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RightMark Audio Analyzer

It was a trouble to measure the characteristics of my Auzen X-Fi Forte 7.1 and I did not obtain ideal results anyway. To remind you, RMAA performs its measurements by recording a reproduced signal via a line input of a sound card, and the result is always limited to the capabilities of that input. The specifications of the WM8775 ADC installed on the Auzen Forte suggest that it is impossible to achieve a SNR better than -102 when measuring via the sound card’s own line input. Therefore I am very curious about how the dynamic range of 116dB was achieved for the front output in the measurement results posted in the Tech Notes section of the official Auzentech website.

My attempts to perform the measurement via higher-quality line inputs of other sound cards were not very successful due to a number of reasons. The maximum output signal of the Auzen Forte is 3V, but it proved to be incompatible with professional sound interfaces from E-MU which could digitize such signal and I did not have other brands’ equipment at my disposal. If the sound volume is decreased to the regular level of 2V, you cannot achieve maximum results. Moreover, the results were worsened even more by a high level of noise and interference, obviously due to the power supply of the Auzen Forte’s analog circuitry (the Balanced Power Generation System). The headphone output delivered much more credible results thanks to lower output resistance, so let’s discuss them first.

Below you can see the characteristics of the headphone output as measured through the Auzen X-Fi Forte 7.1’s own line input at different sample rates as well as through the line input of an ASUS Xonar Essence STX.

The results suggest that the noise (and dynamic range) is indeed limited to the Auzen Forte’s ADC, but the harmonic distortions are almost the same irrespective of the sound card. Let’s take a look at the distortion spectrums.


Auzen X-Fi Forte 7.1 headphones Out distortions; measured via X-Fi Forte line-out


Auzen X-Fi Forte 7.1 headphones Out distortions; measured via Xonar STX line-out

When measuring via the Auzen Forte’s line input, we can see a big difference in the harmonics between the left and right channels which is not observed when the measurement is performed via the higher-quality line input. The second harmonic is somewhat higher when measured via the ASUS Xonar STX but the other harmonics are lower. However, these differences may be due to the reduction of the reproduction volume to 2V rather than to the higher quality of the Xonar STX’s ADC. To make the picture complete, I will show you the official diagram for the AK4396 DAC which is responsible for the card’s front output and headphone amplifier.

My measurements of the card’s line outputs produced the following results:

The front output could not outperform the headphone output in terms of measured characteristics despite the latter’s extra amplifier based on an opamp and eight transistors. Moreover, the rear output is almost no different from the front one if measured via the line input of the Xonar STX, i.e. with the volume level reduced by about 3dB. This does not agree with the data published on the Auzentech website.

Now let’s take a look at the distortion spectrums.


Auzen X-Fi Forte 7.1 front Out distortions; measured via Xonar STX line-out


Auzen X-Fi Forte 7.1 rear Out distortions; measured via Xonar STX line-out

The total harmonic distortion being similar, the rear outputs (a CS4382 DAC with a filter based on an NJM4580 opamp) differ from the front output (an AK4396 DAC with an LME49720-based filter) in having a 10dB lower second harmonic and an almost 10dB higher third harmonic. The rear outputs also have a higher level of the dissonant seventh harmonic.

 
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