HHB Circle 5A User manual

Version 1d: 01.99 Page
Service manual
HHB Circle 5A
Powered Monitor speaker
Manual: Version 1d 01.1999
This manual is subject to change without notice.
Always check with HHB that you are using the latest version.
Also available as an Adobe Acrobat V3 file.
When printing this file, for clear sharp pictures on a black & while laser, it may be necessary
to adjust your printer driver’s ‘Print half tone’ settings. If you have a 600dpi printer, setting the
half tone to around 45 lines per inch will give a clean sharp image, where as the default -
around 60lpi may give a dark image to pictures..
WARNING! DANGER OF ELECTRICAL SHOCK
Opening mains operated equipment like the HHB Circle5A incurs a risk of electric
shock.
DO NOT attempt to open this equipment unless you are qualified to do so, have the neces-
sary test equipment and are operating the Circle 5a from an ISOLATED POWER SUPPLY.
Ensure that only the correct mains voltage is applied, as marked on the module.
NEVER OPERATE OR OPEN THIS SPEAKER IN DAMP OR WET CONDITIONS AND
NEVER ALLOW IT TO BE USED OUTSIDE.
ENSURE THAT ALL POWER AND SIGNAL CABLES ARE IN PERFECT CONDITION AND
ARE CORRECTLY FUSED.
IF IN DOUBT, CONTACT HHB IMMEDIATELY BEFORE PROCEEDING.

Version 1d: 01.99 Page

Version 1d: 01.99 Page 3
Contents
Page 1: The cover and warning
Page 2: Section 1.0 External arrangement and
comments on connectors/controls
Page 3: General arrangement, notes on testing
Page 4: Opening the Circle5A
Page 5: Circuit diagram: active filters
Page 6: Circuit diagram: power stage
Page 7: Circuit diagram: mains input
Page 8: PCB silk screen, top view
Page 9: Parts list
Page 10: Fault finding
Page 11: Modifications and updates
Page 11: Other
THIS INDEX IS UNDER REVISION DUE TO THE
INTRODUCTION OF EARTHED, CLASS 2 VERSION

Page 4
1.0 Externals
This is a view of the external controls on
the Circle5A.
The function of the Master Volume control
is to scale down excessive input signals.
In a set-up where the signal level is
scaled so that set to maximum (fully
clockwide) an input of 0.775vdBv, on the
loudest peaks, will fully drive the power
amplifiers.
Since many studios use the ‘+4’ signal
reference as the maximum, it may be an
idea to reduce the Master Volume to, say,
‘6’ and control the signal at the mixer.
There are two input connectors: a master
input, an isolated XLR following the nor-
mal European wiring convention:
Pin 1 = shield (ground)
Pin 2 = Live, hot, + signal
Pin 3 = Cold, -, return signal
Also provided is a secondary input: a
Phono (Cinch, RCA) connector for unbal-
anced systems. The centre pin is signal +,
and the connector case is the ground.
The selector switch converts the master
input (the XLR) to unbalanced mode suit-
able for the phono input - it does not
switch between the two inputs.
Connect to EITHER the XLR or the
phono, not both.
The metal parts of the panel are isolated
from mains ground - the so called double
isolation standard.
Only use the mains cable supplied.
Replace the mains fuse with the correct
type.

Version 1d: 01.99 Page
Removing the Circle 5a active module from the cabinet
It is absoluletely essential that before removing
the module you have the necessary tools, a
clear space, and sufficient uninterrupted time to
work. Rushing leades to mistakes, and mis-
tekes can be dangerous and impair the excel-
lent performance of your Circle 5a speakers.
Ensure that the mains supply is disconnected
and removed from the module, and is not
reconnected until the module has been fully
refitted.
Please cover your work bench with s soft mate-
rial to protect the underside of your Circle 5’s
from scuffing during removal/replacement of the
module. Also be aware that the module is
heavy and that once the screws are loosened,
it will tend to drop downwards, and that the
heavy aluminium panel of the module will readi-
ly chip the softer wood of the cabinet, exposing
the white MDF board under the black paint.
You will need one two screwdrivers:
1. A 3.0mm cross head screwdriver of the
‘Superscrew’ or ‘Pozidrive’ NOT Phillips type.
The Superscrew type has 4 thin grooves into
which the Superscrew screw driver securely
locates. If the Phillips type is used, the screw-
driver will ‘mash’ the heads, and then it may not
be possible to remove the module from the
cabinet.
2. A larger size (M4, 4mm, No.2) ‘Superscrew’
or ‘Pozidrive’ screwdriver.
Removing the screws
Please follow these instructions exactly. Failure
to do so may well destroy your cabinet and/or
module.
First, using your smaller Superscrew driver,
check that the screwdriver makes a positive fit
to the screws marked 1,2,3,4. Applying as little
force as necessary, unscrew (anti-clockwise)
the four corner machine screws in the order 1,
2, 3, 4.
These screws locate in metal inserts trapped in
the inside of tha cabinet, and the alignment of
the module and the cabinet is precise.
Then, using the larger screw driver, remove the
screws A, B, C, D, E and, as you loosed screw
F, expect the module to drop down. Be ready to
catch it!
The module can then be removed a short dis-
tance from the cabinet, as the internal connec-
tions to the module are on short flexible wires.

2.0 General arrangement
All the signal processing circuitry of the
Circle5A amplifier module is contained on one
double-sided plated-through PCB. There are no
user-adjustable parts.
Although mains voltages do not appear on the
PCB, but care should be taken when examining
and working on the module, since the sec-
ondary of the mains transformer (25-0-25 AC)
is connected to the bridge rectifiers and
smoothing capacitors on the board.
A mute relay prevents power on and power off
‘thumps’ appearing at the drive units, and gives
a silent switch on and off. The correct operation
of the mute relay can be detected by carefully
listening to the module as the speaker is pow-
ered-up: after approx. 3 seconds a small
mechanical ‘click’ should be heard in the vacini-
ty of the heat sink (from the outside of the
speaker), or from the relay, when the module
has been removed.
The very low level of self noise generated in
the circuitry means that, at idle, the best indica-
tion that the speaker is powered and awaiting a
signal is the illuminated power on LED, fixed in
the tweeter face plate.
The power-on LED is driven from the rectified
unregulated transformer secondary, and is a
positive indication that the transfromer, recti-
fiers and smooting capacitors are functioning
correctly. (It does not, directly, confirm that the
12v regulated supply is functioning).
Provision is allowed for optional physical isola-
tion of the audio grounds by use of an input
transformer. Fitting the transformer requires
removal of the PCB.
Two presets - one for bass drive level, the
other tweeter drive level, and both with a range
of approx. ±2dB are pre-set at the factory and
should not be adjusted.
The bass unit is directly driven from a pair of IC
power amolifiers in bridge push-pull mode. The
tweeter is driven from one one IC.
NOTE CAREFULLY:
DO NOT CONNECT EITHER OF THE BASS
OUTPUT TERMINALS TO GROUND SINCE
THIS WILL INSTANTANEOUSLY DESTROY
ONE OR BOTH BASS POWER IC’S. THIS
WILL REQUIRE THE REMOVAL AND
REPLACEMENT OF ONE OR MORE POWER
IC’S, A DIFFICULT AND EXPENSIVE TASK.
USE ONLY BATTERY OPERATED OR
BALANCED AND FLOATING INPUT
ISOLATION TO MAINS OPERATED
EQUIPMENT.

Photograph of the amp module viewed from the inside
Version 1d: 01.99 Page 7

Version 1d: 01.99 Page
Mute-relay modification
A modification involving improving the
switch on/off threshold of the mute relay
was introduced shortly after production
commenced.
This involves the changing of resistor
R46, initially fitted as 100kR to 200k or
220kR. It is not practical or necessary to
remove the PCB, and the fitted resistor
can be cut out, and a substitute resistor
carefully soldered in it’s place.

Version 1d: 01.99 Page
Photograph of the amp module viewed from the inside
Tweeter level (HF level) reduction
Under normal operation, the two presets, one
for HF level and the other for bass level
should not be adjusted as these are individu-
ally set at the factory. It is not possible to
change these drive levels unless audio signal
analysis equipment is available.
As despatched, the tweeter control is normal-
ly fully clockwise (viewed from the perspec-
tive as shown above).
Imagining that one of the arms of the preset’s
X is pointing to 5 c’clock (fully clockwise).
Turning this arm anticlockwise until it points
to 1 o’clock (i.e nearly half way anti clock-
wise) reduces the tweeter level by 1dB; turn-
ing the arm until it points to 12 o’clock
reduces the tweeter by 1.5dB and turning
fully anticlockwise reduces the tweeter level
by approx. 2.5dB, a very noticeable reduction
across the tweeter’s operating range.
Be sure to return the preset adjuster to the
original level or to make a note on the outside
of the module that the Circle 5a is no longer
standard.
DO NOT ADJUST THE BASS LEVEL
ADJUSTER as this is individually calibrated,
and as shipped will be set and sealed to a
unique position.

Version 1d: 01.99 Page 10

Connections to the Circuit board
Version 1d: 01.99 Page 11

Version 1d: 01.99 Page 8

Version 1d: 01.99 Page

Version 1d: 01.99 Page

Harbeth HHB Circle 5 Power
amplifier parts list 1.1999
Bez. Wert
R1 27 K
R2 27 K
R3 27 K
R4 27 K
R5
R6 27 K
R7
R8 0 Ohm
R9 100 K
R10 10 K
R11 10 K
R12 130 k / 1%
R13 5,76 K / 1 %
R14 7,32 K / 1%
R15 25,5 K / 1%
R16 Trimmer 10 K
R17 56 K
R18 5,32 K / 1%
R19 3,3 K / 1%
R20 3,3 K / 1%
R21 6,8 K / 1%
R22 6,34 K / 1%
R23 130 K / 1%
R24 Trimmer 10 K
R25 47 K
R26 100 K
R27 100 K
R28
R29 0 Ohm
R30 100 K
R31 47 K
R32 27 K
R33 10 K
R34 1 K
R35
R36 56 K
R37 56 K
R38 47 K
R39 1 K
R40 27 K
R41 10 Ohm
R42 47 K
R43 27 K
R44 1 K
R45
R46 220 K (formerly 100k)
R47 1 M
R48 10 K
R49 680 Ohm
R50 16 K
R51 2,2 K
R52 10 K
R53
R54
R55 2,2 Ohm
R56
R57
C1 68 pF Keramik
C2 68 pF Keramik
C3
C4 100 nF Folie
C5 100 nF Folie
C6 4,7 nF MKT / 5%
C7 4,7 nF MKT / 5%
C8 4,7 nF MKT / 5%
C9 47 nF MKT / 5%
C10 3,3 nF MKT / 5%
C11 15 nF MKT / 5%
C12 4,7 nF MKT / 5%
C13 1 nF MKT / 5%
C14 68 pF Keramik
C15 68 pF Keramik
C16 100 nF Folie
C17 100 nF Folie
C18 1000 uF/16 V Elko
C19 1000 uF/16 V Elko
C20 68 pF Keramik
C21 100 nF Folie
C22 100 nF Folie
C23 470 nF Folie
C24 68 pF Keramik
C25 47 uF / 50V ELKO
C26 47 uF / 50V ELKO
C27 47 uF / 50V ELKO
C28 100 nF Folie
C29 68 pF Keramik
C30 47 uF / 50V ELKO
C31
C32 47 uF / 50V ELKO
C33 100 nF Folie
C34 470 nF Folie
C35 68 pF Keramik
C36 47 uF / 50V ELKO
C37 47 uF / 50V ELKO
C38
C39 47 uF / 50V ELKO
C40 4,7 uF / 50V ELKO
C41 4,7 uF / 50V ELKO
C42 100 nF Folie
C43 100 nF Folie
C44 470 nF Folie
C45 100 nF Folie
C46 4,7 uF / 50V ELKO
C47 4,7 uF / 50V ELKO
C48 100 nF Folie
C49 100 nF Folie
C50 68 pF Keramik
C51 68 pF Keramik
C52 1 nF MKT
C53 470 nF Folie
C54 4.700 uF / 40V ELKO
(Philips; Pan )
C55 4.700 uF / 40V ELKO
(Philips; Pan )
D1 BZY 18V
D2 BZY 18V
D3
D4 BY 500 oder BY 550
D5 BY 500 oder BY 550
D6 BY 500 oder BY 550
D7 BY 500 oder BY 550
D8 1N4148
D9 1N4148
T1 BC546
T2 BC546
T3 BD135, inverser
Einbau
V1 NE5532
V2 NE5532
V3 NE5532
V4 NE5532
V5 7912
V6 7812
V7 TDA7294V
V8 TDA7294V
V9 TDA7294V
Poly-Switch Poly-Switch RM
5mm
BR4 Brücke oder 0 Ohm
BR5 Brücke oder 0 Ohm
BR6 Brücke oder 0 Ohm
LBR1 0 Ohm
LBR2 0 Ohm
LBR3 0 Ohm
LBR4 0 Ohm
Relay YW2-SN12
Version 1d: 01.99 Page

JP3 Jumper
JP4 Jumper
JP5 Jumper
LED green 2-pol. Berg-Stiftleiste 76384-302
Overload 2-pol. Berg-Stiftleiste 76384-302
LS1 4,8mm Flachstecker
LS2 4,8mm Flachstecker
LS4 4,8mm Flachstecker
OUT2 4,8mm Flachstecker
VCC1 4,8mm Flachstecker
VCC2 4,8mm Flachstecker
GRND4,8mm Flachstecker
Mechanical parts
Kühlblech 315 x 196 x 4 mm
Cinchbuchse Monacor T-706G
Kabelsatz Kaltgeräte, Poti; XLR
Lackierung Platte , Kühlk. , Bügel
Kühlkörper SK 81-300-AL
Isolierfolie 25 x 50mm keraterm
Trafo 120VA , 2x25V
Netzanschl. 6762B , Heil
Sicherung 1,6 A träge
Poti Monacor VRB-141M50
Knöpfe Monacor KN-11/SW
XLR-Anschl. 3 pol Buchse
Schrauben M3x16 , M3x8 , M4x8, M6x70
Schalter Schadow ZFAFA200BKGN2UEE
Bügel 272 x 30 mm 8Q
Abstand-Metall
Abstandshalter 3 x 10, DR701P
Aluwinkel 2 St.
Bearbeitung Kühlkörper
Montage
Subject to change without notice
E&OE
Version 1d: 01.99 Page