Clean AC Power

I read a local audio magazine in which they made an assesment on a "thing" that provide a clean AC supply with adjustable frequency. It work by turning AC supply into DC and turning it back into AC by using sine wave generator. Unfortunately, it is very expensive, something in the range of US$2-3K, for me. Is it possible to built one without costing to much money. Also, does this kind of product will give you a better audio? Any one?
 
mrfeedback said:
Peter, is your UPS online or offline ? - ie is the battery powered invertor stage running constantly and supplying the load ?.
How clean is the sine wave output ?.

Eric.

Depends on amp. I have a DAC and crossover connected to UPS, transport isn't.

With A75 it sounded better when UPS was running from batteries, with Aleph 5 it's better when UPS runs from wall AC. I guess it has to do with tonal balance of both amps. A75 was more metallic sounding and the setup made it more laid back. With Aleph 5 it's just the opposite.

The sine wave was quite decent, although I didn't investigate scope image too much, how it sounded was more important.

Coulomb,

How you get over generating balanced 60V wave?
 
My experince with UPS, both off and on- line has been very negative - severe dynamic constriction and flatenning of stereo perspectives. My main ups is rated at 1200VA.
Power regeneration can be broken down to individual blocks and depending on one's needs can be quite simple. A high quality sine oscillator is very easy to build with distortion less than 0.01% and very low drift. A high power audio amp could follow and a step-up transformer. I haven't been able to get better than 0.4% distortion in the mains regenerated wave, but then again i haven't really tried hard. A good substitute for the audio amp is a bridged amp with STK modules. Depending on the power requirements one can then add additional paralleled STKs.
 
The solution of the power problem is not to feed the amp from a switched power supply via batteries! I can put money on that this switched PSU gives you much more distortion than the AC line alone. If you DO have problems with interference, a stablization transformer will filter rather good and also stabilize the voltage. This big Terminator (I've seen it) look really cool but the weight in the datasheet is wrong. NOT 650 kg (1431 pounds)!!!! More like 65 kg.....

http://www.hificonsult.se/pdf/terminator.pdf

Those of you who can't understand the swedish datasheet, ask me. I don't know if there is a english one.
 
Coulomb said:
Balanced power rules!

Why deliver 120VAC on one Phase when you can deliver 60VAC on two Phase? Noise appears at ground in two equal and opposite phases and sums to zero.

Just like theory behind Balanced inputs and outputs.

Yeah, but then all that leaves you with is just more perfect AC.

Which you then have to run through another transformer for line isolation and to step the voltage up or down which still leaves you with an AC voltage. So you then run that through a bunch of diodes to get a unipolar pulse. Which you then have to run through a bunch of capacitors to turn the pulses into ripples. And then run that into a regulator circuit to get what more or less resmebles actual DC.

It's madness I tell you! MADNESS! :yikes:

se
 
How you get over generating balanced 60V wave?

The load does not see a 60VAC Sine wave, it sees a potential differnce of 120VAC at 60Hz. Well 60 Hz + 60 Hz again actually, but the point is, even though your driving another transformer, both transformers share a common ground.

It's madness I tell you! MADNESS!

And Steve your comment is more or less unfounded in practical application. Yes diodes and caps down the line add interference, but because you now have two reactive currents in the powersupply instead of one in a +/- Powersupply, that noise is eliminated at the common ground.

This is not VooDoo, Hospitals have been using Balanced AC systems for years to lower the noise floor on sensitive equipment. It is not unrealistic to see 6 to 12 dB drop in background noise in a Power supply driven by Balanced AC. This effect is even more noticeable in Digital circuits and Devices.

The difference in video quality is visible to the naked eye when applied to our Video sources and displays.

You can build a decent Balanced AC supply to power all your video and digital equipment for about $700 Canadian. This includes a few HF filters and a line conditioner from Corcom.

Anthony
 

fdegrove

diyAudio Senior Member
2002-08-21 1:20 am
Belgium
TRANSFORMERS

Guys,

The "black art " of designing transformers (be they OTP, PT) seems to be lost in the black hole of history.
And,you don't have to take my word for it, but designing a good powertransformer is just as difficult as a good OPT.
In my early days as an audiophile it was clear already that economics had taken over.
I still have a pair of OTL amps back from 1987 where the powertransformers are actually the heart of the design...
Never seen a transformer like it since,it's a piece of ART.
1.5KVA as it is,it does not vibrate,never has shown any sign of stress no matter what load it saw.
Then again it's big and ugly,it was expensive already,way back then,had center taps where usefull,had static shielding,was self-regulating thanks to its own inductance,you name it.
Having such a transformer custom made now would cost me at least a grand a piece.Sigh...:(
Now on the bright side:for smaller pieces of audio equipment such as CD players,preamps or what have you, it is easily feasible IMHO to design a balancing primary transformer.
No need for black art here?
Looking at the advantages,you make your AC input more symmetrical,reject CM noise,the transformer will consequently vibrate less AND your PSU on the secondary will work in a more relaxed manner.
Economically, I for one see more pro's then con's here.
I don't see any need for the transformer driving another transformer here,it can all be designed into one single trannny!

Rgds,
 
Coulomb said:


The load does not see a 60VAC Sine wave, it sees a potential differnce of 120VAC at 60Hz. Well 60 Hz + 60 Hz again actually, but the point is, even though your driving another transformer, both transformers share a common ground.

No, the load doesn't see 60 volts + 60 volts. The load is the primary of the power transformer which has no center tap. So the load sees the same 120 volts it sees even without balanced power.

And Steve your comment is more or less unfounded in practical application.

Unfounded? How do you figure? I was just poking some fun at all the crap involved in order to hammer an AC voltage into something that reasonably resembles DC. Nothing unfounded about that at all.

Yes diodes and caps down the line add interference, but because you now have two reactive currents in the powersupply instead of one in a +/- Powersupply, that noise is eliminated at the common ground.

All balanced power does is reduce chassis leakage currents in equipment whose chassis are safety grounded. It does nothing to reduce actual power supply noise, ripple, etc.

This is not VooDoo, Hospitals have been using Balanced AC systems for years to lower the noise floor on sensitive equipment. It is not unrealistic to see 6 to 12 dB drop in background noise in a Power supply driven by Balanced AC. This effect is even more noticeable in Digital circuits and Devices.

I never said it was voodoo. It is an effective way to reduce chassis leakage currents. Though it's not the only way or necessarily the least expensive way.

And hospitals use balanced power not so much for lower noise floors but for safey reasons.

While chassis leakage currents in our audio and video systems simply result in annoying noise, in medical equipment which sometimes involves electrical connections to the heart, such leakage currents can be lethal.

You can build a decent Balanced AC supply to power all your video and digital equipment for about $700 Canadian. This includes a few HF filters and a line conditioner from Corcom.

Or I could buy $700 worth of batteries and forget about all the AC nonsense altogether. :)

Or I could do what I've been doing for the past 15 years in my AC powered gear and design it around good quality audio input transformers and just eliminate noise problems due to chassis leakage currents.

Anyway, I'm not saying that balanced power is not an effective solution. Just that it's not the only solution nor necessarily the best in all situations.

se
 
Re: TRANSFORMERS

fdegrove said:
Now on the bright side:for smaller pieces of audio equipment such as CD players,preamps or what have you, it is easily feasible IMHO to design a balancing primary transformer.
No need for black art here?

The "problem" isn't a lack of balance with respect to the power transformers in the equipment. They already are balanced.

The problem is the lack of balance in the AC line system itself.

Specifically, it's due to the fact that the AC safety ground is tied to AC neutral back at the service panel. Because the safety ground is at the same potential as neutral, you have an imbalance in the potentials between the safety ground and hot/neutral.

This results in chassis leakage currents due to capacitive coupling between the safety ground and hot due to the imbalance of potentials.

What balanced power does is use a 60/60 volt center tapped transformer so that the safety ground can then be placed at the center tap rather than neutral. Now you have equal potential between the safety ground and hot/neutral so that node is always at 0 volts.

I don't see any need for the transformer driving another transformer here,it can all be designed into one single trannny!

Alas, no, it can't. :(

se