Serge Auckland wrote:

I don't understand what you hope to achieve by changing the transformer.
Apart from the inconvenience of the on-off switch, what is it about the
present arrangement that is inadequate? 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, and position it where you can conveniently reach
it and switch it off when not in use? A new transformer won't be
significantly more efficient than what you have. A bigger one will be
less efficient at lower draws, and as mentioned above, will have an
increased voltage and stress the DAC components more. If you're
concerned about the total carbon footprint of each item, then throwing
away something existing and buying something new will increase the total
carbon footprint, and you won't recover this unless the new one is a lot
more efficient than the old, which is unlikely.

The on/off switch is my main complaint, but I can't help feeling like
the power supply was done by Cambridge Audio on the cheap. For instance,
sometimes the sound drops out for a fraction of a second when I switch
my CRT TV on. I refuse to believe that the design of this PSU cannot be
improved upon.

I am now thinking of moving the transformer part into something like an
old computer power supply which conveniently already has a physical
on/off rocker switch. There must be some modification I can make to at
least improve the sound a bit. Adding capacitors?

Seems you're making this much more difficult than it needs to be.

I seem to subconciously choose the hard way in life!

David Looser wrote:
"Anton Gÿsen" wrote in message
...
David Looser wrote:
Transformers are designed to produce the nominal output voltage at full
current draw, when under-loaded the output voltage is higher, typically
10-15% higher. This may not damage your DAC, but it will increase the
heat
dissipation within the DAC and increase the stress on the internal
components. In addition an over large transformer is, well, over large;
bigger, heavier and more expensive than you need. Oh, and it will be less
efficient than one of the correct size.
OK so a lower rated transformer would be more appropriate?

Yes, 20VA.

The best I can find is 30VA.

So... when my amplifier for example (which has a toroidal core
transformer) is operating at low volume and therefore drawing a low
current it is stressing the components in the way that you describe?

Indeed, and the amplifier designer will have taken that into account when
specifying components. A DAC, on the other hand, takes a more or less
constant load so the designer will not have had to allow for load current
variations in his design, or the use of an unnecessarily large transformer.

Point taken! Makes sense now.

And what makes you think it would be any more efficient that what you
already have?
Wikipedia reckons they're more efficient than the standard type of cheap
transformers (the name of which escapes me). They seem to be the
audiophile transformer of choice.
They are *slightly* more efficient (if correctly rated). But most of the
total inefficiency is due to the rectifier/regulator part of the PSU,
which
is inside the DAC. Toroidal transformers also have a lower external
magnetic
field, but if the transformer is external to the DAC that isn't
important.
The DAC does get rather warm but I thought that was the DAC ICs.

Much of it will be due to the rectifier and regulator.

Yes I'll take your word for it. I know what you mean because I've seen
the heatsinks they use on voltage regs.

The
"wall wart" PSU gets warm although it is encased in plastic.

It will, it's not a problem.

It's inefficient!

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


The on/off switch is my main complaint, but I can't help feeling like
the power supply was done by Cambridge Audio on the cheap. For instance,
sometimes the sound drops out for a fraction of a second when I switch
my CRT TV on.

Not necessarily due to mains wiring coupling, even if it is changing to the
transformer will *not* help with that. Try an external mains filter (with a
switch!).

David.

"Anton Gÿsen" wrote in message
...

The
"wall wart" PSU gets warm although it is encased in plastic.

It will, it's not a problem.

It's inefficient!

Even toroidal transformers get warm in use! If you are that bothered by
"efficiency" just leave the DAC permanently unplugged, then it will never
get warm :-)

David.

David Looser wrote:
"Anton Gÿsen" wrote in message
...
The
"wall wart" PSU gets warm although it is encased in plastic.
It will, it's not a problem.
It's inefficient!

Even toroidal transformers get warm in use! If you are that bothered by
"efficiency" just leave the DAC permanently unplugged, then it will never
get warm :-)

Truth!

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


The on/off switch is my main complaint, but I can't help feeling like
the power supply was done by Cambridge Audio on the cheap. For instance,
sometimes the sound drops out for a fraction of a second when I switch
my CRT TV on.

Not necessarily due to mains wiring coupling, even if it is changing to the
transformer will *not* help with that. Try an external mains filter (with a
switch!).

I'd like one but can't afford one at the moment.

I'm still convinced that this PSU can be improved in some way, shape or
form.

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


The on/off switch is my main complaint, but I can't help feeling like
the power supply was done by Cambridge Audio on the cheap. For instance,
sometimes the sound drops out for a fraction of a second when I switch
my CRT TV on.

Not necessarily due to mains wiring coupling, even if it is changing to
the
transformer will *not* help with that. Try an external mains filter (with
a
switch!).

I'd like one but can't afford one at the moment.

I'm still convinced that this PSU can be improved in some way, shape or
form.

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.

S.
--
http://audiopages.googlepages.com

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


The on/off switch is my main complaint, but I can't help feeling like
the power supply was done by Cambridge Audio on the cheap. For instance,
sometimes the sound drops out for a fraction of a second when I switch
my CRT TV on.

Not necessarily due to mains wiring coupling, even if it is changing to
the
transformer will *not* help with that. Try an external mains filter (with
a
switch!).

I'd like one but can't afford one at the moment.

If you can afford a new transformer, you can afford a filter!


I'm still convinced that this PSU can be improved in some way, shape or
form.

As a rule equipment is designed to a constant level of build quality &
performance. If one part is cheap and shoddy then so is the whole thing.
Bearing in mind what you said about audio drop-out when you switch on your
TV, I suggest that the DAC is no better than it's transformer.

David.

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


The on/off switch is my main complaint, but I can't help feeling like
the power supply was done by Cambridge Audio on the cheap. For instance,
sometimes the sound drops out for a fraction of a second when I switch
my CRT TV on.
Not necessarily due to mains wiring coupling, even if it is changing to
the
transformer will *not* help with that. Try an external mains filter (with
a
switch!).
I'd like one but can't afford one at the moment.

If you can afford a new transformer, you can afford a filter!

Apparently so.

I'm still convinced that this PSU can be improved in some way, shape or
form.

As a rule equipment is designed to a constant level of build quality &
performance. If one part is cheap and shoddy then so is the whole thing.
Bearing in mind what you said about audio drop-out when you switch on your
TV, I suggest that the DAC is no better than it's transformer.

The DAC sounds great for £200. I'm happy with it (transformer aside).

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?

I get drop-out from the DAC when flicking the mains switch on my Cyrus
tuner, and it's plugged into a different gang plug from the DAC!