The table below lists the basic parameters of the opamps employed on the audio card. It shows that the chip from National Semiconductor is superior to the Burr–Brown’s chip in every parameter except for the settling time, but that parameter is more important for the ADC’s input filter where the OPA2134 is installed.
More about the odd layout of the PCB, the digital-to-analog converter is located very far from the input connectors, almost at the other opposite side of the card. Some of the filtering capacitors recommended by the manufacturer are missing near the converter.
The capacitors that filters converter’s reference voltages have 470µF capacity. Thus, the distortion at frequencies below 80Hz will be higher than the declared level of -110dB.
Hopefully, the filter’s opamps are used in inverting operation. Otherwise, the distortion is going to be higher at the higher frequencies as well.
Comparing Auzentech’s X-Fi Prelude with the top-end product from Creative Technology, you can find quite a lot of things they have in common: the same ADC, four stereo DACs and the same amount of operation amplifiers, two memory chips for X-RAM (one of them is located on the reverse side of the PCB of the SoundBlaster X-Fi Elite Pro).
Apart from the more logical PCB layout and the different set of connectors, the difference boils down to the components used: CS4398 DACs (120dB dynamic range, -107dB THD), NJM2114 operation amplifiers from New Japan Radio Corporation for the output filter of the front output, NJM2068 amplifiers for the other outputs, and some variation of the NE5532 chip from an unknown maker for the ADC filter.
According to the manufacturer specs, these operation amplifiers have a higher distortion than the opamps installed on the Auzen X-Fi Prelude, but it was measured at a tenfold amplification and cannot be compared directly to that of the products from National Semiconductor and Burr-Brown. For reference, the specified distortion of the OPA2134 increases tenfold at such amplification, too. I want to note that the line outputs of both cards lack additional buffers, so the system’s sound may prove to depend on the quality of the cables. The option of plugging your headphones right into the card’s line output is limited, too. The latter comment concerns the Creative card less since the NJM2114 can output much higher current than the LM4562 or the OPA2134.
The main difference between the X-Fi Prelude 7.1 and the X-Fi Elite Pro is about the inputs and outputs. Creative offers one port for digital, line and microphone inputs which are switched by four electromagnetic relays, and three line outputs, two of which have a non-standard 3-pin connector for Creative’s 7.1 speaker systems. The PCB carries an AUX input for a TV-tuner or similar device. The rest of the inputs and outputs are concentrated in an external module attached via a 25-pin 1-meter-long cable.
The external module can be oriented vertically or horizontally. It has two pairs of digital inputs and outputs for coaxial and optical cables, a MIDI input and output, an analog input with RCA connectors, two 1/4” sockets for a microphone, electric guitar and other musical instruments, a digital output for Creative’s speaker systems, and a headphones output with a 1/4” socket and a 3.5mm adapter. The module also offers a control for regulating the volume of the analog outputs, buttons to choose an input and to enable EAX, CMSS 3D and Crystalizer.
Auzentech took a different approach. The user has a full set of standard connectors right on the card: four line outputs, line, microphone and AUX inputs, a digital input and output, and a very useful port that adds a second microphone input and allows connection of the audio ports of standard PC case.
As opposed to the Auzen X-Meridian 7.1 where the headphones output is additionally reinforced with a dual-channel inverting amplifier TPA6111A2, on the Auzen X-Fi Prelude 7.1 it is connected directly to the operation amplifier of the front output filter via 47µF capacitors. The inputs seem to be switched by an ADG412 electronic relay. The card should have acquired broader functionality by means of an X-Tension DIN [URL=http://www.auzentech.com/site/products/x-tension_din.php] module originally developed for the Auzen X-Meridian 7.1 – it provides an additional input for a dynamic or electret microphone (the type is selected with a jumper), SPDIF and MIDI inputs/outputs, and support for Creative’s multi-channel digital speaker systems – but the new audio card proved to be compatible with the MIDI interface and the SPDIF output only.