Violectric HPA V550 PRO User manual

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HEADPHONE AMPLIFIER
Violectric HPA V550 / V550 PRO
USER´s MANUAL

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Content
Theme Page
About 4
Safety Instructions 5
The Earth / Grounding Concept 6
Connection / Connectors 8
General 9
Remote Control 11
Block Circuitry 12
Power Inputs, Controls 13
About PRE-GAIN 15
Outputs / Output Management 17
Reset 20
Software 21
Things to know 21
Disposal 24
Technical Data 25
Dismantling 26
Jumper Settings 27
Conformity Statement 28
Warranty 29
CAUTION!!
THE HIGH OUTPUT LEVELS ACHIEVABLE
WITH THIS UNIT MAY
DAMAGE YOUR HEARING OR THE HEADPHONES
IF OPERATED CARELESSLY!!

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Cordial thanks for your decision in favour of a product!
is a trademark and product line of Lake People electronic GmbH. Lake People
electronic GmbH develops, manufactures and distributes products in the professional range, for
broadcast, television, airports, exhibition halls, festival venues, theatres, large-scale installations,
private studios and more. In the private sector as well, Lake People products become increasingly
popular due to their outstanding quality.
The trademark and product line is specially intended to supply the Hi-Fi and High-
End market with its specific requirements.
Who develops equipment?
The devices are exclusively developed in Germany by the engineers of Lake People electronic GmbH.
In doing so, the team of developers can draw on over thirty years of experience and countless
products for the pro-audio domain.
Among others, the first German-made 20-Bit A/D and D/A converters were developed by Lake
People in the early nineties of the past century.
Who manufactures equipment?
The devices are exclusively manufactured in Germany by Lake People electronic GmbH or
contractors in the company's vicinity.
- put high emphasis on domestic manufacturing.Lake People - and by association
As well, all component suppliers are chosen in order to achieve the main part of added value inland.
How do devices get to the customer?
The devices can be obtained from respective specialist suppliers. If there is none such accessible
regionally, the customer is supported by transregional distribution partners (google may help...) and,
of course, by on-line shop.
…and if it doesn't work like it should?
devices are covered by a 5-years warranty. In case of any malfunction during this
period, they can be shipped to the manufacturer directly. Of course, the client will benefit from the
full technical support even when warranty has expired. Any technical questions or need for advice is
welcome.
is a subsidiary of
LAKE PEOPLE electronic GmbH
Turmstrasse 7a
D-78467 Konstanz
Fon [phone]
Fax [phone]
www.lake-people.de
www.lake-people.com
www.NIIMBUS-audio.de
www.NIIMBUS-audio.com
www.violectric.de
www.violectric.com

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WARNING
For your protection, please read the following:
Water, Liquids, Moisture:
This appliance should not be used near water or other sources of liquids.
Care should be taken so that objects do not fall and liquids are not spilled into the enclosure through
openings.
Power Sources:
The appliance should be connected to a power supply only of the type described in the operating
instructions or as marked on the appliance.
Grounding:
Care should be taken that this appliance is operated with proper grounding only.
Power Cord:
Power supply cords should be routed so that they are not likely to be walked on or pinched by items
placed upon or against them, paying particular attention to cords at plugs, convenience receptacles,
and the point where they exit from the appliance.
This unit is equipped with a 3-pole mains cable with German 3-pin mains plug.
In some countries this unit must be operated with a mains adaptor, supplied by the owner.
Please refer to the table below to connect a mains plug:
U.K. Mains Plug Warning:
A moulded mains plug that has been cut off from the cord is unsafe.
Discard the mains plug at a suitable disposal facility.
NEVER UNDER ANY CIRCUMSTANCES SHOULD YOU INSERT A DAMAGED OR CUT
MAINS PLUG INTO A 13 AMP POWER SOCKET.
Do not use the mains plug without the fuse cover in place.
Replacement fuse covers can be obtained from your local retailer.
Replacement fuses are 13 amps and MUST be ASTA approved to BS 1362.
Mains Fuse:
The mains fuse of this appliance is soldered in place and accessible from the inside only!!
A blown fuse may indicate an internal problem and should be replaced during qualified servicing or
repair work!
Switchable Power Supply:
Connect this unit to the power source indicated on the equipment rear panel only to ensure
safe operation!
This unit is provided with an internally settable mains supply for 230 or 115 V AC.
OVERVIEW: POWER CORD FUNCTION AND COLORS
CONDUCTOR COLOR Alternativ
LLIVE BROWN BLACK
NNEUTRAL BLUE WHITE
E PROTECTIVE EARTH GREEN+YELLOW GREEN

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Service / Repair:
To reduce the risk of fire or electric shock, the user should not attempt to service the appliance
beyond the measures described in the operating manual. All other servicing or repair should be
referred to qualified personnel!
Electromagnetic Compatibility
This unit conforms to the Product Specifications noted as Declaration of Conformity at the end of
this manual. Operation is subject to the following conditions:
- this device may not cause harmful interferences
- this device must accept any interference received,
including interference that may cause undesired operation
- this device must not be operated within significant electromagnetic field
The Earth / Grounding Concept
VOR DEM ÖFFNEN NETZSTECKER
ZIEHEN!! PULL MAINS BEFORE
OPENING!! AVANT D´OUVRIER
RETIREZ LA FICHE MALE!!

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General GROUND-LIFT Jumper
( Accessible from the inside. Mind the SECURITY INSTRUCTIONS):
Ex-works this jumper is set to the LIFT position.
The internal ground potential is “lifted”by means of this jumper.
As a result, the interconnection for DC voltages and lower frequencies (< 150 Hz) will be cut.
Higher frequencies will be bled off to earth potential through the RC filter. The LIFT position is
helpful in case of hum or jitter caused by different ground/earth potentials. Of course, full electrical
protection is granted as the case is always connected to ground/earth potential!
See page 31 "Jumper Settings" for details.
Unfortunately, there is no general recommendation how to solve hum and jitter problems - or even
minimize them. The best way to succeed is to check different options! In case of balanced cables, it
should always be verified if the shield of the cable is connected to the shell of the XLR connector.
The shell is ALWAYS connected to earth potential when the connector is inserted!
Concerning ANALOGUE inputs and outputs, the relationship between ground and earth may be
modified. Electrical safety is always ensured since the earth conductor is permanently
connected to the enclosure!
XLR GROUD-LIFT Jumper
( Accessible from the inside. Mind the SECURITY INSTRUCTIONS):
G(ROUND): Ex-works all jumpers are set to "G" (ground) position.
Pin 1 is connected to the internal ground reference.
High frequency interference is deflected to the case via a 100 nF capacitor.
L(IFT): The interconnection between Pin 1 and ground is open. High frequency interference is
deflected to the case via a 100 nF capacitor. This jumper position is specifically useful
if the unit is equipped with audio-transformers!
C(ASE): Pin 1 is connected to the case, the 100 nF capacitor is bridged. This jumper position
may be varied together with the General GROUND-LIFT jumper.
Please note that with jumpers not in the ex-works position
EMC emission might occur,
for which the user is responsible only!
So, only change these settings when you know what you are doing!

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Connection / Connectors for Analogue Signals

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GENERAL INFORMATION
VIOLECTRIC HPA V550 contains a first-class Preamplifier and a high-grade stereo balanced
Headphone Amplifier designed to drive low-, medium- and high-Z loads (16...600 ohms) as usually
represented by high-quality headphones.
Because of its four built-in amplifiers and the front mounted 4-pin XLR socket it is a real balanced
amplifier. V550 carries its four-pin socket advisably and not to pretend a balanced action. It is not
only a convenience feature !
Due to its specific, highly variable, low-noise and low distortion circuit design especially optimised
for dynamic and orthodynamic headphones, HPA V550 fulfils even highest demands.
Features HPA V550:
-3 analogue stereo inputs, input impedance 10 kOhm, max. level +21 dBu
-1 x balanced via Neutrik XLR, gold plated
-2 x unbalanced via RCA sockets, gold plated
-All inputs switchable from the front
-LEDs for the activated input
-PRE-GAIN = sevenfold gain/attenuation -18 / -12 / -6 / 0 / +6 / +12 / +18 dBr
-Headphone amp with 4 discrete-design power amps with 16 transistors per channel
-Extremely low output impedance
-1 x 4-pin XLR connector, Neutrik, gold plated
-2 x TRS phone jacks, Neutrik, silver plated
-Balanced and unbalanced line outputs via XLR and RCA connectors, gold plated
-Line outputs pre/post (fixed/variable = w/o volume control) switchable
-Line output level with sevenfold gain/attenuation -18 / -12 / -6 / 0 / +6 / +12 / +18 dBr
-Alps RK 27 motorized volume control
-Alps RK 27 balance control
-Output management: headphones active / line-out active / both active / none active (mute)
-LEDs to display the activated outputs
-Remote control for volume, input selection, output selection, mute
-52 transistors, 24 High Quality Audio Op-Amps in the signal path
-High-grade MKP capacitors in the signal path
-0,1 % und 1 % Metallfilm resistors
-Large filter capacity (> 35.000 uF)
-delayed relay-based headphone output during power on / instant cut-off for power off
-Protective circuits for overload, DC, temperature
-2 x toroidal transformers 25 + 25 W
-Rugged Aluminum case, black anodized
-8 mm massive Aluminum front panel
Features HPA V550:
-Motorized volume control, reed relay attenuator with 256 steps of 0,4 dB each
With its dimensions, the VIOLECTRIC HPA V550 ensures optimum flexibility combined with high
output power. During design, high emphasis was put on operational safety even when the unit is
operated inappropriately.

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HPA V550 is equipped with safety circuitry and internal filters to prevent damage to the connected
headphones due to DC voltages at the outputs, power overload and high-frequency overload
beyond the audible range.
THE CASE
of VIOLECTRIC HPA V550 is made of 3 + 4 mm Aluminum and a thick 8 mm aluminum front panel.
This choice of material ensures high mechanical stability and resistance whilst maintaining a high
optical and haptic quality.
GROUND AND PROTECTIVE EARTH
The case of VIOLECTRIC HPA V550 is connected to protective earth.
POWER SUPPLY
Mains power is provided via a three-pin IEC/CEE socket and mating "cold-appliance" mains cord with
Schuko-type plug for units purchased in middle Europe.
The device is set to 230V mains, whereas the actual voltage may vary between 190 and 240 volts for
flawless operation.
The mains voltage may be altered to 115 V AC supply inside the unit with the aid of a mains voltage
selector. In this case stable operation is granted in a range of 85 to 120 V (see page 27).
Two toroidal transformers each with 25 Watt are providing the internal operating voltages
of +/-25 V. Out of these voltages some more operating voltages are generated.
MAINS FUSE
The time-lag fuse is soldered
in place on the circuit board.
In case, it must be replaced
with a fuse of the same type
only.
CAUTION!!
MIND THE SAFETY INSTRUCTIONS:
A blown fuse indicates an internal fault and
should be replaced during
qualified repair or servicing only!

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THE REMOTE CONTROL FOR VIOLECTRIC HPA V550
Function
This remote control sends out infrared rays. For that purpose, there is
an infrared LED on the front. The remote control should point in
direction of the target device to obtain best functionality.
The operating distance is about 5 - 7 meters (15 –20 ft).
With the “VOLUME +/-“buttons the volume can be altered. This is done
with a motor inside the amp to get the volume knob into motion.
With the “MUTE“button the internal mute function is engaged.
A direct “MUTE“can only be released by the remote control.
With the “INPUT 1 / 2 / 3“buttons one of the three analogue inputs may
be selected.
With the “Head-Output“and “Line-Output“buttons you may chose if
the front mounted headphone outputs are active or the rear mounted
line outputs –or both or none.
(pictures show the original size
of the remote control)
Maintenance
The remote control is powered by a little “CR2032“size lithium battery.
The battery diameter is 20 mm, the hight is 3,2 mm –that´s where the
name comes from.
If you share the opinion that the battery is empty you may check this
with the aid of your smartphone. The camera function reacts on the
infrared rays of the remote control which cannot be seen with human
eyes.
So, just point the remote control to the camera of your smart phone
and press a button. When you don´t see any action, the battery is
empty.
Take a paperclip or something similar and bend it like indicated on the
back of the remote control. Plug it in the little hole to force the keypad
to come out the aluminum frame –it is held by magnets.
Now you can carefully take off the electronics to replace the battery.
The (-) pole must point to the PCB.
The (+) pole is the wider part and normally denoted.
It has to point “upwards”.
Re-assemble the keypad, take care of the infrared LED !

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Block circuitry VIOLECTRIC HPA V550

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THE POWER-SWITCH
The unit is put into operation by means of the power switch.
The power-on procedure takes about 5 seconds.
During this time the “PROTECT”LED lights red until all internal parameter
are checked and found OK.
Any breakdown will cause the “PROTECT”LED to come up and the
outputs are muted.
HPA V550 will always start with the last settings of the
input- and output configuration.
THE ANALOGUE SIGNAL INPUTS
THE BALANCED SIGNAL INPUTS
are situated on the rear panel of the unit and are labelled as "XLR IN Left"
and "XLR IN Right". They are fitted with gold plated XLR sockets from
Neutrik.
Please note:
Unbalanced signals can be injected as well by means of an adaptor.
See page 8 to learn more.
THE UNBALANCED SIGNAL INPUTS
For the use with unbalanced signals, gold plated RCA sockets are provided.
They are labelled as "RCA IN Left 1/2”and "RCA IN Right 1/2".
The input impedance on all analogue inputs is 10 kohms.
Maximum input level should not exceed +21 dBu.
It is reduced to +3 dBu when PRE-GAIN +18 dB is engaged.
Balanced XLR
pin-out:
PIN 1 GND
PIN 2 (+) PHASE
PIN 3 (-) PHASE

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HEADPHONE AMP PRE-GAIN
These DIP-switches are situated on the back of the unit inside the field of the analogue inputs.
Settings can be made for the left and right channel - they shall not be different from each other.
With these switches an additional gain or attenuation may be set.
It is dependent on the output level of the input source and the sensitivity of the headphones
connected. By this measure it is maintained to achieve lowest possible noise and maximum travel of
the volume attenuator. The high gain/attenuation range of +/-18 dB (factor 64) ensures a perfect
match of any source with any headphone in the market.
Please see page 15 to learn more about: “Too loud? Too soft? The PRE-GAIN method”
SELECTING / ACTIVATING AN INPUT
With the “ANALOGUE INPUTS“button on the front of VIOLECTRIC HPA V550 one of three analogue
inputs may be activated. The corresponding LED is illuminated.
You can also use the remote control for this purpose.
Press the “INPUT 1 / 2 / 3“buttons to change the analogue inputs.
THE VOLUME ATTENUATOR
is to set the desired volume for
the left and right channel
simultaneously.
Volume can also be set via your
remote control by depressing the
“VOLUME +/-”buttons. For this
purpose, the volume control is
actuated by a servo motor.
Manual operation of the knob at
the same time –although not
useful - is possible without the
risk of damage.

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As an option (HPA V550 PRO), the attenuation is made in 256 steps of 0.4 dB each.
The steps are switched with special “reed relays”. Here, the switching contacts are situated in a tiny
glass tube filled with a protective gas. The contacts are actuated by a magnetic field.
BALANCE CONTROL
is provided to compensate moderate level differences between left and right channel. These may
root in the recorded material itself, noticeable differences between left and right headphone system,
or differences in the user’s individual hearing.
All of the above can be carefully compensated.
The balance control offers a precise centre detent in case no adjustment is necessary. In order not to
impair the perfect crosstalk specs of HPA V550, it takes effect on the right channel only.
Too loud? Too soft? The PRE-GAIN method
The VIOLECTRIC HPA V550 is specially designed to drive headphones. To do so it is placed between
up to three analogue sources and the headphones. Headphones however can present load
impedances from 8 to 2000 ohms and efficiency ratios from 85 to 115 dB per Milliwatt. The sources
may have output levels between 0.5 Volt up to 10 Volt. Thus, it can be quite tricky to fulfil all
demands, since...
…owners of high-efficiency headphones will rarely set the volume control higher
than 9 o'clock in order to exclude hearing damage, while
... the maximum setting may still be too soft for low-efficiency headphones, but
…all users expect highest quality at lowest noise and distortion.
Thus, the circuitry must adapt itself as the headphones will not do and the sources will seldom do!
WE CALL THE SOLUTION TO THIS PROBLEM PRE-GAIN
A single amp of HPA V550 has no gain (gain = 0 dB = factor 1). In case a balanced headphone is
connected two amps are active with a combined gain of +6 dB (factor 2).
By this measure the amps will produce an extremely low self-generated noise which can hardly been
heard even with highest sensitive in-ear-monitors (IEM).
On the other hand, the amps of HPA V550 with very powerful transformers and with their high
operating voltage are able to drive low efficiency or high impedance headphone to the full with ease.
You will be unable to find a headphone driving HPA V550 to its limits. This effortless action will save
your precious headphones as they will never see a distorted signal from the amp.
The alignment between amplifier and headphone is provided by the preamp stage, which can boost
or attenuate the input signal in seven steps of -18 / -12 / -6 / 0 / +6 / +12 / +18 dBr. For this purpose,
two switching devices are located on the rear panel for left and right channel individually.

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HOW TO OPTIMIZE THE PRE-GAIN SETTING
Connect your source to VIOLECTRIC HPA V550 and plug in your headphones. Listen !!
Your amp is adjusted best by the individual PRE-GAIN setting when the volume control for “normal”
listening is positioned around 12 o´clock.
So it is provided that there is enough attenuator travel to boost the signal through lower level
passages or to listen with higher volume. On the other hand, the attenuator travel is optimized to
reduce the self-generated noise from the amp.
THE PRE-GAIN SETTING
Ex works all switches are in “OFF”position, meaning 0 dB gain
In case you cannot reach the 12 o´clock position because the input signal is too loud, feel free to
reduce the signal with the PRE-GAIN steps -6 / -12 / -18 dBr.
In case the signal is too soft even with volume settings above 12 o´clock please use the PRE-GAIN
settings +6 / +12 / +18 dB to achieve more gain.
Other than the above settings are not useful but harmless.
CAUTION
To avoid unwanted level leaps the settings should be altered under the following conditions only:
-the "VOLUME" control should be set to minimum
or the headphone outputs shall be deactivated using the “HEAD“button
-left and right channel settings should be the same
unless you want to settle the amp for different hearing abilities
Ex-factory, all switches are set to their lowest position - i.e. 0 dB PRE-GAIN - which should be
sufficient for most applications.

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THE AMPLIFIER(S)
The input signals are fed to an amplifier stage especially designed for this application, with 2 x eight
transistors per channel. Because of the true balanced operation VIOLECTRIC HPA V550 houses no
less than four of those! All in all, 32 of over 50 transistors of the unit are responsible to process
analogue signals. The channels are physically separated from each other to ensure optimum
crosstalk rejection.
The frequency range covers 5 Hz ... 250 kHz (-0.5 dB) in order to ensure fully linear performance
within the entire audible range. Overall gain is set to 0 dB (unbalanced) or +6 dB respectively
(balanced) to ensure lowest self-generated noise.
ACTIVATING / DEACTIVATING THE HEADPHONE OUTPUTS
Pressing the "HEAD" button will activate or deactivate the headphone outputs.
The white LED shows the activated state.
This procedure is also maintained by the dedicated button of the remote control.
ACTIVATING / DEACTIVATING THE LINE OUTPUTS
Pressing the "LINE" button will activate or deactivate the line outputs on the back panel.
The white LED shows the activated state.
This procedure is also maintained by the dedicated button of the remote control.
HINT:
When the "MUTE“Button of the remote control is pressed, all outputs from HPA V550 are muted,
this concerns the back mounted line outputs and the front mounted headphone outputs.
The front "MUTE“LED is red now.
The mute may be deactivated separately for the headphones outputs or the line outputs by pressing
the dedicated button on the front panel or on the remote control.
For both ways simultaneously the mute may be released by pressing the “MUTE”button on the
remote control again.

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THE BALANCED HEADPHONE OUTPUT
VIOLECTRIC HPA V550
offers a dedicated headphone output
to connect balanced headphones.
The output is situated on the front
panel and comes as a gold plated
4-pin XLR socket.
THE UNBALANCED HEADPHONE OUTPUTS
The HPA V550 offers two stereophonic headphone outputs,
each equipped with a 6.3 mm (1/4") TRS jack socket.
Because HPA V550 has a 4-channel amplifier (2 x stereo),
each socket is driven by a dedicated stereo amplifier
Please note:
The RIGHT phone jack is connected to the in-phase stereo signal, whereas the left phone jack is
connected to the 1800phase shifted signal.
HINT:
To protect the headphones from interferences during powering on/off the outputs are cut during
powering on. This procedure takes about five seconds. When powering off the outputs are cut
instantly.
THE LINE OUTPUTS
THE UNBALANCED LINE OUTPUTS
are located on the rear panel of the unit and are marked as “RCA OUT L/R”.
Gold-plated RCA connectors are implemented here.
THE BALANCED LINE OUTPUTS
are located on the rear panel of the unit and are marked as “XLR OUT L”and “XLR OUT R”.
Gold-plated XLR connectors are implemented here.
Balanced Headphone
Socket Pin-Out:
Pin 1 (+) Left channel
Pin 2 (-) Left channel
Pin 3 (+) Right channel
Pin 4 (-) Right channel
Unbalanced Headphone
Sockets Pin-Out:
TIP Left channel
RING Right channel
SLEEVE GND

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Hint:
With a balanced-to-unbalanced adapter this connection may also be used for unbalanced cables.
PLEASE NOTE THAT IN THIS CASE PIN 3 HAS TO BE LEFT OPEN!
SIGNAL SWITCH: PRE / POST FADER or FIXED-VARIABLE
The "SIGNAL" switch is located on the back panel in the ”LINE OUTPUTS”field.
The line out signal may be sourced from two different positions inside VIOLECTRIC HPA V550.
If you want to use the activated input signal as is, maybe to source a unit with its own attenuator or
a recording device, then the “PRE-FADER”or “FIXED OUT”mode is the right choice. Here, the input
signal is routed directly to the line outputs without any alteration from the volume attenuator.
If you like to operate you VIOLECTRIC HPA V550 as pre-amp device of outstanding quality to drive
some active speakers or power amps, then “POST-FADER”or “VARIABLE OUT”is the weapon of
choice. Now, the line out signal is attenuated by the volume control of VIOLCTRIC HPA V550.
LINE OUT GAIN ADJUSTEMENT (LEVEL ON THE LINE OUTPUTS)
The level of the activated input is buffered and routed unaltered in its level to the line outputs.
To adapt the level perfectly to the subsequent device(s) the "LINE OUT GAIN" switches are useful.
The operation is similar to the setting of the headphone amp pre gain described on page 16.
You may set gain or attenuation in a range of -18 / -12 /-6 / 0 / +6 / +12 / +18 dB.
Hint:
The unbalanced Signal has always -6 dB less level than the balanced signal!
SIGNAL PROCESSING
Inside your VIOLECTRIC HPA V550 the signal is always unbalanced. This is no disadvantage as the
so called “fully balanced”signal processing often generates more issues that solving them.
It is not possible to preserve a reasonable symmetrical integrity of a signal inside a complex
apparatus like HPA V550.
Further, only the unbalanced signal processing is capable to use the device also as a converter
between unbalanced and balanced signals.
Balanced Interconnection
of the XLR Socket:
Unbalanced Interconnection
of the XLR Socket:
PIN 1 GND PIN 1 GND
PIN 2 in PHASE PIN 2 Signal
PIN 3 out of PHASE PIN 3 OPEN !!

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With your HPA V550 you will be able to feed an unbalanced signal and to listen with your balanced or
single ended headphones. Further, you can feed subsequent devices from the unbalanced
and/or balanced line outputs.
You may also feed a balanced signal and listen to it with your balanced or single ended headphones.
Simultaneously you may again use the unbalanced and/or balanced line outputs.
ERROR REPORTING:
To ensure error-free operation and not to harm your valuable headphones in a comprehensive way
your VIOLECTRIC HPA V550 is equipped with a number of protective circuits:
-During powering on there is a five seconds delay to protect your headphones from possibly
unwholesome noises. After the time the headphone outputs are switched to the amp.
Also, the instant cut-off after powering off is intended to protect your headphones.
-DC voltages are no good part of the output signal and must be avoided. If such are detected, the
headphone sockets are cut from the electronics and the ”PROTECT”LED is switched to red.
When the DC voltage has vanished, the amp will automatically return to “normal”operation.
-Overload causes distorted output signals and is also harmful for the headphones. If an overload
was detected, the headphone sockets are cut from the electronics and the ”PROTECT”LED is
switched to red. When the overload disappeared, the amp will automatically return to “normal”
operation.
-All errors will also reset when the unit is switched off and on again.
In case that there is still an error condition the protecting circuits will keep the error mode and
the status LED is red.
RESET OF THE PROCESSORS
Many internal procedures are enabled by processors.
If - of any reasons - nothing seems to work as it should anymore,
follow these instructions to come back to DEFAULT SETTINGS:
Push and hold the “ANALOGUE INPUTS”button whilst powering the unit.
Soon after all LEDs on the front panel will light up.
Now you can release the “ANALOGUE INPUTS”button as all settings had been reset to default.