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Old 4th September 2004, 11:36 PM   #1
mgmopar is offline mgmopar  United States
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Default How clean does power need to be?

I have read much on this forum about the topic of the supply voltage. I really don't know it's full effects on the final audio quality. I am sure so areas have very poor power qualities and this obviously would effect performance. With the prices of UPS units and Inverters going down would the use of equipment such as this at least give a stable source without other appliance and line interference? The interference it would give could be predictable so as could work with. Or is the use of this equipment going to add more unacceptable interference due to it's own operation? Or another way to isolate from the AC line would be to run a motor to spin a Generator with a flywheel. The original source of the electron flow would now be reestablished on location in a controlled isolated environment thus eliminating the power grid interference altogether. I think the most pure source would be a bank of batteries with the final output voltage that that we would run the system. The AC voltage would be ran threw a Transformer to charge the batteries when the system is not being listened to.

This post is just food for thought, I am just fine having my equipment on a dedicated circuit.
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Old 5th September 2004, 01:25 AM   #2
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I think power purity is an important issue. Not to wade too deeply into the issue, for the moment, my sense is that a clean AC source will probably best a battery supply, which is current limited and generates its own noise problems varying with the type of battery used.

On a related topic, if replacing internal wiring with, say, silver wire improves audio throughput, what of the miles of inferior cable bringing AC to your home?
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Old 5th September 2004, 02:02 AM   #3
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Hi,

Quote:
With the prices of UPS units and Inverters going down would the use of equipment such as this at least give a stable source without other appliance and line interference? The interference it would give could be predictable so as could work with. Or is the use of this equipment going to add more unacceptable interference due to it's own operation?
There are basically two types of UPSs:

An off-line UPS has a 'simple' battery charger, an 'up-converter' and a mains failure detector. The battery is kept charged while your load is constantly connected to the supply line. Once power fails, the UPS switches your load from the line to the battery-supplied converter (very quickly).
Obviously, this wouldn't help your equipment power quality.

An on-line UPS transforms the line level voltage down to battery voltage level (using a switching power supply) and uses this to charge the battery and supply it's up-converter at the same time ('in parrallel'). Thus, during a power failure there's no takeover switching and (ideally) no load supply deviation.
While this type delivers good power failure protection even to devices which are sensitive to mains fluctuations, there are other drawbacks.

Almost everything in today's UPS is done using switching regulator principles. While this is good for your THD 'predictability', it won't give you actually low THD. And switching supplies are among the worst mains line polluters!
Using one of them is good for everything with a switching supply itself, but I consider it bad for audio.

Just a thought, either.

Sebastian.
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Old 5th September 2004, 02:20 AM   #4
mgmopar is offline mgmopar  United States
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Quote:
serengetiplains
I think power purity is an important issue. Not to wade too deeply into the issue, for the moment, my sense is that a clean AC source will probably best a battery supply, which is current limited and generates its own noise problems varying with the type of battery used.

On a related topic, if replacing internal wiring with, say, silver wire improves audio throughput, what of the miles of inferior cable bringing AC to your home?

Yes, batteries are current limited as is the current coming into a residence. I think batteries main draw backs would be the space and possibly need for ventilation during charging. Batteries noisy? They do not have the 50 or 60 Hz that has to be evened out for clean power. I would think if enough batteries are used to achieve the desired voltage so as to eliminate circuitry and power transformers and such the system would have the potential of being cleaner. Batteries might have some noise? but isn't that partly why caps are used in power supplies? I am used to automotive and marine batteries that can put out over 800 amps for a short time and 40 or so for many hours. In series at the amps voltage this would have a long play time. If longer time or more amperage was wanted then they could be banked parrlel/series to double the current ability and time. Note these high current DC lines could be very dangerous on of the aspects of safety when towing and servicing electric and hybrid cars.
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Old 5th September 2004, 02:26 AM   #5
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Hi sek

Yea that makes a lot of sense but how about the use of inverters on a batteries bank? or basically a UPS with extra batteries and the line shut off when "noise free" power is desired. Are inverters without the line involvement considered clean or is this also just as bad as the line?
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Old 5th September 2004, 02:59 AM   #6
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Hi mgmopar, I'd be interested hearing the results of your investigations. My intuition tells me if batteries were that much less noisy than AC, they would have made a greater appearance in high end gear, where cost is no object. A few companies, like Edge, have experimented with batteries to good effect, though the jury is out, so far as Edge equipment is concerned, whether the trade-offs involved in using batteries renders an overall audible improvement (comparing audible apples to audible oranges here, I realise).

I've spoken with Serge Schmidlin of Audio Consulting who has experimented rather alot with batteries. He found that battery type noticeably affected resulting sound, and that certain battery types generated too much noise for his liking. I think he prefers the batteries he now uses to AC.
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Old 5th September 2004, 03:16 AM   #7
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Quote:
serengetiplains
I'd be interested hearing the results of your investigations. My intuition tells me if batteries were that much less noisy than AC, they would have made a greater appearance in high end gear, where cost is no object

I would agree but size and ease of use is needed for consumer acceptance. Most consumers would not want to have a bank of batteries in their basements nor the duct work to vent them outside. I also think high end equipment designers would have trouble getting such equipment UL listed.

Quote:
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I've spoken with Serge Schmidlin of Audio Consulting who has experimented rather alot with batteries. He found that battery type noticeably affected resulting sound, and that certain battery types generated too much noise for his liking. I think he prefers the batteries he now uses to AC.
Do you recall what type of batteries made the noise?
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Old 18th September 2004, 08:12 PM   #8
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Sorry for the late answer

Quote:
Yea that makes a lot of sense but how about the use of inverters on a batteries bank? or basically a UPS with extra batteries and the line shut off when "noise free" power is desired.
This is a good idea in order to keep the influences of surges, voltage fluctuations and occasional dropouts small. I've actually seen UPSs used for this purpose in recording studios. But one shouldn't expect too much improvement from a UPS.

Well designed audio gear doesn't really 'suffer' from power line problems. Today's electronics design possibilities make it rather easy for circuit designers to rule out audible influences from the power supply. As an example, most line level equipment and even many power amplifiers achive a reduction of the influence of power line variations better than 1:1000000; which means that a change of one volt on the power line would be recognized by the audio circuit as a change of 0.000001V - and even then, this change wouldn't neccessarily be recognized by the actual audio signal!

As a conclusion, special care to the power line stability is only required with not-so-well-designed gear. A good internal power supply in a good preamp or cd-player doesn't have to fear power line stability too much. OTOH, a cheapish unit won't sound better with better power line quality, it has to be improved in other regards, first. There are actually very few cases in audio where power line stability is a true problem.

If you're planning to achieve high quality audio in the carribean or suffer from occasional power line problems at home, then UPSs are a must, though...

A completely different story is distortion and noise on the powerline, I'll explain that after your next question

Quote:
Are inverters without the line involvement considered clean or is this also just as bad as the line?
It depends.

In general, inverters - and basically all types of swithing power devices - are considered one of the main polluters of the power lines, with only high-power motors and load-switches nearby being much worse.

But there are quiet inverters (or converters, as I prefer to call them), though. That fact just doesn't help you out in case yours is noisy...

The usual inverters in UPSs come in very different flavours, the most expensive devices usually having the quietest inverters. In cheap gear, the up-converters don't even have a real sine wave generator. They just generate an AC waveform, convert this from battery to power line level and clean it 'a little'.

Widespread are inverters with triangular or trapezoidal output waveform. Imagine a triangular wave at 230Volt, carrying 10A of current. Now that's a lot of distortion and noise! Those bugs not only pollute the connected equipment, but also the power line (if any) and anything that might be sensitive to radio frequency interference in an area around them.

On the other hand, there are inverters with true sine wave generators. Those sine waves are mostly generated by ADCs and have a sinusoidal stair step characteristic, but there are some with very good sine wave reproduction. The keyword here is THD, the harmonic distortion that lets the stair step differ from a true sine.

And while the actual power line can have reasonable THD sometimes (due to switching supplies, motors, hair dryers! and such), the real problem is the variation in these properties. The 'same' powerline never measures the same. There usually is a periodic characteristic, a typical difference between night and day, working days and weekends, neighbours' day rhythms (remember: motors, switches, hair dryers...), nearby industry, train schedules and whatever. You can never rely on the distortion properties of your power line...

That's a true benefit of a UPS or a battery with a good inverter. It gets the THD content of the supply line known and kind of 'ensured'. But that's all, there's nothing more an inverter can do to your power line quality.

The distortion and noise it produces have to be something you can get by (or live with), then it's worth a try.

BTW: A UPS of the kind I described as good (e.g. 'active' or 'on-line' type, sinusoidal output wave form with low THD) doesn't need to be unplugged in order to get good sound out of the connected gear, because it can't get lower than it's minimum THD by just unplugging it. At least not to a significant amount, I guess (because then it wouldn't be a device with low enough THD, wouldn't it?).

Oh, and the sealed 'lead-gel' type of batteries used in UPSs doesn't need air conditioning and works independent of orientation. But they are still large, heavy, expensive, ugly, need quality (!) charging and are not noise free! That's probably why they don't come built in inside every cheap stereo or home cinema set

Ciao,
Sebastian.

PS: Oh, and exactly those units as required didn't get much cheaper over the last couple of years. It's the low quality type of inverters that got cheaper due to mass production...
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Old 19th September 2004, 12:09 AM   #9
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Thanks for the info. I probably am just going to continue to use my dedicated circuit to power my system. The information you gave helped me come up with an idea to investigate. I have a various switching power supplies running in my home 24/7 file and web servers as well as UPS supply's (most likly noisey ones). I don't recall if I used the same phase (leg) off the breaker panel. I am going to investigate the circuits in the home and try to divide them to keep cleaner loads on the same leg as I have my audio. Put the nosier loads on the other phase (leg).

They share the same return but I would think this will help isolate the majority of noise created from within my home, from the power line to my audio system.
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Old 19th September 2004, 12:41 AM   #10
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Quote:
I have a various switching power supplies running in my home 24/7 file and web servers as well as UPS supply's (most likly noisey ones).
Are you hosting an ISP at home?

Well if you really have serious power line noise problems in your audio equipment, you should probably try to solve them at the source first, that's right.

Quote:
I don't recall if I used the same phase (leg) off the breaker panel. I am going to investigate the circuits in the home and try to divide them to keep cleaner loads on the same leg as I have my audio. Put the nosier loads on the other phase (leg).
Why don't you just take a long extension cord or cable drum to a wall outlet somewhere completely different, e.g. where you know your switchers have no influence? This saves you the hassle with shutting down servers!

Do you have the possibility to measure your power line wave form with a scope? That would be helpful. You should compare your actual to your temporary replacement power line for THD+N in conjunction with doing listening tests. Perhaps the power line quality is not an issue as much as you think (e.g. perhaps the noise is coupled in via electric or magnetic fields).

Regards,
Sebastian.
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