pandora's mbox

August 21, 2005 4:37 PM

When I turn on the phantom power switch on my new Digidesign mbox, I get a warning that the device is pulling too much power from the USB port (and then it stops working). I'm using a Dell Inspiron 8600 laptop, which is one of the recommended systems on Digidesign's site. I have Win XP Service Pack II installed. What gives?

According to Microsoft, when you get this message, you must use the device's external power source. Which leaves me up shit creak, because mboxes don't have external power sources. HELP!

posted by grumblebee to computers & internet (26 comments total)

Try using a powered USB hub between the Inspiron and the mbox.
posted by b1tr0t at 4:40 PM on August 21, 2005

Marcus, do you have an external powered USB hub? Try one; I have no idea if this will resolve matters, but it should shift the power drain from the PC to the hub, and therefore you should no longer see the warning.

Good luck!

Also, tell us how you like the mbox! I have been eyeing them since they came out but never had sufficient reason to hop on it.
posted by mwhybark at 4:42 PM on August 21, 2005

Thanks, but the protools manual specifically says NOT to use a hub. And I've read online that, indeed, this won't work with the mbox. Why? I don't know. If you folk still think it's worth a try, I'll buy one.

(mwhybark, you OUTED ME! I'm grumblebee on MeFi! I don't know this "marcus" you refer to ;-)

Oh... piggyback question: I foresee many of these audio hardware/software questions looming in my future, and I'm a newby to that whole world. Anyone know any good web forums where I can get help? Thanks.
posted by grumblebee at 4:50 PM on August 21, 2005

something you could use instead (assuming your laptop has another usb port free) is a usb cable with a power tap (i.e. extra usb connector that draws power but not data) on it; a lot of external 2.5" usb drive cases come with such a cable, specifically for times when the machine's usb ports do not provide enough power, e.g. laptops.

but it might be harder to find if your usb device has a regular size connector on it, I've only seen extra-power cables with mini connectors on the device end.
posted by dorian at 4:57 PM on August 21, 2005

Just so you know, you might also want to check to see if there is a firmware update for your device. The way the USB spec is defined, each device and driver will get asked "so, how much current do you draw?" And if the sum of all these is greater than what the hub/root hub can manage, it's raises an error or a warning depending on how far off things are.

Having written USB drivers and firmware, I know that particular chunk of the protocol can be handled a little, well, incorrectly. I had asked hardware people how much the device would draw and never got a solid straight answer, so we basically made stuff up.

If current drivers/firmware don't do it, then I'd contact them because if I were making that hardware, I'd like to know.
posted by plinth at 4:59 PM on August 21, 2005

Dorian and plinth, I will try both of your solutions.
posted by grumblebee at 5:05 PM on August 21, 2005

not sure of the wording in your manual but the product page sez:
100% USB* powered
* Passive USB hubs are not supported

where "passive" simply means: non-powered. since it's unlikely that you'll find a usb cable with a power tap as well as regular size connector, I'd agree with mwhybark and recommend giving a powered usb hub a shot.
posted by dorian at 5:12 PM on August 21, 2005

Make sure that you have no other USB devices connected to your laptop. It used to be on an old Dell of mine that if I connected my camera to my USB keyboard's USB port that a similar warning would come up. The keyboard was USB, it had a USB mouse hooked up to it, and the camera threw it just over the limit for power.

Perhaps on your laptop, all the USB ports share the same amount of power. So you might have a similar situation even if you have several ports.

As for digital audio sites, check out the following:

KVRaudio: Really great forums and digital audio info clearinghouse.
EM411: Resource site.
Create Digital Music: Digital Music weblog.

You'll find that most of the info out there is VSTi related. One of the reasons I never got into ProTools was because I knew no good place to find info about it. It seems that all the knowledge is in the professional world. Also, because you need special gear to really enter that world, there are a lot fewer people that are going to make that jump and talk about it. VSTi's on the other hand, are easily pirated and used by EVERYONE. So you've got everyone posting about them and sharing info.

Regardless, I wish you luck! I hope you get your "rig" (goodness, I hate gear terminology) up and running soon!
posted by redteam at 5:15 PM on August 21, 2005

Do you have mics plugged in when you do this? If so, what kind?

Who did you purchase from? Some dealers offer support that may be better than Digidesign's ... or even AskMe's. :)

mwhy -- I've got an Mbox. I have to say it's not particularly compelling over any other interface... but I bought it because it's the cheapest way to use the Pro Tools software, which I've used since 1994. I think it's good -- I certainly like it -- but as the years go by and other stuff gets better, I'm not sure it's really the best out there.
posted by weston at 5:27 PM on August 21, 2005

From the mbox manual: Mbox will not function properly if connected to a USB hub. If you need to use a hub for other USB peripherals, use a separate USB port; Mbox must have a dedicated port in order to function properly.

From usenet.

...*any* USB audio I/O device should not be used on a hub,
passive or active. Any other traffic coming through the hub will cause
patchiness and lag with the audio signal coming from your USB audio
interface. The only difference between an active and a passive hub is
that an active hub relies on its own power supply to distribute USB
power, instead of the passive method of re-distributing the host
device's USB power.

(A friend of mine uses a second-generation PBG4 as a portable recording
studio for in-the-field voice work for his in-corporate radio show, with
a Digidesign USB-based MBox, going into Pro Tools -- he has tried using
hubs and was plagued with audio dropouts no matter which hub type was
used. He still uses it, and provided it is directly hooked to the PB, it
works perfectly.)
posted by grumblebee at 5:29 PM on August 21, 2005

Weston, my mic is an ATR55 shotgun. It's plugged in.
posted by grumblebee at 5:44 PM on August 21, 2005

Hubs also give you unacceptable latency problems. I've always wondered why mbox doesn't use firewire.

If you've got a free PCI slot, try putting in a new USB card and using it only for the mbox. They're fairly cheap, though you might want a better one than bottom of the line.

And according to the mbox spec sheet at Bananas.com, a "powered hub is just fine" with an mbox. I have had latency problems with other usb interfaces and powered hubs, however.

Finally, does your mic draw phantom power? If so, try turning it off while the mbox handshakes with the usb bus, and then powering it on afterwards. If it doesn't, make sure the phantom power is switched off.
posted by realcountrymusic at 6:02 PM on August 21, 2005

Oh, duh. I just realized you mentioned the problem happened when you turned on phantom power. Okay, another solution would be to supply the phantom power to the mic externally, i.e. with a clean powered mixed. Defeats the purpose of paying for the focusrite preamps in the mbox, however.

You can get an external phantom power supply (see here for a full description of phantom power and your options.

And doesn't the ATR55 take a battery? You shouldn't need the phantom power for that mic, if I recall.
posted by realcountrymusic at 6:06 PM on August 21, 2005

And double duh. I need to read more carefully. Obviously, with a laptop, adding a PCI card is out of the question. Just use battery powered mics or an external phantom supply.
posted by realcountrymusic at 6:08 PM on August 21, 2005

A coworker of mine was having a similar problem, with him it wasn't his laptop's power supply, but that his USB ports weren't grounded, and that caused interference.

What you can do is take a couple of spare USB cables and splice them together so that there is one USB B plug at the device end, and two USB A plugs at the other end: one with the power and ground (plugged into a powered, grounded hub) and the other with just the data (plugged into the computer).

That would essentially give the Mbox it's own power supply. If you were especially brave, you could just graft a 5v AC adapter into a USB cable.
posted by blasdelf at 6:18 PM on August 21, 2005

I just checked thinking my memory couldn't be that bad. The ATR55 terminates in a 3.5mm mini and runs on a battery. It doesn't draw phantom power at all. So that may well be your problem (that and using a shotgun as your main mic!). Shut that phantom power off.
posted by realcountrymusic at 6:29 PM on August 21, 2005

Yes, you're right. The ATR55 doesn't need phantom power. I should have thought of that. But I doubt it will be the only mic I'll use.

I think I'll solve the problem by buying a mixer with phantom power (for when I need it), plugging the mic into the mixer, the mixer into the mbox and the mbox into the laptop. More complicated than I wanted, but if it works, it works.

realcountrymusic, what's wrong with using a shotgun for my main mic? I'm recording speech, by the way. Not music.
posted by grumblebee at 7:24 PM on August 21, 2005

The phantom powered mixed sounds like the way to go. It's just a slight shame to put mics through another preamp stage before the mbox, since the quality preamp is a main selling point of the mbox. Make sure you get a pretty nice mixer.

I was teasing. There's nothing really wrong with a shotgun for voice, but of course it all depends on what you are doing with the recording. Assuming you're using it for voice-over or podcasting or something like that I'd think you'd do better with a condenser mic designed for close miking. The ATR55 is a little cheap, though a good value for the price, and as I recall designed primarily for camera-mounted video work. It has two ranges, but a shotgun mic is ideal for recording sound occurring at some distance from the mic, so generally not ideally suited for either voice-over or music recording in a studio, except specific applications. What kind of audio are you recording? There have been a number of good mic threads on AskMe in recent months.
posted by realcountrymusic at 8:34 PM on August 21, 2005

By "what kind of audio are you recording," I mean, I know you said "speech," but is it your own speech or speech at a distance? Because for most purposes, close-miking a speaker with a large-capsule condenser will give you better sound, even with something as simple as the M-Audio Nova ($100). Or the Rode NT1A.
posted by realcountrymusic at 8:40 PM on August 21, 2005

informative thread, people. thx.

and thanks to Mr. Bee!

;)
posted by mwhybark at 9:04 PM on August 21, 2005

Using a powered hub should solve the problem. The mbox is a USB 1.1 device which means that it operates at full-speed, 12 Mbs. A hub for a full-speed device operates as a simple signal repeater. It does not introduce any latency. The warning about using a hub only means that you should not plug any other devices into the hub except the mbox because it would have to share USB bandwidth which could cause problems. In your case you are using the hub not to share bandwidth among several USB devices but instead to isolate your laptop from the mbox power load. (Although the hub itself has a tiny amount of overhead since the PC must regularly poll the hub for status, but not enough to really affect performance.)

I suspect that the mbox may not be a fully compliant and registered USB device. This means it may not have gone through all of the extensive testing requirements. If you do not see the official USB logo anywhere on the box or documentation, that would confirm my suspicions.

No device connected to USB can use more than 500 mA of power. While the mbox may meet this requirement, it may not meet the in-rush current requirements when it is powered on. It may temporarily exceed 500 mA for a brief instant when it is first turned on. USB ports in some PCs may be more sensitive to this in-rush current than others, tripping an alarm. Hopefully, a powered hub would not be as sensitive to this.

I assume you have your laptop plugged into AC power and are not trying to run the mbox off your laptop battery.
posted by JackFlash at 9:32 PM on August 21, 2005

Just found this article on the digidesign website in which they essentially bless the use of a powered USB hub. JackFlash, thanks for the info. I've assumed for years that hubs (like long USB cables) added incrementally to latency issues. It seems like common sense that you'd lose a few milliseconds by adding anything into the s/p chain. I need to look into this, although these days I wouldn't buy anything but a firewire (or PCI ) audio peripheral.
posted by realcountrymusic at 4:18 AM on August 22, 2005

RCM, the combined delay through a full-speed hub and cable is a maximum of only 70 nanoseconds -- less than one bit time at 12 MHz. So cable and hub delays really don't enter into the picture.

Assuming the mbox is sampling 24 bits at 48 KHz, one channel is about 1.2 Mbs, only 10% of the USB theoretical bandwidth of 12 Mbs. As long as you don't load up the USB port by connecting too many devices to the hub, there should be no problem keeping up with the data stream. A more likely bottleneck that could cause dropouts would be the scheduling and handling of the data requests in the PC. This would depend on all the other processes going on at the same time. That is why for older PCs digidesign recommends turning on DMA for hard drives, turning off TrueType font smoothing, and disabling any background utilities.
posted by JackFlash at 8:22 AM on August 22, 2005

Thanks JackFlash. I've always been pretty clueless about USB. In my audio universe, it's disparaged as "common sense" for being too slow, when in datastream reality it's probably fine for all but serious multitrack audio, vs. Firewire or optical audio cable. I wonder if recording to an external hard drive might not help things for grumblebee (of course an externally powered one) as well. Most people I know doing Powerbook mobile recording (with edirol and motu and alesis outboard gear) also swear by the higher speeds and larger caches of external FW hard drives vs. notebook drives also running the OS and application(s). But they are mostly doing multitrack work.
posted by realcountrymusic at 8:42 AM on August 22, 2005

I just bought a powered hub. When I get home tonight, I'll try it out and let you know the results.

By the way, I am using AC power (not battery) and an external hard drive dedicated for capturing audio.

realcountrymusic, I am going to be recording about five people speaking at once -- not literally at once, but having a conversation together. I can't afford to mic each one separately.

I have asked dozens of sound engineers opinions about which mics to get, and I got dozens of different conflicting answers. One recommended to AT55, it was within my budget, so (having to buy SOMETHING) I bought it. Hopefully, it wasn't a mistake.

As I recharge my bank account, I DO want to look into other solutions. I wish I could borrow 30 mics and try them all.
posted by grumblebee at 9:11 AM on August 22, 2005

RCM, the mbox only supports USB 1.1 which has a maximum bandwidth of 12 Mbs. USB 2.0 high-speed devices support 480 Mbs, 40 times faster, which is comparable to FireWire.

Recording to an external FireWire drive would probably not increase performance because there is additional overhead of making an operating system call to a device driver for each packet transferred. For a zippy PC this should not be a problem. The advantages of an external drive are convenience -- portability, upgradability, etc.
posted by JackFlash at 9:50 AM on August 22, 2005