OK, thanks for the tip. I'm going to order a 220V->16VAC 500 mA transformer then.
I wonder if I can power the O2 and a DAC from the same transformer (different coils), or should I use 2 separate transformers? Perhaps, 1 trans for analog circuits and another for digital?
P. S. Sorry for OT, I kind of forgot this is the PCB GB thread...
I wonder if I can power the O2 and a DAC from the same transformer (different coils), or should I use 2 separate transformers? Perhaps, 1 trans for analog circuits and another for digital?
P. S. Sorry for OT, I kind of forgot this is the PCB GB thread...
I guess there are 2 valid answers:
1) to realize Sansa headphone amp is crappy;
2) to realize you need better headphones.
🙂
OK .... but if the sound is already going through the headphone amp in the player ... and it's already been through the DAC chip ...... does the amp actually improve the sound ...
and yes i need a $1000 pair of headphones ...... anyone willing to buy some for me ?
and yes i need a $1000 pair of headphones ...... anyone willing to buy some for me ?
I can do it, just give me $1500 🙂
Didn't realize you're going to be listening from the same Sansa. Still, you might hear slight improvement after releaving the Sansa amp from its load. For example, my Cowon D2's amp is lacking deep bass with low-impedance phones..
The Clip+ (and Fuze) headphone amp isn't bad if it has enough output for your headphones. Unlike the Cowon I tested, it uses a direct coupled output so it doesn't have a problem with low frequency roll off.
The bigger Clip+ problem, with many headphones, is the maximum output. The Clip+ can't even handle the HD600/650 let alone something like the AKG K701. My blog article on amplifier power explains more about how to figure out if your source has enough power for your headphones.
The bigger Clip+ problem, with many headphones, is the maximum output. The Clip+ can't even handle the HD600/650 let alone something like the AKG K701. My blog article on amplifier power explains more about how to figure out if your source has enough power for your headphones.
Last edited:
I would expect pretty much every unregulated transformer to do the same. I happen to have a spare 15VAC/800mA wall transformer that's rated for 230V mains which I plan to use with my O2. My mains measure 230.xV and that transformer outputs 17.6VAC with no load connected.
Now there might be a difference between a 230V and a 220-240V rated transformer, insofar that the latter might be designed to output the nominal voltage only with 240V mains (in order to avoid damage by secondary over-voltage in countries with this main voltage), but I don't know if this is the case.
Anyway, when a 220–240Vpri/12Vsec transformer outputs 11.5V open-circuit, I find this odd and would surmise that it's an ill-designed transformer unless its output voltage does not sag at all under load.
So if someone happens to already have a 12VAC transformer that he planned on using with the O2, don't throw it out yet. Measure the output voltage.
Many 12 V transformers are intended for halogen lighting and they put out slightly less than 12 V unloaded. Halogen bulbs last very long unless overvolted, so that's why those transformers deliberately put out a little less voltage (typically 11.5 V for a 12 V one or 23 V for a 24 V one) than what's on the label, in order to ensure long life of the connected bulbs.
Yeah, I got that now. Cruel, really cruel.
I do understand that the people that buy those for their bulbs don't need to know and care about the detail, but a small-print technical spec would be kind of useful.
It is a bit of a mixed bag. I have several in my house, some state clearly that they have 11.5 V nominal output for use with 12V halogen lights, and some just say 12 V. But they all are 11.5 V.
That was my problem as well.
I specifically asked for 12V flat, but when I whipped out my multimeter it read 11.5V.
I know and understand the reasons behind it, but when the spec sheet says 12V, that's 12V.
And I double checked with a mathematician to be sure, but 11.5 is not sufficiently close to be called 12.
And as I said, I checked every single transformer in the storage unit (one of every type).
Even the ones not intended for halogen lights put out 11.5V.
(I didn't check the 200VA units, because those would be unusable and uselessly expensive.)
But now Timpert and I have a couple of leads that we're following.
I'm pretty sure we'll find something adequate and affordable...
I specifically asked for 12V flat, but when I whipped out my multimeter it read 11.5V.
I know and understand the reasons behind it, but when the spec sheet says 12V, that's 12V.
And I double checked with a mathematician to be sure, but 11.5 is not sufficiently close to be called 12.
And as I said, I checked every single transformer in the storage unit (one of every type).
Even the ones not intended for halogen lights put out 11.5V.
(I didn't check the 200VA units, because those would be unusable and uselessly expensive.)
But now Timpert and I have a couple of leads that we're following.
I'm pretty sure we'll find something adequate and affordable...
Jokener,
I agree with you that this situation simply sucks and that transformer makers should put true specs on the labels. But the fact that it really hangs on half a volt, seems to indicate that a 12V transformer (even a proper one) is marginal anyway in this application. Better go for a 15 Volt type.
I agree with you that this situation simply sucks and that transformer makers should put true specs on the labels. But the fact that it really hangs on half a volt, seems to indicate that a 12V transformer (even a proper one) is marginal anyway in this application. Better go for a 15 Volt type.
Of course... My quote was for a 15V@load and max 18V idle transformer with 5+VA.
RocketScientist has revised his power supply documentation again yesterday, after doing more extensive tests on these types of situations.
He also does not recommend the common 2.4VA type anymore, as charging the batteries while driving certain headphones could overstep that limit...
RocketScientist has revised his power supply documentation again yesterday, after doing more extensive tests on these types of situations.
He also does not recommend the common 2.4VA type anymore, as charging the batteries while driving certain headphones could overstep that limit...
Unfortunately you are too late. When the boards have been allocated and distributed to the current GB members, any left overs will be sold (price tbc, but something nominal like £5). Keep your eye on the thread for updates regarding that.
The vendor I purchased a number of 12 v adapters (which I discovered were only putting 11.5 v out as well), gave me the line that they are within the + - spec of 10% that they are rated that. Needless to say, they are on the way back to them.. (there were other problems, like they shipped NA type plugs, and they were labeled 100-240v and only put out 5.6v at 110, which leads me to believe they are just a transformer, (and an auto ranging supply would need more circuitry to do the job)..
I'm building my own from scratch with the unit that RS suggested from Mouser..
Any word from Strontronics about their 15 VAC and 18 VAC wall transformers (available with the correct low voltage plug and either the EU or UK mains plug)? Or the Maplin and Jaycar transformers?
A repost from the EU GB
I'm getting these :
NEW AC-AC TRANSFORMER MAINS ADAPTOR 240V TO 16V 700 ma | eBay
Only good for people in the UK, HK and SG.
I'm getting these :
NEW AC-AC TRANSFORMER MAINS ADAPTOR 240V TO 16V 700 ma | eBay
Only good for people in the UK, HK and SG.
I've decided to build them from scratch using the Transformer you posted from Mouser.. I'm canvasing for the various parts now, and I'll be able to provide specific power cords for the various countries, at least for those that are generally available like Australia and EU..
- Status
- Not open for further replies.