Z-Systems z-Q2 User Manual

z-q2 operations manual

Introduction

Z-Systems model z-q2 6-band digital equalizer is based on the highly­successful model z-q1. For those who are familiar with the z-q1, here is a list of the
extensive improvements we’ve put into the z-q2:

•Complete ergonomic upgrade. The z-q2 is much easier and more fun to use.

The front panel has been simplified, keystroke and hand movement greatly
reduced, especially the process of saving and recalling memories. All screens are
now non-modal, which in plain English means that you can navigate instantly from
any menu to any other. The system remembers the last mode of any button that you
used. Left and Right channel equalization can now be separately and easily
adjusted and inspected. The one-line display has some added features keeping it
simple, yet powerful.

•POW-RTM dither. The reknowned dither from the POW-R consortium is now

included. POW-R dither is so transparent that it yields nearly 20-bit
psychoacoustic performance from a 16-bit master with virtually no penalty in tonal
balance, depth, space or width.

•MIDI control. Memory recall can now be recalled by an external MIDI

controller, and the entire state of the memories can be stored or recalled with
Sysex.

•M/S. A bit-transparent M/S encoder and/or decoder can be inserted in the

signal path.

•Range of gains has been optimized for very fine 0.1 dB equalization near 0

dB, and more coarse as the gains become extreme.

•Range of frequencies has been extended to 20 kHz for that ultimate “air

control”.

•Range of Qs now includes a fine range around 1.0, to include the most

common and musically useful Qs.

•Power-Down state. The z-q2 writes its current state into memory whenever

power is lost.

•And all the original low-distortion Zelniker equalization algorithms are still

here!

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z-q2 Operation

Connect AC power of the proper voltage range with an IEC power cord to the
back of the z-q2. If in doubt, verify the internal power selector switch has been set

to the proper voltage for your country before plugging in power!

System Menu

Dither, Wordlength and Sample Rate Display

Connect the z-q2 to an AES/EBU standard digital audio source whose sample
rate is 32 kHz, 44.1 kHz, 48, 88.2, or 96 Khz. The AES LOCK LED will light to
indicate it’s locked to the incoming signal. Now, press the SYSTEM button once.
You should see this display:

in:1 44k 24 dith

If the system is locked, the sample rate appears in the left side, and the
wordlength and dither mode appears in the middle. As in all z-q2 menus, the labels
appear above the knob which affects the parameter. For example, in this menu, you
can change the wordlength and dither by rotating the middle knob to any of the
following:

24 dith 24 bits 20 dith 20 bits 16 dith 16 bits 16 pwr2 16 pwr3

The last two POW-R dither options are only available at 44.1 or 48 kHz. The
sample rate cannot be altered as the system is always slaved to the incoming rate.

Using the dither and wordlength settings

When the z-q2 equalizer is feeding additional digital processors, nearly always
set the output wordlength to 24 dith. This is the maximum wordlength available

in AES/EBU and will send the highest resolution signal to the following device.
The Dither in the z-q2 is a carefully-randomized floating point dither which
removes quantization distortion. The dither noise level at the 24 dith setting is at
approximately -141 dB below full scale, so we doubt you will consider this to be
an audible problem! (To put this in perspective, most people consider analog tape
hiss below about -80 dB to be inaudible, and the noise floor of the best analog
audio console in the world is around -90 to -100 dB below full scale. Microphone
preamplifiers can do a bit better, but in the real world, noises add, and the practical
full band noise of the quietest typical musical recording is rarely better than about

-70 dBFS, excluding fadeouts).

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However, the ear can easily hear signal as much as 20 dB or better below the
wideband noise level, depending on the frequency and masking. That’s why we
have to use dither noise, to eliminate low level distortion caused by DSP
processing. Without dither noise, the sound of quantization distortion can reduce
stereo imaging, and make the sound cold and harsh, something to be avoided in
most cases. The bits menu choices actually truncate the output of the z-q2 without
concern for quantization distortion.

The other dithered wordlength settings are only to be used if the z-q2 is
connected directly to a following device which truncates the wordlength. For
example, use 20 dith if the z-q2 is directly connected to a 20 bit ADAT. Use 16
dith or 16 pwr if the z-q2 is connected directly to a 16-bit storage medium such as
DAT or CDR. A router may be used, but no additional DSP processor should be
between the Z Sys and the 16 or 20 bit device.

The only exception to the dither rule: you might choose to select the 24 bits
option if you wish to bypass the z-q2 without pressing the BYPASS button (in an
automated session, for example, where one tune passes through flat without any
alteration). In this case, select 24 bits and make sure that all the gains and equalizer
levels are set to 0 dB. In the 24 bits setting, with everything neutralized, the z-q2 is
bit-transparent, will pass all incoming AES/EBU signals without data alteration. In
the 20 bits (16 bits) setting, the z-q2 truncates its output to 20 bits (16 bits). These
last two settings will rarely be used. Perhaps you wish to cause some serious digital
grittiness (assuming you are fond of the authentic sound of early digital audio), or
you need to truncate the signal because a preceding device has not done so.
Proceed with care when choosing any of the truncation settings; their use is
extremely rare.

How to use the POW-R Dither

POW-R dither is a psychoacoustically-optimized dither. The two choices in the
z-q2 are POW-R 2 and POW-R 3, at 16 bits only, idealized for CD and DAT
recording. POW-R 3 has the strongest noise-shaping, and yields the highest
resolution. We can’t hear the effect of this shaping, but if you feel the shaping of
POW-R 3 is too strong for you, then by all means choose POW-R 2. POW-R 2
may yield slightly less depth, space and resolution, but the loss is barely
perceptible, probably inaudible, much less loss than with competing noise-shaping
processes.

MIDI

Connect the MIDI output to the input of a MIDI sequencer, and the MIDI input
to the output of the sequencer. Press the SYSTEM button again to arrive at the
MIDI screen, which should look like this:

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