Mbox2 mini interference noise & Pro Tools recording two lines

[itsuka]

Hi there,

I have just bought a Mbox 2 mini and Pro Tools LE in January this year and I am new to it as well as the idea of recording itself, so please bear with me...

Everything was working fine until a few days ago, when it started to make some unpleasant interference noise. The noise is so loud and when I arm a track and press record without connecting anything to the Mbox mini, it records on two lines. To monitor the sound, I use a pair of headphones connected to the front of the Mbox mini.

I started to be aware of the problem the last time I used a microphone. I connected a cheap dynamic mic (which would not record without phantom power so I kept 48V phantom power button at the back on) to Mbox mini using an XLR cable. Then when I finished with it, I turned off the mic first then disconnected the cable from Mbox mini, then I started to be aware of this problem. The model of the dynamic mic is Yoga DM-330B.

I guess this might be an audio interface problem rather than my computer. Turning the Input 1 knob right up on the front of the Mbox mini aggravates the noise. Turning the Input 2 knob does not make any difference.

My settings (via SiSoftware Sandra):
--------------------------------------------------------------------------
Computer
Model : Asus A7Sv
Workgroup : WORKGROUP

Processor
Model : Intel(R) Core(TM)2 Duo CPU T7500 @ 2.20GHz
Speed : 2.2GHz
Cores per Processor : 2 Unit(s)
Threads per Core : 1 Unit(s)
Type : Mobile, Dual-Core
Integrated Data Cache : 2x 32kB, Synchronous, Write-Thru, 8-way, 64 byte line size
L2 On-board Cache : 4MB, ECC, Synchronous, ATC, 16-way, 64 byte line size, 2 threads sharing

Computer
Platform Compliance : Intel Centrino Duo Mobile Technology
Mainboard : Asus A7Sv
BIOS : AMI 203 07/26/2007
Bus(es) : ISA PCI PCIe IMB USB FireWire/1394
Multi-Processor (MP) Support : No
Multi-Processor Advanced PIC (APIC) : Yes
Total Memory : 2GB DDR2 SO-DIMM

Chipset
Model : ASUS Mobile PM965/GM965/GL960 Express Processor to DRAM Controller
Front Side Bus Speed : 4x 199MHz (796MHz)
Total Memory : 2GB DDR2 SO-DIMM
Memory Bus Speed : 2x 332MHz (664MHz)

Video System
Video Adapter : NVIDIA GeForce 8600M GS (16 SM4.0 1.1GHz, 256MB DDR3 2x704MHz, PCIe 1.00 x16)

Graphics Processor
Adapter : NVIDIA GeForce 8600M GS (16SP 2C 1GHz, 256MB 2x704MHz)
Adapter : NVIDIA GeForce 8600M GS (16SP 2C 1GHz, 256MB 2x704MHz)

Storage Devices
FUJITSU MHX2250BT (250GB, SATA150, 2.5", 4200rpm, NCQ, 8MB Cache) : 233GB (C:) (D:) (F:)
HL-DT-ST DVDRAM GSA-T20L (ATA33, DVD+-RW, CD-RW, 2MB Cache) : N/A (G:)

Logical Storage Devices
VistaENG (C:) : 87GB (NTFS) @ FUJITSU MHX2250BT (250GB, SATA150, 2.5", 4200rpm, NCQ, 8MB Cache)
VistaJP (D:) : 29GB (NTFS) @ FUJITSU MHX2250BT (250GB, SATA150, 2.5", 4200rpm, NCQ, 8MB Cache)
DATA (F:) : 110GB (NTFS) @ FUJITSU MHX2250BT (250GB, SATA150, 2.5", 4200rpm, NCQ, 8MB Cache)
Optical Drive (G:) : N/A @ HL-DT-ST DVDRAM GSA-T20L (ATA33, DVD+-RW, CD-RW, 2MB Cache)

Peripherals
LPC Hub Controller 1 : ASUS ICH8M-E (ICH8) LPC Interface Controller
Audio Device : ASUS 82801H (ICH8) HD Audio Controller
Audio Codec : Realtek Semiconductor High Definition Audio
Audio Codec : Silicon Laboratories Motorola SM56 Speakerphone Modem
Serial Port(s) : 1
Disk Controller : ASUS 82801H (ICH8) Ultra ATA Storage Controllers
Disk Controller : ASUS Mobile SATA AHCI Controller
Disk Controller : ASUS JMicron 20360/20363 AHCI Controller
USB Controller 1 : ASUS 82801H (ICH8) USB UHCI #4
USB Controller 2 : ASUS 82801H (ICH8) USB UHCI #5
USB Controller 3 : ASUS 82801H (ICH8) USB2 EHCI #2
USB Controller 4 : ASUS 82801H (ICH8) USB UHCI #1
USB Controller 5 : ASUS 82801H (ICH8) USB UHCI #2
USB Controller 6 : ASUS 82801H (ICH8) USB UHCI #3
USB Controller 7 : ASUS 82801H (ICH8) USB2 EHCI #1
FireWire/1394 Controller 1 : ASUS R5C832 IEEE-1394 Controller

Printers and Faxes
Printer : Visage PDF (1440x1440, Colour)
Printer : Microsoft XPS Document Writer (600x600, Colour)
Printer : hp psc 1200 series (1200x1200, USB, Colour)

Scanners and Cameras
Scanner : Hewlett-Packard HP psc 1200 (Scanner, USB)

Network Services
Network Adapter : Attansic L1 Gigabit Ethernet 10/100/1000Base-T Controller
Wireless Adapter 1 : Intel(R) Wireless WiFi Link 4965AGN (802.11g (ERP), WEP n-bit, 54Mbps)

Power Management
Mains (AC) Line Status : On-Line
Battery No 1 : 100%

Operating System
Windows System : Microsoft Windows Vista Home 6.00.6001 (Service Pack 1)
Platform Compliance : x86

Windows Experience Index
Current System : 4.3
--------------------------------------------------------------------------

This is the noise I get:
http://dl.dropbox.com/u/1691971/Noise.R.wav

And the screenshot of the two lines:
http://dl.dropbox.com/u/1691971/Noise%202.jpg

And the screenshot of how this noise is recorded into Pro Tools:
http://dl.dropbox.com/u/1691971/Noise.jpg


What I have tried so far are (none of which worked):
- Used different USB cable
- Used different USB port
- Disconnected the laptop from the power supply
- Disabled Wifi

Any help is appreciated, as I can't do any decent recording until I solve this problem!

Many thanks
Itsuka

[cwsand]

Originally Posted by itsuka

I connected a cheap dynamic mic (which would not record without phantom power so I kept 48V phantom power button at the back on) to Mbox mini using an XLR cable. Then when I finished with it, I turned off the mic first then disconnected the cable from Mbox mini, then I started to be aware of this problem. The model of the dynamic mic is Yoga DM-330B.

Dynamic mics don't require phantom power. Theoretically it shouldn't be damaged by having phantom power on but I don't know if that's your problem or not. I keep phantom power off for dynamic mics if at all possible, just in case.

[itsuka]

Originally Posted by cwsand

Dynamic mics don't require phantom power. Theoretically it shouldn't be damaged by having phantom power on but I don't know if that's your problem or not. I keep phantom power off for dynamic mics if at all possible, just in case.

Many thanks for the comment,

Yeah I've thought dynamic mics didn't need phantom power but I tested recording without phantom power button on for this mic and for some reason it would not record. As you say, supplying phantom power to mics that don't require it should not damage the interface, while it might damage the mic...

Cheers
Itsuka

[sw rec]

I see you only have one hard drive. This won't cause the problems you're describing, but it is going to give you a lot of buffer errors. You need to procure a dedicated 7200-rpm drive for your sessions. And typically phantom power will NOT damage a dynamic mic.

[TOM@METRO]

This is only the second time I've seen this two line thing. The other was maybe a month ago and I don't remember a resolution short of a total reinstall.

[itsuka]

Originally Posted by sw rec

I see you only have one hard drive. This won't cause the problems you're describing, but it is going to give you a lot of buffer errors. You need to procure a dedicated 7200-rpm drive for your sessions. And typically phantom power will NOT damage a dynamic mic.

Thanks for your advice,

I will sort out a dedicated hard drive... once I solve this problem!

Cheers
Itsuka

[itsuka]

Originally Posted by TOM@METRO

This is only the second time I've seen this two line thing. The other was maybe a month ago and I don't remember a resolution short of a total reinstall.

Many thanks,

I think I should try a total reinstall if I can't find a solution for this noise...

Cheers
Itsuka

[itsuka]

OK, still haven't heard back from Avid Knowledgebase people but I've contacted Digidesign Japan support (to which they responded the next day).

I didn't register the product in Japan so understandably I am not entitled to their customer support but they did mention that the two lines seem to be caused by DC offset.

By Googling, I kind of got some idea that something is interrupting to cause the waveform mean amplitude not to be zero when silent.

I can hear the noise from the Mbox2 Mini when Pro Tools is not open, so again I guess this is the audio interface problem rather than the software.

I have also narrowed it down to the fact that this is the only case with Input1. When I set the input of a mono track to Input2, it is fine.
http://dl.dropbox.com/u/1691971/Wave...Screenshot.jpg

I am kicking myself for not learning science seriously in highschool but just wondering if there is anyone who has got any idea regarding the cause of this... Nothing is more frustrating than when you start out to write, play, record music but you spend a lot more time sorting out technical problems!