Hum and UPS

[philip]

Hi, this is my first post here so I hope this is the right forum.

I´ve recently got a small UPS, a Liebert powersure interactive 1400, to protect my studio and get to nice clean power and it´s working fine. I think the overall sound quality is better but,

I´ve got this 50/60hz hum in my console that has never been there before. And before tearing the studio down, tracking the problem, I just wanted to know if any of you had this problems or similar.

Best Regards.

/Philip, SE

[Geoff_T]

Originally posted by philip
Hi, this is my first post here so I hope this is the right forum.

I´ve recently got a small UPS, a Liebert powersure interactive 1400, to protect my studio and get to nice clean power and it´s working fine. I think the overall sound quality is better but,

I´ve got this 50/60hz hum in my console that has never been there before. And before tearing the studio down, tracking the problem, I just wanted to know if any of you had this problems or similar.

Best Regards.

/Philip, SE

Hi

What equipment are you running on the UPS? I'm assuming your computer but what sort of console have you hanging on it...

Analogue consoles and UPS's are a recipe for noise problems... especially if the console and wiring was quiet before you connected the UPS.

[philip]

Hi, thanks for replying,

Right now everything is running on the UPS, the computer, the console (d&r dayner), mci Jh24, studer c37, my monitors both computer monitors and loudspeaker monitors - a pair of Tannoy ellipse 8 and a pair of event ps8 and all my outboards.

if I strip down the system to only the computer, the console, and my monitors I still got the problem.

I will try to disconnect the console from the ups but then won´t I get grounding problems?

the reason I got the UPS is becasue I got noise (spikes I think) when mastering to the c37. not often but anyway.

And now when I hear how good everything sounds I really want to have everything connected to the UPS.

Best Regards.

/Philip

[Geoff_T]

Originally posted by philip
Hi, thanks for replying,

Right now everything is running on the UPS, the computer, the console (d&r dayner), mci Jh24, studer c37, my monitors both computer monitors and loudspeaker monitors - a pair of Tannoy ellipse 8 and a pair of event ps8 and all my outboards.

if I strip down the system to only the computer, the console, and my monitors I still got the problem.

I will try to disconnect the console from the ups but then won´t I get grounding problems?

the reason I got the UPS is becasue I got noise (spikes I think) when mastering to the c37. not often but anyway.

And now when I hear how good everything sounds I really want to have everything connected to the UPS.

Best Regards.

/Philip

Hi

There's too many factors to comment accurately without knowing all the facts but my gut feel is that you should have investigated the cause of the original spikes before investing in the additional equipment.

What's the total power capability (KVA) of the UPS? That's a heck of a load that you've put on it...

You need to go right back to basics... do you have the hum when the console and monitors are not connected to the UPS?

Is the UPS passing through the same ground as the wall sockets? There shouldn't be a ground issue.

Could you really only get the spikes you heard when you were using the C37? Might it be that the device creating the spikes was (coincidentally) running while you used the C37? The fact that it wasn't continuous smacks very much of a device in your locality that's creating spikes at random intervals.

Thyristor/triac light dimmers are famous for creating spikes so someone turning a light on could cause the problem. All hypothetical but my gut feel is that your use of a UPS is to mask a symptom and not fix the fault.

I'd be tempted to set it up how you originally had it (i.e. no ups and no hum) and see if you can trace the noise cause for the studer... are there light dimmers in the locality? Are you near a car repair shop?

Questions, questions!

[philip]

Hi again, and thanks alot for the help!

I know it´s probably to much load on the UPS but it´s a really fancy one with all kinds of meters and stuff and it won´t alarm for overloading even when listening really loud and everything is on.

I´ve got my studio in an old warehouse and I share electricity with a few others. I don´t know what they are doing but somethimes the light dimmes for a short period as if there was not enough power.

I´ve got a few dimmers in the studio but they are on a separate chord.

There are some small industries in the building and I thought they were making the spikes.

Anyway, I will make some test later this week to see if it helps simply putting the console on a different chord.

I will let you know how it went.

Sorry for bad english, these stuff is really hard to explain on my school english.


Best Regards.

/Philip

[Geoff_T]

Hi

Don't forget that interference doesn't just come through the ac wires (which is the best your UPS can hope to fix) but it may be radiated through the atmosphere. It may be a question of physical location... your tape machine may be parked next to the main high current cable feeding the rest of the building. The machine might be swamped with a strong EMF.

Wild hypothesis but spikes that switch on and off, lamps that dim and sharing buildings with industrial applications would tie together.

I'm very old fashioned and a little set in my ways. The policy.. the simpler the better... can apply to a lot of things and buying an expensive piece of gear to fix another problem... introducing a new one... may not have been the best plan.

I wonder what the distortion and harmonics are on a UPS output?

[Tim Farrant]

I would definitely only run the computor equipment on the UPS, unless the console has an on board computor. If you have noise problems coming down the mains, you can buy a heavy duty filter to remove it.

Tim.

[recordista]

Liebert isn't usually as bad as most, but I have to say that the AC output of most UPSs (especially <10 kVA) is frightfully bad. So-called power condidoning usually includes high impedance series inductors which effectively remove the powerline's ability to absorb noise--more and more of which comes from switchmode power supplies in computers and computer-ish gear. Measure the common mode and normal mode noise on your powerline before and after the installation of a so-called "power conditioner" or UPS and I predict you will be quite thoroughly shocked at what your instruments will show you. Real filtration of 50/60 Hz lines requires big iron and big copper and you just don't see much of this any more. Companies like Oneac and Best (now PowerWare) make small but wellbuilt UPSs using technology you won't typically find in mainline brands like APC (at least until they hit 3-5 kVA or so.)

As soeone else already alluded, equipment with a healthy linear power supply is more likely to be happy with a clean house power feed and will more likely than not be choked by a less-than-capable UPS.

All of these protection systems depend on a low impedance path to ground. Better grounds and cleaner, shorter paths to these grounds are probably the best investments most facilities could make WRT their electrical systems. For well under $100 you can protect an entire building from surge and most lightning damage--and it's a damn shame more haven't.

[oudplayer]

Originally posted by recordista
Liebert isn't usually as bad as most, but I have to say that the AC output of most UPSs (especially <10 kVA) is frightfully bad. So-called power condidoning usually includes high impedance series inductors which effectively remove the powerline's ability to absorb noise--more and more of which comes from switchmode power supplies in computers and computer-ish gear.

Does what you say apply to always-online UPSes, or only to standby and line-interactive ones? We've had good performance with a Liebert online (double-conversion, sine-wave output) UPS that only drives 10 amps, but we're running quite a bit less than 10 amps of equipment with it.

thanks in advance...

[recordista]

Originally posted by oudplayer
Does what you say apply to always-online UPSes, or only to standby and line-interactive ones? We've had good performance with a Liebert online (double-conversion, sine-wave output) UPS that only drives 10 amps, but we're running quite a bit less than 10 amps of equipment with it.

Most online (double conversion) UPSs have builtin power conditioning in the form of a large output transformer or 3-way isolation transformer (one leg each for line, load, and inverter) which has the effect of simultaneously removing HF noise and keeping ground noise out of the neutral line.

It's easy enough to verify this in a few minutes with with a 'scope. Spend an hour or two sometime and you can draw your own informed conclusions.

[cdog]

Originally posted by philip

I will try to disconnect the console from the ups but then won´t I get grounding problems?
/Philip

You've got grounding problems NOW, right?

You never had these issues before, right?

So unplug it.

Don't seems like nos rockets sciences to meezums.

[philip]

yes, I probably will, I did some master to the c37 today and I still got these spikes....

so now I´ve got both hum and spikes.

/philip

[Geoff_T]

Originally posted by philip
yes, I probably will, I did some master to the c37 today and I still got these spikes....

so now I´ve got both hum and spikes.

/philip

Hi

Before you spend any more money on fixes like UPS's, you have to trace the source of those spikes. Do you have any test equipment... a scope at least?

I'm almost willing to bet that virtually every piece of equipment you have is picking up that spike but it's most noticable in the studer. Are there times when you are the only person in the building? Does the spike happen then?

Light dimmers that use thyristors or triacs... even those that claim to switch at zero crossing points.. can radiate Hell and all spikes and it's like a cancer... it radiates from the cables carrying the ac because there is so much energy in a spike... zero to something to zero again in no time... very fast, gets past the big caps in power supplies, and must be treated at source.

If you have solid state light dimmers anywhere, swap them for variable transformer types (variacs).

What do the other businesses in your building do... especially the ones that draw so much current that your lights dim ... you want to pay a lot of attention to that one!

Are you using the same earth/ground as these other guys?

You should really establish the source of your problems, like the power and spikes, and try to eliminate them.

It might be worth having the wiring checked out by a qualified tech.... the power to the building sounds suspect!

[recordista]

Originally posted by Geoff_T
Light dimmers that use thyristors or triacs... even those that claim to switch at zero crossing points.. can radiate Hell and all spikes and it's like a cancer... it radiates from the cables carrying the ac because there is so much energy in a spike... zero to something to zero again in no time... very fast, gets past the big caps in power supplies, and must be treated at source.

This is worth repeating: Much easier to filter or fix close to the source!