E-MU 0404 USB - A Top-Class External Audio Interface

The E-MU 0404 USB interface was first introduced at Musikmesse 2006 and at that very moment became nearly the most anticipated product of the year. I'll say! It was claimed to offer features record for any external audio interface, including top-end converters, good capabilities - all that at some very affordable price of $199. This fall the novelty reached Moscow. And despite being overpriced, the first stock was sold out within 24 hours.

The name "0404 USB" implies the quantity of mono-channels and the USB bus. Onboard there are 2 A-class mic/guitar/line pre-amplifiers, headphone pre-amplifier, coaxial/optical SPDIF switchable to AES/EBU, MIDI I/O and, of course, the 2x2 analog interface based on AKM's high-end DAC/ADC.

As you can see, most controls are located on the device itself. It's surely more comfortable to use hardware controllers, than software sliders. Note the analog output signal level control. It enables to connect the device directly to active acoustic systems without being afraid of dynamic range losses due to digital level reduction.

Technical specifications

0404 USB is one of the first products utilizing the newest AKM AK4396 DAC, which is a dual-channel 24-bit 192 kHz converter tailored for the high-end market and professional equipment. This DAC belongs to the AKM 439X top-end series and is a further development of AKM's advanced multi-bit architecture. The SNR within 20 kHz band is rated 114-120 dBA. The noise spectrum doesn't raise until 80 kHz allowing to avoid problems with intermodulation of good signal as well as modulator noise-shaped signal. THD+N is rated -90..100 dB.

On the front you can see (left to right): 2 combined Neutrik XLR-TRS connectors - mic/line/guitar input (1.5 kiloohm mic and 1 megaohm Hi-Z); SPDIF/AES coaxial I/O; below is optical TOSLINK; rightmost is ¼" TRS headphones output.

On the back: ¼" TRS-balanced output dubbed by unbalanced mini-jack (1/8" TRS, standard for connecting active PC acoustic systems) for more comfortable connection to consumer audio devices; MIDI I/O; power switch; USB2.0 B connector; power connector.

Prima facie, the non-USB power feed seems surprising. But it becomes obvious when you consider that the card consumes current of up to 1 ampere, while a single USB port is limited to 500 mA (even less in real devices). Since noone likes that greyish-white smoke and distinctive smell, the vendor decided to play it safe and implement the main power feed. (Enthusiasts might want to accept responsibility and try feeding the card from 2-3 USB ports. Since the supply voltage is 5V, perhaps, the first engineering samples were bus-powered.)

For that we get a bonus: the interface can work without a PC as an external pre-amplifier. However, to make us completely happy, vendor could add the standalone DAC mode with external clocking.) By the way, we found out that some users still succeeded in making the device work as a standalone external DAC.

The only criticism to the design is that phantom power is enabled on both XLR inputs simultaneously. When using a dynamic mic, you are to make sure it has balanced interface and XLR-XLR cable with a correct pinout. In that case phantom power, when enabled, won't cause any problems (see explanations of Mackie's specialists).

On the bottom we can find 2 miniature ground-lift switches, which are very useful for negating sneak ground circuits occuring when you connect a large number of equipment (usually it's 50 Hz noise pickup with multiple harmonics, can also be cracking, etc.)

Bundle

Though it's rather traditional to supply unnecessary applications as a bonus, this time the software package is rather useful, allowing to start working right away. On the other hand, they could limit it to drivers and reduce the price even further.

ASIO diagnostics

Features:
Input channels: 4
Output channels: 4
Input latency: 22083
Output latency: 22216
Min buffer size: 88
Max buffer size: 22000
Preferred buffer size: 22000
Granularity: 44
ASIOOutputReady - supported

Sample rate:
8000 Hz - not supported
11025 Hz - not supported
16000 Hz - not supported
22050 Hz - not supported
32000 Hz - not supported
44100 Hz - supported
48000 Hz - supported
88200 Hz - supported
96000 Hz - supported
176400 Hz - supported
192000 Hz - supported

Input channels:
channel: 0 (Analog IN A) - Int24LSB
channel: 1 (Analog IN B) - Int24LSB
channel: 2 (SPDIF IN L) - Int24LSB
channel: 3 (SPDIF IN R) - Int24LSB

Output channels:
channel: 0 (Analog OUT) - Int24LSB
channel: 1 (Analog OUT) - Int24LSB
channel: 2 (SPDIF OUT) - Int24LSB
channel: 3 (SPDIF OUT) - Int24LSB

As we can see, the device supports all frequences through 44.1 to 192 kHz. ASIO applications will show 4 I/O channels reflecting physical digital and analog inputs and outputs.

Objective testing

As we found out, connecting the Lynx Aurora 8 and LynxTWO caused the level conformance problem. Lynx has switch for two fixed signal levels: -10 dBV / +4 dBu. Despite E-MU's max. level rated at +12 dBV, the amplitude was significantly lower than Aurora's +4 dBu. The -10 dBV mode introduced amplitude overload, so we had to reduce the signal. Perhaps, that was caused by discordant impedances of input and output stages. Therefore, measurements on Lynx Aurora 8 were conducted with -10 dBV signal level, which didn't allow to achieve rated SNR. But everything else was perfect. E-MU 0404 USB is a really top-class interface that doesn't yield to its PCI siblings.

16-bit 44.1 kHz

Analog output

E-MU 0404 USB -> Lynx Aurora 8

Frequency response (40 Hz to 15 kHz), dB:	+0.03, -0.07	Excellent
Noise level, dB (A):	-96.1	Excellent
Dynamic range, dB (A):	96.3	Excellent
THD, %:	0.0007	Excellent
IMD+N, %:	0.0045	Excellent
Stereo crosstalk, dB:	-97.6	Excellent
IM at 10 kHz, %:	0.0048	Excellent

24-bit 44.1 kHz

Analog output

E-MU 0404 USB -> Lynx Aurora 8

Frequency response (40 Hz to 15 kHz), dB:	+0.03, -0.07	Excellent
Noise level, dB (A):	-110.9	Excellent
Dynamic range, dB (A):	110.9	Excellent
THD, %:	0.0006	Excellent
IMD+N, %:	0.0014	Excellent
Stereo crosstalk, dB:	-107.1	Excellent
IM at 10 kHz, %:	0.0016	Excellent

24-bit 96 kHz

Analog output

E-MU 0404 USB -> Lynx Aurora 8

Frequency response (40 Hz to 15 kHz), dB:	+0.01, -0.08	Excellent
Noise level, dB (A):	-111.2	Excellent
Dynamic range, dB (A):	111.1	Excellent
THD, %:	0.0006	Excellent
IMD+N, %:	0.0013	Excellent
Stereo crosstalk, dB:	-106.5	Excellent
IM at 10 kHz, %:	0.0015	Excellent

Analog input

Lynx Aurora 8 -> E-MU 0404 USB

Frequency response (40 Hz to 15 kHz), dB:	+0.01, -0.07	Excellent
Noise level, dB (A):	-110.9	Excellent
Dynamic range, dB (A):	110.9	Excellent
THD, %:	0.0004	Excellent
IMD+N, %:	0.0013	Excellent
Stereo crosstalk, dB:	-107.1	Excellent
IM at 10 kHz, %:	0.0011	Excellent

Loopback

E-MU 0404 USB -> E-MU 0404 USB

Frequency response (40 Hz to 15 kHz), dB:	+0.01, -0.06	Excellent
Noise level, dB (A):	-113.4	Excellent
Dynamic range, dB (A):	113.4	Excellent
THD, %:	0.0008	Excellent
IMD+N, %:	0.0010	Excellent
Stereo crosstalk, dB:	-108.1	Excellent
IM at 10 kHz, %:	0.0012	Excellent

Interface characteristics are close to the rated and are on par with those of the best internal cards with a similar price. Our expectations were justified.

The card couldn't work in full duplex in the 192 kHz 24-bit mode - due to USB connection. Given the buffer was large enough, playback was flawless. However we still couldn't make the card record acceptably in this mode.

It would be logical to ask why install such codecs then, if you can't use them fully fledged? The answer is that top-end converters produce better results at more traditional frequencies (e.g., 44.1 kHz) - comparing to older models designed for lower frequencies. They left the 192 kHz mode intact, because it might still be useful for someone (and to gain better marketing momentum as well.)

Perhaps, the vendor should think over releasing a Firewire modification of the product with Crystal DAC. In that case it could compete with higher-end rivals. Perhaps, even with Lynx's interfaces.

Drivers

Drivers installation was flawless on every testbed. Controls were as simple as they could be: a single modes window with all the controllers on the interface itself.

Working with ASIO interface, drivers automatically determine and set the required sampling rate. ASIO buffer can be resized without any problems, re-launching, etc., but it can only be done via the ASIO Control Panel. The native control panel doesn't have anything resembling buffer size. Perhaphs, it's fixed for the MME interface. Drivers also lack the MME auto sample rate option.

Subjective testing

For subjective tests the interface was connected directly to ADAM S2.5A monitors. We used high-quality records of various styles obtained by digital EAC copying from CD-DA and DVD-Audio sources. The interface was to compete with ESI Juli@ and E-MU 1212M - the best products in their class offered (that's also important) for a similar price.

All three devices produced similar professional sound. However we could hear the difference on the top-end ADAM S2.5A acoustic system.

Comparing to Juli@, 0404 USB sounded in considerably more detail and produced better attack. We listened to tens of tracks instantly switching from one recording to another. And without a doubt the classic ESI Juli@, one of the best PCI devices out there with AK4358 DAC, yielded to this external interface with the top-end AK4396 converter.

The 1212M card has the same converters as LynxTWO and ProTools HD 192 have and belongs to the mastering product class. In the majority of recordings 0404 USB slightly yielded to 1212M in quality. In some cases we could notice tembre differences between AK4396 and CS4398 that didn't benefit either solution.

Anyway, given the similar price, 0404 USB is more comfortable to use than 1212M: automatic sampling rate adjustment vs. creating new projects in Patchmix 1212M; hardware volume control of 0404 USB vs. software slider in Patchmix. Add to this connection comfort, headphones output... And if you have cheaper monitors, benefits of 1212M fade even more.

According to the vendor, relatively to other products, 0404 USB is a slightly pared-down M-class, which is still better than non-M. Usage of the same pre-amplifiers as AudioDock 1616 has provides higher pre-amplifier quality than that of the original 1820M.

	Frequency response, dB	Pre-amps, SNR	Line-out, SNR	Headphones, SNR
1820	+0.8, -0.1	100 dBA	112 dBA	112 dBA
1820M	+0.8, -0.1	107 dBA	120 dBA	117 dBA
0404 USB	+0.06, -0.035	113 dBA	117 dBA	114 dBA

Performance

Built-in pre-amplifiers performed well and didn't produce noise even at strong amplification (just the white noise, according to spectrum analyzer.) One peculiarity is that controllers allow to set amplification of up to +65 dB. However combined with Oktava MK319, amplification, exceeding about 62 dB, causes pre-amplifier self-excitation (perhaps, due to circuit design) and produces distinctive noise instead of signal. But let's not consider this a disadvantage - the vendor honestly rated pre-amplification at +60 dB.

A soft limiter is a useful feature that allows to avoid signal clipping at when signal pickup is a little bit over the limit.

The only issue we had was with coaxial SPDIF input. For some reason it started to work only after we fed it an AES/EBU signal from LynxTWO. Perhaps, the signal level, not the protocol, was incorrect. There were no problems with optical interface.

The built-in headphones pre-amplifier has output impedance of 22 Ohm and max. output power of 20 milliwatt. Like mic pre-amplifiers, it's A-class, so it should be enough for the majority of popular headphones (though it's still not recommended to connect those super low-Ohm ones with impedance below 22 Ohm). Note that the headphone signal is produced by the primary DAC, not a separate lower-quality one, like they do it in some interfaces.

The 0404 USB amplifier did perfectly well with both high-Ohm Sennheiser HD580 and budget low-Ohm AKG K44. We could find no evident differences, comparing it to the amplifier of Mackie BigKnob. High-quality amplifiers of both devices do not cause signal distortion. Just note the higher power potential of BigKnob.

Conclusions

Our tests showed that E-MU's new professional USB interface justified our expectations and got very close to the best PCI cards from the angle of sound quality produced with top-class monitors. It differs favourably from E-MU's PCI cards by simpler and more user-friendly controls. Our measurements with Aurora 8 also confirmed that the interface has a really high-quality path. It's a major step forward for external interfaces that hardly provide 100 dB SNR with dirty spectrum.

At that 0404 USB has only stereo input and output, so you won't have to pay for multiple channels, which you do not require. Instead, you will get a top-end AKM's DAC, high-quality pre-amplifiers, headphone amplifier, and user-friendly controls.

In the end we'll just mention the rather affordable price and congratulate E-MU with such a successful external USB interface.

We can easily recommend EMU 0404 USB for use in home and project studios, for out-of-studio sound recording, and just as a high-quality solution for listening to music (in headphones as well.)

According to our test results, E-MU 0404 USB gets the "Original Design" award for a technological breakthrough in the field of external USB interfaces.

Vasily Fedoseev aka Vasfed
with the assistance of Maxim Lyadov (maxim@ixbt.com)

November 23, 2006