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Accuphase DG-68 Digital Voice Equalizer – a noble tool for Sound optimisation

A powerful DSP and state-of-the-art algorithms are to form the basis for the new Accuphase DG-68 Digital Voice Equalizer, which not only allows you to adjust the reproduction to the conditions in the listening room, but also to optimise the tonality to suit your own ideas. In the twinkling of an eye, in an almost intuitive way.


For a long time, it was considered the highest virtue of hi-fi to make the reproduction as “neutral” as possible, to interfere with the signal as little as possible. This shows that even the philosophy of how to handle HiFi is subject to trends, because if you look back a few years, this was not only common practice, but even considered a playground for audiophile sound tinkerers. Not only did amplifiers themselves offer various possibilities to influence the sound characteristics at that time, solutions such as equalizers were often an integral part of a HiFi chain.

Recently, it can be observed that the topic of room acoustics is fortunately becoming more and more the focus of attention, to the extent that one does not just try to optimise it with various constructional measures as far as possible, but actually starts again with the electronics themselves. Possibilities that were used for a long time in the home cinema segment alone are now appearing in more and more sophisticated form in stereo components, such as room calibration.

There have always been renowned companies that have relied on a wide variety of solutions that allow the user to optimise the sound characteristics according to his individual preferences. These include the Japanese high-end hi-fi forge Accuphase Laboratory Inc. Not only is sophisticated equalisation to be found in almost all amplifier systems of the Japanese, but they also offer very special solutions which allow for particularly extensive optimisation, and the latest in this field is now the Accuphase DG-68 Digital Voice Equalizer.

Accuphase Laboratory Inc. promotes the new Accuphase DG-68 Digital Voice Equalizer because it offers the ability to create the ideal listening environment in the blink of an eye, as well as the intuitive ability to adjust the playback to your own preferences. Decades of experience and state-of-the-art technology have been combined to create a tool that combines sound field compensation to optimise the acoustic properties of a room with an equaliser to optimise the tonal quality of the musical performance.

The new Accuphase DG-68 Digital Voice Equalizer represents the fifth generation of this concept, which was first presented in 1997 with the Accuphase DG-28 Digital Voice Equalizer. All subsequent models have been optimised to the highest standards, up to the latest Accuphase DG-68 Digital Voice Equalizer, which now features the latest technology and even more sophisticated options, making it a state-of-the-art solution in its field.

The new Accuphase DG-68 Digital Voice Equalizer offers three main functions, namely sound field correction, also known as voicing function, an equalization function, i.e. equalizer, and also the function of a spectrum analyzer.

The basis of all these possibilities is a particularly powerful DSP, namely a 40-bit floating point DSP of the type Analog Devices ADSP-21489, which allows for high-precision fully digital signal processing.

To integrate the new Accuphase DG-68 Digital Voice Equalizer into the HiFi chain, a wide range of options are available. For example, it can be looped in between the preamp and power amplifier, or it can be integrated into a preamp or integrated amplifier via a record out and record in. The Accuphase DG-68 Digital Voice Equalizer can also be integrated into a stereo amplifier, if it offers the possibility to separate the pre and power amplifiers. Since the new Accuphase DG-68 Digital Voice Equalizer has numerous interfaces on analogue and digital level, there are really countless possible scenarios.

In concrete terms, the new Accuphase DG-68 Digital Voice Equalizer offers both unbalanced and balanced analogue inputs, designed as RCA or XLR connections. In addition, there is an optical and coaxial S/PDIF interface as input and output on the digital level. In addition, Accuphase HS-Link, a manufacturer-specific interface designed as an RJ45 socket, is also available, via which audio data can be transmitted in Linear PCM with up to 32 bits and 384 kHz, as well as native DSD up to DSD 5.6.

In order to enable digital signal processing, appropriate converters are of course required. For the new Accuphase DG-68 Digital Voice Equalizer, the developers used 32-bit A/D converters of the type AK5578EN from Asahi Kasei Microdevices, which are used in quadruple parallel configuration. ES9028PRO from ESS Technology are used in eightfold parallel configuration for the D/A converters. In addition, ANCC Technology is relied upon for both A/D and D/A conversion, which stands for Accuphase Noise and Distortion Cancelling Cuircut and is designed to effectively eliminate noise and distortion.

As complex as the technology used in the new Accuphase DG-68 Digital Voice Equalizer is, it should be easy for the customer to use in practice.

The key to this is a very large display on the front of the Accuphase DG-68 Digital Voice Equalizer, because it is designed as a touch screen, which not only allows accurate display of the curves, but also allows them to be edited directly on the display.

The so-called voicing, i.e. the correction of the sound field, can be carried out completely automatically (Auto Voicing) with the help of a measuring microphone, which is part of the scope of delivery in the form of the Accuphase AM-68 together with cable and matching stand. The characteristics of the listening room are thus determined and a corresponding correction is made by 1/6 octave IIR filters with 67 frequency ranges with +/- 12 dB each. Smooth Voicing guarantees that the corrections for the left and right channel are selected in such a way that the differences in frequency response are reduced to an absolute minimum, taking into account the loudspeaker characteristics and room acoustics, so that a very smooth frequency response curve is achieved. If desired, the sound field correction can also be done completely manually (Manual Voicing).

The equalizer is also constructed using 1/6 octave IIR filters and provides a remarkable 80 frequency ranges with +/- 12 dB. This allows for a remarkably precise control. This is where the touch screen shows its full strength, because with the help of a stylus you can actually draw the frequency curve on it easily.

30 memory locations are available for individual corrections, which of course can be given suitable names.

The spectrum analyser of the Accuphase DG-68 Digital Voice Equalizer can be used for control, analysing the frequency spectrum in 35 ranges up to 50 kHz and displaying it on the display. Screen shots can be taken here, which can be stored on a USB stick, as can the settings. The corresponding USB port can be found on the back of the Accuphase DG-68 Digital Voice Equalizer.

Apart from the above-mentioned display, which takes up about half of the front of the new Accuphase DG-68 Digital Voice Equalizer, this is where the input for the measuring microphone, a few function keys, a five-way control pad and of course the main switch are located. Interesting detail on the side, the stylus for comfortable operation is in a separate slot, so it is always available.

It should be emphasised that the Accuphase DG-68 Digital Voice Equalizer, despite all the editing options directly on the unit, is of course supplied with a matching Accuphase RC.330 infrared remote control, which can be used to quickly switch between different presets.

In the proven tradition, the new Accuphase DG-68 digital voice equalizer is of course also equipped with a noble, solid metal housing with a solid top plate and brushed aluminium front, which is completely in line with the design line of Accuphase Laboratory Inc. This means that the new Accuphase DG-68 Digital Voice Equalizer is also equipped with elegant wooden side panels.

The new Accuphase DG-68 Digital Voice Equalizer is available right now in specialist shops. The price is € 14.690,-

Getting to the point

Accuphase Laboratory Inc. promotes the new Accuphase DG-68 Digital Voice Equalizer because it offers the ability to create the ideal listening environment in the blink of an eye, and more importantly, it allows you to intuitively adjust the playback to suit your preferences. Decades of experience and state-of-the-art technology have been combined to create a tool that combines sound field compensation to optimise the acoustic properties of a room with an equaliser to optimise the tonal quality of the musical performance.

Manufacturer:Accuphase Laboratory Inc.
Distribution:R.M.S. State of the Art Audiovisual Products
Price:€ 14.690,-
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Michael Holzinger

Michael Holzinger, founder and editor-in-chief of HiFi BLOG and sempre-audio.at, has been working for years as a journalist in the fields of IT, photography, telecommunications and consumer electronics.

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