AVID HIFI SIGSUM User manual

SIGSUM
High Performance Integrated Amplier
USER MANUAL

2
Topic Page
Welcome 3
Cauon 3
Key Sigsum features 4
Placement 5
Connecon Types 5
Phono Input 6
Line Input 7
Pre-out 8
Loudspeaker Connecons 9
Mains Power 10
Headphone Use 11
Mono Operaon 11
Mute 11
Amplier Protecon 11
Troubleshoong 12
Specicaons 13
Declaraon of Conformity 14
Warranty 15
Table of Contents

3
Welcome to your AVID Sigsum Amplier
Congratulaons on purchasing your AVID Sigsum integrated amplier. Using the highest
quality materials during assembly and built to the highest industry standards, your AVID
Sigsum amplier should provide you with many years of trouble-free enjoyment.
Please read this manual carefully to ensure you understand all the features and operang
funcons available.
Cauon
• This unit is heavy, and it is recommended that at least two people are used when moving the unit.
• Care should be taken to ensure that the unit is switched o and unplugged from the mains before
connecng or disconnecng any other equipment to your Sigsum. This is to protect your speakers from
any momentary high-level signals which, due to the high power capabilies of the Sigsum, could cause
damage.
• There are no user-serviceable parts inside—please do not, under any circumstances, remove the
cover of the Sigsum—doing so would expose you to potenally lethal voltages and void your warranty.
• Only clean your Sigsum with a dry micro-bre cloth.
• Take care to ensure the unit is not exposed to water or other liquids. If you believe water may have
entered the case, turn the unit o at the socket immediately and seek advice from your dealer before
aempng to use it again.

4
Key Sigsum Features:
• 1,100 VA Toroidal transformer—132,000uF Capacitance Reservoir
The ‘heart’ of any amplier, the power supply must provide for any energy demands made by the amplier. Working
together these two key components maintain a massive energy reservoir that allows the amplier to react to the complex
dynamic power demands created by the music. The size of both these devices ensure that the rest of the amplier will
never place demands that cannot be met by the supply
• 50mm, High Quality Volume Potenometer
Illustrang that not all volume controls are born equal! This massive brass-cased device oers a level of transparency
unequalled. It’s reassuringly weighty but smooth acon indicave of the highest levels of build quality and ensures
long-term reliability.
• Fully discrete, high current, output stage
Many lesser ampliers make do with their output devices integrated into a single, large chip—this is very convenient for
the manufacturer, but places some serious limitaons on the performance capability of the unit. With a fully discrete
design, we are able to ensure that the very best devices are used, as well as ensuring that parameters such as peak
current, output impedance and thermal performance are never compromised.
• 4 Line level Inputs—2 Balanced, 2 unbalanced
Up to four line-level devices can be connected to the amplier, the higher quality balanced inputs (with the use of a
suitable adapter) can be converted to unbalanced mode if required. All inputs oer the same high performance levels with
regard to sensivity and bandwidth, with the balanced inputs inherently oering the best performance with regards to
noise rejecon. The input sockets themselves have been chosen to oer the best in terms of audio performance and
long-term reliability
• High performance Phono stage with adjustable gain, input resistance and capacitance
Derived from our hugely successful Pulsus phono stage, the Sigsum's phono stage oers unrivalled performance and
exibility when compared to other designs. Designed to oer the best performance in terms of distoron, noise and
compliance with the RIAA specicaon—but most importantly, it sounds superb.
• Superior headphone amplier, capable of driving almost any convenonal, dynamic headphone
Most headphone ampliers take the form of an aerthought, but nothing could be further from the truth with the Sigsum.
As with the main output stage, this amplier is designed to use discrete components selected to oer the best
performance, and the widest compability with the diverse selecon of headphones available today. Working in pure Class
‘A’ at low to medium volume levels this is a ’proper’ headphone amplier complete with its own dedicated power feed.
• Unbalanced Pre-amp output for future systems upgrades
Whilst the performance of the amplier is exemplary when compared with the very best integrated designs, we know that
with me, people oen look for ways of improving performance further sll. By using the Pre-out sockets built-in to the
Sigsum, it is possible to upgrade to even greater performance levels with the addion of the Celsus power amplier (or any
other power amplier in the AVID range).

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CONNECTION TYPES
Your AVID amplifier can make use of a either Balanced (XLR), Unbalanced (RCA), or any combination of the two
types of input.
WHICH SHOULD I USE?
Whenever possible you should use balanced connections, however in recognition that not all sources provide
balanced connections, unbalanced connections may be used when necessary.
WHAT’S THE MAIN BENEFITS OF USING BALANCED INPUTS?
All audio cables are susceptible to picking up noise (even screened cables). Any wire will act as an aerial, in that they
can pick up electromagnetic interference, whether that be radio signals, or simply the energy created by a something
like a spark from a thermostat being tripped. Balance inputs generally offer higher performance, thanks to their
superior noise rejection characteristics. This reduced noise allows for greater dynamics and generally improved
transparency.
• UNBALANCED CONNECTIONS
Conventional, unbalanced connections make use of two conductors—one carrying the signal, and the other is
a ground reference (0V), which can also take the form of a shield (in the case of coaxial cables). The use of
coaxial cables can improve susceptibility to noise, however it can never be completely removed.
• BALANCED CONNECTIONS
A balanced connection is different in that there are two signal cables, one with the positive phase of the
signal, and the other with the negative (a mirror image of the positive signal, if you like). When the signal
reaches the amplifier, the two signals are effectively subtracted from each other (but as one is negative, the
signal is effectively added). Just like any other cable, they are susceptible to external electrical noise sources.
The difference is that both the negative and positive wires are likely to be equally affected. The benefit here is
that when these two signals are effectively ‘subtracted’ from each other in the amplifier, any noise effectively
disappears leaving a pristine signal.
PLACEMENT
• Place your Sigsum on a sturdy and level surface
• Avoid locaons where your Sigsum may be aected by direct sunlight or damp.
• Keep your Sigsum away from heat sources
• Do not place the Sigsum in an enclosed space such as a closed cabinet unless venlaon has been catered for
• Do not place any objects on top of the amplier, which would obstruct air-ow

6
PHONO INPUT
The phonostage of your Sigsum can be configured for cartridges of various types in terms of Sensitivity, Impedance, and
Capacitance. In the first instance, please refer to your cartridge documentation to ascertain the initial settings for your
cartridge. The phono settings are accessible from beneath the unit—take care when turning the unit over, and ensure it is
resting on a soft, clean cloth to ensure none of the finishes are damaged during the procedure.
The phonostage provides an earthing post that should be connected to the turntable earth cable—failure to do so will result
in high levels of hum.
In the absence of full cartridge documentation, please follow these guidelines
Initial setup
The settings are configured using the switches accessible through the apertures
on the bottom, towards the rear of the case. Using a pen tip, you can slide each
arrow to either the ON of OFF position.
Moving Magnet
A standard Moving Magnet cartridge is the easiest to configure—simply ensure all
the switches are set to OFF—this is a starting
Sensitivity
There are three sensitivity levels available increasing from MM, MC LOW and MC
HIGH.
Check what type of cartridge you have. If you are uncertain, set the dial to MM.
If you have an MC cartridge, then set the dial to MC (mid).
Play a piece of music with which you are familiar. Adjust the volume control to a
comfortable listening level, if the volume control is much beyond the half way
point, you should probably consider increasing the sensitivity level, if the volume is
immediately very loud, then choose a lower sensitivity.
Some very high output MC cartridges work well using the MM setting—no harm
will be done by experimenting with settings.

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Resistance
Normally, the ideal aim is to match the amplifiers input impedance to that of the cartridge, this will ensure maximum signal
transfer, and minimise noise (hiss) —however, if you do not have this information (remember you can check the
manufacturer’s website), you can safely experiment with any of the possible values—again, tune by ear to get the most
pleasing sound.
Most MM cartridges are 47k, high output MC cartridges also tend to benefit from a high resistance setting, however low
output MC cartridges are invariably low impedance, suggesting a low resistance setting. Please experiment with this setting,
as the minor adjustments can make worthwhile improvement to the overall performance.
Capacitance
The effect of the capacitance setting is most obvious at high frequencies, but can be quite subtle. The values chosen are
affected by the design of cartridge, but also but the connecting cables—so there is no absolutely correct setting, and
experimentation is recommended until you find a setting that suits your set-up and personal preference.
Low impedance designs tend to be largely unaffected by capacitance settings, but high impedance designs, and especially MM
cartridges can be greatly affected. Start by okaying a selection of tracks you know well and adjust the setting until you find one
where you feel the best balance of detail and musicality are achieved.
LINE INPUT
The Sigsum has Four line inputs: two Balanced and two Unbalanced— which you choose depends on your source equipment,
but if you have the choice, we recommend using Balanced. These are referred to as Line Level inputs, and can be used to
connect to any standard piece of audio equipment, such as CD, Media Streamer, or FM/DAB Tuner.
Unbalanced
The unbalanced inputs make use of the two pairs of RCA connectors immediately above the three pin XLR sockets—these
sockets are labelled RCA 1 and RCA 2.

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Balanced
The unbalanced inputs make use of the two pairs of RCA connectors immediately above the three pin XLR sockets—these
sockets are labelled XLR 1 and XLR 2.
XLR connectors make use of a locking mechanism—please make sure that the plugs are pushed in all the way, and that these
engage correctly (you should hear a click when they engage).
PRE-OUT
The Sigsum is capable of outputting to an external amplifier should you require. This signal is affected by the position of the
volume control—so your Sigsum takes the role of a high quality Pre-Amplifier, allowing you an upgrade path to the likes of the
Celsus power amplifier

9
Loudspeaker Connections
The Sigsum outputs its power through two pairs of binding posts—these are compatible with both 4mm/banana plugs and
Spade connectors
The Sigsum has a sophisticated protection circuit to prevent damage from DC offsets, short-circuits and overheating, but it is
always wise to avoid situations where these situations may occur.
Always make sure that all connections are tight—loose connections can result in intermittent sound, loss of efficiency and
damage to the terminals, due to arcing.
Speaker cable
Feel free to experiment with the type of loudspeaker cable you use—there is no definitive answer as to which is best, as this
is all to do with system matching– and personal taste. Keep in mind that this is a high current design, so to reap the maximum
benefits, the cable resistance should be kept as low as possible. This can be achieved by keeping cable runs as short as
necessary and using a cable with a large cross-sectional area.
Correct Phase
It is important to ensure that your loudspeakers are connected “in phase”. This simply means that, for both the left and right
channels, the positive output connections are connected to the positive terminals on the loudspeakers, and similarly the
negative outputs are connected to the negative loudspeaker connections. It sounds very simple, but it is surprising how often
mistakes are made with this. You will know if you have got this correct, as when you listen to the system you should have
strong bass and a very obvious centrally located image—out of phase will have a diffuse image, and very weak bass. Use of
the Mono button will help clarify this issue—if you listen to the signal in mono and the speakers are connected correctly, you
should hear a VERY strong centrally located signal—out of phase speaker will sound very diffuse with no discernible image.

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Mains Power
Mains power is supplied via the standard IEC 3-pin connector on the rear panel. The mains circuit does incorporate filtering
circuits to ensure the feed is clean, and therefore the use of external mains filtering systems is unnecessary.
We recommend, for safety reasons, that connecting the mains should be left as the last step.
Switching on
Before switching the unit on, ensure the volume control is turned to its minimum level (fully anticlockwise). Your Sigsum
amplifier has a mains switch, which is hidden on the bottom of the unit, in the middle of the front panel. There will be a few
clicks from internal relays as the protection circuit is activated during the first few seconds. There is a single, blue LED on the
left of the unit (in the large ‘A’) that is illuminated whenever the unit is on.