Sound Reproduction Quality
Comparing the sound reproduction quality of audio equipment is the most difficult part of any review, especially when the differences between devices amount to a few thousandths of a percent as measured electronically. The subjective impression can be influenced by every trifle including the author’s personal predilection towards a specific manufacturer. Therefore I am very meticulous about everything I do before I listen to the devices and recheck myself and my impressions many times before I make up my final opinion, although sometimes this is still not enough.
If you have read my earlier reviews, you may have noticed that my subjective impression about the Creative X-Fi Elite Pro has been getting better with each new test session. It was totally routed by the Auzen X-Fi Prelude but earned my praises for dynamics and detailedness in the ASUS Xonar D2 review. Here, it will be compared with an even more advanced sound card and, running a little ahead, it will be quite competitive. This is no miracle. I am just steadily improving the test methods, particularly such nuances as cables and sound volume settings. In my previous reviews the resulting sound volume was determined by the analog volume control of the C.E.C. HD53R-80 amplifier and all the sound cards worked at the maximum of their capacity. But I had to adjust my method upon performing objective measurements. The amplifier’s volume control is now set at 12 o’clock, the amplification switch is set at the medium position, and the comfortable level of sound volume is set with the sound card’s Master Volume. These settings of the C.E.C. amplifier ensure a compromise between noise, distortions and frequency response.
I want to make one more digression before I get to the tests proper. Upon installing the Xonar Essence into the computer and listening to the first musical compositions on it (it was the XRCD version of Judas Priest’s Wings of Destiny), I realized it was a very, very good sound source. Out of curiosity I connected the amplifier to the card’s headphones output instead of its line output and found the sound to be much more transparent and clear! This impression was subsequently reconfirmed: the line output, implemented with RCA rather than with ordinary mini-jack connectors, delivered a somewhat turbid sound. It does not steal any details and does not spoil the sound scene, but it sounds somewhat sluggishly and makes the imaginable sound sources, especially high-frequency ones, somewhat muddy. It was quite noticeable in comparison with headphone output and X-Fi Elite Pro. Thus, the new card had a worthy opponent. Having made sure of that, I took to methodically listening to one musical track after another, comparing the sound quality of both line and headphone outputs of Xonar Essence with the Creative product.
The musical compositions were in WAV or APE (Monkey Audio) formats and were reproduced via foobar2000 0.9.6 with the ASIO plugin version 1.2.6. The sound cards were were tuned to the highest-fidelity mode: the X-Fi was switched into Audio Creation mode with Bit-Matched Playback and the HF mode was enabled for the Xonar. To avoid disturbance and minimize the time for switching, I used the adapters included with the Xonar Essence, reducing the three different output connectors to a single 3.5mm jack. Then, the sound was transferred to the C.E.C. HD53R-80 amplifier via a cable taken from the Xonar D2 box. A pair of Grado SR 325i headphones was connected to the amplifier’s right output.
The certain blurriness of the sound of the Essence STX’s line output is even beneficial for not-very-high-quality recordings which did not sound well when reproduced via the headphones output. In its turn, the headphones output offered a gorgeous sound in high-quality recordings: an abysmal depth, a crystal clarity, excellent dynamics, and lush overtones. The overtones are also rich in the Xonar Essence STX’s line output, making it better than the Creative X-Fi Elite Pro. The difference is especially conspicuous with the piano, violin and other musical instruments with a large spectrum of overtones. They sound listlessly on the Elite Pro and very natural on the Essence STX. In some cases the Elite Pro outperformed the line output of the Essence STX thanks to a better attack and a more detailed scene, but the status quo was restored as soon as I switched to the headphones output. Conversely, if the Elite Pro sounded somewhat softer and natural than the Essence STX’s headphones output, the latter’s line output proved to be even better.
This could be observed until I came to the What’s Wrong track from the Ecore – Best Of T.I.S. – Audiophile Sampler disc which was obviously reproduced better by the Elite Pro. The main difference was in the sound of the acoustic guitar when it being played with beats into the microphone standing nearby. Irrespective of the output I connected the amplifier to, the Xonar Essence created an annoying humming cloud in the left ear instead of the feeling of the musical instrument with strings and resonating case. This fact raised my earlier suspicions about the use of NJM2114 operation amplifiers on the I/U conversion stage that I had expressed in my ASUS Xonar D2 review. I had Texas Instruments OPA2132P and NE5532P opamps with appropriate DIP package and I decided to check out if the NJM2114 were to blame or not, especially as Texas Instruments recommended using the NE5534 and OPA2134 in the standard circuits for the PCM1792A and TPA6120A2.
The NE5532 being similar to the NJM2114 in its internal circuitry (the latter is sometimes even called a turbo-charged clone of the former), I did not expect them to differ much in sound quality. When I replaced one with the other, the problematic track began to sound somewhat better, at least there was less of the ear-straining hum, but one more track from the same disc, called Cowbell, made me take the sound card out of the computer again. The various drums and percussion of that composition jarred on my ear and the replacement of the NE5532 with the OPA2132 changed the situation dramatically. The sound scene became a single whole and roomier, and the minor tones and reverberations got clearer. It is like watching a scenery first in a water reflection and then – in a clear mirror. That’s the difference between the NJM2114/NE5532 and OPA2132 in the I/U conversion stage. The high frequencies of the Cowbell composition ceased to jar on my ear, the guitar in the What’s Wrong composition got more natural, and the overall sound was more exciting. This refers to the headphone output, though. The line output only got worse from the change: the previously sluggish sound became downright lazy. The bass grew flaccid and the trebles dull. Very much intrigued, I had to make a break in my test session to get some sleep, and the next day the Creative X-Fi Elite Pro refused to work.
Having lost half a day trying to install any driver for the unidentified Creative device the X-Fi Elite Pro had transformed into, I replaced it with an Auzen X-Fi Prelude that had been lying aside due to the total incompatibility of different X-Fi based devices with each other. This sound card had been praised for a very interesting sound, so I thought it would make a good opponent to the ASUS Xonar Essence STX. And when I listened to them, I was shocked because the Prelude was far better! Although the electric guitars of Judas Priest sounded as if from under a blanket and the piano lost its weight, the Prelude was otherwise much more beautiful and interesting, especially in vocals.
So, I took the Essence STX out from my computer again and put the NJM2114 back in place – these opamps had beaten the X-Fi Elite Pro in 90% of compositions. Indeed, when the change was made, the Essence STX became melodic and expressive but its drawbacks returned, too. These were somewhat colored mid frequencies, rather too hissing high frequencies, and a deep but occasionally thick bass. I would say that the default Essence STX provides a true Hi-Fi sound: it is very beautiful, with a broad sound scene, excellent dynamics, accurate reproduction, exciting expressiveness and detailedness. The Prelude, on the contrary, stifles the sound somewhat, is inferior in the naturalism of the timbres of stringed instruments but ensures a more concerted bass and puts less emphasis on sibilants and other fricatives. When listening to the set of test compositions on the two cards, each third composition sounded better on the X-Fi Prelude. When the NJM2114 was replaced with the NE5532 again, the tonal balance of the Essence STX grew so similar to the X-Fi Prelude (including the mentioned stifled quality) that they could only be told apart by smallest nuances – I often could not decide what card was actually better. In some cases I would prefer the Prelude due to the difference in the sound of the high frequencies but the Essence STX would become superior at a reduced sound volume because it would maintain its detailedness and pleasant total balance. The biggest difference in favor of the Essence STX was observed in the Raising Sand album by Robert Plant & Alison Krauss.
Thus, I could not find a universal replacement to the DIP-case NJM2114 but I know where to look for. I have unverified information that the OPA2134 differs for the better from the OPA2132 in the I/U stage, and Texas Instruments uses it in the typical connection scheme of the TPA6120A2. The AD8066 might make an ideal choice but it is not produced in DIP packaging. And ideally, this position should be occupied by an opamp like THS4631. But is it necessary to replace the LM4562? Having performed a number of tests with the Auzen X-Fi Prelude, I returned to the original LM4562. As a low-pass filter it ensures the most realistic timbres and best detailedness. Neither OPA2132/2134 nor AD823/826 could provide the same combination of properties. Therefore, the LM4562 in DIP packaging can only be replaced with SOIC --> DIP adaptors that extend the choice of opamps greatly. Then you can try the LME49722 or the single-channel opamps of the OPA827 class.
Now I must tell a few words about the headphone amplifier integrated into the Xonar Essence STX. Besides a separate output that makes it far easier to use, it features good reproduction quality. I listened to a number of compositions, switching the headphones from the sound card’s connector into the C.E.C. HD53R-80 amplifier connected to the same output of the Xonar Essence. The low impedance of the Grado headphones is a difficult test for amplifiers and the TPA6120A2 specs suggest that its distortions grow up under such load, but it was hard for me to notice a difference in the sound of the two amplifiers. Besides some discrepancies in the sound scene that are hard to describe in words, I can note the more natural sound of the piano and the clearer trumpets on the C.E.C. amplifier. The difference was more conspicuous with Tchaikovsky’s 1812 overture: the TPA6120A2 gets less detailed at spectrally dense moments, its high frequencies becoming muddier and its bass being less controlled, but these are all minor drawbacks you can hear in but a few compositions. I liked some tracks better as reproduced by the TPA6120A2 but the C.E.C. was overall superior with the 32Ohm headphones. You should not forget the much higher cost of the external amplifier, though. The availability of numerous high-quality headphones with 250 Ohm impedance opens wide possibilities for the integrated amplifier of the Essence STX.