Power through FW800 port when Mac is off?

[James Steele]

I have Liquid Mix that is connected to my Mac with a FW800 to FW400 cable. I notice that when I turn off the Mac, the Liquid Mix is still on and drawing power over FireWire. Seems odd. It did not do this when connected to my MacPro 1,1 with a standard FW400 cable.

[MIDI Life Crisis]

Yes, my MP also does that.

[James Steele]

Yes, my MP also does that.

I figured as much. I can't help but unplug the cable from it every time I leave my studio now. Just bugs me to leave it on like that. Can't remember if LIquid Mix had a "screensaver" mode after so many minutes? I doubt it.

[MIDI Life Crisis]

Fortunately my interfaces now all have power switches, but be forewarned: disconnecting Firewires device with power on (even with the Mac itself turning off but supplying power) can fry your ports, including any other FW devices attached to the Mac.

Serious flaw. Read here and if you want to really get the skinny (which is quite fat) follow the link to the Texas instruments PDF.

[MIDI Life Crisis]

ps - I've also found that given the option to self-power, the performance of the devices are more reliable and in audio, eliminate many problems such as pops and clicks.

[James Steele]

Right. Well I suppose I could power the Liquid Mix with external power. There is a jack there, however I've been plugging and unplugging it since I've owned the thing with nary a problem. The thing is so old and relatively obsolete that if it kicketh the bucket, oh well. I think the risk is small. I don't want another damned "wall wart" taking up space under/inside my studio desk.

[MIDI Life Crisis]

The thing is, it won't just fry the device, it'll fry your Mac ports and possibly attached FW devices.

I lost a port on both my G4 and G5 (I didn't know about the problem when I owned both of these). I also lost the port on the M-Audio FW410 and the port on a LaCie FW external drive.

[James Steele]

The thing is, it won't just fry the device, it'll fry your Mac ports and possibly attached FW devices.

I lost a port on both my G4 and G5 (I didn't know about the problem when I owned both of these). I also lost the port on the M-Audio FW410 and the port on a LaCie FW external drive.

You really know how to ruin a guy's day, huh? I've been getting by with this silly Liquid Mix doing that for years. Now I'm paranoid. Is it smart enough that when a power supply is connected to it, there is then no power to the FW cable and you can unplug? Otherwise, only stupid solution is to have the Mac itself plugged into a power strip I can access easily and after the Mac is powered down, flip the switch on the power strip so no current is flowing to the Mac, and THEN unplug Liquid Mix.

MAJOR PITA!

I may live dangerously for a while. I just won't talk about it here. LOL

[James Steele]

Hmm... power strip is gonna be ugly. Well, Mike... from this day forth I shall think of you as I crawl behind my desk and pull the power cable from the backside of my Mac every damned time I want to unplug the Liquid Mix. ARRRGGGHHHHHH!!!

[MIDI Life Crisis]

Well, it's not that you need to disconnect the wall power to the LM as much as disconnect the power TO THE MAC! I know, that seems excessive, but if you don't have an on/off switch on the FW device and don't want it on when connected to the Mac I don't know any other option.

It's a compound problem, kind of like having a bad belt and a bad water pump at the same time. Apple defaulted the FW to be always ON. Who knows why? As long as ANY device provides power and the connector can make that screwy contact described in the TI link, the ports can fry. They even have lots of pictures of fried ports and various connectors and how they damage the ports.

I'm not trying to make more work for you. I do that when I post dumb stuff... I'm just letting you know that ANY firewire connections made or unmade while any device is supplying power can do damage. If I hadn't lost a few hundred bucks in the process I wouldn't have mentioned it...

[James Steele]

Yeah... that's what I said. Disconnect power to my Mac so that no power is coming through the FW cable when disconnecting the Liquid Mix. Of course at that point, I won't have to disconnect the Liquid Mix again. Still it's a PITA.

[MIDI Life Crisis]

A ROYAL PITA!