I agree with the September 2003
comment on the "Subwoofer Filter."
1. The capacitors will degrade the
channel separation at high frequencies.
2. In general, amplifiers don't like a
heavy capacitor load. It could cause
some amplifiers to oscillate and
maybe even burn out. The suggested
resistor will fix this problem.
3. The 195-Hz low-pass filter’s first
stage will saturate at low levels if the
inputs are from the stereo speakers.
Either the inputs could come from
the stereo preamp or the speaker
signal could be attenuated. It would
help a little to reduce the gain of this
stage from 3.1 to 1.
4. I did not look at the second stage
without silk-screen and solder mask
— for only $9.00 each, plus shipping
of about $8.00.
If your layout can be laid out
in an array, they will offer to do the
work themselves and array your
tiny PC board onto a larger board,
providing you with more than two,
although they only charge for the two
boards (plus a charge for cutting
each board). They will work directly
from your board file (not Gerber) for
Eagle, Protel, and Orcad.
Response: The Futurlec pricing is correct. I use them all the
time for my prototypes.
A definitive discussion on PC power
A computer's BIOS will produce a
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decode the beeps of two common BIOS
systems: AMI and Phoenix.
I noticed in the January 2004
issue that you responded to someone about the Futurlec PC board
service. I found that the 20 cents per
inch rate is not correct unless a
large amount of boards is being
made. I found a board house —
Custom PCB ( www.custompc
b.com) — that will sell you two 4" x
5. 5" single-sided boards — with or
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