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Chapter 10 - Optimising sound cards

Make changes only after soundcard installation and reading soundcard instructions. Generally, install cards as far as possible from the CPU and drives (the Gigabyte board is an exception).

Step 1 – disable mapping

Control Panel > Sounds and Audio Devices > Hardware. Highlight the soundcard, right-click [Properties] Properties > Audio Devices. Highlight Soundcard > Properties. Check Do not map through this device.

Step 2 – disable system sounds & set maximum volume

Control Panel > Sounds & Audio Devices > Sounds TAB. Set Sound scheme to ‘No Sounds’. Set Volume to maximum in Volume TAB.

Step 3 – disable unused hardware

Disable soundcard-based non-audio hardware such as game ports:
go to Device Manager > View > Devices by connection, select ACPI Multiprocessor PC > Microsoft ACPI-Compliant System > PCI Bus. right-click on surplus features and select Disable.

Example (Audigy 2 ZS Platinum) with game port and firewire 1394 disabled.

Step 4 – disable unused audio functions

Disable inessential soundcard audio functions. Access the soundcard’s driver settings and disable all DSPs, DACs, soundfonts, etc as well as features like on-screen displays, balloon tips and infrared remote. Where appropriate, leave only pure (24/xxx) output.

Step 5 – use latest drivers

Install the latest drivers but the drivers only – tools are not required but can impact significantly on sound quality. Visit the supplier’s website to obtain updates.

Step 6 - ensure dedicated interrupt (IRQ)

For PCI based cards, make sure the soundcard has a dedicated interrupt.
Control Panel > Administrative Tools > Computer Management > Device Manager > ‘Resources by connection’ under View MENU > Interrupt request (IRQ)).
Changing PCI slot (which changes IRQ assignment) will require software driver reinstallation. On recommended Gigabyte motherboard use PCI slot 1 (i.e. slot nearest to CPU) which ensures a dedicated IRQ.

Diagram shows mobo soundcard (SoundMAX) using IRQ 23 that is shared with USB. Only option here would be to disable the USB port.

Step 7 – optimise ASIO buffers

Set the playback output buffer settings for the smallest buffer size (the lowest latency) that does not affect stability, i.e. there are no dropouts, crashes or crackling.


Optimising USB DACs

The plethora of USB DACs now on the market ranges from high-quality but expensive devices to others providing remarkably good sound for modest prices. Most low-end types are non-oversampling, scantily documented and lacking dedicated drivers though they usually work with ASIO4ALL.

A serious drawback of USB technology is that it is often poorly implemented on motherboards. Where designers (charitably) must keep prices to consumer levels, they reportedly skimp on critical design parameters. Intel also notes that poor-quality power supplies degrade USB performance. It is generally systems laden with devices running at high speeds and/or drawing power from the motherboard that encounter the most severe problems. That scenario may not pertain to PC audio but it does illustrate common problems that do. Some simple steps can help to minmise their impact on sound quality, particularly on a dedicated audio PC. Try some or all of the following:

  1. Connect the DAC to a back-panel socket, not to the motherboard’s on-board USB headers;
  2. Provide the DAC with its own power supply – do not power it off the motherboard;
  3. Some after-market USB cables make a measurable difference. However, devices using Analog Devices’s ADuM4160 isolator such as that sold by Circuits@Home significantly improve the sound quality of most USB DACs and are usually better value for money. For best results, provide it with a high-quality 5-volt power supply, by-pass the on-board voltage regulator and connect it to the DAC with an adapter as shown rather than a cable. (The device has been successfully tested at 96kHz. Though issues have been reported with some DACs at rates over 48kHz, they are almost certainly caused by the drivers.)
  4. Disconnect all other USB devices when playing music;
  5. Disable USB 2 (and 3 if available) in BIOS (enable USB 1 only: USB 2/3 can be re-enabled when needed);
  6. Disable USB power management. Select Control Panel > System > Hardware > Device Manager > Universal Serial Bus Controllers and expand (click on +). Right-click each Root Hub in turn and deselect [Power Management] > Allow the computer to turn off this device to save power;
  7. Disable unused hubs. Select every Root Hub as above and find the DAC’s (right-click, Properties > Power). Disable the rest (perhaps leaving one or two for housekeeping): right-click and select Disable (not Uninstall as XP will reinstall the hub at the next restart);
  8. Remove ‘non-present’ devices. XP notes devices hitherto connected to the USB. To clear the record, launch a command prompt, type set devmgr_show_nonpresent_devices=1 [Enter], then devmgmt.msc [Enter]. Leave the window open. In Device Manager, click View > Show hidden devices and uninstall all USB devices (both ‘ghost’ and current) and reboot with the DAC on. The step may have no effect but can resolve obscure driver issues;
  9. Check the DAC has a unique IRQ (see Step 6 above);
  10. Check PCI latency timing. The values determine how many clock cycles elapse between a device taking and relinquishing control of the PCI bus. Some manufacturers set defaults too high so that their devices deny prompt access to others. The shareware ‘PCI Latency Tool’ can view and possibly adjust them (depends on mobo chipset): if some are unduly high, try reducing them to 64 or 48. Note that crudely setting the DAC high and all else low is counter-productive – the idea is to enable smooth access by preventing any device from bus hogging;

It is not claimed that the above steps will transform the quality of an entry-level DAC but, taken together, they make for more reliable performance and almost always for better sound as well. The AD isolator in particular (step 3) is a significant upgrade and excellent value for money.

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Page last modified on January 02, 2011, at 07:47 AM