I'm looking to put together a little hard disk recorder - essentially six audio channels connected to some sort of audio interface on a motherboard and a storage device (a serial ATA disk).
Essentially, I'm looking for a motherboard with six high quality audio inputs and on-board USB or Firewire. The speed of the CPU is immaterial, it's far more important that the device has low power consumption.
Does anybody in the group have any recommendations for a motherboard? I can't find any board that has this many inputs.
In a word: forgetit. No such thing as a high-quality audio input on a PC-kind motherboard, much less six of them. Multi-channel high-quality audio hardware comes in separate boxes connected to the computer either by high-speed serial line (USB, 1394) or by dedicated cable to an extension card.
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Hans-Bernhard Broeker (broeker@physik.rwth-aachen.de)
Even if all the snow were burnt, ashes would remain.
By "motherboard" I assume you mean a PC motherboard? You won't find such an animal. You can, however, add a multitrack "mixer-board-on-a-card" to a standard motherboard.
The audio input on a normal PC motherboard is far from what I'd call "high quality", by the way.
As Larwe said, getting a mobo with 6 audios will be a problem, have a look here
formatting link
I think they have low power stuff available as well, but it depends on your definition of low power, and your budget. what about kbd/LCD etc.? Check out M Audio for external sound doofers, quite adequate. If you can handle linux, maybe gumstixs modules might work
Just been doing/attempting a 48V very low noise phantom power supply design for 4 condenser mics, at 6.5V in it took 180mA rms. that wasn't even worst case. Think it needs some tweaking.......
I had been thinking for a couple of years about building such a unit, 4 or 8 channels. Would be a bit of a stretch for my skills, but I like "learning experiences". I thought to do the following:
It would be quite hard to put six XLR connectors at the edge of a Mini-ITX motherboard :-).
Seriously, any PC motherboard will have huge DC currents with large current peaks riding on it due to digital switching flowing around the board. These currents will sooner or later end up in the PCB ground planes, causing potential differences between various points on the ground planes.
Connecting a low level audio signal into such hostile environment is going to cause problems, not only from induction from nearby PCB tracks carrying various high current signals, but also due to ground potential problems when unbalanced connections are used.
A careful use of separate analog grounds may help when using a single floating signal source, connecting multiple channels to different equipment that may connected together e.g. through other signal lines or power supply lines, may cause all kinds of ground loop problems, injecting interference into the unbalanced ADC input. I also very much doubt that high quality audio ground routing is the primary target, when designing the motherboard layout.
When balanced audio lines are used (dynamic microphones are initially balanced anyway), much of the inducted noise is cancelled, most of the common mode interference due to ground potential differences can be eliminated and impedances can be used in the shield connection to limit the ground loop current.
I would suggest using a separate board containing the input stages and the ADCs and using some non-galvanic connection (such as ethernet transformer or fibre optic) to carry the digital signals to the computer and/or recorder.
For instance, try to find a motherboard with at least three Toslink optical interfaces, so you could use three separate stereo ADC boxes to handle the six channels.
OT but ... I purchased a Yamaha AW1600 16 track, 8 input direct to HD recorder with *many* bells and whistles for $1K last year. However, the only learning experiences have been how to use it, and how badly I *really* sound recorded ;-)
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Michael N. Moran (h) 770 516 7918
5009 Old Field Ct. (c) 678 521 5460
Kennesaw, GA, USA 30144 http://mnmoran.org
"So often times it happens, that we live our lives in chains
and we never even know we have the key."
The Eagles, "Already Gone"
The Beatles were wrong: 1 & 1 & 1 is 1
Thanks for all the replies, I probably should have been a bit more specific about what I was after.
I pretty much expected that there wouldn't be a motherboard out there with that kind of audio capability. To be honest, I'm not EXACTLY sure what I'm looking for, only that I'll know it when I find it! I'm actually doing this as a three man project, I'm the software developer of the group and I'm sorting out the 'computery' side of the hardware as the electronics wizard doesn't have much specific experience with computer hardware.
We're not going to bother with anything as complex as an LCD panel. The front panel will basically be one gain knob per channel (that's one XLR and one jack input, as on any standard mixer) and then one volume and pan per channel for monitoring only. Each channel would be recorded as a single mono audio file by whatever OS is running on the board (probably a stripped down NetBSD). There'll also be a strip of LEDs to show the overall input level. Nothing complex.
There'll be one USB (or Firewire) port so that the disk can be mounted on any computer over the cable, although I've not decided on a filesystem type as FAT32 has a 4gb filesize limit.
I can't be more specific about the power consumption yet, only that it needs to be a low as possible as we intend to use the unit for outdoor location recording and hope to get about 10-12 hours constant use out of it per session. It'll be powered with portable power cells outside, inside it can just use an ordinary wall socket (obviously).
The reason for this project is frustration at the quality of the rest of the recorders on the market. Each recorder seems to have some fatal deficiency, like too-high power consumption due to the manufacturer shoving every bell and whistle possible into the design, or not having enough inputs, or not having a USB connection. None of them seem to really fit the criteria. Even the closest unit we found (a Fostex something-or-other) only had four inputs and used a FAT32 filesystem, limiting each individual recording to an hour.
I'll have a read through all of the replies and have a look at the individual suggestions in a bit.
Why don't you dedicate one file per channel, and then you can use FAT32 with separate partitions per channel? Now you can use large HDs with suitable partitioning. You also have the option of multiple HDs.
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Chuck F (cbfalconer at maineline dot net)
Available for consulting/temporary embedded and systems.
I do actually use a Delta 66 in my workstation. They're very nice cards.
I would still like to try to put something together though, even if it's only as a learning experience. M-Audio don't seem to have anything that would quite fit our needs.
Initially I did think about just a laptop and a firewire interface, but the ultimate goal for this device is to do a 24 hour unattended recording and I don't see that happening for various reasons.
While the FAT32 _file_ size limit is 4 GiB, the _partition_ size limit is much larger.
Only with FAT16, the 2/4 GiB partition size limit would apply.
If a large disk is divided into 6-7 separate partitions each recording a single channel, the write head would constantly seek between the partitions, slowing down the writing process. Writing to adjacent files in the same partition or even into the same file will reduce the disk head seek times.
A few partitions may be useful when a single day's work is recorded into each partition, thus, when the job is done and the data is transferred to some other safe media, the partition can be cleared entirely and there would not be a need to defragment that partition before reuse.
Even if a few (2-3) partitions are used and defragmentation would be needed, the defragmentation can be done one partition at the time.
Also with more than one partition/disk, there would be less files in the partition and thus the risk for directory and disk allocation table corruption is less.
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