The high quality 5-band parametric EQ – 7-band with included Bass/Treble – is one of the major features that can’t be found on any similar device. The EQ provides a different EQ for the left and right channels, is usable at up to 768 kHz sample rate, easy to set up and adjust, thanks to the graphical display showing the resulting curve.

While no equalization as well as listening only straight linear has been a mantra for many years, research has proven that no ears are identical, and that especially in near-field listening with phones the biological differences alone make individual equalization mandatory. No two pairs of ears hear the same thing, that’s a scientific fact. Additionally personal taste makes people like different sound signatures, which can easily be copied or made more similar (equalized…) on different headphones using a good EQ. The advantages of using an EQ outweigh any alleged disad-vantages – which so often turn out to be wrong at closer inspection.

A unique feature is the ability, to setup different EQs for Speakers and Headphones and use a dual EQ with different filter curves for your left + right ears (see below).

Headphones and speaker sound profiles
The EQ provides presets including individual naming. So whatever EQ setting you need, it is quickly setup, loaded and modified. To make this feature really useful the DAC offers three individual EQ settings – one each for rear out, Phones and IEM.

Room Correction
With the Dual EQ it is possible, to calculate room correction filter curves for your speakers before the final DA conversion, without leaving the signal path and loosing sound quality to external devices.

Dual Mode
These days many people suffer from hearing loss in varying degrees. No matter if it is biological, from abuse or an accident – hearing impaired is a plague of modern times. And – no surprise when thinking about it – it never affects both ears identically. The number of people having one sided hearing problems is huge, but they have learned to live with an industry that totally ignores them. Although the solution is as simple as logical – have the EQ be adjustable independently for left and right. Basically digital EQs are calculated this way, the common controls are just for making it easier to operate. The ADI-2 DAC includes an option called Dual EQ – a heaven send feature for many, for sure.

Another legacy of HiFi amplifiers: Loudness tries to address the changes in frequency-dependent hearing sensitivity over different volume levels.

If one listens to music loud, then drops the level by at least 20 dB, sound loses punch and glitter. HiFi amps tried to fight this effect by adding more bass and treble the lower the volume was set. Unfortunately that never worked as intended, and just became an additional bass/treble booster. Reason: the manufacturer of the HiFi amp could not know what volume any position of the volume knob equals at the customer’s home. Room size, room dampening and efficiency of the used speakers are all unknown.

But the effect of loss in perceived sound exists (read about the Fletcher-Munson curves), and can be easily reproduced with any serious gear by comparing normal volume and DIM state (usually -20 dB). The ADI-2 DAC offers Loudness for the analog stereo outputs, and probably is the first time that Loudness works as intended. The user can decide how much maximum gain in Bass and Treble should occur at lower volume settings. The user also sets the Low Vol Reference, where maximum gain is achieved. After extensive tests a 20 dB range has been defined as range for maximum gain to no gain while increasing volume. That seemed to be the perfect definition of the range that needs to be addressed by Loudness.

Here is an example on how it works: the user’s typical lowest level listening volume is at -35 dB at the unit. This value is now set by the user as Low Vol Ref in the Loudness menu. Then Bass and Treble Gain can be set between 0 and +10 dB. Default is +7 dB for both. Increasing the volume by turning the Volume knob causes the gain in Bass and Treble to be lowered smoothly over a range of 20 dB. So when Volume is set to -15 dB, the music is not only quite loud, but Loudness’ Bass and Treble are then at 0 dB gain. See chapter 31.6 for graphs.

No matter how sensitive the connected phones or speakers are, no matter how much increase in Bass and Treble are desired – with the ADI-2 DAC one can finally adjust it to meet the personal hearing and taste. Loudness finally works as it should have worked from the start – another unique feature in the ADI-2 DAC.

The mid/side principle is a special positioning technique for microphones, which results in a mid signal on one channel and a side signal on the other channel. This information can be transformed back into a stereo signal quite easily. The process sends the monaural mid channel to left and right, the side channel too, but phase inverted (180°) to the right channel.
For a better understanding: the mid channel represents the function L+R, while the side channel represents L-R.

During record the monitoring needs to be done in ‘conventional’ stereo. Therefore the ADI-2 DAC also offers the functionality of a M/S-decoder. The M/S-Processing automatically operates as M/S encoder or decoder, depending on the source signal format. When processing a usual stereo signal, all monaural information will be shifted into the left channel, all stereo information into the right channel (thus the stereo signal is M/S en-coded).

This was another reason for RME to offer this option in a ‘HiFi-DAC’, because the separation of the mono and stereo components provides some interesting insights into the mono/stereo content of modern music productions. Use Balance to switch between left and right only to hear the full details of the result.

The Analyzer is based on RME’s famous Pro Audio Spectral Analyzer in DIGICheck. It uses 29 biquad bandpass filters for high separation between the bands, providing outstanding musical visualiza-tion. Using carefully selected attack and release times the display is responsive, but still easy to read. O

Thanks to the high-resolution display even smallest details are clear to see. Music content analysis is possible even when viewed from a greater distance. The Analyzer operates at any sample rate, and even with DSD from 20 Hz up to 20 kHz.

As opposed to most other solutions no FFT (Fast Fourier Transform) is used. RME’s Spectral Analyzer performs a true band-pass filter calculation, as in professional hardware devices. The frequency distance between the filters is scaled matching human hearing. The highly optimized code allows to run a 30 band analyzer with 60 dB range, sharp filters and 0.5 dB steps accuracy per band, on the ADI-2 DAC DSP, even at 768 kHz sample rate.

The most important application using a Spectral Analyzer is the visualization of frequencies and levels found in music or speech. The Analyzer shows levels and frequencies even at the edge of the human ear’s abilities – or that of the used speakers and headphone. The visual display helps to train ones ears, makes coarse errors visible, and shows what sometimes might stay unnoticed. For example many speakers won’t let you hear frequencies below 30 Hz. Simply look on the Analyzer to see what’s going on in the underground.

Stereo Level Meter
The horizontal stereo level meter below the Analyzer can show the peak level before all DSP processing (Pre, equals the current input level from USB playback and SPDIF In), after all pro-cessing including volume control (Post), or both at the same time (Dual).