HELP!!! MOTU 828mk2 8 tracks at 24 bit live

Yes, we finally figured out what we think is causing our digital noise problem when we record 8 track live…
(see previous thread on “Digital Noise”)

Its a disk access/ write speed/ disk cache problem.
We believe that the cache on our firewire hard drives gets overloaded as we record and the noise is caused as the drive trys to “catch up” with the amount of data being thrown at it.

Assuming that is the problem, is anyone else using the MOTU and going at least 8 live at a time?

If you are, please let us know what you are doing for storage hardware…be as specific as you can, as we need to make a purchase soon, so we can get back to recording our CD.

Up to now, we’ve been using 7200 RPM 200GB Firewire Drives (Oxford 911 chip set) with 2MB of cache (I know, I know we thought we were buying disks with 8MB, and as the problem didn’t rear its ugly head until we upgraded to 8 tracks live, we’ve had them for about a year already… :angry: and our vendor wont help out much)

TIA

Jimi

I’d say it sounds like a pci latency issue as much as anything. Increase the firewire controller and the soundcard, and decrease the video card and/or the sata controller.

Hmmm…don’t think its a PCI problem, as we are using firewire for both the drive and the interface. Our PC is a laptop.

You weren’t specific about your OS in your computer. If you’re recording with Winblows XP SP2, be sure to downgrade your firewire driver back to SP1 driver, because it is not limited to 100MB/s like the SP2 version. Works great. Don’t ask why they’ve limited the speed, sounds like M$ wants to make USB2 look better ???

There is a “tweak” to get your FireWire buss running at full speed on SP2.

You will find it HERE.

HTH,

TG

The hercules fw16/12 needs a hotfix for SP2 too. It’s different to the one posted above, and I couldn’t find it on the MS site, but it’s firewire/sp2 related - Hercules will mail it to you if you ask for it - but I dunno if it will help in your situation. KB888076.

Hmmm went back to sp1 and still had the problem…

Oh get this…we recorded over the weekend and with all the same settings equip. etc. the problem didn’t show!!!

God I hate computers

Stress-tested my new MOTU last night… My laptop (4200RPM-HDD) could only record a handful (maybe 4) of tracks without suffering from glitches in the recording everytime it wrote to the HDD. My desktop (SATA-HDD) could record 10 tracks at a time while playing back 20 or so (no FX) without a hitch.

how many tracks of audio can firewire support in reality?
I used Cool Edit Pro to see that a 1 sec 24 bit 44.1khz is 172kb.

Microsoft states that
• Data transfer speeds of up to the rate of 400 megabytes (MB) per second. (The maximum speed is presently 200 MB per second.)

so if the bandwidth is supposedly 200,000 kb/sec
one should be able to have 1162 tracks running per second which works out to 581 at full duplex…(581 recording, 581 playing back)

Is that correct? Obviously the rest of the computer would have to be able to handle that amount of throughput and such, but I’m shocked that this number is so high…

the 400 mb/sec will double it? and the firewire 2 (800mb/sec) will double that? unbelievable…

I’m not any kind of PC expert but I have something to add here. You can download a free (for non-commercial use) hard disk speed test utility from Simplisoft called HDTach. Using this, my brand new 7200rpm 8MB cache 160GB Western Digital firewire external HD clocked up an average 40MB/s, after installing the XP SP2 firewire speed fix noted in gtr4him’s post above. My internal HD (Toshiba laptop) was about half that. Much less than the theoretical 400MB/s. Also interesting is the CPU usage, around 8% for the external disk and 5% for the internal. I can’t record more than 2 tracks simultneously so I can’t comment on recording 8 tracks, but I can play back huge Gigastudio samples and sound fonts from either disk with no problems, while playing back 10 or 12 audio tracks in n or Cubase LE.

Fun innit.
Happy tracking
TusterBuster ???

Note that FireWire (IEEE 1394b) is 400 MegaBITS per second. Not 400 MegaBYTES per second. So using your example of 24/44.1 audio (mono) for 1 second yields 1,058,400 BITS per second BUT (There’s always a but… :( ) You have to figure in network overhead as well. Plus driver efficiency may not be the greatest… You get the idea. FireWire still has the bandwidth for copious amounts of audio. I have read many reports of people tracking 18 channels at 24/48 with great success. As with almost anything in this twisted game we are playing…tweak…tweak…tweak. Then when it ain’t broke, don’t try to fix it.

TG

so if the actual firewire limit is 200,000,000 bits per second, and a byte is 8 bits, we get 25,000,000 bytes/sec. if our 1 second of audio at 44.1 24bit is 187 kb per second (192,044 bytes) then we get approximately 130 tracks of audio per second? that looks much more correct :)

Partially correct. With the correct drivers and chipsets, 400 megabit is doable and actually the norm for Mac users. Leave it to Microsoft to muck things up for us PC users. 800 Megabit cards are available for the PC platform now. Don’t know how good driver support is though.

TG

Thanks TG for the enlightenment. So when HD Tach reports 40 Megabytes per second for my external firewire hard disk, that translates to 40 x 8 = 320 Megabits per second, which seems fair compared to the theoretical maximum of 400 Megabits per second. I shall sleep better now. But I think that computerese is a bit like French; designed to deter foreigners. I’m studying French right now, currently drowning in the subjonctif. A bit like deconstructing PC language!
Cheers
TusterBuster :;):