[flashbackk]

My ideal setup would have usb dac and a rechargable batterry that could share my notebook adapter. Is that even an option? Are the notebook power supplies good enough?

 

[mono]

A notebook adapter could recharge the battery but it's a relatively noisey power source, not so good for directly powering it while playing.

 

[flashbackk]

Thanks. That is about what I expected. Am I right in thinking that an amp would run directly off the battery and it would be ok to charge off the laptop charger. Or, would it be a better idea to just carry a wallwart and forget the whole thing.
I am actually looking for a portable version of my Corda Aria.
I use my laptop for source and if I had a portable amp I'd be set. I don't use portable players much and I was glad to see the aria designed for a guy like me ( old ). That new Mini Cubed amp of theM3 clan http://headwize.com/ubb/showpage.php?fnum=3&tid=6096 combined with one of the usb dac pojects on here in a clear annodized case velcroed to the back off my Dell would be the bomb.

 

[mono]

Quote:

Originally Posted by flashbackk Thanks. That is about what I expected. Am I right in thinking that an amp would run directly off the battery and it would be ok to charge off the laptop charger. Or, would it be a better idea to just carry a wallwart and forget the whole thing. I am actually looking for a portable version of my Corda Aria. I use my laptop for source and if I had a portable amp I'd be set. I don't use portable players much and I was glad to see the aria designed for a guy like me ( old ). That new Mini Cubed amp of theM3 clan http://headwize.com/ubb/showpage.php?fnum=3&tid=6096 combined with one of the usb dac pojects on here in a clear annodized case velcroed to the back off my Dell would be the bomb.

I don't understand what you mean by "would run directly off the battery". Generally no, if you have the power source plugged in and electrically connected to the battery (to charge), thus it must be electrically continuous to the rest of the amp too since the battery would be to power it. You can leave the adapter plugged in long enough to charge then unplug it when you play off the battery.

It would charge a battery fine, potentially that is if the charger has higher voltage than the peak voltage of the battery pack. Otherwise you'd need more voltage boost circuitry to gain the necessary voltage. Shedding voltage, dropping down to what is appropriate for the pack charging is far easier, a simple linear regulator or resistor (or both) scheme would work.

Towards that end, no need to carry separate wallwart. Separate wallwart with a small linear regulation stage after it (and/or in the same wart casing even if size is a major concern) would be prudent if you need to power the amp while recharging. The latter can be handy if you make extensive use of it or your habits or needs result in needing it before battery had a chance to recharge. IE- it can be handy in "some" situations to be able to recharge while it's playing.

Laptop as a source is another potential problem. Is the audio output ground electrically continuous with the power ground? If so it wouldn't work with many circuits that use a virtual ground on the amp that's held inbetween the positive rail and negative- since negative rail is continuous with notebook audio ground. I am unfamiliar with your Corda Aria version so unless someone else knows specifics about it, if this need to power it from the notebook adapter is still present you might want to post a schematic (or link to one) if you can't deterime if the audio ground and power ground issue mentioned above is present. It is on the Mini3.

 

[Voodoochile]

I have built an amp with a similar power arrangement before. It had a switch that would toggle the battery lines to either the trickle charger or the amp board.

In the ON position, the amp was connected to the battery; in the off position, the battery was connected to the trickle charger.

And yes, most laptop PSUs are pretty noisy. You can quiet them down some with filters and regulation, but it's as much or more trouble than starting straight from AC. Some switchers are very noisy.

 

[pacemkr]

I am just wondering can a usb port provide enough juice to power an amp.

 

[mono]

Quote:

Originally Posted by pacemkr I am just wondering can a usb port provide enough juice to power an amp.

Yes, sometimes. You're guaranteed 100mA, up to 500mA if there's no need for the device to be recognized by the operating system.

However it's 5V, with most (decent) amps requiring more than 5V so you have a very real limit there else a boost circuit which is expected to be pretty noisey.

 

[pacemkr]

You could connected to two USB port at the same time and set em up to be two Vsources in series giving you 10V. Just brainstorming.

 

[mono]

There's no way to connect two USB ports in series. The grounds are common to each other, and the 5V to the other 5V as well. You'd either have 5V still, or short it out if connecting either USB 5V pin to either USB Gnd. That would at a minimum, blow a fuse in the laptop, hopefully no worse.