Octave V 70 Class A User manual

V 70 Class A
Owner's Manual
English

3
INTRODUCTION
Congratulations and thank you for choosing OCTAVE
V 70 Class A
You are now the owner of one of the world's most innovative and reliable amplifiers. Look
after it, and it will provide you many years of listening pleasure.
You often hear people claim that tube amplifier design has not progressed for years. The
operating principles of tubes have indeed been documented extensively and are well
known to amplifier designers. Of course, the same can be said for transistor amplifiers.
However, advances in both technologies are still possible thanks to the development of
innovative and improved components, our greater appreciation of the fundamental
principles and, of course, deeper and more advanced insights into the interaction of
amplifier and loudspeaker. With tube amplifiers in particular, a general reluctance to
depart from the classic circuit designs has not done the technology any favors. Although
today's loudspeakers and source equipment provide better performance than ever before,
they also present greater demands on amplifiers. Modern sound reproduction equipment
delivers a level of performance at a price that simply would not have been possible 20 or
even 10 years ago.
These advances have been achieved through the application of the latest technological
developments as they become available and affordable. OCTAVE has specialized in tube
amplification for the past 30 years, during which time we have developed a number of
innovative technologies that have earned us a reputation as one of the leaders in the
field.
Here's wishing you many happy hours of musical pleasure!
Andreas Hofmann

4

5
CONTENTS
Page
Introduction ................................................................................................. 3
1. Description of the V 70 Class A ................................................................ 7
2. Safety instructions .................................................................................... 8
2.1 Before you begin .......................................................................................... 8
2.2 Placement .................................................................................................... 9
2.3 Warranty ....................................................................................................... 9
3. Getting started ............................................................................................ 10
3.1 Unpacking, package contents ...................................................................... 10
3.2 Removing the grille ...................................................................................... 10
3.3 Installing the power tubes ............................................................................ 11
3.4 Switching on for the first time: the Soft-Start feature ................................... 11
3.5 Checking the power tubes (BIAS) ................................................................ 12
3.6 Connecting other components ..................................................................... 12
3.7 Connection options: overview ...................................................................... 13
4. Front panel controls .................................................................................. 14
5. Rear panel connections ............................................................................. 16
6. Advanced functions ................................................................................... 18
6.1 Power Selector, alternative output tubes ..................................................... 18
6.2 Protection ..................................................................................................... 19
6.3 Soft-Start ...................................................................................................... 19
6.4 Ecomode ...................................................................................................... 20
6.5 Front Channel ............................................................................................. 21
6.6 Regulated preamplifier output – Pre-Out ..................................................... 21
7. Tubes ........................................................................................................... 22
7.1 Removing the grille (see 3.2) ....................................................................... 22
7.2 Tube layout .................................................................................................. 22
7.3 BIAS Control Display .................................................................................... 23
7.4 Replacing the tubes ..................................................................................... 24
7.5 Running in the tubes .................................................................................... 24
7.6 Tube Service Life ......................................................................................... 24
8. Remote Control .......................................................................................... 25
9. Option Phono MC/MM ................................................................................ 25
10. Option (Super) Black Box .......................................................................... 26
10.1 Option Black Box .......................................................................................... 26
10.2 Option Super Black Box ............................................................................... 27
11. Troubleshooting ......................................................................................... 28
11.1 Faults caused by external issues ................................................................. 28
11.2 Faults caused by tubes ................................................................................ 30
12. Specifications and Dimensions ................................................................ 32
13. Frequently Asked Questions (FAQ) ......................................................... 35

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7
1. DESCRIPTION OF THE V 70 Class A
Class-A. A promise that has fuelled the highest expectations in the audiophile scene since the very
beginning. For most, Class-A simply stands for pure sound, but often enough it has been coupled
with limited output power.
In short, a “Class A concept” technically means a higher quiescent current setting and therefore
has less distortion (almost only second-order harmonics, referred to as k2), but also a limited full
modulation with less power. Push-pull concepts, on the other hand, can give 4-16 times the power
compared to Class-A, but struggle with inharmonic distortions (i.e. odd harmonics k3 and k5). Two
opponents, if you will: sound versus power. Of course, Andreas Hofmann was tempted to combine
both concepts into something new.
The result of many years of development is a typical Octave amplifier, the V 70 Class A, a Class A
push-pull amplifier in a pentode circuit.
For this, an absolutely unique and completely new class-A technology had to be developed:
The Dynamic Bias Control.
Dynamic Bias Control (DBC) means that A. Hofmann has found ways to dynamically shift the
limited dynamic range, and thus the limited power of the Class-A-concept, according the power
requirements. The development of the dynamic operating point setting (DBC) made a self-
regulating Class-A-amplifier possible with approximately twice the output power of 50 W RMS, with
up to 70 W peak power. This technology combines the tonal purity of Class A with the dynamics
and performance of push-pull A/B technology.
The modern concept of a Class-A push-pull amplifier in a pentode circuit enables the Class-A
virtues to be guaranteed across the entire frequency response up to maximum modulation. The
enormous power, with up to 70 watts of music power, is significantly above the output level of
conventional Class A amplifiers and is more than sufficient to drive virtually any loudspeaker.
This new integrated amplifier is equipped with a symmetrical input as standard and if a turntable is
to be connected, the optional phono board (either MC or MM) offers the ideal solution.
The V 70 class A uses an automatic bias circuit. The amplifier adjusts itself to the tube used and
requires no further adjustments. The proven BIAS measurement with the colored LED lights is still
used. However, this is only used to check that the four tubes are working properly.
Similar to the other top models from Octave, the V 70 Class A features the power selector: power
High and Low, in order to be able to optimally adapt the amplifier to different power tubes. Due to
the high output power in Class A operation, a KT 120 or KT 150 tube must be used for power High.
KT 88 or 6550 variants should be operated at power Low. Then there are still about 15 W Class A
and 25 W peak Power available.
Characteristic technologies from Octave are used, such as power management with electronic
monitoring of the working conditions, along with the unique ECO mode, the modern home cinema
bypass circuit and the practical, regulated preamplifier output (which allows the direct connection of
a subwoofer). Our special power supply technology protects the amplifier against mains
disturbances.
Growing fluctuations in the network and high frequency mains disturbances no longer cause sonic
fluctuations.
This makes the Class A tube amplifier technology even easier and more flexible to use and you
can relax with the Octave V 70 Class A to concentrate on the essentials: relishing in pure musical
enjoyment.

8
2. SAFETY INSTRUCTIONS
2.1 Before you begin
Before using the V 70 Class A for the first time, remove the grille and install the power tubes! (See
Section 3.2 „Removing the grille"). Mount the grille again before switching ON the V 70 Class A.
Operating the amplifier without its protective grille is dangerous and not recommended
In case of damage: disconnect the plug from the mains supply
Never use an amplifier that is damaged or faulty. Make sure it has been labeled as defective and
that it cannot be used until it has been repaired by a qualified service engineer.
Make sure that there is easy access to the IEC socket and power cable.
Do not open the case
There are dangerously high voltages and hot tubes inside this equipment. To avoid a burn or the
risk of electric shock, never allow anyone except qualified personnel to open the case or remove
the grill.
Service and maintenance
For reasons of safety, please ensure that servicing, repairs and other modifications to OCTAVE
equipment are carried out only by a qualified technician. Defective fuses should also only be re-
placed by a qualified technician. Always replace fuses with ones of the same type and rating. If
your amplifier requires servicing, please ship or take your equipment directly to OCTAVE or to one
of our authorized service centers.
Symbols and terms used in warnings
The general danger symbol, in conjunction with the terms CAUTION, WARNING, or
DANGER, warns of the risk of severe injury.
The triangle symbol with the lightning bolt warns of non-isolated, dangerous voltages
inside the case and of hazards posed by electrical shocks. Follow all subsequent in-
structions to avoid injury.
ATTENTION Indicates a danger that could lead to damage or destruction of the device.
CAUTION Indicates a danger that represents a low or medium risk of injury.
WARNING Indicates a danger that represents a high risk of injury.
Before connecting
Make sure that the voltage of your amplifier matches your local supply voltage.
Grounding
This amplifier is a protection class 1 device with an earth conductor. To avoid the risk of electric
shock in the event of a fault, the unit must be grounded. To do this, use the power cable supplied
with the amplifier

9
2. SAFETY INSTRUCTIONS
2.2 Placement
1. Location
OCTAVE equipment is designed strictly for use in a dry domestic environment. Do not use it in the
open air or in damp environments!
Never place plants or liquid-filled containers on your OCTAVE equipment. Take care to avoid
dropping objects or spilling liquids into the case. Should this happen, remove the mains plug
immediately and have your amplifier checked by a qualified service technician.
Condensation may form if the amplifier is taken from a cold environment into a warm one. If you do
this, wait until the amplifier has reached room temperature and is dry before switching it on.
Avoid installing the unit close to sources of heat such as radiators or anywhere that may be in
direct sunlight.
Do not operate the unit near flammable materials, gases or vapors. Avoid areas where there may
be heavy accumulations of dust or where the unit may be subject to mechanical vibration.
Place your OCTAVE amplifier on a stable, level surface.
2. Grille
Never operate the amplifier without the protective grille in place.
3. Ventilation
Make sure that your amplifier has an adequate flow of air around it. If you intend to install your
equipment into a cupboard or on a wall shelf unit, ensure that there is at least a ten centimeter (4
inch) gap between the ventilation slots and the walls all around the amplifier. The rear panel of
cupboards should have ventilation holes to prevent heat build-up. Do not rest the equipment on a
soft surface such as carpet or foam sheeting.
2.3 Warranty
OCTAVE can only guarantee the safety, reliability and performance of this unit if modifications and
repairs are carried out by specialized personnel and when the amplifier is operated in accordance
with the instructions contained in this manual.

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3. GETTING STARTED
3.1 Unpacking, package contents
Scope of delivery
 V 70 Class A
 1 set power tubes with tube layout diagram
 Power cord (3-core cable with 3-pin plug)
 Remote control
 1 x 2,5 mm Allen key for removing the cover
 Owner's manual with warranty card
 Cloth and gloves
3.2 Removing the grille
Procedure
For your own safety, make sure that the amplifier is not connected to power outlet
 Completely remove the 4 hexagonal screws using the Allan key supplied. There are 2
screws on each side
 Carefully pull the grille upward to remove

11
3. GETTING STARTED
3.3 Installing the power tubes
The power tubes (4 x KT 120) are in a separate box in the tube compartment
Insert the power tubes into their sockets as shown on the tube layout. Ensure that you correctly
locate the anti-rotation lug on each of the tubes.
Anti-rotation recess
in the tube socket
3.4 Switching on for the first time – the Soft-Start feature
The V 70 Class A is equipped with a multi-stage soft start turn-on protection circuit that significantly
extends the lifespan of components and tubes by protecting against stresses caused by high inrush
currents when switching on.
Procedure

Check that the Ecomode switch on the rear panel is in the "Eco off" position
 Connect the V 70 Class A to the mains. (On new units, this ECOMODE switch is set to "off"
at the factory)
 Switch on the V 70 Class A using the amplifier’s mains power on/off switch.
Some LEDs will illuminate, depending on the position of the input rotary switch.
In any case the Power LED (indicates that the unit is switched on) and the Soft-Start LED
will be lit. The Soft-Start LED will extinguish a minute later once the unit has booted up.
The V 70 Class A is now ready for work.
Ecomode
Eco
o
ff
Eco
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Amp
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3. GETTING STARTED
3.5 Checking the power tubes (BIAS)
The V 70 Class A has an auto-bias device, which means that you no longer have to adjust the
quiescent current of the tubes yourself. The four power tubes adjust themselves to the correct qui-
escent current (BIAS) due to the Class A circuit concept. The quiescent current remains constant
even with aging of the end tubes.
In order to check whether the tubes are all working properly, there is a control option, the BIAS
control display that indicate the correct BIAS with LEDs
Turn the mode selector knob clockwise to position 6 = BIAS. The input LEDs will extinguish.
Five LEDs will now illuminate: The power LED and the 4 BIAS LEDs in the center of the display,
one for each power tube. If the amplifier is still cold, the LEDs will initially illuminate "yellow".
Please wait five to ten minutes.
After an additional 5 minutes, the BIAS control LEDs will change from yellow to green. This
indicates the correct bias and the unit is ready. If you notice any irregularity in the display please
refer to chapter 7.3.
3.6 Connecting other components
Procedure


Be sure to switch off the V 70 Class A again!
 Connect the other components in your system to the appropriate sockets on the rear of the
V 70 Class A. (See chapter 5 "Rear panel connections". See also chapter 3.7. "Connection
options: overview")
 Check that the switch positions on the front and rear of the amplifier are in their
recommended settings.
 Switch on the V 70 Class A using the on/off switch and wait until the Soft-Start LED
extinguishes. Now you can play music

13
3. GETTING STARTED
3.7 Connection options: overview

14
4. FRONT PANEL CONTROLS
Legend


Power switch 0 = off; 1 = on. Power LED and Soft-Start LED illuminate. The Soft-Start
LED extinguishes after the start-up period of 50 seconds.

Input selector This is used to select the desired input signal. A blue LED indicates the
selected input in the display.
Pos. 1: CD 1 RCA line level input for CD, SACD and similar
Pos. 2: Tuner RCA line level input for tuner, etc.
Pos. 3: Aux 1 RCA line level input for video, etc
 Pos. 4: Aux 2 RCA line level input for video, etc.
 Pos. 5: CD 2 XLR line level input for CD, SACD or similar
Pos. 6: The electronic BIAS measurement system is
activated (see chap. 7.3).
Pos. 7: Front Ch. Multichannel input. In this mode, the V 70 Class A
functions as a two-channel power amplifier. The
volume control is bypassed. (See chap. 6.5)
The record output is switched off in this position


LED indicators Indicating the active input


Bias adjustment LED display of the quiescent current of the output tubes V1 and V2

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4. FRONT PANEL CONTROLS
Legend


BIAS adjustment LED display of the quiescent current of the output tubes V3 and V4
 Remote control receiver To ensure optimum operation of the IR remote control, do not cover
this window
 Status indicators Power Indicates that the unit is switched on.
Protection Red LED lights up when the electronic protection
system has switched off the amplifier due to an
error (see chapter 6.2.).
Soft-start Lights up during the soft-start process immediately
after switch-on. This LED extinguishes after about 1
minute when soft-start has been completed (see
chapter 6.3.).
 Front Ch. Illuminates when multichannel-bypass function is
selected (see chapter 6.5.).


Volume control Remote controlled motorized potentiometer

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5. REAR PANEL CONNECTIONS
Legend
 Ecomode
Eco off: Ecomode automatic is off.
Eco on: Ecomode automatic is on.
Amp off: The power stage of the amplifier is
off. (See chapter 6.4.).
 CD 1 CD line level input, RCA
Tuner Tuner line level input, RCA
AUX 2 RCA line level input for Video etc. or MM/MC input with Phono option
AUX 1 RCA line level input for Video, etc.
Tape Rec Record output for tape or DAT
GND Ground connector for Turntable.
Front Channel Input for the front channel of a multichannel receiver / DVD player
(see chapter 6.5).
Pre Out Regulated preamp output for active subwoofer, etc. (see chapter 6.6.).
CD 2 CD balanced line level input, XLR.
Power Selector Sliding switch to adjust the output power of the V 70 Class A.
(see chapter 6.1)
Ecomode
Eco
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ff
Eco
o
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Am
p
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ff

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5. REAR PANEL CONNECTIONS
Legend
CD 2 Pin configuration for XLR connectors (CD line level input,
XLR
Loudspeaker outputs Speaker connection terminals.
Red = positive terminal, Black = negative terminal.
The negative speaker terminal is connected to ground
(Super) Black Box
connector
The (Super) Black Box is an outboard power supply
capacitance upgrade for the power amplifier section (see
chapter 10).
You must switch off the V 70 Class A using the power
switch before connecting and disconnecting the Black
Box!
AC supply socket IEC socket with integrated fuse holder.
The fuse is located in a pullout compartment underneath
the socket. You can open the fuse compartment after
removing the mains plug.
Fuse For 230/240V: 4 A slow-blow H (T4AH- size 5 x 20 mm).
For 115/240V: 6.3 A slow-blow H (T6.3AH size 5 x 20 mm).
For 100V: 6.3 A slow-blow H (T6.3AH size 5 x 20 mm).
Model identification plate Model and serial number
230V~ / 50-60 Hz / 350W
V 70 CLASS A
Integrated amplifier

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6. ADVANCED FUNCTIONS
6.1 Power Selector, alternative output tubes
Position „HIGH“: KT120, KT 150
Position „LOW“: KT88, 6550
The Power Selector allows adjusting the V 70 Class A in accordance to the output tubes. Position
HIGH is reserved for the standard KT 120 tubes. In the HIGH Position the V 70 Class A is able to
deliver up to 2 x 50 W RMS Output Power. The slightly weaker tubes type KT 88 or 6550 can be
used in the position LOW. In this position the maximum output power is limited to 2 x 25 W to avoid
overloading these tubes. The rather rare tubes of type KT 90 and KT 100 can be used also in the
LOW position.
Tubes of Type 6L6, KT 66, 5881, EL 519 and EL 156 are not suitable for the V 70
Class A.
Please turn OFF the mains push button, before switching the Power Selector switch

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6. ADVANCED FUNCTIONS
6.2 Protection
The V 70 Class A features a comprehensive electronic monitoring and protection system. This
system switches the V 70 Class A off automatically if an overcurrent occurs in the power section.
The purpose of the protection system is to protect the device from consequential damage caused
by overloading of any kind and to protect the power tubes against overcurrent caused by
overloading and short-circuiting the loudspeaker cables
The red “Protection” LED lights up in (No.[6] rear panel) to indicate that the protection system has
tripped.
The amplifier will not play music once the protection system has tripped and you will
not be able to check the BIAS.
The BIAS LEDs will show "yellow" for each of the four output tubes.
If a Black Box or a Super Black Box is connected to the V 70 Class A, the front panel (operate)
LED of the Black Box / Super Black Box will go out. If the Super Black Box is connected, tripping
the protection system will automatically activate the discharge circuit of the (Super) Black Box (see
chapter 10).
The following conditions can cause the protection system to trip:
- Overdriving the V 70 Class A to excessive levels or with excessive levels of low frequency.
- A speaker cable short circuit while the speakers are being driven at high listening levels.
- A fault in one or more of the output tubes.
- A fault in one of the preamp tubes which overloads the affected channel.
Once the protection system has cut in, the only way you can turn the V 70 Class A back on, is to
turn the on/off switch off and then on again. Allow the unit two minutes to cool down before
switching it back on. If possible, identify and eliminate the cause of the problem (see chapter 11
"Troubleshooting").
If it is not clear what has caused the protection system to trip, we recommend that you check the
BIAS before using the amplifier again. Tube faults can result in widely varying BIAS settings. When
these settings exceed a particular value they can cause the protection system to trip.
6.3 Soft-Start
The V 70 Class A input and output tube heaters as well as its high-voltage rails are logic controlled
to ensure that the conduction of the output tubes as well as input stage voltages are constantly
monitored and controlled by the Power Management system to protect the vital internal parts
(tubes, rectifier, electrolytic caps, switches, etc.) against excessive turn-on current. This increases
the lifetime not only of the tubes, but also the caps, while all power related components derive
benefit through this system.
The Soft-Start is always activated within the first 60 seconds after the unit is switched on. During
this time you cannot listen. The Soft-Start delay is indicated with the Soft-Start-LED.
During the Soft-Start-phase, verification of the correct BIAS is not possible. During the
starting phase only the yellow minus LED of the respective output tube lights

20
6. ADVANCED FUNCTIONS
6.4 Ecomode
The Ecomode serves to reduce heat and unnecessary power consumption when the unit is
switched on but not in use. After 10 minutes without receiving signal, the V 70 Class A Ecomode is
activated, turning down the power. In this “sleep” mode, the V 70 Class A draws less than 20 W
Idle current. Therefore the running unit produces no heat, because the heater voltage and the high
voltage for the power amplifier section are switched off. When the music signal is once again
sensed by the V 70 Class A, the Ecomode circuit will turn the unit back on, with a warm-up/start-up
delay of approximately 30 seconds before the unit will operate.
The Ecomode also serves to increase the lifetime of the tubes, while having an added benefit of
improved safety allowing the V 70 Class A owner a level of security against any problems when
leaving the unit powered on. The Ecomode is a safety and energy-saving feature that automatically
switches off the amplifier's tube circuitry during breaks of more than 10 minutes.
Ecomode reduces the overall power consumption of the amplifier to under 20W, compared with
190W in normal operation. When detecting a signal, the V 70 Class A reactivates automatically and
is ready for use again within 30 seconds.
Rear panel switch settings
Eco off: The Ecomode electronic is off, the amplifier is on.
Eco on: The Ecomode electronic is activated. Ecomode is signal-controlled; after a 10-
minute silence, Ecomode switches in automatically. The soft-start LED [6] indicates
that the Ecomode was turning down the unit. As soon as the Ecomode circuit
detects a input signal (from the CD player, for example) it will automatically power
the V 70 Class A up. The process takes approximately 30 seconds, after which
time the soft-start LED will extinguish to show that the V 70 Class A is ready for
use.
Note:
If you switch on the V 70 Class A with Ecomode active, it will go through the start
procedure. If it fails to detect a music signal, it will shut down after 10 minutes.
As well as saving electricity, Ecomode has a number of other advantages:
- Extended tube life
- Reduced heating of the whole unit
- Increased passive safety if the unit is left on by mistake
Ecomode is not the same as standby, however, because certain sections of the
amplifier remain on.
Important!
You cannot check the BIAS in Ecomode once the amplifier has powered
down! The BIAS control then displays always yellow.
Powered down during Ecomode is indicated by the soft-start-LED.
Amp off: The power section of the amplifier is off.
This setting is recommended if only the input section is in use. For example, this
would make sense by using the V 70 Class A as a distributor for a signal for an
external headphone amplifier perhaps. Record-Out and regulated Pre-Out is active.
The signal is not activating the Ecomode to turn on the power section.
E
como
d
e
Eco
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ff
Eco
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Amp
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6. ADVANCED FUNCTIONS
6.5 Front Channel
The Input labeled “Front Channel“ is coupled with a relay that bypasses the volume regulator. In
the “Front Channel” selector position, the V 70 Class A functions as a stereo amplifier. The overall
Gain of the V 70 Class A is reduced to 20dB in this position. The signal of the front channel input is
not available on the record output.
6.6 Regulated preamplifier output – Pre-Out
Using with an active subwoofer
The regulated preamplifier output is most commonly used to drive an active subwoofer. The Pre
Out is decoupled via a separate buffer to prevent the V 70 Class A against the load of the
subwoofer. The input impedance of the subwoofer is therefore non-critical.
The Pre Out does not have a separate muting function to prevent switch-on or switch-off plops from
the V 70 Class A. This is not normally needed, however, since the active crossover in the
subwoofer electronics will block unwanted DC and low frequency signals.