This is only a preview of the February 2024 issue of Silicon Chip. You can view 36 of the 112 pages in the full issue, including the advertisments. For full access, purchase the issue for $10.00 or subscribe for access to the latest issues. Articles in this series:
Items relevant to "Microphone Preamplifier":
Items relevant to "Mains Power-Up Sequencer, Pt1":
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Your unit wouldn’t be the first one,
as we only just published it. The following information should help you
narrow it down.
The August 2014 design fits in a
small box with a GPO mounted on top,
roughly the same size as the box. The
February 2009 version also has a small
GPO socket on top, although it is in a
much larger box with a clear lid (and
a mostly empty PCB visible inside).
None of the other versions have direct
mains switching.
Of the remainder, the August 2002
and May 2012 versions were housed in
slim instrument cases with LCD panel
meters mounted on the front (on the
left for the August 2002 version and
right for May 2012).
Both used thermocouples as temperature sensors. That leaves the
March 2010 Altronics kit, housed in
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a Jiffy box with an alphanumeric LCD
in the middle of the lid.
Component values for
Headphone Amplifier
I need clarification on how to configure my Studio Series Headphone
Amp (November 2005; siliconchip.
au/Article/3231). I want it as versatile as possible, so I have wired in a
four-way switch to switch diodes D2,
D4, D8 & D10 so I can use 8W or 32W
headphones.
I am also going to wire in a dual
50kW log pot as a volume control. I
want to be able to connect it to a CD
player or a preamp. Please tell me what
combination of R1, R2, R3, & C1 etc I
should use and any other considerations for my configuration.
I have mostly built the power supply
Australia's electronics magazine
board from the October 2005 issue and
have heatsinks ready to fit on the regulators. I am also wondering whether
the 100W and 330W 5W input current
limiting resistors are required for this
headphone amplifier, or are they only
required for the preamp? (N. G., Blue
Haven, NSW)
● To avoid high sound volumes,
R3 and R6 should be 2kW for use
with a directly connected CD player
and 0W when connected to the preamplifier.
The amplifier gain for the 8W headphones should be set with the standard
values: R1 & R4 = 1kW, R2 & R5 = 1kW
and C1 & C2 =1.2nF.
For 32W headphones, the resulting
volume may not be sufficient, so the
gain can be increased. Amplifier gain
can be increased to 7.2 times (17dB)
to allow the full rated output power to
February 2024 111
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