Octave RE 320 User manual

RE 320
Owner's Manual
English

3
INTRODUCTION
Congratulations and thank you for choosing OCTAVE!
RE 320
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
CONTENTS
Page
INTRODUCTION......................................................................................................... 3
1. DESCRIPTION RE 320.................................................................................. 6
2. SAFETY INSTRUCTIONS
2.1. Before you begin ............................................................................................ 8
2.1.1. In case of emergency: disconnect the plug from the mains supply ............... 8
2.1.2. Do not open the case ..................................................................................... 8
2.1.3. Service and maintenance............................................................................... 8
2.1.4. Symbols and terms used in warnings ............................................................ 8
2.1.5. Before connecting .......................................................................................... 9
2.1.6. Grounding....................................................................................................... 9
2.2. Placement....................................................................................................... 9
2.2.1. Location .......................................................................................................... 9
2.2.2. Cover .............................................................................................................. 9
2.2.3. Ventilation....................................................................................................... 9
2.3. Warranty ......................................................................................................... 9
3. SETTING UP.................................................................................................. 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 tubes – setting the bias ............................................................ 12
3.6 Connecting the unit ........................................................................................ 12
4. OPERATION
4.1. RE 320 front panel ......................................................................................... 13
5. CONNECTIONS
5.1. RE 320 rear panel ............................................................................................... 14
6. ADVANCED FUNCTIONS.................................................................................. 16
6.1 Power selector, alternative power tubes ............................................................. 16
6.2 Soft-Start, Inrush current limitation...................................................................... 16
6.3 Electronic Protection System .............................................................................. 17
6.4 Muting Function................................................................................................... 17
6.5 Electronic Balanced Input Circuit ........................................................................ 17
6.6 Ecomode (power saving mode) .......................................................................... 18
7. TUBES ................................................................................................................ 19
7.1 Removing the grille.............................................................................................. 19
7.2 Tube layout.......................................................................................................... 19
7.3 BIAS measurement electronic............................................................................. 20
7.3.1 How to set the BIAS ............................................................................................ 21
7.3.2 LED graphs, advanced adjustment of the BIAS setting ...................................... 22
7.4 Replacing the tubes............................................................................................. 23
7.5 Running in the tubes ........................................................................................... 23
7.6 Tube service life .................................................................................................. 23

5
CONTENTS
Page
8. OPTION BLACK BOX AND SUPER BLACK BOX
8.1 The Black Box option .......................................................................................... 24
8.2 Connecting to the amplifier.................................................................................. 24
8.3 The Super Black Box option................................................................................ 25
8.4 Technical Data .................................................................................................... 25
9. TROUBLESHOOTING........................................................................................ 26
9.1. Faults caused by external issues ........................................................................ 26
9.1.1. Buzzing and hum in the speakers ....................................................................... 26
9.1.2. Mains interference............................................................................................... 27
9.1.3. Channels are not balanced ................................................................................. 27
9.2. Faults caused by tubes ....................................................................................... 28
9.2.1. Mechanical tube faults that do not trip the protection system ............................. 28
9.2.2. Tube faults that trip the protection system .......................................................... 29
10. TECHNICAL DATA
10.1. Specifications ................................................................................................. 30
10.2 Dimensions..................................................................................................... 31
10.3. Diagrams ........................................................................................................ 31
11. FREQUENTLY ASKED QUESTIONS (FAQ)................................................ 33

6
1. DESCRIPTION OF THE RE 320
The new Octave RE 320 stereo power amplifier is designed to deliver 2
x 130 W RMS output power (into 4 ohms loads).Peak Output Power
climbs up to 200 W per channel. As with all Octave models, all research
and development (R&D) and production has been conducted exclusively
in-house, and the amplifier is comprehensively safeguarded against user
error and parts wear – including catastrophic power tube failure.
The RE 320 is based on the stable and reliable SE technology of the
MRE220 model, while incorporating the benefits of the recently-
developed KT150 power tube.
SE Technology The SE technology offers great improvements in the fine resolution, the
dynamics and the microdistortions- often simplified described as noise
The KT150 allows an output power of more than 150 W with two tubes
in push-pull mode, while its current capacity is higher compared to the
classic KT88 tube designs. Increased stability with difficult, low
impedance speakers is achieved through the increased bandwidth and
OCTAVE’s specially designed output and mains transformers. The
average Output power of the RE 320 is limited to increase the stability
and the lifetime of the tubes
The configuration of the output stage of the RE 320:
push pull pentode circuit, class A/B; negative grid voltage adjustable
separate for each power tube through ten turn precision regulators.
Special wideband output transformers using high efficient PMZ core.
BIAS Measurement The RE 320 is fixed BIAS, and utilizes external precision BIAS trim pots
and LED confirmation which allows the user to readily monitor the output
tubes and simply correct their BIAS individually at the front panel of the
unit without the need of a micrometer let alone any special knowledge or
tools – just the supplied 3 mm flat-head screwdriver.
(Super) Black Box
Option The RE 320 is fitted with a connector for the optional Octave “Black
Box” capacitance modules – available in normal and “Super” versions.
The use of the Black Box or Super Black Box significantly increases
power supply capacitance to stabilize current delivery and reduce
impedance interaction of the load, thus improving dynamic range,
separation, depth, soundstage size and articulation. This enables
optimizing the RE 320 in respect to the speaker, which is a tremendous
benefit if the speaker is difficult to drive.
Input Section Unlike other designs, the RE 320 offers single ended RCA and true
balanced XLR inputs with a very high common mode rejection ratio that
eliminates unwanted hum and high frequency distortion induced in the
small signal connection to the preamp

7
1. DESCRIPTION OF THE RE 320
Power Management
The RE 320 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 the input stage voltages are constantly monitored and
controlled by the Power Management System, which serves to protect
the vital internal parts (tubes, rectifier, electrolytic caps, switches, etc.)
against excessive turn-on current. This increases the lifetime of not only
the tubes, but all power related components as each derives benefit
through this system. The Power Management ensures stable operation
even situations where the mains voltage is not stable
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 RE 320 Ecomode is activated,
turning down the power. In this “sleep” mode, the RE 320 draws only 20
W Idle current. Therefore, the unit produces no heat while it remains
switched on. When a music signal is once again detected by the RE 320,
the Ecomode circuit will power the unit back on, with a short warm-
up/start-up delay (approximately 35 seconds) before the unit will
operate.
The Ecomode also serves to increase the lifetime of the tubes, while
providing an added benefit of increased safety allowing the RE 320
owner a level of security against any problems when leaving the unit
switched on.

8
2. SAFETY INSTRUCTIONS
2.1. Before you begin
2.1.1. In case of emergency: disconnect the plug from the mains supply
Never use an amplifier that is damaged or faulty. Make sure that 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.
2.1.2- 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.
2.1.3. 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 replaced
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.
2.1.4. Symbols and terms used in warnings
The following warnings, symbols and terms are used in this document in compliance with the
American National Standard ANSI Z535.6-2011:
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 instructions to avoid injury or death.
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 could lead to death or severe injury.
DANGER Indicates a danger that will result in death or severe injury.
Warning format
WARNING TERM
Type and source of danger
Consequences of ignoring the warning
►Action needed to avoid danger

9
2. SAFETY INSTRUCTIONS
2.1.5. Before connecting
Make sure that the voltage of your amplifier matches your local supply voltage.
2.1.6. Grounding / Earthing
This amplifier is a protection class 1 device, which is the operation with an earth conductor. As a
result, a three-pin power cable with a protective ground contact must be used (included in the scope
of delivery).
2.2. Placement
2.2.1. Location
OCTAVE equipment is designed strictly for use in a dry domestic environment. Do not use it in
open air or in damp environments!
Never place plants or liquid-filled containers on your amplifier. Take care that objects do not fall
or liquids are not spilled into the enclosure. Should this happen, disconnect 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. In
this case, wait until the amplifier has reached room temperature and is dry before switching it
on.
Avoid installing the amplifier close to sources of heat, such as heaters, or anywhere that it may
be in direct sunlight.
Do not operate your OCTAVE amplifier near flammable materials, gases, or vapors. Avoid areas
where there may be heavy accumulations of dust or where the amplifier may be subject to me-
chanical vibration.
Place your OCTAVE amplifier on a stable, even surface.
2.2.2. Cover
Never operate the amplifier without the cover.
2.2.3. Ventilation
Ensure sufficient air circulation around your amplifier. If you intend to install your equipment in
a cupboard or a shelf unit, ensure that there is at least a 10 centimeter gap between the venti-
lation slots and the walls all around the amplifier.
To prevent heat accumulation, the back of the cupboard should have ventilation holes.
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 if the amplifier is operated in accordance with
the instructions contained in this manual.

10
3. SETTING UP
3.1. Unpacking, package contents.
Scope of delivery
RE 320 tube stereo power amplifier
1 set power tubes packed separately
Tube layout diagram
Power cord
4.0 x 100 flat-bladed screwdriver for adjusting the bias
Owner's manual with warranty card
3.2. Removing the grille
Operating the amplifier without its protective grille is dangerous and not recommended!
To remove the grille:
1. For your own safety, switch the amplifier off using the on/off switch or disconnect the
power cord.
2. Pull the grille upward to remove.

11
3. SETTING UP
3.3. Installing the power tubes
The power tubes are packed 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
on the tube socket
3.4. Switching on for the first time – the Soft-Start feature
The RE 320 is equipped with a multi-stage Soft-Start-Turn-On protection circuit which extends
component as well as tube life considerably by protecting against stress caused by typical high
inrush currents during switch on.
1) Connect the RE 320 to the mains.
2) Switch on the RE 320 using the amplifier’s mains power on/off switch (see chap. 4 front panel
).The Power-LED will illuminate.
Turn the Input Rotary Selector to Muting – the Muting LED goes out
Turn the Function Rotary Selector to Eco off – the Ecomode LED on the top side goes out.
(see chap. 6.6 Ecomode)
3) After approx. 30 seconds you hear a relay click noise. The soft start phase is finished and the
power tubes start to work.

12
3. SETTING UP
3.5. Checking the power tubes – setting the BIAS
For the first function check you don’t have to connect the loudspeakers or the preamp.
The trim pots are located next to their respective tubes. Next to each trim pot you will see a pilot
lamp, which shows which tubes have been selected with the bias selector switch. A row of LEDs in
front of the transformer cover assists you in setting the bias correctly. It shows three conditions: bias
too low, correct, and too high.
Before checking the BIAS please wait five to ten minutes. Because the tubes are still cold you
would adjust the wrong BIAS
Turn the BIAS-selector switch clockwise to position V1 = BIAS setting for the tube V1. The LED
next to the tube will illuminate, and one of the three BIAS LEDs will illuminate, normally first the
Minus LED, than the OK-LED.
The LED display:
Ecomode LED Indicating the status of the Ecomode (see chapter 6.6)
Yellow "-" LED BIAS setting of the selected output tube is too low
Green “OK” LED BIAS setting of the selected output tube is correct
Yellow "+" LED BIAS setting of the selected output tube is too high
Red "off" LED Indicates that the electronic protection has switched off the
amplifier (see chapter 6.3)
After an additional 5 to 10 minutes, the BIAS control LEDs will change from yellow to green in case
the BIAS Measurement Electronic is switched to tube 1 for example. This indicates the correct
BIAS. Check all four tubes and switch OFF the BIAS electronic during listening.
If you notice any irregularity (“+” = High BIAS) in the display please refer to chapter 7.3.
3.6. Connecting the unit
1) Make sure that the RE 320 is switched off!
2) Connect the other components in your system to the appropriate sockets on the rear of the RE
320. (See chapter 5 "RE 320 rear panel").
3) Check that the Input switch (2) on the front is in the right position (RCA or XLR).
4) Switch on the RE 320 using the on/off switch and wait a few minutes until the unit is powered.
Now you can listen to music.

13
4. OPERATION
4.1. RE 320 front panel
Legend


Power switch 0 = off; 1 = on. The Power LED illuminates that the unit is ON

Input selector This is used to select the desired input signal.
RCA: RCA Input
XLR: Balanced XLR Input, see Chap. 6.5
Muting: Muting Function of the Input’s, see Chap. 6.4


Power LED lights up when the Power Switchis on 1


Muting LED goes out when the Input Selector Switch is in position “Muting”
Ecomode
Selector Eco On: The Ecomode electronic is activated, the Ecomode LED
lights up in green
and Eco Off: The Ecomode electronic is disabled, and simultaneously
the BIAS measuring electronic is Off
Bias
Measurement Position V1 - V4: The BIAS measuring electronic is connected to the
relevant tubes. To ensure the accuracy of any adjust-
ment, switch On the Muting function
NOTE:
The RE 320 is equipped with a Soft-Start circuit and a Power-Up delay timer.
The amplifier is ready for use after a delay of approximately 2 minutes. Because there are
no relays in the signal path, a low-level, slightly distorted signal from your source equipment
may be heard through your loudspeakers during warm-up. This circuitry extends tube service
life and also protects the power section from voltage spikes and excessive inrush currents.

14
5. CONNECTIONS
5.1. RE 320 rear panel
Legend


XLR Input Balanced Input: Pin 1: Ground, Pin 2: +, Pin 3 –
RCA Input Unbalanced Input
Loudspeaker Terminal
Right channel loudspeaker output
Binding posts to connect the speaker cable.
Red = positive terminal, Black = negative terminal.
You can connect either 4 mm Banana connectors or spades.
The negative speaker terminal is internally connected to ground.
Black-Box-Connector
The (Super) Black Box is an outboard power supply capacitance
upgrade for the power amplifier section
(see chapter 8).
You have to switch off the RE 320 using the power switch before
connecting and disconnecting the Black Box!

15
5. CONNECTIONS
5.1. RE 320 rear panel
Legend
Power Selector Sliding switch to adjust the output power of the RE 320 depending
on the Output Tubes. (see chapter 6.1)
Loudspeaker Terminal
Left channel loudspeaker output
Binding posts to connect the speaker cable.
Red = positive terminal, Black = negative terminal.
You can connect either 4 mm Banana connectors or spades.
The negative speaker terminal is connected to ground.
Model identification
plate Model and Serial Number
Fuse holder
Fuse for 230/240V: 4 H slow-blow IEC Type (5 x 20 mm).
Fuse for 115/120V: 6.3 H slow-blow IEC Type (5 x 20 mm)
Fuse for 100V: 8 H slow-blow IEC Type (5 x 20 mm).
Mains supply
receptacle
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

16
6. ADVANCED FUNCTIONS
6.1. Power Selector, alternative output tubes
The Power Selector allows adjusting the RE 320 in accordance to the output tubes. Position HIGH
is reserved for the standard KT 150 or KT 120 tubes. In the HIGH Position the RE 320 is able to
deliver up to 200 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 75 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.
The EL 34 can be used in the LOW Position in cases of speakers with an impedance higher than 6
ohms.
Tubes of Type 6L6, KT 66, 5881 are not recommended for the RE 320
EL 519 and EL 156 are not suitable for the RE 320.
Before switching the Power Selector turn OFF the mains rocker switch
After switching from power LOW to HIGH and vice versa the BIAS should be corrected in case of
using the same output tubes. Normally there is only a slight correction necessary.
When using different tubes the BIAS has to adjust according to chapter 7.3
6.2. Soft-Start, Inrush current limitation
The RE 320 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.
During the Soft-Start-phase, adjusting the BIAS is not possible.
Position „HIGH“:
KT150, KT120
Position „LOW“:
KT88, 6550, KT90, KT100
(EL34 with Restrictions)

17
6. ADVANCED FUNCTIONS
6.3. Electronic Protection System
The RE 320 features a comprehensive electronic monitoring and protection system. This system will
automatically switch off the RE 320 in case of a fault occurring in the power section.
The protection system has been designed to keep the unit safe from the consequences of overloads
of any kind and to protect the output tubes from current surges.
The RED “Protection” LED lights up 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 or adjust the BIAS setting.
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 RE 320, 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 8.2).
The following conditions can cause the protection system to trip:
-Overdriving the RE 320 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 output stage.
Once the protection system has cut in, the only way you can turn the RE 320 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 9 "Troubleshooting").
If it is not clear what has caused the protection system to trip, we recommend that you check the
BIAS before attempting to use the amplifier again. Tube faults can often result in widely varying BIAS
settings. When these settings exceed a particular value they can cause the protection system to trip.
6.4 Muting Function
The Muting Function is switching Off the RCA and the XLR Inputs of the unit. In this way you can
connect or change the cables without the need of switching Off the unit. You can connect or
disconnect the signal or speaker cables in this mode.
6.5 Electronic Balanced Input Circuit
As standard the Balanced Input is equipped with a precision low noise electronic balanced input
receiver. The Gain of this converter is -6dB, which means that in case of the usual +6dB of the
balanced signal of an electronic balanced preamplifier you will have the same Output level in respect
to the RCA connection.

18
6. ADVANCED FUNCTIONS
6.6. Ecomode (power saving mode)
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 RE 320 Ecomode is activated, turning
down the power. In this “sleep” mode, the RE 320 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 RE 320, 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 RE 320 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
180W in normal operation. When detecting a signal, the RE 320 reactivates automatically and is
ready for use again within 30 seconds.
Eco off: The Ecomode function is off, the Ecomode
LED on the top doesn’t burn
Eco on:
LED display on the top side:
The Ecomode function is activated. The
Ecomode LED lights up in GREEN.
After a 10-minute silence, Ecomode turn the
Unit down. The Ecomode LED changes to
RED indicating that the Ecomode circuit is
powering down the unit.
Note:
If you switch the RE 320 on 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. Ecomode is not the same as standby,
however, because certain sections of the amplifier remain on.
Important!
You cannot adjust the BIAS in Ecomode once the amplifier has powered down!
The signal switching level of 0.6mV results in approx. 40µW output power of the RE 320. In
case of a speaker with a high efficiency an adjusted listening level can be lower than this
value. The Ecomode would drive the unit down. In such cases the Ecomode should be
switched off

19
7. TUBES
7.1. Removing the grille
Operating the amplifier without its protective grille is dangerous and not recommended.
To remove the grille:
1. For your own safety, switch the amplifier off using the on/off switch or disconnect the
power cord.
2. Pull the grille upward to remove.
See chapter 3.2.
7.2. Tube layout
Output tubes: V1 - V4: KT 150 TS standard
V1 + V2 left channel
V3 + V4 right channel
Driver tubes: V5, V6, V7 ECC802, ECC 82,12 AU 7, 5814, 6189
Standard tube layout:
V6 = ECC802 JJ, V5, V7 = 12 AU 7 Tung Sol
All driver tubes should have a system Gain match close to 0.2dB

20
7. TUBES
7.3. BIAS measurement electronic
The BIAS measurement electronic makes it easy for you to check and adjust the idle current of the
output tubes. Getting the BIAS setting right for all four tubes is critical for both the sound of the power
amplifier section and for the service life of the tubes. This feature guarantees consistent sound quality
over the entire lifetime of the output tubes.
That is why we have built this BIAS measurement electronic into the RE 320 – to allow you, the user,
to carry out the adjustment yourself without the need for test equipment. The use of precision op
amps makes it possible for you to set the BIAS to accuracy within 0.2%, making it superior to any
other method.
Using selected output tubes only makes sense if the idle current is adjusted accurately, as is clearly
shown in Fig. 1 Technical Data.
The LED display:
Ecomode LED indicates the status of the Ecomode Electronic
Yellow - LED indicates that the BIAS is Low
Green OK LED indicates that the BIAS has the correct value
Yellow + LED indicates that the BIAS is too high
Red OFF LED indicates that the Protection Electronic has turned off the Power supply of
the Tube section

21
7. TUBES
7.3.1 How to set the BIAS
Make sure that no signal is playing through the amplifier when you are adjusting the BIAS. It is
sufficient to switch on the Muting function; there is no need to disconnect the speakers.
The tubes should have reached operating temperature. The unit should run at least 15 minutes
before you adjust the BIAS. If you notice high BIAS at one or more of the output tubes in cold state
you should reduce the BIAS in any case.
Procedure
1. Switch on the Muting function
2. Set the bias selector switch to V1. The green LED next to the trim pot for tube V1
will light up to show that you have chosen to adjust the bias for tube V1
3. The bias setting for this tube is correct when the green OK LED on the display illu-
minates
If the yellow + LED illuminates, the bias is set too high.
Turn the trim pot counter-clockwise until the OK LED illuminates.
If the yellow - LED illuminates, the bias is set too low.
Turn the trimmer clockwise until the OK LED illuminates.
Repeat this procedure with the other three tubes
4. Switch the bias selector back to its "off" position.
If there is no change in the BIAS of a tube while turning the BIAS regulator, the corresponding output
tube is faulty.
Note:
It is not possible to adjust the bias if the amplifier's electronic protection has cut
in (as indicated by the red "off" LED in the display), or if the Ecomode has
powered down the unit. When you activate the measuring facility under these
circumstances, the-LEDs will illuminate for all tubes. You must fix the fault or
switch off the Ecomode before using the measuring facility. If a defective tube is
causing the problem, you should locate and replace it. (See Troubleshooting
Chapter 9)