38 Silicon chip Australia’s electronics magazine siliconchip.com.au
with ]Bass & Treble Controls
]Motorised Volume Control
]Infrared Remote or Manual Control
]Relay input switching and isolation
]Suits practically ANY amplifier modules!
by
John ClarkeLast month, we introduced our state-of-the-art stereo preamplifier. Along
with almost unmeasurable noise and distortion (typically 0.0003%
THD+N!) it sports remote volume control, input selection and muting
plus bass and treble adjustment knobs on the front panel. Now let’s build
the input selection boards and power supply.
T
he circuits of the optional input
selector board and front-panel
pushbutton board were shown
in Figs.8 & 9 last month.
We also listed the parts required to
build those two boards in that article.
Figs.10 & 11 show the PCB overlay
diagrams for these two boards, so you
can see how those parts are fitted.
By the way, you don’t have to build
either of these boards if you don’t need
the ability to select between more than
one set of stereo inputs.
In that case, you would connect the
chassis-mounted input sockets direct-
ly to CON1 and CON3 on the main
preamp board.
And if you do want the input selec-
tor but only need the remote control
feature, and don’t want front panel
pushbuttons/input indicators, you
could build the input selector board
(Fig.10) but not the front panel push-
button board (Fig.11).
You can then use the remote control
to select between the three inputs, al-though it won’t show which is selected- you will have to remember the last
selection you made.
Incidentally, we haven’t listed all
the features and specifications again –
refer to the March issue for these and
performance graphs. You’ll agree, this
is an outstanding performer!
Input selector construction
The input select board is easy to
assemble. It’s built on a double-sided
PCB coded 01111112 which measuresUltra Low Noise
Preamplifier Part II
Ultra Low Noise
Preamplifier Part II