WEISS MEDUS User manual

Weiss Engineering Ltd.
Switzerland
www.weiss-highend.com
MEDUS
OWNERS MANUAL

OWNERS MANUAL FOR WEISS MEDUS D/A CONVERTER
INTRODUCTION
D ear C stomer
Congrat lations on yo r p rchase of the MEDUS D/A Converter and welcome to the family of Weiss
eq ipment owners!
The MEDUS is the res lt of an intensive research and development process. Research was
cond cted both in analog and digital circ it design, as well as in signal processing algorithm
specification.
On the following pages I will introd ce yo to o r views on high q ality a dio processing. These
incl de f ndamental digital and analog a dio concepts and the MEDUS converter.
I wish yo a long-lasting relationship with yo r MEDUS.
Yo rs sincerely,
Daniel Weiss
President, Weiss Engineering Ltd.

OWNERS MANUAL FOR WEISS MEDUS D/A CONVERTER
TABLE OF CONTENTS
4 The MEDUS D/A Converter
4 Feat res
7 Operation
12 Technical Data
15 A short history of Weiss Engineering
16 O r mission and prod ct philosophy
17 Advanced digital and analog a dio concepts explained
17 Jitter S ppression, Clocking
19 Up-sampling, Oversampling and Sampling Rate Conversion in General
22 Reconstr ction Filters
22 Analog O tp t Stages
23 Dithering
25 Contact
26 Addend m for the FireWire option
33 Addend m for the ST Glass Fiber inp t option

OWNERS MANUAL FOR WEISS MEDUS D/A CONVERTER
THE MEDUS D/A CONVERTER
The MEDUS is a State Of The Art D/A Converter which handles PCM as well as DSD signals. Both digital and analog sections are
designed with great care for all the details which make the MEDUS a tr ly remarkable DAC.
Feat res
Inp ts:
There are three AES/EBU inp ts on XLR connectors, one on Toslink (optical), three RCA connectors, one USB connector. The
accepted sampling freq encies are 44.1, 48, 88.2, 96, 176.4 or 192 kHz. The USB inp t also accepts DSD Signals. Sampling
freq encies of 88.2kHz and higher can also be fed sing the d al wire scheme, i.e. one cable per channel.
Up-sampling:
Signals at 44.1 or 48 kHz are p-sampled in the MEDUS’ DSP chip, sing o r own st dio q ality p-sampling algorithms. Th s
the DAC chip always receives signals at a 88.2kHz minim m sampling rate.
Synchronization:
Several signal re-clocking schemes are combined for extremely high jitter atten ation, making the MEDUS virt ally imm ne to
jitter over a very wide bandwidth.
Converters:
The DAC chip p-samples the inp t signal to abo t 1.5MHz. Fo r D/A conversion channels are sed per a dio channel,
res lting in exceptional performance specifications. The I/V conversion after the DAC chip ses two of o r own discrete OP-
AMPs (the OP1-BP) per channel.

OWNERS MANUAL FOR WEISS MEDUS D/A CONVERTER
O tp ts:
O r discrete OP-AMPs are also sed in the o tp t stage, two per a dio channel for a differential o tp t. O tp t levels can be
set between –4.0dB and +27.0dB (6dB less on asymmetrical o tp ts). The level setting is done in 1dB steps via a rotary
switch at the back of the nit. Both o tp ts are set to the same level at any time. The o tp ts are symmetrical on XLR
connectors and asymmetrical on RCA connectors. No so nd degrading servo mechanisms are sed.
The Weiss OP1-BP discrete OP-AMP
Power S pply:
A powerf l non-switching power s pply is sed. All sensitive voltages have their own reg lators which are separated between
left and right channels. The res lt is an analog o tp t free of "digital noise" and channel crosstalk. The power switch activates
a semicond ctor relay which only switches on or off at zero crossings of the mains voltage. This ass res a glitch free power
switching.

OWNERS MANUAL FOR WEISS MEDUS D/A CONVERTER
Mechanical Design:
The MEDUS employs a twin metal frame. The inner chassis is made of steel and acts as a very effective shield against
electrostatic and electromagnetic radiation. The o ter frame is made of massive anodized al mini m for additional shielding,
res lting in optimal heat convection and bea tif l looks.
Front panel controls:
•Fo r switches with corresponding bl e LEDs are sed for selecting one o t of fo r inp t so rces.
•A display.
•A power switch.
Back panel elements from left to right:
•Analog o tp ts on XLR and RCA connectors with o tp t level switch.
•Digital inp ts 1 – 4 (three XLR, three RCA, one Toslink, one USB connector).
• Mains connector with f ses and voltage selector.

OWNERS MANUAL FOR WEISS MEDUS D/A CONVERTER
Operation
Unpacking and Set p of the MEDUS
Caref lly npack the MEDUS. The following items sho ld be enclosed:
•The MEDUS D/A Converter nit
•The MEDUS Remote Control nit
•This Owner’s Man al
•A Certificate of G arantee
The MEDUS sho ld be placed horizontally on a plane s rface. Avoid p tting any other eq ipment or
any other material on top of the MEDUS as not to compromise the MEDUS’ heat convection system.
Mains Connection
Before connecting the mains cable make s re the voltage selector switch on the back of the nit
(integrated into the mains connector) is set to the appropriate voltage. If this is not the case then
open the mains selector lid with a strong screwdriver. The mains pl g m st not be pl gged into the
connector for that p rpose. Now yo see a black selector dr m with appropriate voltages written in
white letters. Remove this dr m, t rn it to the appropriate voltage and reinsert it. Now firmly close
the lid again. Connect the MEDUS to the wall o tlet with the mains cable.
Driver installation
For OSX (Apple) operating systems it is not necessary to install any driver for USB. For Windows based systems a driver is
incl ded on the CD in the MEDUS man al.

OWNERS MANUAL FOR WEISS MEDUS D/A CONVERTER
Inp t So rce Connection, Selection and Synchronization
Connect so rces with sampling freq encies of 44.1, 48, 88.2, 96, 176.4 or 192kHz to the inp t
connectors at the back of the nit. Note that there are a total of fo r inp ts. The following
connectors are available:
Inp t # 1: one XLR and one RCA connector ( se either XLR or RCA at a time, i.e. yo may
connect two so rces sim ltaneo sly, b t only one so rce nit m st be switched on at a time).
Inp t # 2: The same as Inp t # 1 applies here.
Inp t # 3: one XLR and one USB connector ( se either XLR or USB at a time, i.e. yo may
connect two so rces sim ltaneo sly, b t only one so rce nit m st be switched on at a time).
Inp t # 4: one TOSLINK (optical) and one RCA connector ( se either TOSLINK or RCA at a time,
i.e. yo may connect two so rces sim ltaneo sly, b t only one so rce nit m st be switched on at
a time).
The inp t so rce p shb ttons correspond to the fo r inp ts as described above.
Inp t # 1 (left) and Inp t #2 (right) can act as an inp t for so rces s pporting the two wire
scheme, i.e. one cable per channel. The MEDUS a tomatically detects whenever s ch a so rce is
connected to inp ts #1 and #2 and switches to the appropriate conversion mode. In that mode
both LEDs of inp t #1 and #2 are lit. The two wire scheme is sed by some so rces with sampling
rates of 88.2kHz or higher.
If a valid AES/EBU or S/PDIF formatted signal is present at the selected inp t, the display indicates
the sampling rate and the word length (the n mber of active bits in a digital sample) of the inp t
signal. If the format and/or the sampling freq ency is not valid, the word “ nlocked” is shown in
the display. In that case the analog o tp ts are m ted.
The MEDUS a tomatically synchronizes to the incoming signal. If the sampling rate of the signal is
not within a range of +- 80ppm of one of the nominal sampling rates (44.1, 48, 88.2, 96, 172.4,
192kHz) then the bl e LED of the active inp t is flashing. The analog o tp ts are m ted in that
case.
The states of all settings are stored in non-volatile memory, i.e. the act al inp t selection, vol me
control etc. are retained when powering the nit off.

OWNERS MANUAL FOR WEISS MEDUS D/A CONVERTER
O tp t Level and O tp t Connection
Connect yo r preamplifier or power amplifier to the o tp t connectors of the MEDUS. Use either
the symmetrical (balanced) lines (XLR connectors) or the asymmetrical ( nbalanced) lines (RCA
connectors). Or both, if yo need to feed two amplifiers. Symmetrical is preferred, provided yo r
preamplifier s pports symmetrical connection.
The basic o tp t level is set either via the rotary switch on the back panel or via the remote control
“gain trim” switches. This level setting is done in the analog domain and is sed to set a basic level
s ch that the s bseq ent amplifier is operating at its preferred inp t level.
If yo se the remote control to change the basic o tp t level press and hold the ALT key and then
press the gain trim + or – keys to adj st the level. The display shows the maxim m o tp t level
for both XLR and RCA o tp ts in dB .
The position of the switch on the back panel does not indicate the basic o tp t level. The switch
merely acts as a rotary encoder, i.e. rotating clockwise increases the basic level and vice versa.
Use the back panel switch or the remote control to adj st the basic o tp t level to a val e which
matches yo r amplifier. If yo r amplifier has a vol me control, adj st the MEDUS o tp t s ch that
yo get a normal listening level with the amplifier’s vol me control set to abo t midway between
minim m and maxim m vol me.
Note, it is normal when after setting the basic o tp t level the MEDUS o tp t m tes again for a
short time.

OWNERS MANUAL FOR WEISS MEDUS D/A CONVERTER
Remote Control
The Remote Control allows to control the following
parameters:
-basic o tp t level with the gain trim keys as described
above
-o tp t vol me in the digital domain with 0.5dB steps
over a range of 60dB. With the 0dB setting (maxim m
level) the vol me control is bit transparent
-o tp t m te
-p-sampling filter A/B selection
-absol te polarity (0 / 180°)
-inp t n mber 1…4
-display brightness
A paper on the topic of digital level control (incl ding so nd
examples) can be fo nd here:
http://www.weiss-highend.ch/comp terplayback/Digital_Level_Control.pdf

OWNERS MANUAL FOR WEISS MEDUS D/A CONVERTER
Display
The display shows the following parameters:
-inp t n mber: 1…4
-inp t sampling rate: nlocked, 44.1, 48, 88.2, 96, 176.4, 192 kHz, DSD
-inp t word length: 16, 20, 24 Bit (shown if an a dio signal is present)
-gain: 0…. –60dB in 0.5dB steps (shown inverse if m te is activated)
-absol te polarity: no display / 180°
-p-sampling filter type: A/B
-basic o tp t level: in dB (shown d ring selection of the basic o tp t level)

OWNERS MANUAL FOR WEISS MEDUS D/A CONVERTER
Technical Data
Digital Inp ts:
(3) XLR connectors, (1) Toslink connector (optical)
(3) RCA connectors
(1) USB connector
All inp ts accept professional or cons mer standard , i.e. accept AES/EBU or S/PDIF signals
Sampling Freq encies: single wire scheme: 44.1, 48.0, 88.2, 96.0, 176.4 or 192kHz on any of the fo r inp ts
Sampling Freq encies: d al wire scheme: 88.2, 96.0, 176.4 or 192kHz on inp ts 1 and 2
DSD: On USB inp t
Sampling freq ency tolerance: +-80ppm
Maxim m inp t word length: 24 Bits
Analog O tp ts:
(2) XLR Connectors
(2) RCA Connectors
Servo-less, DC co pled, short circ it proof o tp t circ itry
O tp t impedance: < 100 Ohm
O tp t level: variable from -4.0dB to +27.0dB balanced on XLR connectors
(-10.0dB to +21.0dB nbalanced on RCA connectors) with 0dBFS inp t, in 1dB steps
(-4dB is 0.49V, +27dB is 17.35V, -10dB is 0.245V, +21dB is 8.67V)
O tp t stage: Discrete Class A

OWNERS MANUAL FOR WEISS MEDUS D/A CONVERTER
D/A Converter chip:
Over-sampling sigma-delta converter
Fo r converters per channel
Synchronization:
Synchronized via inp t signal
Extremely efficient Jitter atten ation down to s bsonic freq encies
Sampling Freq encies: 44.1 kHz, 48.0 kHz, 88.2kHz, 96.0kHz, 176.4khz, 192kHz
DSP algorithms:
Up-sampling, jitter red ction
Power:
Mains Voltage: 100...120 / 200...240 Volt
F se rating: 500 mA slow blow
Power cons mption: 80VA max.
Power cons mption in standby: 2VA max.

OWNERS MANUAL FOR WEISS MEDUS D/A CONVERTER
Meas rements:
The meas rements below have been taken at the following conditions ( nless noted otherwise):
+24.0dB o tp t level (-3dBFS inp t level), 192.0kHz sampling freq ency (fs).
Frequency Response:
@ fs = 44.1kHz: 0Hz ... > 20kHz: within +- 0.25dB
@ fs = 48.0kHz: 0Hz ... > 20kHz: within +- 0.25dB
@ fs = 88.2kHz: 0Hz ... > 30kHz: within +- 0.75dB
@ fs = 96.0kHz: 0Hz ... > 30kHz: within +- 0.75dB
@ fs = 176.4kHz: 0Hz ... > 40kHz: within +- 0.75dB
@ fs = 192.0kHz: 0Hz ... > 40kHz: within +- 0.75dB
Total Harmonic Distortion plus Noise (THD+N) ratio
@ 1kHz:
< -112 dB @ -3 dBFS inp t (0dBFS = +27.0dB )
< -115 dB @ 0 dBFS inp t (0dBFS = +27.0dB )
Si nal To Noise Ratio (SNR) @ -40dBFS input:
> 129dB n-weighted (relative to f ll scale o tp t)
> 132dB A–weighted (relative to f ll scale o tp t)
Linearity:
at 0 to -100dBFs inp t level:
< +-0.05dB deviation from ideal
at -100 to -120dBFs inp t level:
< +-0.2dB deviation from ideal
Crosstalk:
< -110dB, 0..20kHz

OWNERS MANUAL FOR WEISS MEDUS D/A CONVERTER
A SHORT HISTORY OF WEISS ENGINEERING
After st dying electrical engineering, Daniel Weiss joined the Willi St der (St der - Revox)
company in Switzerland. His work incl ded the design of a sampling freq ency converter and of
digital signal processing electronics for digital a dio recorders.
In 1985, Mr. Weiss fo nded the company Weiss Engineering Ltd. From the o tset the company
concentrated on the design and man fact re of digital a dio eq ipment for mastering st dios. Its
first prod ct was the mod lar "102 Series" system. After 23 years, this system is still p to date
(24 bit / 96kHz) and is still being sold. H ndreds of Mastering St dios aro nd the world se it
every day.
In the early nineties the „Gambit Series“ was la nched, taking ergonomics and sonic q ality to new
heights. The „Gambit Series“ consists of stand-alone nits like Eq alizer, De-noiser / De-clicker,
Dynamics Processor, A/D converter, D/A converter, Sampling Freq ency Converter, Dithering etc.
40 bit floating point processors and sampling rates p to 96kHz are employed.
In 2001 we have decided to enter the High-End Hi-Fi market which offers a comparable clientele
to that of the Mastering St dios. Both consist of critical and discerning listeners, who are in
constant search for the best a dio reprod ction eq ipment or the best a dio tools respectively.
O r list of clients incl des big names, like SONY, BMG, EMI, Warner, Hit Factory, Abbey Road,
Teldec, Telarc, Unitel, Gateway Mastering (Bob L dwig), Bernie Gr ndman Mastering, Masterdisk,
Sterling So nd, Whitfield Street, Metropolis and h ndreds more.
For a more comprehensive list yo are invited to visit o r pro a dio website at www.weiss.ch.

OWNERS MANUAL FOR WEISS MEDUS D/A CONVERTER
OUR MISSION AND PRODUCT PHILOSOPHY
The wealth of experience we have gained in over 20 years of designing prod cts for top Mastering
Engineers, we now apply to the design of o tstanding High-End Hi-Fi prod cts.
O r mission is to create eq ipment which becomes classic right from the o tset; - o tstanding in
sonics and design.
These are some of the milestones at Weiss Engineering:
1985 Introd ction of the "102 Series", a 24 bit mod lar digital a dio processor for Mastering St dios
1986 Introd ction of one of the first sample rate converters for digital a dio
1987 Introd ction of one of the first digital eq alizers
1989 Introd ction of one of the first digital dynamics processors
1991 Introd ction of the "Ibis" digital mixing console, b ilt for the mix-down of classical m sic
1993 Introd ction of the "Gambit" Series of digital a dio processors, which employ 40 bit floating point processing and
sport an extremely ergonomic ser interface
1995 First 96kHz sampling rate capable prod cts delivered
2001 Introd ction of the MEDEA, o r High-End Hi-Fi D/A converter and the first prod ct in o r High-End Series
2004 Introd ction of the JASON CD Transport
2007 Introd ction of the CASTOR, o r High-End Hi-Fi Power Amplifier
2008 Introd ction of the MINERVA Firewire DAC, VESTA Firewire Interface, ATT202 passive atten ator
2010 Introd ction of the DAC202 DAC, INT202 Firewire Interface, MEDEA+ DAC
2012 Introd ction of the MAN301 Network Player
2013 Introd ction of the MEDUS DAC, INT204 USB/DSD Interface

OWNERS MANUAL FOR WEISS MEDUS D/A CONVERTER
ADVANCED DIGITAL AND ANALOG AUDIO CONCEPTS EXPLAINED
Jitter S ppression and Clocking
What is jitter and how does it affect a dio q ality? In the a dio field the term jitter designates a
timing ncertainty of digital clock signals. E.g. in an Analog to Digital Converter (A/D) the analog
signal is sampled (meas red) at reg lar time intervals; in the case of a CD, 44100 times a second
or every 22.675737.. microseconds.
If these time intervals are not strictly constant then one talks of a jittery conversion clock. In
practice it is of co rse not possible to generate exactly the same time interval between each and
every sample. After all, even digital signals are analog in their properties and th s are infl enced
by noise, crosstalk, power s pply fl ct ations, temperat re etc.
Hence a jittery clock introd ces errors to the meas rements taken by the A/D, res lting from
meas rements being taken at the wrong time. One can easily observe that the level of the error
introd ced is higher d ring high a dio freq encies, beca se high freq ency signals have a steeper
signal form.
A good designer takes care that the jitter amo nt in his/her design is minimized as well as
possible.
What type of eq ipment can be compromised by jitter?
There are three types: The A/D Converter as described above, then there is the D/A Converter
where the same mechanism as in the A/D Converter applies and the third is the Asynchrono s
Sample Rate Converter (ASRC). The ASRC is not something s ally fo nd in Hi-Fi systems. It is
sed by So nd Engineers to change the sample rate from e.g. 96kHz to 44.1kHz, or e.g. for
p tting a 96kHz recording onto a 44.1kHz CD.
Yo may now arg e that in High-End Hi-Fi there are s ch things as „Over-samplers“ or „Up-
samplers“.

OWNERS MANUAL FOR WEISS MEDUS D/A CONVERTER
Yes, those are in essence sampling rate converters, however in a well designed system these
converters employ a synchrono s design, where jitter does not play any role. Of co rse a
conversion between 96kHz and 44.1kHz as in the example above, can be done in a synchrono s
manner as well. An ASRC in fact is only req ired either where one or both of the sampling
freq encies involved are changing over time („varispeed“ mode of digital a dio recorders) or where
it is npractical to synchronize the two sampling freq encies.
So basically in Hi-Fi jitter matters where there are A/D or D/A converters involved. CD and DVD
players are by far the most n mero s type of eq ipment employing D/A converters. And of co rse
stand-alone D/A converters. Jitter, being an analog q antity, can creep in at vario s places. The
D/A converter b ilt into CD or DVD players can be „infected“ by jitter thro gh vario s crosstalk
mechanisms, like power s pply contamination by power h ngry motors (spindle / servo) or
microphony of the crystal generating the sampling clock or capacitive / ind ctive crosstalk between
clock signals etc.
In the standalone D/A converter jitter can be introd ced by inferior cables between the so rce
(e.g. CD player) and the D/A converter nit or by the same mechanisms as described above except
for the motors of co rse.
In the case of a stand-alone D/A converter (as the MEDUS), one has to take two different jitter
contamination pathes into acco nt.
One is the internal path where internal signals can affect the jitter amo nt of the sampling clock
generator. Here, all the good old analog design principles have to be applied. S ch as shielding
from electric or magnetic fields, good gro nding, good power s pply deco pling, good signal
transmission between the clock generator and the act al D/A chip.
The other path is the external signal coming from the so rce to which the sampling clock has to be
locked. I.e. the D/A converter has to r n synchrono s to the incoming digital a dio signal and th s
the freq ency of the internal sampling clock generator has to be controlled so that it r ns at the
same sampling speed as the so rce (CD transport). This controlling is done by a Phase Locked
Loop (PLL) which is a control system with error feedback. Of co rse the PLL has to be able to follow
the long term fl ct ations of the so rce, e.g. the sampling rate of the so rce will alter slightly over
time or over temperat re, it will not be a constant 44.1kHz in the case of a CD. B t the PLL sho ld
not follow the short term fl ct ations (jitter). Think of the PLL as being like a very slow-reacting
fly-wheel.

OWNERS MANUAL FOR WEISS MEDUS D/A CONVERTER
In the MEDUS we employ a two stage PLL circ itry which very effectively s ppresses jitter. A
common problem with most PLLs sed in a dio circ itry is that they s ppress jitter only for higher
freq encies. Jitter freq encies which are low (e.g. below 1kHz or so) are often only marginally
s ppressed. It has been shown that low freq ency jitter can have a large infl ence on the a dio
q ality tho gh. The MEDUS s ppresses even very low freq ency jitter components down to the
s b-Hertz range.
This means that the MEDUS is virt ally imm ne to the q ality of the a dio so rce regarding jitter.
For a CD player as a so rce this means that as long as the data is read off the CD in a correct
manner (i.e. no interpolations or m tes) yo sho ld hardly hear any difference between different
makes of CD players or between different pressings of the same CD. Also „accessories“ like disk
dampening devices or extremely expensive digital cables will not make any difference in sonic
q ality. Of co rse it is always a good idea to have a good q ality cable for digital (or analog) a dio
transmission - b t within reason.
Upsampling, Oversampling and Sampling Rate Conversion in
General
In cons mer a dio circles the two terms oversampling and p-sampling are in common se. Both
terms essentially mean the same, a change in the sampling freq ency to higher val es. Up-
sampling s ally means the change in sampling rate sing a dedicated algorithm (e.g.
implemented on a Digital Signal Processor chip (DSP)) ahead of the final D/A conversion (the D/A
chip), while oversampling means the change in sampling rate employed in today’s modern D/A
converter chips themselves.
B t let’s start at the beginning. What is the sampling freq ency? For any digital storage or
transmission it is necessary to have time discrete samples of the signal which has to be processed.
I.e. the analog signal has to be sampled at discrete time intervals and later converted to digital
n mbers. (Also see "Jitter S ppression and Clocking" above)). This sampling and conversion
process happens in the so called Analog to Digital Converter (A/D). The inverse in the Digital to
Analog Converter (D/A).

OWNERS MANUAL FOR WEISS MEDUS D/A CONVERTER
A physical law states that in order to represent any given analog signal in the digital domain, one
has to sample that signal with at least twice the freq ency of the highest freq ency contained in
the analog signal. If this law is violated so called aliasing components are generated which are
perceived as a very nasty kind of distortion. So if one defines the a dio band of interest to lie
between 0 and 20 kHz, then the minim m sampling freq ency for s ch signals m st be 40kHz.
For practical reasons explained below, the sampling freq ency of 44.1kHz was chosen for the CD. A
sampling freq ency of 44.1kHz allows to represent signals p to 22.05kHz. The designer of the
system has to take care that any freq encies above 22.05kHz are s fficiently s ppressed before
sampling at 44.1kHz. This s ppression is done with the help of a low pass filter which c ts off the
freq encies above 22.05kHz. In practice s ch a filter has a limited steepness, i.e. if it s ppresses
freq encies above 22.05kHz it also s ppresses freq encies between 20kHz and 22.05kHz to some
extent. So in order to have a filter which s fficiently s ppresses freq encies above 22.05kHz one
has to allow it to have a so called transition band between 20kHz and 22.05kHz where it grad ally
b ilds p its s ppression.
Note that so far we have talked abo t the so called anti-aliasing filter which filters the a dio signal
ahead of the A/D conversion process. For the D/A conversion, which is of more interest to the
High-End Hi-Fi enth siast, essentially the same filter is req ired. This is beca se after the D/A
conversion we have a time discrete analog signal, i.e. a signal which looks like steps, having the
rate of the sampling freq ency.
S ch a signal contains not only the original a dio signal between 0 and 20kHz b t also replicas of
the same signal symmetrical aro nd m ltiples of the sampling freq ency. This may so nd
complicated, b t the essence is that there are now signals above 22.05kHz. These signals come
from the sampling process. There are now freq encies above 22.05kHz which have to be
s ppressed, so that they do not ca se any intermod lation distortion in the amplifier and speakers,
do not b rn tweeters or do not make the dog go mad.
Again, a low pass filter, which is called a „reconstr ction filter“, is here to s ppress those
freq encies. The same applies to the reconstr ction filter as to the anti-aliasing filter: Pass-band
p to 20kHz, transition-band between 20kHz and 22.05kHz, stop-band above 22.05kHz. Yo may
think that s ch a filter is rather "steep", e.g. freq encies between 0 and 20kHz go thro gh
naffected and freq encies above 22.05kHz are s ppressed to maybe 1/100'000th of their initial
val e. Yo are right, s ch a filter is very steep and as s ch has some nasty side effects.
For instance it does strange things to the phase near the c t-off freq ency (20kHz) or it shows