DIYHiFi.org

So, does it make sense to use a UPS to isolate a PC from the mains?

No, it doesn't

I'm assuming that your worry is that your computer's switchmode power supply will spit all sorts of noise into the mains/AC line/whatever you call that thing on your wall, and that this noise will enter your nearby audio system.

Will a UPS "isolate" your computer from this? Well, when it's on battery mode, yes - - but keep in mind that most UPSs charge the batteries using a switchmode power supply that's even noisier than the one in the computer.

If you want that sort of isolaton, you might be better off using a laptop, and running it only on battery mode when you're using it to drive audio devices.

Or you could just make sure that your audio equipment has properly filtered and regulated power supplies. Your house probably has lots of line-noise-creating devices other than your computer (ever keep a cell-phone charger plugged in? Those are very noisy), so your safest bet is to isolate your audio equipment.

Any idea what would work?


I'd rather have all my electro things in my home isolated(there aren't really that many) than isolate the audio stuff...

One thing I find extremely noisy is the computer's ground. It was so bad that my ASRC would lose lock intermittently until I put a transformer on the sound card's coaxial output (there was already a transformer on the DAC input). I'm not sure of the best way to reduce the computer ground's noise.

The computer ground shouldn't be a problem if you are using the computer to send SPDIF to a DAC and your SPDIF outputs and inputs are transformer-isolated (as they always should be).

You should make sure that neither your SPDIF driver's output transformer secondary nor your DAC input transformer primary are connected to the circuit ground or the chassis ground. In other words the BNC cable (or if you're unlucky the RCA cable) running between the system should have a shield that isn't grounded to the computer, and ideally shouldn't be grounded to the DAC either... best way is to do it differential (this forum has lots of good material on how to fix it that way).

If that's the case, and assuming your DAC has a reasonable power supply (get yourself a line-filter choke if you don't have one already), then your computer's noisy ground should have nothing to do with your audio system.

Back to this old topic.
Many UPS devices regenerate the AC even when the battery is not used. That's the feature I'd like to use.

Any experience with them? Not just theory, but real experience.

The ones I've used tend to regenerate the battery voltage, using an inverter, into something like a 50Hz or 60Hz square wave.

No need for nice sine waves, or noise filtering, when you're feeding the signal into the back end of a switchmode supply that's gonna garble it back to DC. So what comes out of the UPS is much more like a 120/240VAC square wave.

Just like the power inverters you plug into your car's lighter socket. Try powering your hi-fi devices with one of those. It can be done, but the noise is audible even to non-golden ears.

(Also, for audio, why turn nice clean DC it into synthesized AC when your equipment is just going to turn it back into DC again?)

the best units I've seen are balanced out. Check out gearslutz.com. A forum for the pro/studio guys. Balanced units are used a lot in studio for the reasons you're talking about.

Sorry, I thought you were referring to computer UPS units - - those are really not a good idea for audio.

To offer you some more constructive advice, here's what I use in my big audio setup. It's a home-brew equivalent of a lot of the studio isolator units.

I run my line power from the wall into a 1500VA toroidal transformer with dual 120VAC secondaries - - a fully isolated and screened unit from Plitron in Canada.

It's housed in one of those die-cast Hammond enclosures they use for waterproof outdoor applications, bolted in very securely, with a nice power cable connecting it to the wall. The transformer is protected with a breaker and a soft-start circuit (one of those ones that shunts it for half a second through a big power resistor).

It's a centre-tapped transformer. The primary is connected to live and neutral... the house ground/earth is connected to the box, and at one point, through an RC ground-isolator circuit, to the centre tap of the transformer's secondary.

That secondary generates balanced power: That is, the "live" and "neutral" pins are both perfectly symmetrical sine waves centred on the ground, which is pegged to the centre tap. So that any common-mode noise on the line is theoretically nulled out - - as opposed to the usual live/neutral arrangement. The big transformer also provides enormous inductance for filtering, plus full galvanic isolation...

On the output, I have a single 10uF polypropylene motor-runcapacitor, to absorb any noise the hi-fi components might try to pass between one another on the line.

That's, in my opinion, the best "reconstruction" of AC you're going to get - - i.e. you're isolating it and creating a true symmetrical signal, with one phase on each side of the primary of your hi-fi unit's transformer - - assuming you've got the AC end of your hi-fi unit wired properly.

Now, there are caveats about using balanced power.

First, and crucial, is this: Your ground is going to be 120V, or 60V, above your "neutral." If you try to plug in a piece of equipment that ISN'T attached to your balanced-power isolator, you could blow something. Or give yourself a shock.

Second, you need to open up your components and make sure they have the AC section wired properly - - i.e. with "live" and "neutral" going to opposite legs of the power transformer's primary and the "ground" going to the chassis, if anything, and THE AUDIO GROUND NOT CONNECTED TO THE AC GROUND. Just to be safe, and to make sure you're actually getting the benefits of balanced power.

That's my advice... better than any UPS.

I am refering to double conversion ones.


I was thinking about getting a used one off ebay, get rid of its batteries and just use it for it's power regeneration capabilities. Just saw a nice 6kVA(~4.2KW) beast made by Riello that could do just that.

Going balanced is not really acceptable for me.

Edit: That's not for separating the PC from the mains anymore. It would be for running the audio system off of it.

I guess I don't understand what problem you're trying to solve. What makes you think that the regenerated AC coming out of an inverter would be better, in any way, than the AC coming out of your wall? You know how inverters work, don't you? Not a pretty way to produce power for audio systems.

There are some expensive UPS witch have pure sinus at the output.
The big problem is they are very expensive. APC has some, but still, I prefer not to use UPS for audio.
Better than that is a high power toroidal tranformer to isolate and balance mains power from audio equipment.
There is an approach to what you want: Paul McGowan's Power Plant Premier... Don't ask for the price of that!...
Better to buy a 230VACin 2x115VACout 1000VA toroidal transformer...

_________________
Pedro Martins

Playing with Canon EOS 5D mkII...

I really wonder why people are so impressed by toroids.

From an isolation point of view they are clearly the
worst choice available. primary and secondary are
wound over each other, with just some plastic foil
in between, maximizing the coupling capacity for noise.

A transformer with separate chambers for prim
and sec would be much better, preferably with some space
in between.

It may take some effort to make it non-humming.

Gerhard

(and, over at TheOtherPlace in this blowthing thread,
if JC boasts that he uses 4 mains transformers in
a preamp and that, oooooh, it improvez the sound so much,
that shows that he's driven by marketing to lowbrow John Doe.)

_________________
Everything has been said already - but not yet by everyone. (Karl Valentin)

Sometimes there may be no alternative... It seems everybody's nuts about toroids.
I live in Germany just like you, a few years ago I found a source for R-Core transformers, but they are not around anymore.

In my Pre I use 4 transformers, one small toroid for standby, one small toroid for digital controller and 2 R-Core for analog audio. I'd use R-Core in my DAC as well, but I couldn't find any that suit my needs.
Do you have any suggestions as to what would be better and already available here in Germany, or in EU for that matter?

No huge preference for toroids - - just that most of the readily available high-isolation transformers in the 1000 to 2000VA range that aren't mechanically awful or prone to humming or impossible to mount in an enclosure are toroids.

The point is to isolate your mains and create a balanced AC line using a big power transformer. Toroids are "good enough" for this application, I think - - if you need more isolation than that, you probably have line problems that need other solutions.

And they're much easier to mount into a reasonable-looking enclosure. A 2000VA EI transformer is a truly nasty beast.