www.audiophilerecordingstrust.org.uk

Section 2 - Audio PC and Recording Equipment
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Recording Head
This is now a 6 channel version with extra side channels to enhance Left and Right Side images. It is an open frame (not a solid baffle) using absorption to provide front to rear separation.	Mk 4 version, 20-05-2007	Dimensions: Width: 500mm Height: 350mm Head microphones: Front: Rode NT2-A, Rear: Rode NT2-A (not shown in the image) Side microphones: Rode NT1-A, cardioid Dummy Heads: Polystyrene
		6mm Felt is now used to provide absorption and the front and rear heads now have minimum separation.
1. Recording Post Processing	Match the gain of front channels to correct for microphone and system gain errors. Repeat for the rear channels.
2. During Playback With Physical Dividers	1. The high levels of room absorption required for good playback affect the normal balance of speakers. For best results it is necessary to boost the midrange to restore a flat response. See the following article. 2. Play back side channels at the standard 10dB lower level reference front and rear channels and with a 350Hz high pass 2 pole filter.

Audio PC	A fan-less pc is easily constructed. Details of our equipment are as follows.
		Supplier (in the UK)
Motherboard	ASUS A8N-SLI Premium	www.microdirect.co.uk
Processor	AMD Athlon 64 3500 Venice Core, Socket 939	www.microdirect.co.uk
Memory	1Gb DDR SDRAM, PC3200, 400MHz	www.microdirect.co.uk
Hard Drive	Maxtor Diamond, 16Mb cache,200Gb, 7200rpm, ATA133, IDE	www.microdirect.co.uk
Hard Drive acoustic damping	Scythe drive enclosure	www.quietpc.co.uk
Graphics Card	Sparkle or similar (not critical) nVidia 32Mb	www.microdirect.co.uk
Sound Interface	RME Hammerfall Multiface	www.dolphinmusic.co.uk
Power Supply	Silentmaxx 450w	www.quietpc.co.uk
Processor Heat sink	Scythe Ninja for Socket 939	www.quietpc.co.uk
Case	This has to be at least 200mm width to accommodate the Ninja heat sink
Operating System	Linux, Demudi Agnula distribution	www.agnula.org

Installing and Setting up the Operating System Most users would use Microsoft Windows as an operating system and any problems relating to this are well covered elsewhere on the web. Experienced Linux users would no doubt prefer to use the open source solution. Detailed installation instructions are not necessary for hardened Linux users so the notes below will only list unexpected problems that we have encountered.

1. RME Hammerfall Multiface driver	The Agnula distribution includes the latest ALSA drivers however the firmware loader is omitted. The following error message will appear at boot. “cannot load firmware multiface_firmware_revII.bin” The distribution is a modified Debian distribution, it has no c compiler installed therefore will only install .deb files. If another Linux pc is available, download the RME Hammerfall DSP 9562 driver from the ALSA site and unpack the tar, or, download the file from this location here and install the file manually. Copy the file to the “/usr/lib/hotplug/firmware” directory.
2. Other RME issues	The mixer has to be initiated before any programs will recognize the sound driver. The only way to do this appears to be to open the hdspmixer program which is installed with the distribution. The suggested programs, alsamixer, will not work “straight of the box”.
3. Which recording software to use ?	There are only 2 which seem to work well with multichannel high bit/data rate recording. 1. Ardour, if you like gui interfaces 2. Ecasound for flexible, low overhead, command line processing. This is our preferred option.
4. Generating crosstalk canceled files (see Section 3)	See Brutefir from Anders Torger www.ludd.luth.se/~torger/brutefir.html and the required deb files from HTTP://packages.debian.org/unstable/sound/brutefir The version we used may be copied from the following locations:- brutefir and fftw3 (required fft library)

Last modified 2007-02-20