Where you hifi gets it power from

People always say that its important to have good mains to realise your systems full potential. So why is it that no hifi's are battery powered as this way the power is totally clean? anybody have any ideas on this?

Chris

 

cos its a bloody pain to keep recharging them, and amplfiers run at more than 30 volts. Valves, typically 300v +. Find a battery to do that.

I have a valve dac that has batteries in it, to bias the valves, 2 volts or so, and am a total convert, I shall do this with every valve pre and phonostage I get.
Far superior to cathode resistor or led biasing. As big a difference as a mains filter.

1 or 2 commercial things are, pink triangle had a battery psu for a dac, there may be others...

 

there is a naim battery psu here : http://www.audio42.com
aparently there were 'response' issues with old lead / acid battery technology which are eliminated or lessened with newer technology which put a lot of manufacturers off. perhaps it's time they revisited it for preamps and source output stages although from what i understand the never connected jobbie does a similar job as a battery without a lot of it's problems.
cheers


julian

 

Batteries cant deliver power on tap like the mains, apparently

 

penance,
that was aparently with lead acid batteries. newer technology such as li/ion or li/polymer are aparently much better in this respect.
cheers

julian

 

Technics did do a preamp in the late 90s that ran off a PP3 9V battery (Su-C1000 I think).

The kind of battery you'd need for any significant power amp though would be phenominal. It would need a capacity of tens if not hundreds of Amphours at a significant voltage (100V or so for a ~150W amp). For example, this would be about 16 car batteries. (assuming 50Ah per battery, 12V. 8 in series (to give 96V) and another 8 parallel (to double capacity to 100Ah).

 

There's Final Music, of course. And I think Rowland may still have something. As others have said, the quantity of battery needed is not trivial. These things always seem to end up somewhat expensive. Then there's the problem that batteries always seem to die at the most inconvenient times.

Another approach to mains quality, which seems to me to have more legitimacy than replacing the last six feet of cable between you and the power station, is mains regeneration (built-in to some Levinson stuff, maybe others - and stand-alone by PS Audio, and others). Again, it's costly.

 

Apart from the charging/battery life issues, the power is not as clean as you might expect. Batteries measure well under no load, but once you start drawing current, all sorts of random noise spikes appear, because of the chemical conversion on demand. The noise levels are somewhat higher than even a simple but well-sorted mains supply. Batteries also have higher internal impedances, which compounds the problem. There's some good discussion on the details in teh archives of www.diyaudio.com

With that in mind, and the need to provide a charging supply, reliance on batteries rather falls into the 'why bother?' category.

 

Amazon TTs run from battery power - sound great as well as being very good value..
There's also a make of hifi from Singapore (whose name I can't remember) which is all run by batteries, not cheap though.

 

There are also the wonderfully-bonkers Final amplifiers: www.finallab.com from Japan.

 

didn't dnm have some early kit that ran from batteries ?

plus of course the early mission 776 preamp ran from batteries.
"In 1981 came the Mission 776, the world's first DC-powered pre-amplifier, and the 777, the fastest MOSFET power amplifier of its day. "

 

that is, without doubt, the ugliest bit of kit ever.
looks like something the local skanks would prop yer wheels hubs on overnight.

 

Also, there's options like "virtual batteries" - check the Never Connected Power Supply as raved about a couple of months ago in HiFi+..
However, if you ask, say, JJ at SOM he'll tell you you're wasting money with mains regeneration a la PS Audio/Isotek etc.. And my amp's instruction book tells you not to use it either, as it would most likely restrict the amount of current the amp could draw..

 

Leonard,

I wouldn't always take what the manual says as granted sir
I'd quite happy to prove that with your recent purchase at any time if you wish. Won't be using either of the 2 you mentioned either.
The N/c are rather good, you were listening to 5 of them the other day, we had a hand in the later development and beta testing.
They are capable of removing upto 96% of all mains bourne interferance, with the transformer being 'never connected' to the equipment its attatched to. Simple but rather effective

 

When I'm minted again, and after I've bought the pre-amp (thinking about Levinson 320s on special as well as the Burmester at the mo) I'll be well up for a visit - mebbe my old pro-audio prejudices can be swept aside

 

That mission is very clever design, the front panel reads ...mission