Creative Extigy

Testing this USB device was a positive experience. We tested it using Windows 98 and a HP laptop running a Pentium 3 700 MHz and 64 Mb RAM. The installation was smooth, but we had to turn off the device, and then turn it on again, after the installation to get it to work properly. Since the Soundblaster Extigy worked so well, it is likely that the Soundblaster Audigy (which is a sound card for stationary PC) will also work.

What you should know when using this device:

If you experience problems with feedback, you must go to the sound card output mixer and make sure that Microphone and Line-In is muted and turned down. Again make sure you do it for the output mixer, not the input.

In Measurement->Sound Card..., go to Output line and select the lower Wave, not the upper (two Wave’s are displayed in the list).

Input Mixer shoud be set to below -7 dB (30000 uncalibrated) to get optimum SNR.

Output Mixer should be set to below -4 dB (40000 uncalibrated) to get optimum SNR.

If you want to calibrate the mixer levels, the files containing the mixer conversion factors, are available in WinMLS. We recommend that you go to to Measurement-> Calibration... and select Creative SB Extigy as WinMLS mixer OUTPUT relative calibration as shown below.

For the WinMLS mixer OUTPUT relative calibration section, you have to know if you are measuring using the microphone input or the line input, since the mixer levels are slightly different in the low range. If you use the microphone input ,select Microphone - Creative SB Extigy, else select Line-In - Creative SB Extigy.

Input Mixer shoud be set to below -7 dB (30000 uncalibrated) to get optimum SNR.

Output Mixer should be set to below -4 dB (40000 uncalibrated) to get optimum SNR.

In order to get the best results, we have also provided mixer files where we have removed the levels that do not give good results. These have (Good SNR) appended to their names and can also be selected from Measurement-> Calibration, example Microphone - Creative SB Extigy (Good SNR).

If you want to calibrate the sound card to measure input voltage, we found the Sound Card Input conversion to be 9.681. You may also use this number as a nominal settings, but it applies only if the mixer is calibrated.

First go to Measurement->Calibration..., then click on the upper Settings... button, then type the number in the Sound Card Conversion edit box. Do check if your measurements are reasonable using this conversion factor.

Negative: If you want a portable system it is not so good that it needs 12 Volts power supply.

Start Record/Playback can vary with 200 samples, which means that initial time-delay can only be measured correctly if using loop-back. But when measuring with loopback, we found that the End sync pulse was not detected. This was not a problem in our case, since it seems always to give correct measurement (the purpose of the End sync pulse is to detect gaps in recording/playback which ruins the measurement).

96 kHz sampling frequency was a disaster, It was not possible to get a decent measurement above 24 kHz because the filters seem to be the same as for Fs= 48 kHz. Also, we had problems sometimes getting overloaded input level.

16 and 24/32 bits use different filters, so the frequency response using 16 bits is 3-23 kHz, while for 24 bits it is 3-18 kHz using 48 kHz as sampling rate.

Positive: The price is very low. It can be used with any PC, stationary and laptop. The mixer can be calibrated. Gives very good results when used properly. Using measurement system correction, we were able to get the magnitude frequency response within +-0.01 dB from 1 Hz to 20 kHz measuring output-input loopback (using seq. order 16).