Musical Fidelity M6X DAC User manual

Instruction Manual
Manual in different languages available from www.musicalfidelity.com
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Contents
Introduction .........................................................................................3
Safety Information...............................................................................4
Precautions & User Information..........................................................4
Installation ...........................................................................................5
Facilities & Connections......................................................................6
Operation .............................................................................................7
Remote Control Handset.....................................................................9
Digital Filters…….. ..............................................................................10
Troubleshooting…..............................................................................11
Technical Specifications....................................................................12
Item Disposal Information for Europe...............................................13
*Manuals in other languages can be found on the Musical Fidelity website. Please navigate to the
Downloads section of the M6x DAC product page to access them.

3
Introduction
Our M6x DAC is a new milestone in the history
of Musical Fidelity DACs.
Its predecessor, the M6s DAC was one of the
first to use the critically acclaimed ESS 32-bit
HyperStream II DAC architecture. With the
M6sR DAC, we continued to improve the
firmware and added a few other quality of life
improvements. DSD was now easier to use, we
had full Roon Support and in- & outputs were
updated to keep up with the fast moving digital
audio landscape. And the other big thing: the
M6sR DAC was now being made in the EU!
With the M6x DAC we went even further.
Building on our knowledge and experience with
Sabre ESS chips, we upgraded them to the
newer ES9038Q2M, and now use two of them
in dual differential mode for a pristine dual
mono design. The inclusion of a Time Domain
Jitter Eliminator results in superb SNR and
THD+N performance with unbelievablely
detailed transient response.
Other advances in the DAC section include
upsampling and re-clocking. Upsampling can
independently be switched on or off.
The 16-core XMOS and CPLD MAX II Altera
processors ensure there is always enough
headroom for these operations, the new digital
filters and the MQA processing.
The single ended RCA and balanced XLR
outputs each have their own output buffer. Via
the XLR plugs you can enjoy a fully-differential
amplifier design enabling a fully balanced
output.
Both output stages deliver superior audio quality,
exhibit very low noise, large output voltage swing and
high current drive. The excellent gain bandwidth and
very fast slew rate produce exceptionally low
distortion.
The M6x DAC displays our continued development of
our Super Silent Power Transformers. Industrial
grade power sockets with EMI filter and DC blocker
stop interferences and eliminate transformer hum.
The encapsulated toroidal transformer with low core
saturation is ideal for audio applications and
especially perfect for digital audio due to its
extremely low electromagnetic radiation. Digital to
analogue converters, compared to analogue
amplifiers, present their own design challanges. They
work in different domains, have their own
requirements and need to be treated as such. Power
requirements are unique and solutions designed for
amplifiers will not show similar results when paired
with digital circuitry.
We have always held circuit board design and layout
up to the highest of standards at Musical Fidelity. We
are not believers of flashy board design just for the
sake of looks. The design & layout need to be
custom-tailored to each application, measure well
AND sound as envisioned. Only then have we done
our job. At this point, we have given the listener a
palpable sense of the recording venue that places
the performers in a real-time holographic space in
their own homes.

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Note: Unauthorized opening of the equipment
will invalidate any warranty claim.
Safety Information
This unit is supplied with a mains lead fitted with
a moulded 13-amp plug . If, for any reason, it is
necessary to remove the plug, please remove the
fuse holder and dispose of the plug safely, out of
reach of children . It must not be plugged into a
mains outlet.
The wires in the mains lead supplied with this
appliance are coloured in accordance with the
following code
WARNING - This appliance MUST be earthed .
The colours of the wires of the mains lead of this
appliance, may not correspond with the coloured
markings identifying the terminals in the plug,
proceed as follows:
•The wire which is coloured green and yellow
must be connected to the terminal in the plug
which is marked with the letter E or coloured
green or green-and-yellow, or by the earth
symbol:
•The wire which is coloured brown must be
connected to the terminal which is marked
with the letter L or coloured red .
•The wire which is coloured blue must be
connected to the terminal which is marked
with the letter N or coloured black .
•If connecting to a BS1363 plug, a 13-amp
fuse must be used .
Precautions & User Information
WARNING: Any modifications to this product,
not expressly approved by Musical Fidelity,
who is the party responsible for standards
compliance could void the user’s authority to
operate this equipment.
This new M6x DAC is designed and built to
provide trouble-free performance . As with all
electronic devices it is necessary to observe a few
precautions:
•Heed all warnings shown on the back of the
product .
•Only connect the M6x DAC to a mains outlet
having the same voltage as marked at the
back of the unit .
•Always ensure that when disconnecting
and reconnecting your audio equipment the
mains supply is switched off .
•Position the mains lead and signal
interconnects where they are not likely to
be walked on or trapped by items placed on
them .
•Do not use near water, or place water-filled
containers on the M6x DAC, for example, a
flower vase or potted plants . If water does
spill inside, immediately pull out the mains
plug from the wall socket and inform the
dealer, who should then check the unit before
further use. Entry of liquid into the M6x DAC is
dangerous and may cause electric shock or
fire hazard.
•Do not place the unit near direct heat sources
such as radiators, direct sunlight or other
equipment.
•Do not remove any covers or try to gain access
to the inside . There are no user adjustments
or fuses to change without qualification. Refer
all service work to an authorized Musical
Fidelity agent .
The electronics in modern hi-fi equipment are
complex and may, therefore, be adversely
affected or damaged by lightning . For
protection of the audio system during electrical
storms, remove the mains plugs . If after-sales
service is required, to help the dealer identify the
M6x DAC please quote the serial number
located on the rear panel of the unit .
Green and yellow...................................Earth
Blue ................................................... Neutral
Brown............................................................ Live

5
Installation
Introduction
This unit will deliver the ultimate performance
possible from any digital source. It is designed to
upgrade CD players, TVs, set-top-boxes, DAB
tuners, USB Streamers and PCs and Laptops and
any other source providing a variety of digital
outputs.
Note: In normal operation, the unit dissipates a
small quantity of power at all times, and it is
important that it is adequately ventilated. The
M6SRDAC must be protected from humidity –if
the unit is moved from a cold place to a warm
room, leave the unit for an hour or so to allow
sufficient time for the moisture to evaporate.
Cleaning
Before cleaning the unit, switch off power at the
mains switch and remove the mains plug from the
wall socket . Clean the cabinet and remote-control
unit using a moist cloth . Using solvents, white
spirit or thinners is not advised, as they could
damage the surface finish.
Installation
Position the M6x DAC on a stable, horizontal
surface where there is no risk of it being
knocked or subjected to vibration such as from
loudspeakers .
Power Connections
The M6x DAC is supplied with a standard IEC
mains cable which plugs into the IEC socket at the
back of the unit .
Audio Output Connections
RCA audio outputs: Use good quality RCA phono
audio cables (fully connected signal and ground),
for optimum signal transfer .
XLR audio outputs: Use good quality XLR audio
cables (fully connected hot and cold signals and
ground), for absolute optimum signal transfer .
Digital Input connections
COAXIAL input: Connect RCA digital source to
digital input RCA socket. Use a good quality fully
connected (signal and ground) coaxial digital
cable, for optimum signal transfer.
OPTICAL inputs: Connect optical digital source to
optical input socket. Use a good quality “Toslink”
cable, for optimum signal transfer.
USB input: Connect computer or similar USB
“host” source to USB input socket. Use a good
quality USB 2.0 type cable (not supplied), for
optimum signal transfer. Try to keep USB cable
length to a minimum for best reliability. The USB
standard maximum for a single cable is 5M, after
which repeaters (normally mains-powered USB
hubs) are required. We do however; recommend
avoiding such a setup if at all possible.
AES/EBU input: Connect a balanced AES/EBU
source to digital input XLR socket. Use a good
quality XLR cable, specifically designed to carry
digital signals and not XLR cables for analogue
audio transmission!
Interconnects
Note: Musical Fidelity currently do not make any
interconnecting cables other than those supplied
with the unit. Musical Fidelity does not endorse
any other manufacturer’s cables.
If necessary, please refer to the dealer who can
advise on quality cables for any particular setup.

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Facilities & Connections
7 8 9
1 2 3 4 5 6 10 11
1Power/Standby/Mute button and LED’s
2IR Receiver
3Filter selection
4Reclock LED
5Input selection
6Output Selection
7PCM Sample rate LED’s
8DSD Rate LED’s
9MQA LED’s
10 Volume Control
11 Headphone Socket
12 13 14 16 17 18 19 15
12 RCA Analogue output L/R
13 XLR Balanced output L/R
14 OPTICAL Digital inputs 1,2
15 230/110 V switch
16 COAXIAL Digital input
17 AES/EBU Balanced digital input
18 USB Digital input
19 Mains IEC socket
Standard XLR Balanced input/output
lead connections:
(for reference only, no XLR signal leadssupplied)
Pin functions:
1Ground, 0V
2Normal polarity (“hot” or “+”)
3Inverted polarity (“cold” or “-”)

7
Operation
Once the M6x DAC unit is correctly wired up, and
plugged into mains, the orange STBY led should be
lit .
In this mode the M6x DAC is consuming a minimal
amount of power .
To switch the unit on, press the Power button (1) on
the front of the unit . The blue PWR indicator will light
along with the red MUTE indicator . After a few
seconds, when it has stabilised, the MUTE function
will switch off and the unit is ready for use .
Input selection
The M6x DAC has a total of five inputs available.
These are Optical 1 and 2, Coaxial, AES/EBU and
also USB.
When the power cable is inserted into the Mains IEC
socket 19 the Optical 1 input is selected by default.
When the M6x DAC is taken out of sleep mode, it will
default to the last input selected.
From the front panel you can cycle through the inputs
by using the ◄ and ► buttons (5). Pressing ► while
on the USB input will cycle back to Optical 1. Whilst
on Optical 1 the ◄ button will take you to the USB
input again.
The remote control has direct access buttons for
each input. Simply press the appropriate button to
move directly to that input.
When a valid signal is received on the selected input,
an indicator in either group 7, 8or 9will light to show
you the incomming sample rate.
Optical and coaxial inputs
All optical and coaxial inputs are capable of
accepting up to 24 bit 192 kHz PCM stereo data
streams and MQA data streams. The incoming data
sample rate is displayed on the front panel LED’s for
reference.
Note: The indicators 7, 8and 9show the actual
sample rate of the digital data received by the M6x
DAC. Some playback software may have altered this
compared to the original file.
USB Input
The USB input is capable of accepting up to 32 bit
768 kHz PCM, DSD 256 (native DSD 512) data
streams and MQA data streams.
Computer settings for USB
A good quality USB 2.0 cable is required to connect
the unit to the computer. Normal USB standards
stipulate that this should be 5M or less; and we
recommend keeping it as short as possible.
WARNING: Older USB cables are often heavy and
bulky and must be supported to avoid damage to
the USB socket. Any physical damage caused to this
socket will not be covered by warranty.
The computer should now detect the M6x DAC. A
driver installation is only required on Windows.
• Linux kernel 2.6.33 or later (no driver required)
• Apple OS X® 10.6.4 or later (no driver required)
• Windows 10 Creators Edition or later (driver
found on included CD or on Musical Fidelity
website)
For playing native DSD on Windows a driver
installation is required.
Any device that is compliant to the USB Audio Class
2.0 standard should also operate with the M6x
DAC. However Musical Fidelity are unable to
provide support for operation with anything other
than the system listed above.
CD, MP3, WAV, AAC/+, OGG, FLAC, and any other
audio file types played on suitable playback
software will now play through the unit.
Note: This USB input has a high-speed serial data
processor, and by its nature, requires a very high
volume of USB bandwidth. It will benefit greatly
from being the only device connected on its USB
‘bus’. Sharing the same bus with other devices
could cause unwanted artifacts such as dropouts or
temporary loss of signal. This especially includes
the use of the unit on a USB hub/splitter whether
alongside other USB components or not. A direct
connection to the host computer by shortest USB
2.0 lead possible is very much recommended.

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Digital Oversampling FIR Filters
The digital oversampling FIR filters can be set with
the buttons 2 on the front panel. For a detailed
description of each filter see page 10.
Note: When playing MQA files, the user’s filter
setting is not active, the MQA filter is always used.
The MQA filter is a proprietary custom-made filter by
MQA for our DAC to ensure the best possible MQA
experience.
During DSD playback, the the DAC's internal DSD
filter is turned on and the digital filters have no
effect.
Filter 8 –Oversampling Bypass
Using filter setting 8, the oversampling FIR filter is
bypassed, the source data is upsampled to
352,8kHz/384kHz on the XMOS chip and sourced
directly into the ESS 9038’s IIR filter.
Upsampling is automatically switched on when
using filter 8 and it is not possible to change the
volume. Therefore, only filters 1-7 can be used when
VAR output is used. If you want to use upsampling,
switch to FIX output beforehand.
When filter 8 is set and you switch from FIX to VAR
output, or when headphones are connected, filter 8
is automatically switched to filter 1 so that the
output volume can be changed.
When playing a PCM format with a sampling
frequency of 705.6 / 768kHz, filter 8 is
automatically turned on (NOTE: without
up/downsampling to 352,8/384kHz), which turns
off all remaining filtering, improving audio
parameters and the frequency spectrum by yet
another step.
Reclock
Reclocking synchronizes digital audio signals with
the master clock in the M6x DAC. This feature is
always on for all inputs and ensures best audio
performance at all times.
Upsampling
For incoming PCM signals, upsampling can be
turned on or off with button 4on the front panel.
When turned on, incoming PCM data up to 192kHz
sample rate is resampled to the sampling frequency
of 352,8kHz or 384kHz according to the original
multiple of the sampling frequency.
Note: Upsampling is automatically turned on
for filter 8 for sample rates between 44.1 and
192 kHz.
MQA (Master Quality Authenticated)
The M6x DAC includes MQA technology which
enables you to play MQA audio files and deliver the
sound of the original master recording. Visit
mqa.co.uk for more information.
MQA Indicators:
MQA - Green LED - Audio is valid MQA.
MQA Studio - Blue LED - Audio is valid MQA Studio.
OFS - Magenta LED - MQA Unverified (Original
Frequency Spectrum) –The device receives an
MQB signal which is an MQA signal already decoded
by a downstream application with an MQA decoder,
such as Tidal or Roon.
Outputs
On the rear of the unit are 2 sets of outputs .
RCA (single ended) and XLR (balanced). You
can connect the M6x DAC to your amplifier
using whichever is more convenient.
FIX/VAR Switching
The outputs can operate as either fixed or
variable mode. Fixed mode is suitable for
connection to other equipment which offers a
volume control. Variable mode allows
connection directly to power amplifiers or
active speakers where the M6x DAC provides
the volume control.
Choosing between these settings is done by
using the button 6on the front panel. Keep the
button pressed for 2 seconds to switch
between FIX and VAR output.

9
Headphones
The M6x DAC also includes a high quality
headphone amplifier. Connecting headphones
to socket 11 will automatically mute the main
outputs. The volume control on the front panel
10 or the remote control now adjust the volume
sent to the headphones.
Note: When headphones are connected with the
output set to FIX, the output automatically
switches to VAR and the volume level is set to -
40dB.
When headphones are connected with the
output set to VAR and the volume level is
greater than -40dB, the -40dB level is
automatically set for a safe volume in the
headphones. The volume level on the VAR
output without headphones connected is
remembered by the device even after it has
been switched off. With headphones connected,
the device will remember the volume level if it
is less than -40dB and only until it is switched
off.
Remote Control Handset
The remote control shown below enables
functions from this and other units from the
M3, M5 and M6 ranges to be operated from a
convenient distance.
The remote control buttons are split into 3
distinct areas.
The three rows of grey buttons at the bottom
are used to control the M6SRDAC and are
detailed below.
The blue buttons control an amplifier such as
the M6si. Consult the amplifier manual for
more information.
The remaining grey buttons located in the upper
section control a CD player such as M6scd.
Consult the CD player manual for more
information.
As the handset uses an invisible infra-red light
beam, the front edge must be pointed directly
towards the receiver window at the front of the
player, without visual obstruction between
them. If the range of the remote control greatly
decreases, replace the batteries with new ones.
Do not mix old and new batteries –two are
required, size AAA, LR03 or SUM-4.
Please dispose of used batteries in accordance
to local battery disposal regulations.
OPTICAL 1 selects OPTICAL input 1
OPTICAL 2 selects OPTICAL input 2
COAX selects COAXIAL input
AES/EBU selects balanced AES/EBU input
USB selects USB input
STBY switch the M6SRDAC between standby and
operating mode
UPSAMPLE enables or disables upsampling
FILTER selects digital filter
VOLUME ▼▲ controls main output of M6SRDAC
in variable mode or headphone level when
connected.

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Digital Filters
The M6x DAC allows for detailed tuning of the audio experience. It comes with multiple preset
reconstruction filters built-in. Musical purists can simply unpack the M6x DAC, carefully cable it up, just
leave it at its standard settings and feel the immediate musical integration: the whole sound is sweet and
clear; the treble is completely grain free and extended. The bottom end sounds endless with tactile bass
dynamics.
As you get reintroduced to your music library, you might, at some point, want to discover what else is
possible and hear it from different stages. It is then, when the customizability and settings turn the M6x
DAC into a powerful tool for experts, which elevates it into a league of its own. Explore the sound stage
with upsampling or without and see if you are drawn in deeper.
Choose between the different digital filters and tailor the sound reproduction to your specific liking or to
your specific setup. In a way the M6x DAC can be used like a professional tool for the experienced user:
1. Linear phase fast roll off - Most common filter with clean overall suppression and excellent rejection,
best for music with large transients. Provides crisp clean highs.
2. Linear phase slow roll off - Low group delay - and symmetrical input response. Less ringing than
linear-phase fast roll-off. Punchier bass than LPFR, with clean highs.
3. Minimum phase fast roll off - Minimal pre-ringing, preferred for imaging and soundstage. No aliasing
in frequency domain. Stronger bass than linear-phase, clean highs.
4. Minimum phase slow roll off - Non-symmetrical filter designed to minimize pre-ringing. Strong punchy
bass with good transient attacks.
5. Apodizing fast roll off –A version of the linear-phase fast roll off filter optimized to improve pre-
ringing.
6. Hybrid fast roll off –A combination of linear-phase and minimum-phase. Fast transient attack, strong
punchy bass, crisp highs.
7. Brick wall - One of the earliest designs, intended for highest suppression possible, with high delay and
pre-ringing. Linear-phase, crisp clean highs.
8. Oversampling bypass - The oversampling FIR filter, used for the 7 above mentioned presets, is
bypassed and source data is upsampled to 352,8kHz/384kHz on the XMOS chip and sourced directly
into the ES9038Q2M IIR filter. Bypassing the oversampling filter reduces the on chip PSU / ground noise
and consequently reducing signal correlated clock modulation on the ESS DAC’s silicon die. When the
source data is 705.6 / 768kHz, filter 8 is automatically turned on (NOTE: without up/downsampling to
352,8/384kHz), which turns off all remaining filtering, improving audio parameters and the frequency
spectrum by yet another step.