Electronic Pages  Die Homepage der Familie Beis

Currently Being Developed:

8-Channel Fully Digital Parametric Equalizer

( Deutsche Version: 8-kanaliger, voll-digitaler parametrischer Equalizer)

Option: 8-Channel ADCs and DACs



The development of this equalizer is very far advanced. Now it's about finding out the interest in such a device. Whether it is worth to risk the costs for further prototypes and a small series. My fear is that the need for such a device is too low, because DAWs or digital mixing consoles are sufficiently equipped with equalizers and other applications rarely exist. That is why I want to present this development here and perhaps also demonstrate the laboratory sample on one or the other occasion. Maybe I can even arouse enthusiasm with the features of the equalizer?


Concerning its settings this equalizer is similar to the 2-channel analog equalizer TwinEq-1 MK2 of the Estec company. Great emphasis has been placed on the "analog feeling". Most settings are made with analog rotary encoders which have such a high resolution that in spite of the very fine level settings a quick and precise adjustment in real time is possible as with potentiometers in analog devices.

The selected frequency responses are displayed in real time during the setting. On the one hand this display serves as visualisation of the settings currently being made. On the other hand it also serves for quick orientation, e.g. after retrieving preset values or after undo and redo actions, to assess where and to which extent the equalizer affects the signals now. The graphics from frequency responses act like symbols providing a high recognition value for the associated application. This is of course considerably more informative than, for example, the tick marks on a multitude of potentiometers.

Basically, digital circuits and software solutions, if they are done correctly (which is not as self-evident as one should think), have the properties to behave very, very widely ideal, for example:

Additionally the digital technology offers further possibilities, e.g. the storage and retrieval of preset values or the synchronous setting of several channels simultaneously, which are not impossible in the analog world, but can only be realized with great effort.

Front View

Preliminary design of the front panel (Click to enlarge)

The front panel, from left to right:

Inputs and Outputs

Channel Preselection

Channels can be set individually or in groups. Within groups all channels receive identical settings. A typical group consists of e.g. two channels being joined to one stereo pair.

Building groups: Groups are built by preselecting and holding the key of the channel whose settings shall be copied. Then each further desired channel key is pressed. The corresponding keys are flashing. The copying of the settings and the building of the group takes place in the moment when any setting is changed in this state. Then all keys of the group are illuminated.

Preselecting groups: When a channel assigned to group is preselected, the whole group is preselected. All keys of the group are illuminated.

Disbanding groups: By pressing a key of an already preselected group only this channel is preselected. All other keys of the group go out. The channel is disbanded from the group in the moment, when any setting is changed in this state. It is also possible to disband several channels from a group simultaneously. In doing so a new group is created.

Equalizer Channel

Settings for each equalizer channel

Equalizer Operation

Low- and high-cut:
Bell and bell/shelf filter:
Master gain:


Graphic Display

Top left:

Top center:

Top right:

Middle Area:

Bottom left:

Bottom center:

Bottom right:

The Synchronous System

The equalizer works with sample rates of 16, 22.05, 24, 32, 44.1, 48, 64, 88.2, 96, 128, 176.4 and 196 kSa/s. The equalizer can generate these sample rates in master mode or resynchronize resp. de-jitter them as slave by means of VCXOs (Voltage Controlled Crystal Oscillators) within +/-100 ppm. It can also work with all sample rates in between, but then there is no de-jitter and the frequency responses are shifted as well. For sample rates which cannot be resynchronized the sample rate display is highlighted in yellow.

As a slave the equalizer can be synchronized via word clock or one of its 4 AES inputs. The selection is done automatically: The word clock input has priority, followed by the AES inputs, adjustable in the order of 1 to 4 or 4 to 1, so that e.g. input 4 can be used for DARS synchronization. Without a digital input signal the equalizer works with the preset default sample rate, which in practice is relevant only with existing ADCs.

Option 8-Channel ADCs and DACs


In Planning

State of the Development

The development of this equalizer is very advanced. All settings concerning the acoustic properties are fully available in the laboratory sample and can be demonstrated. Essentially the basic configuration settings are still missing, like e.g. default sample rate, the input and output routing and ADC and DAC reference level. Most of these configuration settings, however, only concern the ADC/DAC option. The operation with ADCs, DACs and word clock synchronization is prepared, but cannot be demonstrated in the laboratory sample at the moment.

Photo of the equalizer's laboratory sample (Click to enlarge)


Last update: October 13th, 2015 Questions? Suggestions? Email Me! Uwe Beis