[Impression] FiiO E7 (warning: lot of pics!!!) - Page 5

If you are only getting the uDAC, then you won't be able to use it with your iPhone. If If you are only getting the T3, then you won't have a DAC for your laptop. However, If you get a uDAC for your laptop and a T3 for both laptop and iPhone, you will be spending almost 2.5 times more than an E7 is going to cost you. I think I would be very sorry myself if uDAC and T7 combo doesn't turn out to be noticeable better.

First, let's talk about your laptop: It already has a headphone-out, but probably not very good sounding. You can connect an amp to the headphone-out but the result won't be good (crap-in-crap-out). To get the best sound, you will need an external DAC (which is basically an external soundcard), likely connected to your laptop via USB such as uDAC or E7. They take the digital signal from your PC from the USB and turns it into analog signal, bypassing your laptop internal sound card all together. You can connect another amp to uDAC as it also support line-out function, but it will work by its own.

Now let's talk about your iPhone: it has both headphone-out and line-out (if you buy a line-out dock / LOD). To get the better sound, you will want to connect your iPhone to an amp by LOD. Since iPhone doesn't have an USB port (nor support USB host function), you don't need an DAC for it. All you need is an amp, which are either T3 or E7 (as it also has a line-in, beside the DAC) in this case.

The point of E7 is it provides the benefit of a portable amp and a DAC in one package, as opposite to uDAC which is only an DAC or T3 which is only an amp. Since E7 is budget oriented, and do both jobs at the price of one, I think you shouldn't expect it to outperform an dedicated device such as uDAC or T3 - but for its asking price, I think it is a great USB DAC amp of its own. However, you should pay for what you will use the most.

Yes, there is a battery indicator on screen. The quoted battery life is 80hrs, which is quite possibly the case. I have been using it to burn-in some of my IEM and I disable the battery charger for a whole night and it didn't even reduce a single bar on the battery indicator.

If it is 5V and less than 1A, I think it should be fine.

Small update: After roughly 100 hours of burn-in, I give E7 another listening against T4 and W1 using RE252. I can't say in 100% certainty but it does feel the soundstage is opened up by a tiny bit. Still not quite as good as T4 or W1 but it is better than before as background detail is easier to notice in comparison. The overall presentation seems less grainy and edgy than before. On previous listening, I preferred T4 just a little bit over E7, but now I think the line is really blurring.

Yes I was.