I have a plumax enclosure. This one that I bought from dealsonic.
Enclosure information Link

This is the power supply information.
Power Supply: 100-240V, 50/60HZ, 50 Watt

I heard that the Oxford 911 chipset allows having two drives connected. So I could have a drive as master and slave. But I was wondering if I got a power supply Y splitter cable could I safely power both drives with the enclosure power supply? I have a Benq 1620 and a seagate 200GB harddrive that I want to connect to the enclosure. Is it safe?

Thanks for all your replies.

Most enclosure's I've used are ~36W ... [2A on 12V = 24W + 2.5A on 5V = 12.5W] .... but considering that most drives have labels of power consumption .... you should add that up and check it against the label on the powersupply of the case .... If the sum is below - then it's fine ... but for a HDD+Optical it looks probably fine if it's really 50W

One thing you might want to consider too. What brand is the power supply. I recentlly got a couple of mad dog enclosures and while the chipset is decent, the external power supply is made by powmax, a notoriouslly cheap and crappy power supply manufacture. It claims 2 amps 12v, 2 amps 5v, but honestlly, I wouldn't trust it to power two hard drives. Is there a brand on the power supply?

Thanks for your help Lui.. but I dont understand how you are calculating the wattage.. Is there a formula for calculating the wattages?

The benq has 5V-1.6A,12V-1.8V
The seagate says +5v 0.48A +12V 0.56A
So will it work if it is really 50W

@ripit how do i figure out what power supply my enclosure has.. It doesn't have any labels..

Wattage(W) = ampere(A) multiplied with volts(V), ie. 12V x 1.5A = 18W.

BenQ drives consume ~24W totally. Most of enclosures can handle this load without a problem.
Note though, the USB2 (or firewire) bus speed is not enough to run both your burner and HDD at same time...

If you are lasy and don't want to do the math just use this.
http://www.pelco.com/support/tools/voltagecalc.aspx
As far as knowing the power or brand of the power supply, mine has an external power supply with a label and ratings. Short of having markings, I'm not sure how you would figure it out. Maybe go to the manufactures website and check their faq, or even call or email tech support (and ask what the power ratings are).

Thanks for all your replies..

So for the Benq it would be ~21.6 Watts.
And for the harddrive it would be ~6.7 Watts. So it is under 50Watts. Right?

Is this correct? Do I have to factor in the 5V? Sorry, I was never good at electric circuits.

You do have to factor in the 12v and 5v. Unfortunatlly, without specs from the manufacture (which may not always be avalable, welcome to computer hardware), you have to play a guessing game and maybe take a little risk (most liklly wont hurt the hardware, at least not at first), but if it crashes/corupts (at all), It might be a good sign that there is not enough power. I'm just going on a wild tangent here (I really don't remember accuratlly), but I seem to recall benq burners (earleir models anyway), having a habit of performing very badlly if they do not have enough power. Tht might be a good indication, if you try it and your burner has problems.
As far as actual power, you are really playing a guessing game (a possibly dangerious one). People go off on how inportant a power supply is for your computer (and I'm defanatlly one of them). While it is most important to the motherboard/cpu/ram, it is important to every device in your system. I'm a little nervious running that pow max power supply at all.
If you are good with electronics, here is a test. With the enclosure open so you have access, check the voltage on the lines with the computer running and one device installed. Just tap into the molex's that feed the drives, and hook up a multi meter. Check both if you have two multi meters or one at a time. With the drive conected, a multi meter conected, and the computer on (conect both before you power up), check voltages with just a hard drive (at idle for a little while). Then check what happens with sandra file system test running (or anything that will max the hard drive). then hook up both drives. Monitor it with it just idle. If the voltage is very much more unstable, stop there, it probably isn't providing enough power. If it is still stable (fluctuations are fine but should be close to voltage), with both drives hooked up, check voltage with one drive taxed (Like during an actual high speed burn, and or a sandra benchmark, but NOT both at the same time). If voltages are still stable, then do both, tax your burner (like a high speed burn), and tax your hard drive (like a sandra benchmark on the hard drive), at the same time. If voltages remain stable, do it again, if they are still stable, the enclosure is woring fine and the power supply seems to handle both drives just fine.

I'm sorry and that seem very complicated, but without any specs or brand to go off of, thats the only way I know to test a power supply?
Fyi, if there are any ul numbers/symbols+numbers on it anywhere, you might be able to track it to the manufacture if the power supply is seperate (it may be built in but still seperate).
Hope that help some.

have you thought about how you're going to connect both of these drives to the enclosure safely? asin are both of these drives going to be exposed hanging out on your desk etc? if is was you i'd play it safe and buy an ide controller card or another enclosure.