "on" if on the same circuit.
These devices have thermostats and when the cut-in cut-out, line voltage sometimes can sag/spike.
Cheers,
Raghu

 

[oldmonk]

do you have a separate line from your mains taken specially for Audio ?

This might not be related to the humming though

 

[Miany]

If trying this, just make sure a geyser or AC is not "on" if on the same circuit.
These devices have thermostats and when the cut-in cut-out, line voltage sometimes can sag/spike.
Cheers,
Raghu

Thanks.. Will remember this point...

 

[Miany]

do you have a separate line from your mains taken specially for Audio ?

This might not be related to the humming though

Yes. There is a separate socket taken out only for connecting the UPS. Actually my dedicated listening room is on the first floor, which is having a separate power connection (separate meter) altogether.

 

[Miany]

I had some voltage issues while I was in Bangalore and some one recommended Vertex servo stabilizers. I used it and find it reliable.

Yes... I might take this route too... let's see if there is improvement in UPS output once the earthing issue is fixed..

 

[oldmonk]

Yes. There is a separate socket taken out only for connecting the UPS. Actually my dedicated listening room is on the first floor, which is having a separate power connection (separate meter) altogether.

What is the thickness of this electrical cable Which comes from the MCB or mains to your audio socket 15 amps ?

 

[Miany]

What is the thickness of this electrical cable Which comes from the MCB or mains to your audio socket 15 amps ?

No idea.. need to check.. if I connect directly to this socket bypassing the ups, there is no hum...