Phil Allison wrote:
"Eiron"
Assuming that inside the DAC is a bridge rectifier, a big capacitor, and
a regulator, it should be just as happy with a DC input as with 12v AC.

** Very bad assumption.

The main reason makers use AC output adaptors instead of DC ones is to
generate MORE than one DC voltage rail inside the device.

Two diodes and two filter caps gives +/- 18 volts DC from 12 volts AC.

More diodes and more caps can increase the number of rails even further.

Won't work with DC - see:

http://hyperphysics.phy-astr.gsu.edu...c/voldoub.html

That's all very well and I'm sure you often teach your grandmother to
suck eggs
but we are considering what's inside this box:
http://www.cambridgeaudio.com/summary.php?PID=320

--
Eiron.

Arny Krueger wrote:

It is common to build regulated power supplies for 120 volts that work well
when the power line is 90 or 100 volts. For example a power transformer for
a power supply that puts out 12 volts might be based on a 16 or 18 volt
transformer. The voltage regulator will take up the slack most of the
time.


When modders get in and change the internal circuitry about, say trying
upgraded opamps, then the power supply is the next natural target for
the upgrade.

The following document, for my dac-in-the-box is one approach of said
improvements (I've not tried this - I'm happy as the item is) where the
proposer has also had to upgrade the voltage regulators and then find a
better PSU. And suffer more regulator heat dissipation.

http://www.audioasylum.com/images/DITBMOD.pdf

--
Adrian C

"Arny Krueger" wrote in message
...
"Anton Gÿsen" wrote in message

Anton Gÿsen wrote:

The power input on the DAC requires 1.5 amps AC.

Forgot to mention, it's 12 volts.

Designing power supplies is a cookbook process.

The transformer you linked to is vast overkill, but also inadequate. You
don't need a 6 amp transformer for a DAC. Even 1.0 amp might be overkill.

If you want to build a power supply that puts out 12 volts, you will
probably need a power transformer that puts out more than 12 volts. The
extra voltage will be taken up by losses, particularly in the regulator.

You must have missed the "AC" in the OPs post.

David.

Anton Gÿsen wrote:

doesn't have a physical
on/off switch so it's constantly drawing a current unless you unplug it,
and I like to save evergy where I can.

I've got a Pioneer 'audio digital timer' in my Hifi stack. It's original
use is switching the mains supply to my cassette, tuner and minidisc
decks for autostart unattended recording. However, I've also added the
power supply for my turntable, it's preamp and the dac-in-the-box, all
wall warts.

So, to turn on all of those - i just hit the timer over ride button.

--
Adrian C

David Looser wrote:

You must have missed the "AC" in the OPs post.

Very dangerous to mis the 'AC' in the OPs post. The society misfit who
posts in his underwear and socks will be knocking the rum bottle back to
start screaming again.

--
Adrian C

In article ,
Phil Allison wrote:

"Dave Plowman (Nutcase)"
Phil Allison

** You cannot legally build your own AC "plug pack" - such items
require specially design transformers and must be made and ** agency
approved ** to meet the Class 2 safety standard.

You are familiar with the regs in every country, are you?


** The asinine, ****wit OP stated he had no interest in any safety laws,
whatever.

Quite the reverse. But I doubt you know all the wiring regs in your own
country - let alone others. And since these vary widely applying bits from
one to another is anything but 'safe'.

So maybe he lives on another planet.

Lets hope he goes STRAIGHT to HELL real soon

- and meets up with YOU.

Having problems with that caps key again?




.... Phil

--
*You sound reasonable......time to up my medication

Dave Plowman London SW
To e-mail, change noise into sound.

"Anton Gÿsen" wrote in message
...
Serge Auckland wrote:

A mains filter will cost a few pounds/euros. You're not thinking of an
audiophile one are you? That's a £€5 part in a £€ 50 box with a £€ 1000
price tag.

I can only find the audiophile ones. Would you kindly show me where I
can get one a lot cheaper than that?

http://cpc.farnell.com/FT00727/compo...ts-fe-sc-ca-sw

£ 3.63 including VAT.

You just need to wire that to the plug on your DAC or to the item which
causes the glitch, or just to a plug and plug it in to the mains strip the
DAC is on or the offending item . I had the same problem with a fridge many
years ago, and one of these fixed the problem perfectly.

S.

--
http://audiopages.googlepages.com

Jim Lesurf wrote:

Eeyore wrote:
Serge Auckland wrote:

If you want to add an on-off switch, then why not make a small mains
extension, and put a torpedo switch near the socket

I think 'torpedo' switches are now illegal...

That seems unlikely. I bought one a few weeks ago, and IIRC the CRC leaflet
I just got advertises them.

Crikey !

Care to give a link ? I wouldn't touch one with a bargepole !

Graham

"Dave Plowman (News)" wrote:

Phil Allison wrote:
I am wishing to build a replacement transformer for my Cambridge Audio
DacMagic DAC (the new one that's just come out). I am unhappy with the
original PSU because it is inefficient and doesn't have a physical
on/off switch so it's constantly drawing a current unless you unplug it,
and I like to save evergy where I can.

** You cannot legally build your own AC "plug pack" - such items
require specially design transformers and must be made and ** agency
approved ** to meet the Class 2 safety standard.

You are familiar with the regs in every country, are you? Or just spouting
your usual negative bile?

Just about every country now.

And he's right. Look up BSEN60065 (specifically for the UK) or IEC 60065 (in
English and French) for worldwide use. It'll cost though.

I have a slightly old copy right here. Plus I've been a 'standards expert' for
over 20 years, starting at Neve.

Graham

Eeyore wrote:

Jim Lesurf wrote:

Eeyore wrote:
Serge Auckland wrote:
If you want to add an on-off switch, then why not make a small mains
extension, and put a torpedo switch near the socket
I think 'torpedo' switches are now illegal...
That seems unlikely. I bought one a few weeks ago, and IIRC the CRC leaflet
I just got advertises them.

Crikey !

Care to give a link ? I wouldn't touch one with a bargepole !

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

--
Eiron.