"Eeyore" wrote in
message
Arny Krueger wrote:

"Eeyore" wrote

He's in the UK though.

Yes, but you've got to have power line fluctuations, and
the slings and horrors of field operations.

You don't really get power line fluctuations of any note
in the UK. Better infrastructure you see.

It is not lost on me in the least, that using twice the mains voltage means
you get equal line regulation (as a percentage) with only 25% as much
copper. Also, 3 phase power seems to be far more widely distributed.

Advantage: Europe as you got to rethink distributing electrical power while
you were rebuilding your infrastructure after that war during the 1940s.
We're just not so good at blowing ourselves up, so we have a lot of stuff
still in service from the 'teens, twenties, and thirties. My house, for
example.

I even figured that out about 40 years ago when I lived in Germany, and
noticed that they were wiring buildings with what seemed to be doorbell wire
with heavy insulation. Then I did the math... ;-)

"Eeyore" wrote in
message
Arny Krueger wrote:

"Eeyore" wrote
Adrian C wrote:

Use a PC switchmode power supply?

To make it sound REALLY crappy ?

I've run a lot of audio gear off of PC power supplies
without bad things happening.

Car audio stuff is pretty happy running off of the 12
volt lines, which have pretty impressive current ratings.

Car power rails are massively noisy so if course they're
designed to cope with that.

But the 12 volt rails in PCs aren't all that bad.

I just probed the major DC lines that supply the hard drives in an
operating PC with my Fluke 85. As you probalbly know, the Fluke 85 is not
one of those meters that rolls off jst below 1 KHz like many, but is pretty
flat up to 100 KHz or more. It's less than 0.1 dB down at 20 kHz.

The 5 volt supply line had less than 1 mv of broadband AC on it.

The 12 volt supply line had less than 4 mv of broadband AC on it.

I've seen a lot of switchmode supplies in DVD players
and the like.

So ? You can make an SMPS very quiet if you know how. I
do for example.

My point is that:

Just because its a switchmode supply, it doesn't necessarily create problems
with sonics.

The classic 300 watt ATX PC power supply is not all that shabby.

"Eeyore" wrote in
message

NEVER put capacitors across switches without a serious
watty R of about 100 ohms in series too.

Agreed.

I've seen the results. DRAMATIC barely explains it.

Not only that, but without the R you might be creating a high-Q resonant
circuit that actually makes the arcing of the switch appreciably worse.

Ever seen a capacitor literally EXPLODE and shower the
internals with metallised foil ?

No scare stories needed - a carefully-chosen series resistor generally makes
the bypass in *more* effective at reducing EMI when the switch is operated.
I daresay that the possible high currents with a high-A circuit sets the
stage for the capacitor failure in some cases.

Arny Krueger wrote:
"Eeyore" wrote in
message

NEVER put capacitors across switches without a serious
watty R of about 100 ohms in series too.

Agreed.

I've seen the results. DRAMATIC barely explains it.

Not only that, but without the R you might be creating a high-Q resonant
circuit that actually makes the arcing of the switch appreciably worse.

Ever seen a capacitor literally EXPLODE and shower the
internals with metallised foil ?

No scare stories needed - a carefully-chosen series resistor generally makes
the bypass in *more* effective at reducing EMI when the switch is operated.
I daresay that the possible high currents with a high-A circuit sets the
stage for the capacitor failure in some cases.



Products like the Quencharc come to mind

http://www.futureelectronics.com/en/...4M06QC100.aspx

It incorporates a 100 ohm resistor in series with a capacitor.

d

Eeyore wrote:

Agreed. Especially with his wonky mains wiring.

What makes you say that when my mains voltage is right in the middle of
the specification for European mains (220-240V). ISTR you said you were
getting 240V+?

Jim Lesurf wrote:

I was thinking of individual beads on each of the wires, followed (i.e. on
the DAC side) by an RF cap between the wires. Having just a series ferrite
increases the RF impedance and losses along the wiring, but that doesn't
always ensure good suppression. Indeed, might act as an antenna in some
situations. :-)

If the ferrite is something like a clip-on 'box' or a loop you can unthread
without damaging the wires it might be worth experimenting and seeing if
taking it off makes any difference. But if you aren't bothered by the
intereference I'd recomment not bothering if it would mean haveing to
rewire at all. If the interference is mains conveyed a filtered
distribution block will probably help, and will give you a mains switch if
you choose the right design. See something like the CPC catalogue for
examples.

I don't think I'm getting much interference, there is little or no hiss
from the DAC so I'll take your advice and not bother.
I will have a look at the CPC catalogue though, cheers.

Eeyore wrote:

Anton Gÿsen wrote:

Phil Allison wrote:

but we are considering what's inside this box:
http://www.cambridgeaudio.com/summary.php?PID=320

** Huh ?

No link to any " box " there - ****head.
You have to create a session by selecting a country, then try accessing
the link again and it will bring you do the DacMagic page.

Uh ?

1) Click the link that was given
2) Select a country from the list
3) Click the link again

"Phil Allison" wrote in message
...

"David Looser"
"Serge Auckland"

And yet my Black & Decker drill and a Weller solder gun both have just a
capacitor across the mains switch. Both date from the 1970s (I'm not
hard on my tools) so perhaps rules or good practice has changed since
then.


Special capacitors were made for that job which have a high internal
resistance.


** That is ABSOLUTE CRAP !!!!!!!!!!!!!!!!!!

Just demonstrating your ignorance again are you Allison? Just because
you've never heard of them doesn't mean they don't exist. As it happens I've
used them in various pieces of kit over the years, still got some in the
spares box somewhere.

David.

Eeyore wrote:

Anton Gÿsen wrote:

Serge Auckland wrote:
"Anton Gÿsen" wrote
Eeyore wrote:
Anton Gÿsen wrote:

I have a capacitor rated 0.22 microfarads 250 V AC which came out of a
broken power tool (it was wired in series with the mains supply IIRC) -
would that do?
GOD, you're thick. You shouldn't be allowed ANYWHERE NEAR electricity.
Keep spreading the love, Graham.
What I'm sure Graham meant to say was that the capacitor you have was
designed to go across the mains switch of the power tool as a
suppressor. It would only be in series with the mains supply when the
switch was off, and be shorted out by the switch when switched on. I
would not want to use capacitor rated at only 250 volts on the mains, I
would prefer one rated at least 350v.
Thanks.

And it MUST be 'X-rated'. Don't expect to find it in Maplin.

Only X and Y rated caps are approved for use in mans application.

X for 'across the mains'
Y (pref Y2) for 'mains to ground'

See BSEN 60065.

Why couldn't you have said that in the first place?

"Dave Plowman (News)" wrote:

Phil Allison wrote:
"Eeyore"

http://www.maplin.co.uk/Module.aspx?ModuleNo=13156

I don't see any safety approval mark.

** Such switches are approved for use in 2 wire circuits - ie lamps.

So you cannot use one to switch an extension lead - which MUST be 3
wire by law.

More ******** from our resident clown.

Two core extension leads are available from any shed. Designed for use
with suitable appliances.

As Phyllis often says, called double-insulated or 'Class II'.

Graham