USB High, Low Power, and Fuses Blowing?

[Pete B]

USB 2.0 has been around for a long time obviously, but I've recently been reading about certain devices not working on certain USB ports with power issues or even blowing fuses. I've never had this happen but then I've not used a huge number of different USB devices. Or any Firewire devices.

I've read that USB ports on a computer or laptop should all meet the power spec of .5A. And that USBs extended to a monitor, for example, are often "low power", probably for a mouse or whatever.
So, I did some reading and it seems that ports and devices start out in low power mode, .1 A, and they negotiate up to high power, .5A, if the connector supports it - interesting. This actually makes a lot of sense so that the device can be plugged in, then if it has large caps slowly charge them up at .1A, then switch to full power.

I'm asking because I don't want to blow any fuses on the motherboard etc. I want to use a fairly complex USB powered audio interface, the E-MU 0202 with my X61s and I'm wondering if I should take any precautions.

I read here the the right front USB on the X60 is higher power, the spec is .5A but I wonder if some do more, beyond the spec, just for some headroom:
http://forum.thinkpads.com/viewtopic.ph ... +power+usb

I suppose I'll start with the right front USB, but if anyone has any thinkpad or X61s specific info I'd appreciate it.

I've also heard of power fuse issues with Firewire and I also just bought a used M-Audio 410 that has a warning about blowing out Firewire ports if it is hot plugged. I don't think it is an issue with the X61s because the Firewire port is not powered and the 410 must run off of the wall adapter - it does have the option of being powered from the larger powered Firewire socket.

Here is link to a writeup about this issue:
http://www.soundonsound.com/sos/oct05/a ... sician.htm

A quote from there, it seems that Hot Plugging doesn't work in some cases with Firewire:
"The final possibility is the most worrying and concerns Firewire devices that are powered parasitically from the Firewire buss (AKA 'self-powered'). When you push the Firewire plug connecting such a device into the socket, the power is applied to it, resulting in a momentary startup spike appearing on its data output, which is then transmitted to the computer's port. If your self-powered Firewire device has a separate power switch, you can minimise the chances of this happening by plugging in the device and only then powering it up, so that all the connections are already properly made before power is applied. A further precaution might be to buy a cheap powered hub, so that if the worst happens you only have to replace the hub rather than the computer port.

M Audio and Tascam both recommend that all Firewire connections and disconnections be made with the power to both the device and the computer switched off, and while Edirol maintain that their interfaces can be hot-plugged, they still prefer that you avoid doing it regularly, 'just in case'. Firewire peripherals that have their own mains power supplies should normally be treated in the same way: plug them into your computer's Firewire port, then switch them on, then switch on your computer. However, there may be exceptions, so always follow any attachment and power-up advice given by the peripheral manufacturer."

[automobus]

I am wholly not qualified to give advise concerning any engineering, including sound, computer, electrical. My worthless opinion follows.

Do not worry about it.

I wish to commend or congratulate you for being cautious. I wish all consumers were as smart and careful as you are. (Maybe then, the world would be much, MUCH less polluted and stuffed with forced-obsolete trash.)

Your subject interface, E-MU 0202, should work with your ThinkPad. It is not a power-burning appliance, not a power amp, not a heat radiator. It might seem smart to think about bus-sourced electrical current headroom, but that will almost certainly not be a problem. You can do A-B listening, or use an audio analyser program, to test whether different host USB ports provide different performance. You can also monitor power consumption. Retail off-the-shelf tools, such as Smartronix ST034TT05-01-001 USB Power Monitor or CENTECH CT-USB-PW USB Power Meter, can be used to measure peak electrical current.

It is too bad, after spending only two minutes, I did not find any audio interfaces in certified compliant USB catalog. When companies buy-out other companies, great numbers of catalog entries are removed. Today, when fewer implementers seek compliance than ever before, I wonder if certified compliant USB catalog is shrinking. (I wonder whether more records are vanishing, than new records are being added.)