Violectric HPA V281 User manual

1
HEADPHONE AMPLIFIER
HPA V281
USERS MANUAL

2
Content
Theme Page
About Violectric 3
Safety Instructions 5
The Earth / Grounding Concept 7
Connection / Connectors 9
General 10
Block Circuitry 13
Operation 11
Things to know 24
Disposal 29
Technical Data 30
Dismantling 31
Jumper Setting 32
Conformity Statement 34
Warranty 35
CAUTION !!
THE HIGH OUTPUT LEVELS ACHIEVABLE
WITH THIS UNIT MAY
DAMAGE YOUR HEARING OR THE HEADPHONES
IF OPERATED CARELESSLY !!

3
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 ?
devices are exclusively developed in Germany by the
engineers of Lake People electronic GmbH. In doing so, the team of
developers can draw on twenty 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 ?
devices are exclusively manufactured in Germany by
Lake People electronic GmbH or contractors in the company's vicinity.
Lake People - and by association - put high emphasis
on domestic manufacturing. As well, all component suppliers are chosen
in order achieve the main part of added value inland.

4
How do devices get to the customer ?
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 Lake People electronic GmbH themselves.
… and if it doesn't work like it should ?
devices are covered by a 24-month warranty. In case of
any malfunction during this period, they can be shipped to the
manufacturer directly. Of course, the client will benefit from
's and Lake People's 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.violectric.de www.violectric.com
www.lake-people.de www.lake-people.com

5
General Safety Instructions
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:
OVERVIEW: POWER CORD FUNCTION AND COLORS
CONDUCTOR COLOR Alternativ
LLIVE BROWN BLACK
NNEUTRAL BLUE WHITE
E PROTECTIVE EARTH GREEN+YELLOW GREEN
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.

6
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 115 / 230 V AC.
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
VOR DEM ÖFFNEN NETZSTECKER
ZIEHEN!! PULL MAINS BEFORE
OPENING!! AVANT D´OUVRIER
RETIREZ LA FICHE MALE!!

7
The Earth / Grounding Concept
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

8
hum or jitter caused by different ground/earth potentials.
Of coarse full electrical protection is granted as the case is always
connected to ground/earth potential !
See page 32 "Technical Appendix" 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
been 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 ANALOG 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 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 !

9
Connection / Connectors for Analog Signals

10
GENERAL INFORMATION
The HPA V281 is a stereophonic headphone amplifier designed to drive
low-, medium- and high-Z loads (16...600 ohms) as usually represented
by high-quality headphones.
Because of its 4 built in amplifiers and the 4-pin XLR socket on the front
it is also suited to connect balanced headphones.
Due to its specific, variable and low-noise and distortion circuit design
especially optimised for dynamic headphones, the HPA V281 fulfils
even highest demands.
Features:
- Balanced inputs with gold-plated Neutrik XLR connectors
- Unbalanced inputs with gold-plated premium RCA connectors
- Digital input as an option, coaxial, optical, USB, up to 192 kHz
- inputs selectable on the front panel
- PRE-GAIN = switchable input gain in five steps
- Balanced and unbalanced line outputs with RCA resp. XLR sockets,
gold plated, pre-post fader assignable
- Independent-channel design
- ALPS RK27 High-Grade volume control
- Remote controlled and motorized volume control, input/output selection,
mute as an option
- High-Quality op-amps in the signal path
- High-quality MKP capacitors in the signal path
- 0.1 and 1% metal film resistors throughout the unit
- 4 Discrete-design power amps with 8 transistors per channel
- Output management: headphones active /
line-out active / both active / none active (mute)
- 2 silver-plated Neutrik headphone outputs
- 1 4-pin XLR socket, gold plated for balanced headphones
- delayed relay-based headphone output cut-off
- 2 x Toroidal transformers, 25 + 15 W
- Large filtering capacitors in the power supply (36.000 uF)
- Switchable ground lift
- Rugged aluminium case with Nextel coating
- Solid, laser-engraved aluminium front panel

11
With its small dimensions, the HPA V281 ensures optimum flexibility
combined with high output power. During design, high emphasis was
put on operational safety even when the unit is operated inappropriately.
The HPA V281 is equipped with internal filters to prevent damage to the
connected headphones due to high-frequency overload beyond the
audible range.
THE CASE
The HPA V281's case as well as the front / rear panels are made of
solid aluminium. This choice of material ensures high mechanical
stability and resistance.
EARTH AND GROUND
The HPA V281's case is grounded. Internal reference ground is set to
“LIFT” position ex works but may be reconfigured to “GROUND” position
if required. ( see also: page 7 "Earth/Ground concept", page 32
"Technical Appendix" ).
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 32).
Two toroidal transformers with 15 and 25 Watt are providing the internal
operating voltages of +/-30 V. Out of these voltages some more
operating voltages are generated.

12
MAINS FUSE
The 0.25A 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 !!

13

14
POWER SWITCH
The unit is put into operation by means of the power
switch.
Power-on status is indicated by the blue LED below.
The power-on procedure takes about 5 seconds.
During this time the LED of the last selected input is
flashing and the outputs are muted.
Always the last setting is recalled.
BALANCED SIGNAL INPUTS
The balanced signal inputs are situated on the rear panel of the unit and
are labelled as "BAL IN LEFT" and "BAL IN
RIGHT". They are fitted with gold plated XLR
sockets with metal flange from Neutrik.
Please note:
Unbalanced signals can be injected as well by
means of an adaptor. Also see page 9.
Balanced XLR
Pin-out:
PIN 1 GND
PIN 2 (+) PHASE
PIN 3 (-) PHASE

15
UNBALANCED INPUTS
For the use with unbalanced signals, gold plated premium RCA sockets
are provided. They are labelled as "UNBAL IN LEFT" and "UNBAL IN
RIGHT".
Input impedance for all inputs is 10 kohms.
Maximum input level should not exceed +21 dBu.
This value is reduced to +15/+9 dBu if PRE-GAIN is set to +6/+12 dB !!
THE OPTIONAL DIGITAL INPUT
Currently the HPA V281 can be fitted with one out of six D/A converter
types, with three different inputs and a max. sample rates of 96 or 192
kHz:
The COAX input accepts digital PCM audio data in S/P-DIF format, at
sample rates from 28 to 108 kHz (or 210 kHz resp.).
The OPTO input, fitted with a TOS-LINK interface, accepts digital audio
data at sample rates from 28 to 108 kHz (or 210 kHz resp.).
The USB type “B“ input can be connected to a host computer (PC or
laptop). The USB module will automatically be detected as an audio
device.
The USB 96 input is compatible with USB 1.1 and 2.0 standards. It
accepts digital audio formats up to 24 bit at sample rates of 44.1, 48 and
96 kHz, while 88.2 kHz is not supported.
The USB 192 input is compatible with the USB 2.0 standard. It requires
a proprietary driver, which can be downloaded from www.violectric.de.
Digital audio formats up to 24 bit at sample rates of 44.1, 48, 88.2, 96,
176.4 and 192 kHz are supported, as well as the so-called
“asynchronous mode”.
The 96 kHz digital modules comprise a D/A converter with a dynamic
range of 110 dB and –100dB THD+N, thus ranging in the upper-mid
performance class.
The 192 kHz modules are equipped with a top-notch converter offering
a 115 dB dynamic range and –103 dB THD+N, along with significantly
improved analog output circuitry.

16
NOTES:
- After inserting the USB connector, it may be necessary to close
and restart running media applications on the host computer.
- Volume of the host application should be set to 100%.
INPUT SELECTION / ACTIVATION
By means of the “XLR / RCA / DIG“ pushbuttons on the HPA V281’s
front panel, either of the analog inputs or the digital input (if present) can
be activated. The LED next to the corresponding button will light up
accordingly.
Inputs can also be switched by means of the remote control:
- press “1“ on the remote control to select the XLR input
- press “2“ on the remote control to select the RCA input
- press “3“ on the remote control to select the DIG input.
Alternatively, the “channel up/down“ rocker button or “up/down” on the
directional pad can be used to step inputs through.

17
THE VOLUME CONTROL
The desired volumes for left and right channel are set simultaneously by
means of the “VOLUME“ control.
Volume can also be set via remote control. For this purpose, the volume
control is actuated by a servo motor. Manual operation of the knob at
the same time is possible without the risk of damage (although not
useful…).
Press the rocker button “Volume Up/Down” in order to increase or
decrease volume. Pressing “left/right” on the directional pad will have
the same effect.
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 center detent in case no adjustment
is necessary. In order not to impair the V281’s perfect crosstalk specs, it
takes effect on the right channel only.
THE AMPLIFIER
The input signals are fed to an amplifier stage especially designed for
this application, with eight transistors per channel. The V281 houses no
less than four of those ! Channels are physically separated from each
other to ensure optimum crosstalk rejection.
The frequency range covers 5 Hz ... 70 kHz (-0.5 dB) or 3 Hz…200 kHz
respectively (-3 dB), in order to ensure fully linear performance within
the entire audible range. Overall gain is set to +8 dB (unbalanced) or
+14 dB resp. (balanced) to ensure sufficient volume reserve also for
high-impedance headphones.

18
Too loud ? Too soft ? The PRE-GAIN method
The V281 is specially designed to drive headphones. Headphones
however can present load impedances from 8 to 2000 ohms and
efficiency ratios from 85 to 115dB per milliwatt. 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 headphone won't !
WE CALL THE SOLUTION TO THIS PROBLEM PRE-GAIN
The alignment between amplifier and headphone is provided by the
preamp stage, which can boost or attenuate the input signal in four
steps of 6dB each. For this purpose, two switching devices are located
on the rear panel for left and right channel individually.
CAUTION !!
The switch settings should be altered under the following conditions
only:
- The unit must be switched OFF
- the "VOLUME" control must be set to minimum
- left and right channel settings should ALWAYS be set the same
- never increase the setting by more than ONE switch per channel
If you find your HPA V281's volume could be somewhat softer (in order
to improve volume control range e.g.), push the switch labelled "-6 dB"
(half gain) or "-12 dB" (quarter gain) in upward direction.
If you find your HPA V281 should provide more gain, do so with the
switch labelled "+6 dB" (double gain) or "+12 dB" (quadruple gain).
Ex-factory, all switches are set to their lowest position - i.e. 0 dB or unity
gain - which should be sufficient for most applications.

19
DE- / ACTIVATING THE HEADPHONE OUTPUTS
The headphone outputs can be activated
or deactivated by pressing the “HEAD“
button on the front panel.
The green LED displays the activated
status.
This function can also be switched via
remote control.
Press „RED“ ( the red button).
THE BALANCED HEADPHONE OUTPUT
The HPA V281 offers a balanced headphone output.
This is equipped with a gold plated female 4-pin XLR connector.
UNBALANCED HEADPHONE OUTPUTS
The HPA V281 offers two stereophonic headphone outputs, each
equipped with a 1/4" (6.3mm) jack socket.
Because HPA V281 offers 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.
Balanced Headphone socket pin-out:
Pin 1 (+) Left channel
Pin 2 (-) Left channel
Pin 3 (+) Right channel
Pin 4 (-) Right channel
Unbalanced Headphone
socket pin-out:
TIP Left channel
RING Right channel
SLEEVE GND

20
On power-up and power-down, the outputs are cut from the amplifier
circuitry by relay.
THE BALANCED LINE OUTPUTS
are located on the rear panel of the unit and are marked as “BAL OUT
LEFT” and “BAL OUT RIGHT”. Gold-plated, metal-flange Neutrik XLR
connectors are implemented here.
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 ! See also page 9 for details.
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 !!