battery power versus traditional power

[Steve Eddy]

Nobody here seems to have addressed the biggest advantage
of battery operation - the near total isolation from the AC line,
both in terms of the field of a power transformer located near
the circuit and the capacitive coupling (usually through the
transformer) to the AC line. This capacitance can allow quite a
bit of crap into the circuit

Yup. And just as importantly I think, between circuits. Or rather between components. Unless what gets capacitively coupled to the local ground by way of the power transformer is absolutely identical in terms of magnitude and phase, it ends up at the next component's input due to the IR drop across the ground connection between the two components.

The former is addressed by moving the transformer away, but
it's tougher to get rid of the latter, which is substantial. With
batteries, this issue goes away.

But no matter how far away you move the transformer, crap on the AC line still capacitively couples through the transformer to the local signal ground.

AC power is rather hilarious when you really think about it. Especially if you take it "all the way."

You get yourself a dedicated line using specialty AC wiring. This gets hoold up to specialty AC outlets which then go to specialty power cords. Then come the various specialty balanced transformers, line filters and conditioners, regenerators, etc. Then on to some more specialty power cords. And that's all before we even get to the power supply proper.

And even if we had a perfect AC power source, that perfect AC is of no use. We need DC for the circuit.

So we take the AC and chop it up into half sine pulses. Then run that into some amount of capacitance to try and smooth it out. Which is about as far as most power amp power supplies go but if you want to get closer to actual DC, you need to add some inductance. To get closer still, some active voltage regulation circuitry.

An externally hosted image should be here but it was not working when we last tested it.

se

 

[medum]

I'm honoured by the visit to my humble thread by Mr. Pass and Mr. Eddy.

.............the near total isolation from the AC line,
both in terms of the field of a power transformer located near
the circuit and the capacitive coupling (usually through the
transformer) to the AC line. This capacitance can allow quite a
bit of crap into the circuit

The former is addressed by moving the transformer away, but
it's tougher to get rid of the latter, which is substantial. With
batteries, this issue goes away.

The Charge circuit will be placed far away from vital electronics. And the charger wil be turned down when playing.

................
And even if we had a perfect AC power source, that perfect AC is of no use. We need DC for the circuit.
................

It seems, that I must get out and buy 6 car batteries for my power amp. I think, that Jean Hiraga did that when he made the Monster, didn't he?
If I went "all-the-way", should I use only big caps for filtering or ....

 

[john curl]

I agree with both Nelson and Steve in this case. Batteries are best, all else being equal. However, batteries are expensive to maintain and replace. Trust me on this, they just don't last, and you have to replace them, far earlier than any AC supply. This is a hassle, expensive, and time consuming as well. Think about it. The battery develops problems, usually a cell short. The voltage drops below normal. You have to replace the battery, but you also have to turn the old one in for recycling.

 

[ALW]

There is another way

I find it surprising that John Curl rates batteries highly. They are far from noise-free and far from linear.

Also, without mentioning specific cell chemistries it's a highly unspecified recommendation, different chemistries exhibit different characteristics.

There are also ways fo acheiving the total reverse isolation that batteries can offer, from a mains-powered PSU. The 'Never Connected' supplies (http://www.never-connected.com) acheive this and from the experience of a number of manufacturers and reviewers, are capable of producing improvements that are hard to obtain by other means.

This may also be of interest, from a fellow member here, this has some measured analysis of different cell chemistries: -

http://www.tnt-audio.com/clinica/regulators_noise1_e.html

In my experience I've never heard a battery supply that sounds close to a well-implemented mains supply, despite the obvious daftness of the process. I've heard a number of devices recently using very high frequency switching supplies, which sounded truly astonishing and unlike what I had expected.

In concept at least there would seem to be some sense in a PSU that can charge faster than the demands placed upon it, unlike a conventional 50 (60) Hz supply. Some cell technologies, on the other hand, exhibit a very slow (chemical) response to load (e.g. Pb-based cells). This narrow bandwidth wouldn't normally be considered a good thing in an audio PSU.

Andy.

 

[Steve Eddy]

However, batteries are expensive to maintain and replace.

How are they expensive to maintain? The only "maintenance" is recharging.

Trust me on this, they just don't last, and you have to replace them, far earlier than any AC supply.

The same can be said of vacuum tubes, particularly power tubes.

This is a hassle, expensive, and time consuming as well.

The same can be said of vacuum tubes, particularly power tubes.

Think about it. The battery develops problems, usually a cell short. The voltage drops below normal. You have to replace the battery, but you also have to turn the old one in for recycling.

That's not a huge problem. There is a fairly mature recycling infrastructure in place for that.

Certainly batteries demand a bit more from the end user, but they can also return more in the end.

So it just depends on what one's priorities are.

If Plug-N-Play has an edge over sonics, then an AC supply would be the way to go.

se

 

[Steve Eddy]

Re: There is another way

I find it surprising that John Curl rates batteries highly. They are far from noise-free and far from linear.

The same thing can be said of many highly regarded electronics. SET power amplifiers for example.

If what sounds best to every individual was simply a matter of the best objective specs and measurements, then audio would be nothing but a numbers game.

However there's a great diversity among individuals and what might sound best to one individual isn't what necessarily sounds best to another individual.

se

 

[jcarr]

Andy:

>In my experience I've never heard a battery supply that sounds close to a well-implemented mains supply<

Subjectively this has been my experience as well. And I _have_ designed and built preamps and phono stages with both battery power and various forms of mains power. In fact, one of the phono stages currently in my audio system is powered by an integrated recharger-and-battery solution.

The battery-powered phono stage certainly sounds better than a phono stage with a comparatively simplistic mains-based solution, but at least in my experience the battery design has not been able to keep up with the more sophisticated mains-powered designs that I have been working on.

In any case, the outcome will depend on the sophistication of the total design, and therefore your own capabilities as as designer. Rather the expending energies on searching for magic words like "batteries" or "abacadabra", personally I find it far more productive to study more, work harder, and improve my own capabilities as a designer.

my 2 cents, jonathan carr

 

[SY]

Andy, I haven't actually tried battery supplies myself- the necessary pack to get to the 500V B+ I use would be rather unwieldy. And I would have been skeptical about your noise comment until I saw the results that Werner Ogiers put up on his website. I went back and looked at some batteries I had on hand (9V jobs) and, whaddaya know, he's right. They're noisier than a moderately good regulator.

As a former member of The Electrochemical Society, I shouldn't be surprised, but I was. Embarrassing.

 

[Nelson Pass]

Re: There is another way

I find it surprising that John Curl rates batteries highly. They are far from noise-free and far from linear.

I've heard a number of devices recently using very high frequency switching supplies, which sounded truly astonishing and unlike what I had expected.

1) They can be bypassed, filtered, and even actively regulated.

2) Very high frequency transformers have very low capacitance
from primary to secondary.

 

[Steve Eddy]

Andy, I haven't actually tried battery supplies myself- the necessary pack to get to the 500V B+ I use would be rather unwieldy. And I would have been skeptical about your noise comment until I saw the results that Werner Ogiers put up on his website. I went back and looked at some batteries I had on hand (9V jobs) and, whaddaya know, he's right. They're noisier than a moderately good regulator.

Which site's that?

ALW posted some noise plots here too some time back.

se

 

[paulb]

Nobody here seems to have addressed the biggest advantage
of battery operation - the near total isolation from the AC line,
both in terms of the field of a power transformer located near
the circuit and the capacitive coupling (usually through the
transformer) to the AC line. This capacitance can allow quite a
bit of crap into the circuit

For home DIYers, I think the simplest solution that gives the best results will be batteries. I'm sure there are better, more complex solutions.
So if I have a 36V battery array, and a supply splitter to give me a ground reference, what about a double capacitance multiplier afterwards and no regulators?

 

[GRollins]

Paul,
For all their advantages, the thing that annoys me about batteries is that the voltage slowly sags. Granted, most circuits don't come unglued if you drop the voltage a bit, but given that some of the circuit parameters will deteriorate as the voltage drops (e.g. distortion), I'd like to use a regulator to assure that I was getting the performance I saw on the bench.

Grey

 

[SY]

Which site's that?

ALW posted some noise plots here too some time back.

se

Posts here under the handle "Werner." Has a "www" button on his profile. He was posting in one of the 317 regulator threads form the past few days with links to this specific data.

I'll let you do the member search, I've got to go wake my kid up.

 

[Nelson Pass]

For all their advantages, the thing that annoys me about batteries is that the voltage slowly sags.

Regulation after batteries is no problem, and if you want to
get past the problems that regulators produce, you bypass/
filter the crap out of their output.

 

[hifi]

you bypass/ filter the crap out of their output

Something rarely seen in diyaudio..wouln´t you say? *joke*

 

[mercator]

This is turning into a great thread, not least because of the respect I have developed for many of the respondents (on both sides of the debate) from reading their contributions to this site.

It seems to me that if the cost and size of the batteries can be managed, then regulators and filters should make it possible to create a far smoother dc supply. Since my interest is for a preamp, I guess I would be surprised if there was an issue of voltage sag due to power demand, assuming I select suitably large units.

Dave

/still shopping for batteries, am I crazy?

 

[medum]

Welcome to Mr. John Curl and many other new visitors -
Thank you for a lot of information, everybody!

...magic words like "batteries" or "abacadabra...

You're right about "abacadabra", but to me "batteries" are not just a magic word. It's just hardware in my toolbox.

Mr. Curl -
I'll be very careful to make my batteries last for a long term. They'll be kept in their own box with only a small amount of heating electronics (charging transformer in a seperate box). And I'll charge the SLA's very gentle using a modern electronic charger (Velleman kit K 8012). I've been told, that SLA's properly treated could last for at least 5-6 years. And after that I'll spend my 70-100 $ and by 4 new Panasonics. I don't find that overwhelming.

Jørn

 

[Steve Eddy]

They'll be kept in their own box with only a small amount of heating electronics (charging transformer in a seperate box).

Just make sure the box is well ventilated.

se

 

[Werner]

saw the results that Werner Ogiers put up on his website. I went back and looked at some batteries I had on hand (9V jobs) and, whaddaya know, he's right.

Wow. The last thing I wanted to become is the resident battery expert. I only did some simple measurements in an uncontrolled and unscientific way and posted them, with as sole intention to provoke thought and perhaps move some people into doing more measurements and publish those. That's all.

For those still searching, the article is here:


http://www.tnt-audio.com/clinica/regulators_noise4_e.html


But anyway, with the EU WEEE directives effectively outlawing lead and cadmium from 2006 on and the USA following soon after (?) this discussion gets a decidedly academic taste.

 

[medum]

Just make sure the box is well ventilated.

se

The box will have bottom and sides made of masonite with a lot of holes-

Jørn