Topping Pro E4x4 Pre USB Audio Interface

designed to get the best possible results from headphones With the rise in producers working and mixing in headphones, it is surprising that the headphone output on most affordable interfaces is often underpowered and unable to work with good volume and low distortion with all but the most efficient, low impedance headphones.

Topping Pro’s Interface range are designed to get the best possible results from headphones, so even for hard to drive models you won’t need an external headphone amp.

The E4x4 has dual headphone outputs, each with up to 580mW of power and a Hi/Lo gain switch. It is equally suitable for high impedance models as ones with low impedance and low sensitivity such as many Hifiman and Dan Clark Planar Magnetic headphones that struggle on most interfaces and require a dedicated amp. In comparison, most similar priced interfaces have a max output power of between 25 & 150mw.

The Dual headphone outputs have separate Amplifiers and can have separate mixes assigned to each, managed through the control centre software.

Low noise inputs Topping have implemented extremely low noise (-128dB EIN) microphone and instrument preamps that would not be out of place on high end premium interfaces, even low output dynamic mics like the SM7B work fantastically well without the need for an external preamp. All of the Topping interface stock at Scan are revised models with the increased 1.5K input impedance.

Samples rates of up to 192kHz 24 Bit / are supported on Mac & PC, but there is also iOS and Android compatibility when using a standard external USB power supply. The additional power supply also means that any particularly challenging, power hungry condenser mics would be no issue on any platform.

The control centre has four 12-channel input mixers, the E4×4 Pre allows you to easily adjust and control levels for monitoring and loopback. Having multiple loopback and DAW channels means you can configure routing flexibly. Looping back audio output back into an input means you can not only record the audio of desktop applications into your DAW, but also capture audio from DAW applications for live streaming or to go into Zoom or Teams type calls combined with your mic input.

1. Headroom for Peaks & Transients Headroom is very important in headphone mixing, you want to be able to hear when distortion kicks in in the music you are working on, not when your headphone amp clips on volume peaks. This is extra power available in the amplifier above the average level you are listening at, before it starts clipping and distorting, to cope with dynamic changes in the music.

These changes could be short, loud transients of drums or percussion , or slower changes in volume in different parts of the the music. This is especially important when you are mixing records as opposed to listening to a finished piece of music, as you will have much greater dynamic changes on your master output as opposed to a mastered record.

2. Headphone EQ Correction Headphones have very differing frequency responses, even with ‘studio reference’ type models and can be made more accurate with EQ based correction. This can be done in a plugin or your mix bus, or the end of your master bus if you don’t have one . This can be done manually, or using a plugin that has profiles for different headphone models, such as Sonarworks Sound ID Reference, Toneboosters Morphit, D-soniq Realphones, Acustica Sienna or Waves NX.

Whenever any of these plugins makes a boost to correct the dip in the headphones frequency response , it uses up headroom, it is not uncommon to see corrections of 10dB in some profiles, especially boosting the sub region of open back headphones where the bass rolls early. A 10dB boost is a perceived doubling of the loudness, but takes 10 times the amplifier power.

3 . Equal Loudness Curves Human ears perceive the balance of sound at differently dependent on the voume of the sound. This is why Hifi systems often have ‘Loudness’ buttons on them to compensate for lower bass and treble at low volumes. When making your final mix decisions, you want to monitor at somewhere between 75-83dB(c) , for the tonal balance to be as even as possible to your ear, however, it is very hard without a calibrated dummy head to monitor headphone volume.

You do not have to monitor at these levels all the time, but doing so at least for your final mix will hive the most even balance. To do this at home, we suggest using an App on your phone that has a ‘C’ Weighted DB meter, adjust the volume of your speakers until you get a 75-83dB average (dependent on the size of your room, big rooms should be louder) and then adjust your headphone volume to be close to your speakers as you take them on and off.

You probably are not used to seeing headphone output impedance commonly on specs, but matching it to the impedance of your headphones is very important for linearity of the frequency response.

To get a linear frequency response for your headphones, ideally they want to ideally be more than 8 times (and certainly no less than 5 times) the output impedance, so any headphone with an impedance of more than 8 ohm will have an uncoloured output on a Topping Pro interface, Which is practically every headphone and IEM.

Most other popular interfaces at a similar price have output impedance between 10 Ohm (recommended 50- 80+ Ohm Headphones) & 90 Ohm (recommended 450-720 Ohm Headphones). Using headphones with impedances below the 8 times rule predominately results in a bass bump, which will be larger the further away you are from the number. An unwanted bass bump in the response means your mixes will probably translate bass light.

As a comparison, The latest generation of a popular 2 in, 2 out, red cased interface has a headphone output impedance of 50 Ohms, so only completely even with headphones above 400 Ohms, however its’ amplifier has less than a quarter of the power of the one in the Topping Pro Interfaces at 400ohms.