How many VA/Watts UPS for outboard gear? Do you really need Pure Sine Wave?

[shull99]

Amir over at Audio Science Review …..every device already has a "regenerator" in it turning the AC into DC and filtering it. It's called a power supply.

I agree, but there are extenuating circumstances - like when the incoming power is really unstable - low voltage or high ripple. Most wall wort powered gear has just enough power supply - when the mains are good - but deliver pretty poor results when the mains are compromised.

Several very notable studios and hi folks rooms are running off batteries and waveform generators.


I have to add - I always have to consider who makes the statement “ no measurable difference “ and “ you can’t hear a difference “.

I work everyday within tolerances that are mostly immeasurable but are often discernible.

Much of what we hear can not be measured and much of what we measure can not be heard.

And no I’m not into voodo audio science. Everyone has to make their own tests and decide how important the difference is to Their goals.

 

[Ricardus]

I agree, but there are extenuating circumstances - like when the incoming power is really unstable - low voltage or high ripple. Most wall wort powered gear has just enough power supply - when the mains are good - but deliver pretty poor results when the mains are compromised.

This is one of the audiophile unicorn arguments? Where are these people living with such bad mains power?

Several very notable studios and hi folks rooms are running off batteries and waveform generators.

Snake oil.

I have to add - I always have to consider who makes the statement “ no measurable difference “ and “ you can’t hear a difference “.

I work everyday within tolerances that are mostly immeasurable but are often discernible.

Much of what we hear can not be measured and much of what we measure can not be heard.

And no I’m not into voodo audio science. Everyone has to make their own tests and decide how important the difference is to Their goals.

So by what mechanism are these unmeasurable things audible? Please do a paper on these things you've discovered. You'll win a Nobel in physics. Until then it's junk science.

So once again, I say to the mods, what is up with all of these new accounts promoting snake oil and bad science? Are they bots or just trolls?

 

[BillyDee203]

In my experience, I've had some broadcast gear not 'play nice' when connected to UPSes without a pure sine wave. Perhaps it depends on the gear, but I've noticed in my own tests some tend to run a lot hotter than with a pure sine wave unit. Of course, much of this gear have traditional linear power supplies. I might assume that gear with switching power supplies may be a bit more forgiving.

 

[CJ]

We had somebody down the street using some type of machinery that was putting a huge spike on the power line every 5 seconds,

Looked like a 10 volt dip followed by a spike. The boss figured out that it was somebody stamping car fenders or something like that.

Had to have a sine wave generator as well as an auto variac to drive it otherwise calibration was a real hassle.

 

[sodderboy]

Best to leave the OB off a UPS unless you have at the very least an isolation transformer or best a tight balanced power transformer (either rated higher power than the UPS.
Even COTS UPS “pure”AC outs have harmonics that pass into analog and switching power supplies. A linear supply will NOT “filter” them as they are traveling on the earth line as well.
If anyone here is so crucial that they need to track/mix during a blackout rather than do some file housekeeping or anything else then they can spring for an appropriately sized Equitech after the UPS and never think about it.
Thinking about thinking about it, a cots unit has your mains going through silicon junctions when the power is ON, passing it through. No contactor in there. Just putting it inline is a poor decision. Great for the DAW side though!
Mike

 

[Matt Syson]

Since all gear you plug into the mains will have a bridge rectifier (either directly or after a step up/ down mains transformer), it will always distort the incoming AC supply wherever it is from. The distortion will be lower if the incoming supply has a LOWER impedance so the 'raw' mains supply is most likely to be the lowest 'source impedance' you can get. Even a truly massive isolation transformer would simply add it's own secondary impedance onto the incoming line impedance and then if you were to be thinking of a UPS of any sort the output impedance would again most likely be a lot greater than your incoming mains (Solar array or whatever).
Thus any sort of UPS or even 'so called balancing transformers' will worsen the distortion on the line (by the time you have plugged a couple of bits of gear into it.).
I had 228.7 Volts 50Hz with 2.3% distortion in a studio in France yesterday. I was using an Audio precision to check a little battery oscillator to find out if it was anywhere near +4dBu (which it wasn't) but it had 43% distortion!. It was a 'cable testing box' with a 'handy oscillator' so not exactly audio gear.
Mains wiring is already 'balanced' by the way. It must be otherwise in most regions of the world (that use Differential circuit breakers) the Live ant Neutral return MUST be the same equal (balanced) otherwise the breakers would keep tripping.

 

[MisterCMRR]

Yes, Australia has some very creative power distribution systems. SWER (single wire earth return) is commonly used at the edges of the grid and is exactly what it sounds like. You get a single wire with some volts on it and you plug the other end into the soil. What voltage and waveform you get depends what the neighbours are up to.

Wow, that's a pretty frightening thought! I guess Australia has more to worry about than just the collection of deadly snakes and insects!

 

[MisterCMRR]

Mains wiring is already 'balanced' by the way. It must be otherwise in most regions of the world (that use Differential circuit breakers) the Live ant Neutral return MUST be the same equal (balanced) otherwise the breakers would keep tripping.

I think you may be confusing voltage and current "balance" here. Live and Neutral currents must be equal, otherwise GFCI (RCD in Europe) will trigger on the difference current. But so-called "Balanced Power" units make their output voltages symmetrical with respect to safety-ground (PE in Europe). For example, 240 V line and 0 V neutral would come out as 120 V on both line and neutral prongs - that's why they're not allowed by Code on lighting circuits and must have a GFCI on their output. No one expects to find 120 V on the neutral! And, with regard to system noise, the reduction, if any, is insignificant. Most of its touted benefits arise from plugging all system gear into their closely-spaced outlets - a benefit you can get for a tiny fraction of the price with a simple outlet strip.
Remotely relevant short story: I was once paid to create a schematic of the Nordost "Thor" power conditioner (it sold for about $3,000). Although it contained some impressive-looking parts (most of which did nothing but power the blue LED on the front panel), the only functional parts were several rather ordinary MOVs at the output outlets. Just one example of "audio jewelry" marketed to audiophiles.

 

[sodderboy]

Maybe it is a language thang like with earth, ground, etc. I am talking symmetrically balanced AC power referenced to mother earth.
Speaking to US electrics, AC power is unbalanced as the neutral is referenced to earth at a generation source, and again at a distribution station, and again (hopefully) at the distribution box. There's nothing balanced going on when a neutral bus bar is bonded to the box, and the box is connected out to mother earth (or maybe, maybe building steel in commercial).
Referenced to mother earth, AC power is unbalanced. If I look up at HV transmission lines anywhere in the world, I see four lines, not seven. Call it even numbers, not odd, when there are multiple lines running overhead.* Same leaving a distribution station. Just try swapping 'balanced' hots and 'colds' in a local fuse box like you can on a mic patchbay! You will never get a breaker to stay ON.
AC is unbalanced on purpose for cost and safety reasons. You might call some loads balanced, but that's it.
Mike
* we snuk in on Niagra Mohawk property upstate NY following a rockhunting tip. The gates were open so we headed for an outcrop. The wires running through there were just smacking with energy. You physically felt it, even though they were a few hundred feet away. Maybe they are 50 kV? Didn't stay long.

 

[JohnRoberts]

This is a pretty well discussed topic around here but most US mains distribution is AC voltage dropped down to a lower voltage center-tapped winding. Delivering 240VAC or 120V-0-120V. This center-tap is grounded at the power drop (fuse box, whatever) and typically bonded to mains neutral.
==
Bill is quite correct what people refer to as "balanced power" is symmetrical voltage wrt ground. In theory 2x 60VAC opposite polarity waveforms "should" cause less interference than one 120VAC waveform. In practice properly designed gear with properly executed interfaces and wiring do not have problems.

JR

 

[MisterCMRR]

Maybe it is a language thang like with earth, ground, etc. I am talking symmetrically balanced AC power referenced to mother earth.
Speaking to US electrics, AC power is unbalanced as the neutral is referenced to earth at a generation source, and again at a distribution station, and again (hopefully) at the distribution box. There's nothing balanced going on when a neutral bus bar is bonded to the box, and the box is connected out to mother earth (or maybe, maybe building steel in commercial).
Referenced to mother earth, AC power is unbalanced. If I look up at HV transmission lines anywhere in the world, I see four lines, not seven. Call it even numbers, not odd, when there are multiple lines running overhead.* Same leaving a distribution station. Just try swapping 'balanced' hots and 'colds' in a local fuse box like you can on a mic patchbay! You will never get a breaker to stay ON.
AC is unbalanced on purpose for cost and safety reasons. You might call some loads balanced, but that's it.
Mike
* we snuk in on Niagra Mohawk property upstate NY following a rockhunting tip. The gates were open so we headed for an outcrop. The wires running through there were just smacking with energy. You physically felt it, even though they were a few hundred feet away. Maybe they are 50 kV? Didn't stay long.

Most AC power in the world (including the US) is generated and distributed on long hauls as 3-phase - see the attached picture, where there are two 3-phase feeders, one on each side of the tower. The line across the top is an intentional "target" for lightning strikes and is tied to each earth-grounded tower. These distribution lines generally operate at 100 kV or higher. These voltages are reduced in substations and generally don't become single-phase until a 5 kV or 10 kV line is routed through residential areas. Then, the pole-mounted transformers reduce that (in the US) to 240 V "split single phase" that enters your home - each split having 120 V with respect to the grounded neutral. Heavy 240 V loads (electric ranges, water heaters, air conditioners, etc.) being fed across those two "legs" to have 240 V. The reason 3-phase distribution is used until residential distribution is that most large high-horsepower industrial motors are 3-phase.

 

[JohnRoberts]

Phase is one of those words that people think they understand until the subject of mains power distribution comes up.

I will not try to explain and cause even more confusion, just be aware of the context when you see that word used.

JR

 

[pvision]

I'd keep the UPS for the computer, drives, USB hub, DSL modem and screen. I think the rest can take care of itself

One reason is that you generally need rather more runtime than you think when trying to make a backup. And, if connected, that tube gear would just be sitting eating runtime...

 

[Matt Syson]

I wasn't confused by referring to balanced as there is obviously a difference between current balance (which I was really referring to), and voltage balance. Interference when concerned with gear 'humming' is due mostly to magnetic field causing current to flow in your wanted circuit (mic or whichever) so having the conductors suitably twisted together largely nulls the 'radiated field, and conversely rejects an external magnetic field (flipsides of the same coin).
VOLTAGE balance is less of a problem in low impedance circuits where coupling is by capacitive effects and not magnetic for which a conductive shield reduces and usually eliminates that problem.
I have not found anywhere in Europe (or anywhere outside America really) that uses 240 Volts with a centre tap to ground. Neutral is almost always grounded and you have 3 'phases' that are 120 degrees phase shifted which if you measure between any two phases gives 400/415 Volts (230/240 per phase) and depending whether 'industrial' or domestivc may be used in Star or Delta connection (Delta only using the 3 live phases and star using the Neutral as well. Neutral is bonded to ground at the main incoming distribution board (supplied by the electricity company, together with fuses and metering) and this common ground connection has to be bonded to all metalwork pipes (water and gas) so that there should never be a significant voltage difference in any given building. Some European countries do not bring an earth with the 4 (3 phase + Neutral) incoming wires from the overhead cabling but then require a suitable low impedance ground 'spike' and/or the galvanised protection on an underground feed cable. In France I have a 4 conductor 'twisted bunch' from a pole (3 phase +Neutral with a 500milliamp 'current differential breaker (which manages to unravel the difference from each of the 3 phases and the common Neutral?) and main switch. All 3 phases I use have separate differential breakers with 30 Milliamp trip currents and as a domestic premises I use the 3 phases independently.

 

[sodderboy]

In practice properly designed gear with properly executed interfaces and wiring do not have problems.
JR

From my practical experience I would write that "In theory. . . ." Once a system design approaches 72 I/O and there is no console in sight, things change. Especially if any MIDI instruments are involved.

I was a symm-bal AC atheist until I did a with 50+ pieces of analog outboard, 48 I/O DAW, and no console. The bastards! That room totally schooled me, took me to the river, dropped me in the water, and I was a believer.

Mike

 

[thor.zmt]

I have this 1500VA/900W UPS that produces ON BATTERY Pure Sine Wave at 900W.
https://www.cyberpowersystems.com/product/ups/pfc-sinewave/cp1500pfclcd/
I am considering sharing this UPS for my computer with my outboard gear but unsure whether it can handle it, if not, I might just buy another one.

Off mains power supplies using classic transformers, as opposed to modern switching mode supplies require sine wave sources with very limited levels of distortion at close to the nominal frequency. Any other option may cause mechanical noise from the transformer or lead to damage on the equipment being powered.

You can for example not operate a 50Hz Transformer at 400Hz (or reverse) reliably.
I doubt however that your problem will be in any way solved using a UPS or other power regenerator.

See my reply in your other thread:

Reducing hum, noise and ground loops?

Past that, do not guess or estimate power consumption, it is easy to measure. So measure it.

Thor

 

[abbey road d enfer]

Referenced to mother earth, AC power is unbalanced. If I look up at HV transmission lines anywhere in the world, I see four lines, not seven.

You may think of 3-phase distro as 3 unbalanced signals with a common "ground", but actually each signal (phase) balances with the two others.
Like a 3-cylinder engine is balanced although not symmetrical.

 

[JohnRoberts]

Dead thread walking....

JR