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VPA
Ultimate 845 amplifiers
Instruction manual
2
Nagra – VPA
Table of contents
Security warnings ....................................................................... 3
Warranty ................................................................................... 3
Congratulations .......................................................................... 4
Package contents ....................................................................... 4
Setting-up the amplifiers ............................................................... 5
Installation of the feet ................................................................ 5
Installation of the tubes .............................................................. 6
Installation of the tube protections ............................................... 7
VPA connections ......................................................................... 8
Connecting the VPA to the source ................................................. 8
Connecting the loudspeakers ....................................................... 8
Connecting the AC mains power ................................................... 9
Operation .................................................................................... 10
The main selector ..................................................................... 10
Selecting the correct speaker impedance ..................................... 11
Tube ageing and replacement .................................................... 12
Tube compatibility .................................................................... 12
Tube bias adjustment ............................................................... 12
Technical specifications ............................................................. 13
Declaration of conformity ............................................................. 14
3
Nagra – VPA
Security warnings
• Carefully read this manual before installing your new VPA;
• Should you have any questions on how to set-up or use your
amplifiers, contact your Nagra dealer;
• AUDIO TECHNOLOGY SWITZERLAND SA declines all responsibility in
the event of an accident caused by the non-observance of these
instructions or any other form of user negligence;
• Do not attempt to open the unit under any circumstances. Refer any
service/repair work to qualified personnel. There are no user
serviceable parts inside the amplifier;
• The Nagra VPA is designed to be used indoor only;
• The Nagra VPA runs very hot, install it in a safe place to avoid any risk
of injury, especially with children and domestic pets;
• Should you need to ship or transport your amplifier, always use the
original packing supplied by Nagra.
Warranty
AUDIO TECHNOLOGY SWITZERLAND SA, certifies that this instrument was
thoroughly inspected and tested prior to leaving its factory and is in accordance
with the data given in the accompanying measurement protocol and test sheet.
We warrant the products of our own manufacture against any defect arising from
faulty manufacture for a period of three years from the date of delivery to the
user.
Warranty will be void if the serial number has been removed from the unit.
This limited warranty covers the repair of confirmed defects or, if necessary, the
replacement of the faulty parts, excluding all other indemnities.
All freight costs, as well as customs duty and other possible charges, are at the
customer's expense.
We decline any responsibility for any and all damages resulting, directly or
indirectly, from the use of our products.
We reserve the right to modify the product, and / or the specifications without
notice.
Disposal of Old Electrical & Electronic Equipment (Applicable in the
European Union and other European countries with separate collection
systems).
This symbol on the product or on its packaging indicates that this
product shall not be treated as household waste. Instead it shall be
handed over to the applicable collection point for the recycling of
electrical and electronic equipment. By ensuring this product is
disposed of correctly, you will help prevent potential negative
consequences for the environment and human health. The
recycling of materials will help to conserve natural resources. For more
detailed information about recycling of this product, please contact your
local authority, your household waste disposal service or the shop where
you purchased the product.
4
Nagra – VPA
Congratulations
Congratulations, you have just purchased one of the best amplifiers ever made!
The VPA were created by an engineering team with more than 60 years of
experience designing world-class products for the professional audio, national
security and military businesses.
Since its inception in 1951, Nagra builds products that continue to earn a
reputation for delivering ultimate sonic performance. Numerous awards have
been bestowed upon Nagra for its technical innovation, excellence in design and
flawless construction including three Oscars
®
and one Emmy
®
.
The hi-fi products and field recorders are developed by the same R&D
Department. Nagra philosophy is to provide innovation and technology in order to
design high quality products. The hi-fi range was created to implement innovative
designs and provide Nagra expertise to a new field.
Thank you for being our customer and enjoy your new VPA amplifiers
!
Package content
In addition to the user manual:
• 2x VPA monoblocks;
• 2 mains cables *;
• Set of spare fuses;
• Hex screwdriver (to install the tube protections);
• 2x Sets of tube protections;
• 2x Sets of feet;
• 2x Sets of 845 tubes;
• Microfiber gloves (from Swiss Haute Horlogerie);
• Measurement protocol, this is the actual electrical measurement of
your amplifiers.
If anything is missing, please contact your dealer.
*depending on your country, the AC mains cable features either bare wired, US,
European or Swiss plug.
5
Nagra – VPA
Setting-up the amplifier
Installation of the feet
The VPA needs to stand on its feet to be stable, please install them.
Turn each of the two VPA mono blocks on their side on the edge of a
table.
Step 1 Start by removing the transportation screws
Step 2 Install the feet, using the longer screws provided
6
Nagra – VPA
Installation of the tubes
Step 1 Using the hex screwdriver provided, remove the top rings.
Be careful not to drop a screw inside the amplifier!
Step 2 Insert the 845 tubes
Please use the gloves provided; they are custom made for Nagra using
state of the art “Haute Horlogerie” micro-fiber fabric.
Each VPA has its own set of tubes with a serial number written on the
socket. Each tube is also marked “FRONT” or “REAR” which indicates
the correct location for the tube on the particular amplifier.
This dent must
face the rear of
the unit.
Step 1 Insert the tube, make sure the dent is in the correct position
Step 2 Rotate the tube clockwise, until it clicks.
1
2
7
Nagra – VPA
Installation of the tube protections
845 tubes run extremely hot, more than 300° C, it is mandatory to
install the tube protections for safety reasons. Even with the tube
protection, you should be careful not to get too close to the tubes and
especially to keep children away from the amplifier.
You should also make sure to keep any object or fabric (like curtains
for instance) away from the amplifiers to avoid any fire risk.
Gently slide the tube protection
down.
Make sure the screw holes are
placed above those of the VPA.
Using the hex
screwdriver provided put
the screws back in place
8
Nagra – VPA
VPA connections
Connecting the VPA to the source
Connect the source preamplifier to the XLR balanced input or the RCA
connector.
Input panel
Speaker terminals
Ground connector (ask your
dealer how to use it)
Voltage selector
Mains switch and IEC connector
The white jumper allows
you to select either XLR
balance input (as shown
on the picture) or RCA
unbalanced
9
Nagra – VPA
Connecting the loudspeakers
On the rear of each VPA mono block there are four gold plated WBT
loudspeaker terminals. The loudspeaker cables should be connected
between the right-most terminal marked “LO” for
-
and the correct
terminal according to the impedance stated by the manufacturer of the
loudspeaker for the
+
.
Should you have any doubt about your speaker’s impedance, start with
8 Ohms. You will learn in the “Load Match Meter” section, how to take
full advantage of the VPA unique features to get the best performance
out of your speakers.
Connecting the AC mains power
Before connecting the AC power cables, verify that the AC mains
voltage selector (located on the rear panel) is in the correct position
corresponding to the supply voltage available in your country.
Here the selector is on 220 V.
If the selector is not in the
right position, make sure to
change it, and check the fuse
value:
110 – 120V operation two 10A fuses should be installed;
220 – 240V operation two 5A fuses should be installed.
Fuse compartment
Mains electrical switch
Warning:
Units for Japan are factory adjusted for 100 V and carry a special
sticker. If you live in Japan and don’t find this sticker, please contact
your Nagra dealer and do not attempt to power the unit.
10
Nagra – VPA
Operation
The main selector
Turn the Mains switch (on the rear) to the I position. Then, place the
main selector on the “MUTE” position, the tubes are now powered and
will light up. In this position the amplifier is powered and the audio
signal is muted. Turn the main selector to the ”ON” position, the
amplifier is now fully operational. The best performance will be
obtained after 15 minutes operation (warming-up time).
Mains switch
(rear)
Main selector
position
What is happening
O Any The unit is completely off
I OFF The unit is in standby
I MUTE The unit is On, sound is muted
I ON On
To prevent tube ageing, it is better leave the amplifier on for longer
periods rather than turning it on and off several times a day. For more
information on tube ageing and replacement, refer to Tube ageing and
replacement on page 12.
Main selector
Modulometer
Rear tube selector
(for bias)
11
Nagra – VPA
Selecting the right speaker impedance
The Load Match Meter was specially designed to help you match your
amplifier with your speakers. The Nagra VPA’s output stage features a
custom hand-made Nagra transformer that offers 3 different output
windings for 4, 8 and 16 Ohm speakers.
Start by verifying the nominal impedance of your loudspeakers, either
from their technical specifications or on the rear of the speaker. Then
connect the “+ve” speaker cable to the correct terminal on the VPA.
The modulometer features two pointers, the red pointer indicates the
peak cathode current and the black pointer indicates the peak anode
voltage of the output tube. They will allow you to know if the
impedance match is right.
When playing music (main selector in the ON position)
Needle position What is happening Solution
Red needle > Green
needle*
Output impedance is
too high
Choose a lower
output (8 or 4 Ohms)
Green needle > Red
needle
Output impedance is
too low
Choose a higher
impedance (8 or 16
Ohms)
Needles follow each
other
The match is perfect Enjoy your music
* as shown on the picture
NB the two needles will almost never superimposed one above the
other, but should not be too far apart, this is subjective; spend a little
bit of time to know how to “read” the needles.
12
Nagra – VPA
Tube ageing and replacement
845 tubes are supposed to operate for around 5’000 hours.
Internal tubes can last about the same.
As a rule, you should replace all tubes at once on both units.
Internal tubes must be replaced by a Nagra dealer.
It is normal to adjust the bias once in a while. From time to time,
before listening, check the bias and eventually adjust it to make sure
you get 100% performance out of your amplifiers.
Tube compatibility
Nagra selected 845 tubes go through a rigorous selection: 24 hour
burn-in, individual measurement and selection and are paired using a
Nagra unique process. Using 845 from other suppliers will void
warranty.
Tube bias adjustment
Please refer to the instructions found in the tube package to learn how
to set-up the bias.
13
Nagra – VPA
Technical specifications
The following table shows the general specifications for all Nagra VPA amplifiers.
Your personal amplifier’s measurements are provided on the accompanying
"measurement protocol" document.
Type Pure class A
Tube type 845
Output power 50 W rms
Input impedance > 100 k Ohms
Inputs
1 RCA, 1 XLR balanced
Selection by jumper
Frequency response 20 - 40 kHz +0 / -3dB
Signal-to-noise ratio > 100 dB ASA A
Output impedance 4, 8, 16 Ohms
Bare wires up to 4.2 mm
4mm banana plugs
6.35mm spade lugs
Driver tubes 2x ECC83, 1 E182CC
Voltage range
108
-
1
21
V or
216
-
24
2
V
(Japan 100 V)
50 – 60 Hz
Power consumption 250 W continuous
Dimensions 335 x 115 x 375 mm 13 x 4 ½ x 14 ¾ inches
Net weight (each VPA) 13.5 Kg 30 lbs
14
Nagra – VPA
Déclaration de conformité
Declaration of conformity
FABRICANT: AUDIO TECHNOLOGY SWITZERLAND SA,
1032 Romanel, SUISSE
MANUFACTURER: AUDIO TECHNOLOGY SWITZERLAND SA,
1032 Romanel, SWITZERLAND
APPAREIL : VPA
MODEL:
VPA
Par la présente nous déclarons l'équipement conforme à toutes les
exigences fixées dans les normes:
We hereby declare that the equipment conforms to all the requirements
outlined by the following norms:
NORMES GENERIQUES APPLICABLES :
APPLICABLE GENERIC NORMS:
CENELEC EN 61000-3-2
61000-3-3
50081-1
50082-1
Avertissement.
Bien qu’étant conforme aux normes, cet appareil peut, dans des cas
exceptionnels, provoquer des interférences. Dans ce cas, il peut être
demandé à l’utilisateur de prendre des mesures appropriées.
Warning.
Although this equipment conforms to the stated norms, under certain
exceptional circumstances it may provoke interference. In this event
the user may be asked to take appropriate measures.
Other electrical regulatory certification pending.
Cheseaux 1
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trimestre 2000
Cheseaux 1
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quarter 2000
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