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r
DB 4
Power outlet curve
F i g . D B . 8 i l l u s t r a t e s a n a d d i t i o n a l c i r c u i t w h i c h c a n b e a d d e d t o
reduce this surge. One circuit may drive several 260s, but the
capacitor C1 should be doubled for two 260s, trebled for three. etc.
DBg
Applications
DB9.2 Full Bridge Circuit for 60w
The circuit of DB9.2.1 shows how two Z60s can be connected back-
to-back in a full bridge to double the output power. Each 260 in
effect operates into half of the speaker. Speaker impedance should
DB 9.1.2 Oscillator outouL
VOLTS OUT
( R M S )
POWER SUPPLY
VOLTAGE (DC)
DB 9.2.1 Full bridge circuit
be 8O or more, since with an 8[l speaker each 260 ,sees, 4O and will
(from fig D84) give approximately 40w into this 4f] load (from bOv
s u p p l y ) . T h u s b o t h t o g e t h e r w i l l d r i v e a n S O s p e a k e r a t u p t o 8 0 w .
( f i g D 8 9 . 2 . 1 )
S i m i l a r l y t h e c i r c u i t c a n g i v e u p t o 6 0 w i n r o l 6 e ( e a c h a m o l i f i e r
o p e r a t e s i n t o 8 O a n d g i v e s 3 0 w ) .
C a r e m u s t b e t a k e n w i t h t h e w i r i n g w h i c h s h o u l d b e a s s h o r t a s
possible. Fig D89.2.2 shows the wiring of the bridge with the two
amplifiers mounted aboul 1/2" to 1" apart (one of the heatsink blocks
s h o w n i n f i g A ' l . 2 i s i d e a l ) . N o t e i n p a r t i c u l a r t h a t p i n s 1 - 1 , 2 - 2 , 3 - 3
are joined together with one wire f rom each pair to the earth point.
POWER
SUPPLY
DB 9.2.2 Full bridge wiring
This arrangement can suit two bridges, with a common point for
b o t h .
Heatsinking is of prime importance on the bridge - a 60w bridge
may have to dissipate 30w itself, so all surfaces in contact must be
flat and all holes must be deburred. Silicone grease must be used to
ensure good heatflow.
One PZB will drive two bridges -
but will slightly restrict full
output with SQ,speakers. lf maximum power is required, two pZgs
can be used (when two transformers will be needed), one for each
bridge. Two earth points can now be used -
one for each
bridge / PZ8 combination.
40
a
t
: 3 0
i
R z o
F
f
o
F
3 r o
20
25
30
SUPPLY VOLTAGT
+ V E S U P P L Y
- D
P I N 7 2 6 0
a
+ P l N 7 2 6 0 b
10 0 KJI
DB B
Switch-on surge
z 5
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