Z Systems z-Qualizer User manual

z-Qualizer manual Z-Systems Audio Engineering
1
z-Qualizer Operations Manual
Welcome!
Congratulations on purchasing the z-Qualizer, the first low-cost outboard digital EQ
capable of world-class mastering performance. The z-Qualizer comes from a distin-
guished lineage of mastering processors that Z-Systems has been making for nearly
a decade. You’ve already heard our EQ algorithms on countless recordings and now
you have the chance to hear what they can do for your very own projects.
We urge you to read the following manual before using the z-Qualizer. We’re confi-
dent that anyone can learn to use it on their own, but it might be helpful to read the
manual and learn some of the finer points before diving in.
S -02.4 2k50 0.8
4
gain
3
z-Qualizer
signal
gain freq Q
byp
load
save
S
R
L
m-s &dither
MIDI
2
Z. SYS
MIDI in
MIDI through
1
9V DC
@500 mA
ATTENTION/AVIS:
Risque de choc electronique.
Ne pas ouvrir.
To minimize risk of fire, use only the
specified power adapter.
AES/EBU
outputinput
Designed and manufactured in
the US by Z-Systems Audio
Engineering.
Do not open. Risk of electrical
shock. No user-serviceable
parts inside.
Powering Up
Plug the DC power adapter that was included with the unit into an AC power outlet
and connect the other end of the DC power adapter to the DC power inlet on the back
of the unit. The z-Qualizer will power up quickly. Next, connect the z-Qualizer to an
AES/EBU standard digital audio source. The signal LED will light to indicate the pres-
ence of a valid incoming signal.
Gain and Channel Offsets
We should mention a general rule at this point. The z-Qualizer is a stereo unit and it
can be operated in either dual-mono or stereo-linked modes. Dual-mono means that
the EQ parameters can be adjusted independently for the left and right channels. In
stereo-linked mode, the left- and right-channel EQ parameters track one another. The
Land Rpositions on the left knob are used to select between the left- and right-

z-Qualizer manual Z-Systems Audio Engineering
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channel parameter banks, whereas the Sposition puts the unit into stereo-linked
mode. The left-most edge of the alphanumeric display will always show whether the
unit is in L, R, or Smode.
When the unit powers up, the left knob will be set to S, for “stereo” and the right
knob will be set to gain as indicated by the respective LEDs surrounding the left and
right knobs. In this mode, the only parameters showing in the alphanumeric display
will be an S(indicating the z-Qualizer is stereo-linked) and a number above the gain
knob indicating, in dBFS, the amount of gain (or attenuation) applied simultaneously
to the left and right channels:
S +00.0
Turning the gain knob adjusts the stereo gain. To apply different gains to the left and
right channels, rotate the left knob to L, for “left channel.” Observe that the alpha-
numeric display changes to show an Lindicating that the z-Qualizer is now in dual-
mono mode, with the left-channel parameters currently active. Rotating the gain knob
changes the left channel gain. The procedure is similar for the right channel. If you
turn the left knob back to S, you’ll see that the stereo gain is still the same as before.
The z-Qualizer is designed so that the left, right, and stereo gains can be different.
This allows you to dial in an offset between the left and right gains and then maintain
that offset by manipulating only the stereo gain.
Equalization
The equalization in the z-Qualizer is performed with floating-point arithmetic and uses
very special proprietary low-distortion algorithms developed. There are six bands, in-
cluding two first-order (6 dB per octave) shelves and four parametrics (bell curves).
Stereo-linked mode:
Make sure the left knob is in the Sposition and turn the right knob to the low shelf
position (one click counter-clockwise from the gain position). The low shelf LED will
light and the alphanumeric display should look like:
S +00.0 1K00
Rotate the gain knob to change the gain of the low frequency shelving equalizer. Ro-
tate the freq knob to change the frequency below which the shelving action takes
place. This frequency is at the nominal 3 dB point of the curve. The first-order equal-
izer is extremely gentle and quite natural-sounding.
Dual-mono mode:
Rotate the left knob to put the z-Qualizer in left-channel mode. The alphanumeric
display now reads:

z-Qualizer manual Z-Systems Audio Engineering
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L +00.0 1K00
Here you can display and adjust the left channel shelf independently. Similarly, turn
the left knob to the Rposition and adjust the right channel. If you then return to ste-
reo-linked mode, the Land Rfilters retain their settings until you change a parameter
in Smode. For example, if the Land Rgains are different for the low shelving filter, if
you return to stereo-linked mode and adjust the gain, it gets copied to both the Land
Rfilters.
Important: You will notice that the “L” indicator in the display is blinking. This is to
remind you that the z-Qualizer is in dual-mono mode. The same is true for the “R”
when you are adjusting the right-channel parameters.
The other bands:
The high-shelf filter is accessed by turning the right knob one click clockwise from the
gain position, and performs exactly as above for stereo-linked or dual-mono equaliza-
tion. The freq knob controls the frequency above which action occurs.
The four bell-shaped parametrics are numbered as 1, 2, 3, and 4on the right knob.
Turn the right knob to any of these positions and you will see:
S -00.0 1K00 0.4
This indicates, in order, stereo-linked or dual-mono mode, boost/cut, center fre-
quency, and quality factor, or Q. As always, the label is above its corresponding knob,
and as above, turning the left knob to Land Rwill allow you to control the left or right
channel separately. Q is the inverse of bandwidth. It is the product of center fre-
quency divided by the 3 dB down bandwidth. Thus, a Q of 0.4 produces an extremely
wide curve and will be rarely used. A Q of 0.6 or 0.7 corresponds with the bandwidth
of a typical midrange EQ in an analog equalizer.
M/S & Dither
Dither
Turn the left knob to m-s & dither, The alphanumeric display will appear as follows:
24 un ENC:N DEC:N
As in all z-Qualizer menus, the labels appear above the knob which affects the pa-
rameter. For example, in this menu, you can change the wordlength and dither by ro-
tating the left knob to any of the following:

z-Qualizer manual Z-Systems Audio Engineering
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24 un
24 di
20 un
20 di
16 un
16 di
16 p2
16 p3
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-Qualizer 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-Qualizer is a carefully-randomized floating point dither which removes
quantization distortion. The dither noise level at the 24 dith setting is at approxi-
mately -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).
However, the ear can easily hear signal as much as 20 dB or better below the wide-
band 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 undith-
ered menu choices actually truncate the output of the z-Qualizer without concern for
quantization distortion.
The other dithered wordlength settings are only to be used if the z-Qualizer is con-
nected directly to a following device which truncates the wordlength. For example,
use 20 dith if the z-Qualizer is directly connected to a 20 bit ADAT. Use 16 dith or 16
pwr if the z-Qualizer 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 undithered
option if you wish to bypass the z-Qualizer without turning the left knob to the byp po-
sition (in an automated session, for example, where one tune passes through flat
without any alteration). In this case, select 24 un and make sure that all the gains

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and equalizer levels are set to 00.0 dB. In the 24 un setting, with everything neutral-
ized, the z-Qualizer is bit-transparent, (i.e., it will pass all incoming AES/EBU signals
without data alteration). In the 20 un (16 un) setting, the z-Qualizer truncates its out-
put 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 set-
tings; 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-
Qualizer are POW-r 2 and POW-r 3, at 16 bits only, idealized for CD and DAT re-
cording. 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, and much smaller
than with competing noise-shaping processes.
MS encode and decode
This versatile feature can be used in several ways. Let’s return again to the alpha-
numeric display:
24 un ENC:N DEC:N
The middle knob changes encode from no to yes, the right hand knob changes MS
decode from no to yes. The MS encoder in the z-Qualizer is located in front of the
gain, left and right channel adjustments and in front of the stereo equalizers. The MS
decoder is located after all processing and before the dither. In the z-Qualizer, the MS
encoder is at unity gain, and the decoder drops the gain by exactly 6 dB, which turns
out to be perfectly symmetrical---but you don’t need to know how the math works to
take advantage of MS mode. If the mode is set to ENC:Y DEC:Y and all equalization
and gains are set to 0 dB, the system remains perfectly bit transparent, since its MS
encoder and decoder are exactly symmetrical, down to the last mathematical bit. You
can leave the system in ENC:Y DEC:Y mode if you wish and operate it as a stereo
equalizer without any concern for losses.
MS stands for Mid-Side, or Mono-Stereo. When in MS Y, Y mode, internally the z-
Qualizer becomes an MS-style equalizer instead of a stereo equalizer. However, the
input remains stereo and the output remains stereo. It is useful to know that an MS
encoder contains the same circuit as a decoder. This means that you can use the en-
coder to decode and the decoder to encode if you wish. For example, you could feed
an MS signal into the z-Qualizer, decode it to stereo, manipulate the left and right
balance and eq, and then reencode it to MS for further processing in MS mode.
There are about 16 permutations you could think of, so the limit of flexibility is com-
pletely up to your imagination!

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Taking advantage of M/S
The most common use of MS equalization is to deal with center channel information
which needs separate EQ than the sides. If you feed a stereo recording into the z-
Qualizer and set the mode to MS Y, Y, the left channel gain control becomes the M
gain (or center gain), and the right channel gain control becomes the S gain (or side
gain). These controls can manipulate the width of the stereo image, while also reduc-
ing the ratio of the mix of center-located instruments to side-located instruments. Try
it. Feed in a good stereo recording with a center-located vocalist. Turn the right knob
to gain and turn the left knob to L. Turn the gain knob counterclockwise until the L
gain is at -95 dB. The vocalist (and all center instruments) should virtually disappear,
and you will be left with a widely separated, out of phase mono representation of the
instruments and stereo vocal reverb. See what happens if you turn down the R gain
instead.
For equalization, you can cheat the frequencies for the M channel up or down sepa-
rately from the S channel to manipulate the recording in creative ways. All the L la-
bels are interpreted as M and the R labels as S. In MS Y, Y mode there is no way to
adjust full channel balance because the L and R gain controls have become M and S
controls, respectively.
The presets (see below) remember the M/S state, so, for example, you can work on
one tune in MS mode and another in stereo mode.
Presets
Loading Presets
Rotate the left knob to the load position. The alphanumeric display will look some-
thing like this:
a=01 load
Rotate the gain knob (which is directly below the a=01 display) to choose the mem-
ory number from 00 to 99 from which to load, memory 00 is a factory default, which
is set to: MS N, N; 24 bits; all gains and eqs at 0 dB. Memories 1 through 99 are
user-adjustable. To return the z-Qualizer to flat settings, simply use the following pro-
cedure with preset #00.
Let’s assume we want to load the contents of memory #34. Rotate the gain knob un-
til the alphanumeric display looks like this:
a=34 load

z-Qualizer manual Z-Systems Audio Engineering
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Then rotate the Qknob (below the word load in the alphanumeric display). This loads
memory #34 and places an arrow next to the preset number to let you know the
memory has been loaded:
a=34< load
It’s that simple. If you change the preset number from the one that’s currently
loaded, the arrow disappears, indicating that you have to load again if you want this
new memory. Of course, the previously loaded memory is still in the equalizer until
the next load. Try it. It’s easy and intuitive.
The preset load function remembers the last memory you were working on, and it will
come back to that mode when you return to this screen.
Saving Presets
Rotate the left knob to the save position. The alphanumeric display will look some-
thing like this:
a=01 save
You cannot save anything into preset 00. To save the current equalizer state into any
memory, rotate the gain knob to choose the memory, then rotate the Q knob (in ei-
ther direction), and the display now looks like:
a=01< save
To save the current state of the equalizer into a series of memories, just increment
the memories with the left knob, rotate the right knob, and repeat. This is very useful
when you have been doing a job and want to neutralize a bunch of memories.
MIDI
Setting the MIDI channel
Connect the MIDI output to the input of a MIDI sequencer, and the MIDI input to the
output of the sequencer. Turn the left knob to the MIDI position and the alphanu-
meric screen will look like this:
ID=02 read dump
To change the midi channel, rotate the gain knob. The channel is preserved in non-
volatile memory at power down.

z-Qualizer manual Z-Systems Audio Engineering
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SysEx Read
For a SysEx restore of all 99 presets from a MIDI sequencer, turn the freq knob (be-
low the word read in the alphanumeric display) in either direction to prepare the z-
Qualizer to receive SysEx data. Start your sequencer playing the sysex dump. While
the dump is proceeding, the word read will change to a numerical countdown from
99 to 1 to indicate the memories which are being restored. This takes only a few
seconds. When the SysEx restore is complete, the word read re-appears in the alpha-
numeric display.
SysEx Dump
For a sysex dump of all 99 presets to a MIDI sequencer, first start your MIDI se-
quencer recording. Then rotate the Q knob to start the dump. During the dump, the
word dump will blink and the sequencer should indicate that it is receiving MIDI data.
After all 99 memories have been sent to the sequencer, the display returns to dump.
MIDI Program Change
Connect the output of a MIDI sequencer to the MIDI in jack. Any time the z-Qualizer
sees a program change whose value is from 00 through 99, it will load the corre-
sponding memory. In the preset load mode the memory number will change to the
one sent by the MIDI program change command. Any other screen will display the
results of the program change.
Specifications
 Input/Output: AES/EBU (transformer-isolated, 110-ohm terminated)
 Input/Output precision: up to 24 bits
 Gain control: from -95 dB to +12 dB
 Gain resolution: 0.1 dB increments between 0 and 3 dB (gain or loss), 0.2
dB increments from 3 dB to 12 dB (gain or loss), 1 dB increments from –
12 dB to -20 dB, 2 dB increments from -20 to -50 dB, 3 dB increments
from -50 to -62 dB, 4 dB increments from -62 to -70, 5 dB increments
from -70 to-95 dB.
 Filter types: 4 parametric, 2 shelving
 Center frequency resolution: 1/6th octave ISO from 28 Hz to 20 kHz
 Filter gain/cut: from -95 dB to + 12.0 dB with the same increments as the
gain control.
 Filter bandwidths: Q=0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4,
1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.5, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0
 Shelf filter slopes: 6 dB/octave (first order)
 Channel separation: Effectively infinite
 Dither types: 24 bit, 20 bit, and 16 bit proprietary floating-point tech-
niques, and 16 bit POW-r Dither (two types)

z-Qualizer manual Z-Systems Audio Engineering
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 Digital filter architecture: proprietary minimum roundoff-noise structure
 Dynamic range: better than 144 dB
 Ergonomic Stereo-linked and dual-mono operation
 Number of user-alterable presets: 99. Factory Preset: One (preset #00)
 THD+N: better than -135 dB
 Processor type: TMS320VC33 32-bit floating point DSP
 Digital audio demodulator/modulator: Crystal Semiconductor
 Sample rates supported: 32 kHz, 44.1 kHz, 48 kHz, 88.2 kHz, 96 kHz
 Auxiliary-bit status handling: unit is transparent to channel status, validity,
and auxiliary bits
 Power supply: 9 VDC @ 500 mA.
Z-Systems One-Year Warranty
All Z-Systems products come with an automatic one-year full warranty. We warrant to
the original purchaser that the product purchased will be free of defects for a period
of one year from the date of purchase. Z-Systems will, without charge, replace or re-
pair, at its option, defective products or component parts upon delivery to the manu-
facturer. This warranty does not apply in the event of misuse or abuse as a result of
unauthorized alterations or repairs. For warranty service work, simply contact the
manufacturer to arrange for return and repair. Z-Systems will not be liable for any
consequential damages, including, without limitation, damages resulting from loss of
use.
An Invitation to You
After you have used your Z-Systems product for a while, call, fax or email us and tell
us what you think. We enjoy hearing from you. Many of our new products, updates
and modifications were designed as solutions to technical problems encountered by
our end-users. Our enthusiastic customers help spread the good word about Z-
Systems. We would like you to be one of them.
Z-Systems Audio Engineering
1325 NW 53rd Ave Suite B
Gainesville, FL 32653 USA
[phone] (voice)
[phone] (fax)
[email protected]