Using a DC power supply in place of a AC transformer

[ginetto61]

Hello !
please excuse me for a maybe silly question
I have a dac using an external transformer with out of 12VAC

I have a very good power supply with 12VDC out
Can i try it without problem ?
I think so but i am not so sure
Thanks a lot indeed
Kind regards,
gino

 

[DF96]

Does it assume a floating supply? Is your DC supply floating? Most likely answers are Yes and No, respectively.

Does it assume 12V RMS AC, so there is headroom for DC voltage stabilisation down to 12V DC? Most likely answer is Yes.

My guess is that it probably won't work.

 

[still4given]

12vac rectifies to around 16.5V. Your 12vdc supply is already rectified to 12v.

 

[paulb]

It may use the 12VAC in a half-wave voltage doubler arrangement to get a +/-DC supply, so your external DC supply wouldn't work. You need the schematic to tell.

 

[ginetto61]

Thank you very much indeed for all the valuable advice
Out of curiosity i tried and does not work. I get noise and distortion.
Nevertheless the stock external transformer seems a little weak and cheap (as it must be)
I am going to try a EI 12VAC transformer of better quality like the one in the picture

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

My understanding is that this type of transformers provides a better isolation from noise in the mains (and digital equipment are very sensitive in this regard)
More than normal toroidals
Unfortunately they are heavier and bigger for the same VA
Am i wrong ?
Thanks a lot again
Regards,
gino

 

[still4given]

Looking at the pic you posted, it says 12V 1500mA "USE SUPPLIED PSU ONLY"

Why are you trying to use something else?

 

[Jsixis]

I hope you plan on buying another device if you are going to experiment with the one you own.

 

[nigelwright7557]

It may use the 12VAC in a half-wave voltage doubler arrangement to get a +/-DC supply, so your external DC supply wouldn't work. You need the schematic to tell.

That's how my usb mixer works.
The +ve pulse goes to the +ve supply.
The -ve pulse goes tyo the -ve supply.
With DC only the +ve supply would get charged.
Then the mixer would distort badly.

 

[iggy2k]

you can just ask them for a replacement via this form - Cambridge Audio - DacMagic power supply

 

[ginetto61]

Looking at the pic you posted, it says 12V 1500mA "USE SUPPLIED PSU ONLY"
Why are you trying to use something else?

Hello ! well there is always written this like do not open the unit. Risk of shock !
And so on.
The actual question is ... a transformer with better specs will have a positive impact on the sound of the unit or not ?
I am sure the stock one is cheap and not high quality for simple commercial reasons. It is a cheap dac after all.
And it is even undersized !!! ... Output 12VAC/1,33A !
I was thinking to something like 12VAC/3A of good quality (EI type)
This test will cost me very little. Why not try ?
Kind regards,
gino

 

[ginetto61]

That's how my usb mixer works.
The +ve pulse goes to the +ve supply.
The -ve pulse goes tyo the -ve supply.
With DC only the +ve supply would get charged.
Then the mixer would distort badly.

Thanks a lot for the explanation !
Actually i got distortion. Bad try. I will never do it again
But a trasfo upgrade ... what do you think ?
A good 12VAC/3A unit will cost almost nothing
An it should work greatly
Kind regards,
gino

 

[ginetto61]

you can just ask them for a replacement via this form - Cambridge Audio - DacMagic power supply

Hello ! the original is working ok. It is not damaged.
I want something better
I do not know if this could improve the sound anyway
I mean ... better specs would mean something or not ?
If not why look at the specs ? just go and buy one cheap and go with it
Am i wrong ?
What i am looking for is a better isolation from the mains
To be honest i cannot find this in the specs
The one i intend to use is just great in this respect because we have tested it.
Very very good at blocking noises at high freq
Kind regards,
gino

 

[bbp]

Hello !
please excuse me for a maybe silly question
I have a dac using an external transformer with out of 12VAC

I have a very good power supply with 12VDC out
Can i try it without problem ?
I think so but i am not so sure
Thanks a lot indeed
Kind regards,
gino

I think a 14V DC will work, 12V maybe to low for the internal LDO.
Trust me

 

[DF96]

The actual question is ... a transformer with better specs will have a positive impact on the sound of the unit or not ?

Not. You can reasonably assume that Cambridge Audio supplied the correct transformer. If in doubt, ask them.

 

[ginetto61]

I think a 14V DC will work, 12V maybe to low for the internal LDO.
Trust me

Hello ! actually i measure 14,5 VAC at the trasfo outs.
Maybe with the load this value will decrease ?
The only way to understand would be to look at the schematics
Thanks a lot and regards,
gino

 

[bbp]

Hello ! actually i measure 14,5 VAC at the trasfo outs.
Maybe with the load this value will decrease ?
The only way to understand would be to look at the schematics
Thanks a lot and regards,
gino

Every transformer has a regulation ration, for the output series resistor is exists in every transformer.
So the voltage drop is reasonable.

External pre-regulated DC source for such a device do reduce its hum level. Trust me!

 

[ginetto61]

Not. You can reasonably assume that Cambridge Audio supplied the correct transformer.
If in doubt, ask them

So you think that the quality of the transformer does not have any impact on the sound of this unit ?
Of course the stock one works. I would be surprising if it would not.
In general you can have two parts with the same value, for instance two resistor. Same ohm, same wattage.
One costs 50 times the other.
There must be a reason if not the expensive one would not have market
Unfortunately i cannot open this transformer without destroying the unit
I think they seal also to avoid looking inside.
The key here is better isolation from the mains noise i think
Thanks and regards,
gino

 

[ginetto61]

Every transformer has a regulation ration,
for the output series resistor is exists in every transformer.
So the voltage drop is reasonable.
External pre-regulated DC source for such a device do reduce its hum level. Trust me!

Thanks again but which VDC value ?
My main goal is just to improve better isolation from the mains noise that with digital i think is a key factor indeed.
Maybe i should try a noise filter ?
Regards,
gino

 

[bbp]

So you think that the quality of the transformer does not have any impact on the sound of this unit ?
Of course the stock one works. I would be surprising if it would not.
In general you can have two parts with the same value, for instance two resistor. Same ohm, same wattage.
One costs 50 times the other.
There must be a reason if not the expensive one would not have market
Unfortunately i cannot open this transformer without destroying the unit
I think they seal also to avoid looking inside.
The key here is better isolation from the mains noise i think
Thanks and regards,
gino

Transoformer do affects its sound. I think so.
All the thinks I said above is to tell you that an external DC source for such a Audio stuff will work OK. Not argue about the sound quality.

Best regards
Paul

 

[bbp]

Thanks again but which VDC value ?
My aim is just to improve isolation from the mains that with digital i think is a key factor indeed.
Regards,
gino

A DC higher than 14V, below 17V will be OK.