Violectric HPA V280 User manual

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HEADPHONE AMPLIFIER
HPA V280
USER´s MANUAL

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Content
Theme Page
About Violectric 3
Safety Instructions 5
The Earth / Grounding Concept 7
Connection / Connectors 9
General 10
Operation 11
About balanced headphone amps 17
Things to know 24
Disposal 29
Dismantling 30
Jumper Settings 31
Technical Data 32
Conformity Statement 33
Warranty 34
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 ?
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.

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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]
Mail: [e-mail]
www.violectric.de www.violectric.com
www.lake-people.de www.lake-people.com

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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
L
LIVE
BROWN
BLACK
N
NEUTRAL
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.

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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!!

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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
hum or jitter caused by different ground/earth potentials.
Of coarse full electrical protection is garanteed as the case is always
connected to ground/earth potential !
See page 25 "Technical Appendix" for details.

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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 mains 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 !

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Connection / Connectors for Analog and Digital Signals

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GENERAL INFORMATION
The HPA V280 is a stereophonic headphone amplifier designed to drive
low-, medium- and high-Z loads (16...600 ohms) as usually represented
by high-quality headphones.
V280 contains four amplifiers (2 x stereo) to enable proper driving of
balanced headphones.
Due to its specific, variable and low-noise and distortion circuit design
especially optimised for dynamic headphones, the HPA V280 fulfils
even highest demands.
Features:
-Balanced inputs with gold-plated Neutrik XLR connectors
-Unbalanced inputs with gold-plated ALPS RCA connectors
-switchable unbalanced outputs with RCA connectors
-Digital input as an option, coaxial, optical, USB, up to 192 kHz
-PRE-GAIN = switchable input gain in five steps
-Independent-channel design
-DC-coupled (switchable)
-ALPS RK27 High-Grade volume control
-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 with famous V200 technology
- 1 balanced headphone output, Neutrik 4-pin, gold plated
-2 silver-plated Neutrik headphone outputs
-Relay-based headphone output cut-off
-Dual Toroidal transformer
-Large filtering capacitors in the power supply
-Switchable ground lift
-Rugged aluminium case with Nextel coating
-Solid, laser-engraved aluminium front panel
The HPA V280 is equipped with internal filters to prevent damage to the
connected headphones due to high-frequency overload beyond the
audible range.

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THE CASE
The HPA V280's case as well as the front or rear panels are made of
solid aluminium. This choice of material ensures high mechanical
stability and resistance.
EARTH AND GROUND
The HPA V280's case is grounded. Internal reference ground is bridged
to protective earth by means of a jumper. If required, the jumper can be
set to 'LIFT' position (see also: page 7 "Earth/Ground concept" and
page 25 "Technical Appendix").
POWER SUPPLY
Mains power is provided via a three-pin IEC/CEE socket and mating
"cold-appliance" mains cord with a dedicated wall plug. The device is
set to 230 or 115 V AC mains internally, whereas the actual voltage may
vary between 190 …240 V for 230 V and 85 …120 volts for 115 V for
flawless operation. Altering the mains voltage can easily done by a
simple internally accessible switch. Two large toroidal transformers are
providing the internal operating voltages.
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 !!

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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
XLR sockets.
Please note:
Unbalanced signals can be injected as well by means of an adaptor.
Also see page 9.
Balanced XLR pinout:
PIN 1 GND
PIN 2 (+) PHASE
PIN 3 (-) PHASE
UNBALANCED INPUTS
For the use with unbalanced signals, RCA sockets are provided. They
are labelled as "IN/OUT LEFT" and "IN/OUT RIGHT", and can be
configured as either inputs or outputs.
(about their configuration, see page 25)
RCA sockets as inputs:
The RCA sockets are factory-preset as inputs and are equipped with
integrated switch contacts !
When a RCA plug is inserted, it cuts possible signals applied to the
balanced input automatically. I.e. the RCA input has priority.
Input impedance for all inputs is 10 kohms.

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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 !!
RCA socket as outputs:
The RCA sockets can also be operated as outputs. This offers the
possibility of using a refreshed balanced or USB input signal for further
purposes.
Output levels equal the levels applied to the inputs, i.e. the signal is
amplified by 0dB (unity gain) at an output impedance of < 1 ohms.
See also page 25 "Technical Appendix"
THE OPTIONAL DIGITAL INPUT
Currently the HPA V280 can be fitted with one out of seven D/A converter
types, with three different inputs and a max. sample rate 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 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.
There are TWO different USB 192 modules, compatible with the USB
2.0 standard. Both require 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”.

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By now we recommend the “Tenor”chip-set for Windows applicatons
and the “X-Mos”chip-set for Mac users.
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.
Please note:
-The digital input has priority over all other inputs and will mute these
when a valif digital signal is detected
-When a USB cable is inserted, it may be required to restart running
media applications on the host.
-Volume control of the host application should be set to 100%.
Too loud ? Too soft ? The PRE-GAIN method
The V280 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-effectivity 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

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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 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 should ALWAYS be set the same
-never increase the setting by more than ONE step per
channel at a time.
If you find your HPA V280's volume could be somewhat softer (in order
to improve volume control range e.g.), push the switch labelled "-6dB"
(half gain) or "-12dB" (quarter gain) in upward direction.
If you find your HPA V280 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.
OPERATION
Most control elements and indicators are located on the front panel.
POWER SWITCH
The unit is put into operation by means of the power switch. Power-on
status is indicated by the blue LED below.
VOLUME CONTROL
The "VOLUME" control sets the desired output volumes for left and right
channel simultaneously.
THE AMPLIFIERS
The input signals are fed to a special stereo amplifier which is equipped

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with two power stages per channel to generate balanced signals. The
amp circuitry is derived from the famous Violectric V200 !
The individual-channel design provides optimum crosstalk rejection.
The amplifier's frequency range stretches from DC to over 200kHz
(-3dB cutoff frequency) in order to obtain absolutely linear character-
istics within the audible range. Overall gain is set to +8 dB in order to
provide sufficient reserves also for high-impedance headphones.
THE BALANCED HEADPHONE OUTPUT
The HPA V280 offers a balanced headphone output.
This is equipped with a gold plated female 4-pin XLR connector.
Balanced Headphone socket pinout:
Pin 1 (+) Left channel
Pin 2 (-) Left channel
Pin 3 (+) Right channel
Pin 4 (-) Right channel
THE UNBALANCED HEADPHONE OUTPUTS
The HPA V280 offers two stereophonic headphone outputs, each
equipped with a 1/4" (6.3mm) jack socket.
Unbalanced Headphone socket pinout:
TIP Left channel
RING Right channel
SLEEVE GND

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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. On power-up and power-down, the outputs are cut from the
amplifier circuitry by relay.
HINTS FOR THE BALANCED OPERATION
OF HEADPHONES
As there is no common standard about how to make the connectors of
balanced headphones and headphone amplifiers, we decided to equip
our unit(s) with 4-pin XLR connectors. In contrary to most XLR
standards the female socket is situated on the amp.
If you are not familiar in altering your headphones with matching
connectors we offer this work as a service. Please ask !!
ATTENTION:
Your headphone is double as loud as normal in balanced mode !!!
About Balanced Headphone Amplifiers
Different kinds of balanced applications and their advantages
The balanced signal line …
…is used to maximize the noise and hum immunity of the signal line.
Who ever made a military service perhaps knows about the “field telephone”
which is a very simple thing without any electronics inside and without a power
supply. It is hooked to another field telephone with a simple twisted cable. This
cable can be as long as some kilometers and communication is still possible.
This is caused by the advantages of the twisted cable, the balanced line.
An easy and reliable approach to a balanced line is the use of transformers on
both ends.
This can be done even without the need of power.
Unfortunately those are expensive and suffer from unlinearities.

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Electronically balanced signals can be made with two op-amps. Here, out of a
present unbalanced signal (a) an inverted or 1800phase shifted signal (-a) is
formed with another op-amp.
Both signals are fed to a cable consisting of a twisted pair which must not
necessarily be shielded.
On the way to the receiving device interferences may show up and disturb the
signal.
Inside the receiving device the signals are input to a differential amp. As the
name explains, this amp forms a difference out of both signals like this: a –(-a)
= 2a. The same procedure is applied to the interferences: s-s = 0.
As an ideal result there is double the original signal amplitude and no
interferences on the output of the differential amp. In the real world this is not
achieved by 100%.You have to consider voltage- and impedance-ratios what
can be determined as CMRR or Common Mode Rejection Ratio. The higher the
technical efforts, the better the results.
Besides the fact that balanced signals offer enhanced interference immunity
compared to unbalanced signals, the next advantage is that the screen from the
cable only serves for the protection of the signal and for the potential
equalization between devices. It only has a static function.
Looking at unbalanced cables, here the cable shield also serves to leading back
signals.
The ground of unbalanced connected devices is not static but is modulated by
the reflux of the signals.
Whereas a balanced line serves mainly to have an interference-free signal distri-
bution and a static ground, there are other things in the forefront concerning …

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“Balanced”amps.
Let´s take a look at a simple amp:
The left and right input signals are amplified and are fed to the left and right
load.
“Balanced”amps
are not new at all
but known for a long
time e. g. in car
radios where this
technique is taken
to achieve quad
power out of a
limited supply
voltage (12 V).
“Balanced”amps
are also called
Push-Pull Amps or
BTL amps (Bridge-
Terminated-Load).
Take a look:

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The input signals are fed to the loads via two amplifiers per load. The trick is,
that one of these amplifiers is working “normal”, the other inverted respectively
1800phase shifted.
While one amp is “pushing”, the other amp is “pulling”. In doing so the output
amplitude is doubled and the power is fourfold compared to a “normal”amp with
the same supply voltage.
Unfortunately the real life is not as easy as the above simple schematics.
Here is the “normal”amp with problem zones:
Besides the load, which has to be driven there are several other impedances
which should be taken into account. All these are able to impair the proper
driving of the load.
Impedances are a complex mix of resistive, capacitive and inductive parameters
which may lead to an instable operation of an amp when the capacity of a cable
is too high.
To keep things simple, for the following examinations only the resistive parts
shall be taken into account.
Every aboveresistive load will cause a voltage drop which is responsible for a
none-linear behavior inside the system.
Some problems are apparent at first glance:
·The higher the resistive load, the lower the parasitic impedance
influences
·The lower the resistive load, the higher the parasitic impedance
influences