The newest version of the Cambridge Audio DacMagic that is...
I just went to unplug the PSU from the socket, and the top came off! It is an AC PSU so contains only a transformer, nothing else at all.
Rated 230V/50Hz @ 150mA --> 12V @ 1500mA 18VA
It was plugged into a 6-way power strip, with plenty of space around it and no other 'wall-warts' next to it, yet the plastic that the screws go into had become brittle, with signs of melting in various places.
It's been plugged in 24/7 since last December, although I do not leave the DAC powered on all the time, only when I use it.
The transformer inside was very hot. The laminations too hot to touch for more than a few seconds even after the PSU had been unplugged for 10-15 minutes.
I do not know at this stage if the DAC has some kind of fault whereby it is drawing too much current, or if the PSU is simply not man enough for the job. My DAC does get rather warm when it's been on for a few hours.
I just did some tests with my multimeter, and note that the mains is 10% over the 230V.
AC mains (I'm in UK): 249V AC
Output (unloaded): 15V AC
Output (DAC on):14.5V AC
Load current (DAC on but not playing): 600mA
Load current (DAC playing from SB3): 700mA
I'm going out shortly to buy one of these:
Maplin 12VAC 3A PSU
People have said the DAC sounds better with this PSU anyway.
Small review of PSU
Hopefully the voltage under load won't be any higher, as this will be dumped straight into the regulator heatsinks inside the DAC making it run hotter of course.
Check your own PSUs!
DacMagic owners in other parts of the world will have been supplied with different PSUs of course.
I just went to unplug the PSU from the socket, and the top came off! It is an AC PSU so contains only a transformer, nothing else at all.
Rated 230V/50Hz @ 150mA --> 12V @ 1500mA 18VA
It was plugged into a 6-way power strip, with plenty of space around it and no other 'wall-warts' next to it, yet the plastic that the screws go into had become brittle, with signs of melting in various places.
It's been plugged in 24/7 since last December, although I do not leave the DAC powered on all the time, only when I use it.
The transformer inside was very hot. The laminations too hot to touch for more than a few seconds even after the PSU had been unplugged for 10-15 minutes.
I do not know at this stage if the DAC has some kind of fault whereby it is drawing too much current, or if the PSU is simply not man enough for the job. My DAC does get rather warm when it's been on for a few hours.
I just did some tests with my multimeter, and note that the mains is 10% over the 230V.
AC mains (I'm in UK): 249V AC
Output (unloaded): 15V AC
Output (DAC on):14.5V AC
Load current (DAC on but not playing): 600mA
Load current (DAC playing from SB3): 700mA
I'm going out shortly to buy one of these:
Maplin 12VAC 3A PSU
People have said the DAC sounds better with this PSU anyway.
Small review of PSU
Hopefully the voltage under load won't be any higher, as this will be dumped straight into the regulator heatsinks inside the DAC making it run hotter of course.
Check your own PSUs!
DacMagic owners in other parts of the world will have been supplied with different PSUs of course.
Just found that the transformer gets too hot to touch, even when plugging it in from cold, without a load attached.
How can that be?
How can that be?
Just to update on the Maplin PSU...
Runs luke-warm, and output voltage is 14.9VAC with no load, dropping to 14.6VAC under load (with 250V input), so there are no compatibilty problems with this unit as a replacement for the wall wart.
It's quite a bit bigger and weighs much more.
I could well be imagining it, but it sounds quite a bit tighter and smoother. More listening tomorrow.
More importantly, it won't burn the house down!
Runs luke-warm, and output voltage is 14.9VAC with no load, dropping to 14.6VAC under load (with 250V input), so there are no compatibilty problems with this unit as a replacement for the wall wart.
It's quite a bit bigger and weighs much more.
I could well be imagining it, but it sounds quite a bit tighter and smoother. More listening tomorrow.
More importantly, it won't burn the house down!
Great response from Cambridge - instant response to an email. You don't get that too often these days!
The guy's office is at London Bridge and I go there everyday so I'll drop it off at the London Bridge Richer Sounds tomorrow. He'll pop around and collect it from there, as he is very concerned and wants to see it. I have found evidence on the net that I'm not alone in this.
I noticed that Ru$$ Andrew$ has a replacement PSU and amusingly this reviewer of it had a similar experience with the original PSU:
The guy's office is at London Bridge and I go there everyday so I'll drop it off at the London Bridge Richer Sounds tomorrow. He'll pop around and collect it from there, as he is very concerned and wants to see it. I have found evidence on the net that I'm not alone in this.
I noticed that Ru$$ Andrew$ has a replacement PSU and amusingly this reviewer of it had a similar experience with the original PSU:
Attachments
It's the same PSU as they use for the 540/640p phonostages. So it's well used in the field. The 3A Maplins unit makes no discernible difference to the phonstage in a blind test.
however replacing the internal monolithic voltage regulators does......
however replacing the internal monolithic voltage regulators does......
The DAC will be a much tougher assignment than the phono stage. It definitely does make a significant audible improvement on the DM. I was sceptical (expecting no improvement) but I was wrong.
TrickyMicky said:
Don't let it put you off - it's a bought in PSU and does in no way reflect the quility of the DAC it is powering.
Just budget an extra £16 for the Maplin unit.
And bear in mind that all DACs in this price range (MF, Beresford, etc.) seem to benefit from a better PSU anyway.
sq225917 said:
It is not the same psu as they use for the 640p phonostage. I've got both (DAC and Phonostage) and the psu's are very different. The phonostage comes with a 500mA 12VAC psu and the DAC comes with a 1500mA 12 VAC psu. They are both rather cheap looking units with thin wires and they both run rather hot, so the quality may not be too good.
But I guess that's another reason to start tweaking around.
Attachments
Mine looks the same as yours, except the model ends in BS not GS. I guess that's because my one fits a UK socket.
You mains voltage is probably 10% lower than mine though!
You mains voltage is probably 10% lower than mine though!
you can use a musical fidelity x-psu to power it, or buy a 120vac toroidal 12-15vac and a couple of sockets. have a look at
www.rock-grotto.co.uk for details of how to build one.
www.rock-grotto.co.uk for details of how to build one.
Glenn2 said:
Yes, you are right. We run pretty much exactly 230 VAC around here. But even at that voltage they still get rather hot.
Seriously £90 for a transformer, what planet are you on, russandrewsworldofscam, Go to Maplins and buy their 3amp 12 volter for £15. it's a huge chunk of metal and it runs cool.😉
http://images.maplin.co.uk/full/l55br_newlogo.jpg
http://images.maplin.co.uk/full/l55br_newlogo.jpg
sq225917 said:
Yep though my Maplin one still gets quite warm, but you can't fry eggs on it like the stock one.😀
Nice post, and resolution Glenn.
Small transformers are inefficient, because the magnetising current can be quite a high % of the permissible load current; and it depends on the transformer design , too. Small transformers designed for higher isolation (lossier coupling) can have higher losses; but a transformer that is run on too high a voltage will also run hot. As will one that is 'cost engineered' by running a small core harder. Finally , even just a watt or so in such a tiny volume will reach high temperatures after a while - and its not unusual for small transformers running at full rating to be at 105degC in the core (! but depends on rating/approvals class)
Could also be that the transformer might be fine, but the case is ill-considered. Or that the transformer was actually 'sized' for 230 or even 220v Mains use... made in China, perhaps?
In a phrase - copper and iron loss.
Small transformers are inefficient, because the magnetising current can be quite a high % of the permissible load current; and it depends on the transformer design , too. Small transformers designed for higher isolation (lossier coupling) can have higher losses; but a transformer that is run on too high a voltage will also run hot. As will one that is 'cost engineered' by running a small core harder. Finally , even just a watt or so in such a tiny volume will reach high temperatures after a while - and its not unusual for small transformers running at full rating to be at 105degC in the core (! but depends on rating/approvals class)
Could also be that the transformer might be fine, but the case is ill-considered. Or that the transformer was actually 'sized' for 230 or even 220v Mains use... made in China, perhaps?
Well when the chap from Cambridge picked up my bad PSU he left me a replacement.
It still got very warm after a few hours of being plugged in with no load.
I think I'll just keep using the Maplin one. 😉
If he ever comes back to me with an update, I'll add the news to this thread.
It still got very warm after a few hours of being plugged in with no load.
I think I'll just keep using the Maplin one. 😉
If he ever comes back to me with an update, I'll add the news to this thread.
I've had loads of these in at work and yes they do run too hot. Also on the inside the heatsink for the +/-15V cooks. The tolerances for the heat/cooling are very tight with these units.
Brent
Brent
I have been looking at making my own ac psu for these dacs to compliment the upgrades. The biggest problem with the heat issue inside is the +/- 30V thats generated from a capacitor network. This is having to be regulated down to +/-15 for the output and then to 5V for the dac through another reg.
I have found using a 9V ac transformer does the trick and infact sounds better than a 12v tx (just). The 9v transformer can supply more current than a 12v transformer of the same type and va.
For example a 30VA 9V transformer is 1.67A where the 12V is 1.25A.
So for anyone buying a tx go for a good 9V one
Brent
I have found using a 9V ac transformer does the trick and infact sounds better than a 12v tx (just). The 9v transformer can supply more current than a 12v transformer of the same type and va.
For example a 30VA 9V transformer is 1.67A where the 12V is 1.25A.
So for anyone buying a tx go for a good 9V one
Brent
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