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Detailed entries for one subject from the INDEX TO HOW TO DO IT INFORMATION.
Click on a see also (sa) or tracing (xx) to view detailed entries about a related subject.
The entries are in alphabetical order by magazine name and then in chronological sequence.
To obtain a copy of any magazine article contact your local public library or the publisher.


Mk. I dynamic hiss filter. How to design and build a tunable, low-pass filter controlled by the content of the music (or other audio) passing through it.
AUDIO AMATEUR 2/1973 [Apr 1974] (v.4#2) pg. 3

A test bench filter set for audio measurements. Contains a bias trap, a 20kHz noise bandwidth low pass filter, an ASA weighting network, and an inverse RIAA equalization network.
AUDIO AMATEUR 1/1975 [Jun 1975] (v.6#1) pg. 16

Op amps for audio. Active audio filters. Part 1. VCVS filters (2nd and 3rd order high and low pass filters with Butterworth and Bessel characteristics).
AUDIO AMATEUR 1/1975 [Jun 1975] (v.6#1) pg. 22

Op amps for audio. Active filters. Part 2. Multiple feedback filters (highpass, bandpass, etc) and super filters (biquad).
AUDIO AMATEUR 2/1975 [Nov 1975] (v.6#2) pg. 28
Correction AUDIO AMATEUR 3/1975 [Jan 1976] (v.6#3) pg. 42

A L.F. garbage filter. A 30Hz high-pass (rumble) filter with other uses. Constructing a general purpose VCVS filter card.
AUDIO AMATEUR 4/1975 [Mar 1976] (v.6#4) pg. 14

Op amps for audio. Active filters. Part 3. The state variable filter and its applications.
AUDIO AMATEUR 2/1976 [Jul 1976] (v.7#2) pg. 32
Correction AUDIO AMATEUR 3/1976 [Oct 1976] (v.7#3) pg. 39

Adjustable audio windows. Fundamentals of audio filters and a practical 4th order bandpass filter you can build.
AUDIO AMATEUR 2/1980 [Mar 1980] (v.11#2) pg. 19

Test report on Logical Systems' Model 318 Silencer dynamic noise filter kit.
AUDIO AMATEUR 3/1980 [Jun 1980] (v.11#3) pg. 46

"A" weighting filter circuit is used to make weighted noise measurements of audio gear.
AUDIO AMATEUR 3/1981 [Jun 1981] (v.12#3) pg. 25

Your power line, just 60 Hz. A review of interference from AC power lines, fluorescent lamps and switching power supplies that can affect the performance of audio systems. Describes the use of a commercial power-line filter (the Adcom ACE-515 AC enhancer) to reduce the problems.
AUDIO AMATEUR 2/1991 [Apr 1991] (v.22#2) pg. 46
Added Info AUDIO AMATEUR 4/1991 [Oct 1991] (v.22#4) pg. 36 (Power Wedge II AC Power Conditioner)
Added Info AUDIO AMATEUR 3/1993 [Sep 1993] (v.24#3) pg. 32

A continuous-time monolithic filter that is as simple to use as a monolithic sampled filter.
AUDIO AMATEUR 1/1993 [Mar 1993] (v.24#1) pg. 37

Passive filters for digital audio. Design and build your own.
AUDIO AMATEUR 4/1994 [Dec 1994] (v.25#4) pg. 30
Added Info AUDIO AMATEUR 3/1995 [Aug 1995] (v.26#3) pg. 46

Review of the Digital Antidote, a "black box" passive filter designed to correct the phase distortion inherent in CD reproduction.
AUDIO AMATEUR 4/1994 [Dec 1994] (v.25#4) pg. 44

Using filtering to overcome mistracking of a Dolby processor when a "noisy" CD player with 1-bit DAC technology is being recorded on a cassette deck.
AUDIO AMATEUR 3/1995 [Aug 1995] (v.26#3) pg. 37

Tip on reducing audio noise by using line filters and grounding them only to the AC power line ground and not to the chassis of the audio equipment.
AUDIO ELECTRONICS 2/1997 [Apr 1997] (v.28#2) pg. 33

Notch-filter design. How to use a desktop computer to solve the complex arithmetic needed to design state-variable filters for audio use. Construction of a tunable notch filter for measuring harmonic distortion is featured.
AUDIO ELECTRONICS 1/2000 [Jan 2000] (v.31#1) pg. 10

HUSH stereo noise-reduction system. Rid your system of audio noise (white-noise "hiss" or waterfall sounds) with this noise-reduction system. Effective for professional and amateur broadcast or recording applications. HUSH combines a dynamic filter and downward expander.
AUDIO ELECTRONICS 1/2000 [Jan 2000] (v.31#1) pg. 18

A filter for treble distortion in recordings. Deals with the distortion between 2k and 3kHz. Includes information to expand the design into a complete high-quality room equalizer.
AUDIO ELECTRONICS 6/2000 [Nov 2000] (v.31#6) pg. 6
Correction AUDIOXPRESS May 2001 (v.32#5) pg. 78

Tilting with tubes. A previously published tilt control (filter circuit) is adapted to add a warm sound to a vacuum tube amplifier.
AUDIOXPRESS Jan 2001 (v.32#1) pg. 74

e-Bass: An application of phase linear sub-base equalization. A filter-circuit solution to the problems associated with bass reproduction on permanent-magnet loudspeakers.
AUDIOXPRESS Mar 2002 (v.33#3) pg. 38
Added Info AUDIOXPRESS Nov 2002 (v.33#11) pg. 68

Circuit for an easily adjusted switched-capacator 60-Hz hum filter.
COMPUTERS & ELECTRONICS Aug 1983 (v.21#8) pg. 100

Build a "synthetic" crystal filter to plug into your headphone jack which does a better job than RC active filters in screening out nearby RF noise. Features two CW bandwidths, two phone bandwidths, and two notch filters.
CQ. THE RADIO AMATEUR'S JOURNAL Apr 1990 (v.46#4) pg. 18

Vocal stripper device filters out a lead singer's voice from a stereo recording, but leaves the background music. Ideal for singing along with a recording similar to Karaoke. Est. cost: $50.

Universal dynamic noise-reduction system can be added to any stereo signal source. Est. cost: $95 (kit).

High-pass and low-pass active audio filters. How they work and how to design and use them.
ELECTRONICS NOW Feb 1995 (v.66#2) pg. 61

Active audio filters for signal processing and control. How they work and how to use them in circuit designs.
ELECTRONICS NOW Mar 1995 (v.66#3) pg. 87
Added Info ELECTRONICS NOW Jun 1995 (v.66#6) pg. 12

Twin-T notch filter circuit for use in a distortion meter to test audio amplifiers.
ELECTRONICS NOW Jul 1997 (v.68#7) pg. 8

A universal stereo noise filter and compressor will reduce noise and increase clarity of any audio signal. Est. cost: $95 (kit).
ELECTRONICS NOW Oct 1999 (v.70#10) pg. 27

Active hum filter is connected between tape recorder and amplifier to take out objectionably high hum level.
ELEMENTARY ELECTRONICS May-Jun 1971 (v.11#2) pg. 52

Get better selectivity with an amateur radio receiver with this active audio filter. This bandpass filter can be adjusted to Q values between 1.4 and 15. Its center frequency can be adjusted from 375 to 1500 Hz.
ELEMENTARY ELECTRONICS Jan-Feb 1980 (v.20#1) pg. 63

Audio crystal filter will improve selectivity and eliminate virtually all audio fuzz from your CW rig. Est. cost: $2.
HANDS-ON ELECTRONICS Sep 1988 (v.5#9) pg. 32

Adjustable speech filter.
POPULAR ELECTRONICS [1] May 1964 (v.20#5) pg. 49

A 60-Hz reject network (attenuator).
POPULAR ELECTRONICS [1] Apr 1968 (v.28#4) pg. 77

Combination test instrument is both a high-Q audio filter and a low-distortion sine, square or triangular wave generator. Est. cost: $35.
POPULAR ELECTRONICS [1] May 1971 (v.34#5) pg. 58

Noise and interference filter for shortwave receiver. Active audio filter improves selectivity with a cutoff frequency of 3 KHz. Est. cost: $8.
POPULAR ELECTRONICS [1] Jan 1974 (v.5#1) pg. 56

Filter removes the 60-Hz hum you get when using hi-fi headphones with a shortwave receiver.
POPULAR ELECTRONICS [1] May 1975 (v.7#5) pg. 88

Circuit for a scratch filter to attenuate the surface noise on old 78-rpm phonograph records.
POPULAR ELECTRONICS [1] Feb 1978 (v.13#2) pg. 84

Build a super audio filter. Capacitance multiplier reduces hum in hi-fi equipment by 80dB. Est. cost: $20.
POPULAR ELECTRONICS [1] Sep 1978 (v.14#3) pg. 74

Circuit for filtering out interstation hiss on FM receivers.
POPULAR ELECTRONICS [1] Mar 1979 (v.15#3) pg. 78

Build a dynamic audio noise filter. Cleans up radio, tape, and record signals from any stereo system. Est. cost: $129.
POPULAR ELECTRONICS [1] Apr 1979 (v.15#4) pg. 51

Low-cost ultrasonic/infrasonic circuit (scratch and rumble filter) plugs into preamp's external jacks. Est. cost: $10.
POPULAR ELECTRONICS [1] May 1980 (v.17#5) pg. 50

Circuit for a tunable notch filter (band-rejection filter or band-stop filter) that can be tuned to reject or block a narrow band of audio frequencies.
POPULAR ELECTRONICS [1] Aug 1982 (v.20#8) pg. 90

Two circuits for active notch filters designed to filter out the 60-Hz hum caused by a power line.
POPULAR ELECTRONICS [1] Sep 1982 (v.20#9) pg. 105

Scratch filter for a record player is built around a LM3900 quad op-amp.
POPULAR ELECTRONICS [2] Apr 1989 (v.6#4) pg. 22

Tunable audio filter takes the incoming signal and amplifies it, while attenuating all other frequencies.
POPULAR ELECTRONICS [2] Nov 1989 (v.6#11) pg. 101

Audio-squelch circuit can be connected between a receiver's audio output and a loudspeaker to suppress the background noise that's present between transmissions and during tuning. The circuit can also be used as a power amplifier for headphone use.
POPULAR ELECTRONICS [2] Oct 1990 (v.7#10) pg. 80

Passive noise limiter circuit that is inserted between the audio output of a receiver and the earphones. It contains both series (threshold) and shunt noise-limiter configurations.
POPULAR ELECTRONICS [2] May 1991 (v.8#5) pg. 78

Audio-enhancement circuits (filter circuits). (1) Bandpass filter. (2) Super bandpass filter. (3) Notch filter.
POPULAR ELECTRONICS [2] Jun 1992 (v.9#6) pg. 67

Universal dynamic noise-reduction system for any stereo signal source. Uses the concept of "auditory masking" to change the bandwidth so that noise can't pass through. Est. cost: $95 (kit).
POPULAR ELECTRONICS [2] Jul 1994 (v.11#7) pg. 31
Correction POPULAR ELECTRONICS [2] Oct 1994 (v.11#10) pg. 4

Adaptive noise filter. Part 1. Build this dynamic, variable cutoff, low-pass filter which removes the snap, crackle and pop from records and tape. Est. cost: $70.
RADIO-ELECTRONICS Aug 1979 (v.50#8) pg. 43

Adaptive noise filter. Part 2.
RADIO-ELECTRONICS Sep 1979 (v.50#9) pg. 54

Build this combination hi-fi noise filter and dynamic range extender. Part 1.
RADIO-ELECTRONICS Mar 1981 (v.52#3) pg. 41

Build this combination hi-fi noise filter and dynamic range expander. Part 2.
RADIO-ELECTRONICS Apr 1981 (v.52#4) pg. 70
Correction RADIO-ELECTRONICS Jun 1981 (v.52#6) pg. 24
Added Info RADIO-ELECTRONICS Sep 1981 (v.52#9) pg. 26

Build this low frequency filter for your hi-fi. Eliminates rumble and acoustic feedback without affecting the quality of the audio. Est. cost: $50.
RADIO-ELECTRONICS Nov 1981 (v.52#11) pg. 47
Correction RADIO-ELECTRONICS Apr 1982 (v.53#4) pg. 29

A look at digital filters and how they work.
RADIO-ELECTRONICS May 1982 (v.53#5) pg. 67

A simple solution to power-supply ripple (noise).
RADIO-ELECTRONICS Mar 1985 (v.56#3) pg. 98

Click and pop filter for your stereo. Build this inexpensive scratch filter. Est. cost: $80. Part 1.
RADIO-ELECTRONICS May 1986 (v.57#5) pg. 46

Click and pop filter for your stereo. Build this inexpensive scratch filter. Part 2.
RADIO-ELECTRONICS Jun 1986 (v.57#6) pg. 55, 70

Circuit for (1) an active bandpass filter that can be used to drive the midrange amplifier of a tri-amped three-way speaker, and (2) a subsonic filter to eliminate turntable rumble and tape-recorder flutter. Both circuits use SGS Semiconductor Corp's TDA2320A stereo preamplifier IC.
RADIO-ELECTRONICS Jun 1988 (v.59#6) pg. 38

Vocal stripper. Unique audio filter removes the lead vocals from a stereo recording, leaving just the background music. Est. cost: $50.
RADIO-ELECTRONICS Sep 1990 (v.61#9) pg. 33

A selective filter removes 60 Hz or 120 Hz hum from tape recordings without adversely affecting other frequencies. Useful for the amateur who does a lot of tape dubbing from both domestic and foreign produced tapes.
RADIO-TV EXPERIMENTER Apr-May 1968 (v.24#2) pg. 83

Notch filters. The theory and practical application of notch filters (frequency discriminating circuits).
SPEAKER BUILDER 2/1986 [May 1986] (v.7#2) pg. 24
Added Info SPEAKER BUILDER 4/1986 [Oct 1986] (v.7#4) pg. 46

Fast and easy active filter calculations for electronic filters and crossovers. Includes a computer program to calculate values for Sallen & Key filters.
SPEAKER BUILDER 4/1987 [Dec 1987] (v.8#4) pg. 15

Digital filters. Their use in high-quality audio applications is explored.
SPEAKER BUILDER 2/1989 [Mar 1989] (v.10#2) pg. 19
Added Info SPEAKER BUILDER 3/1989 [May 1989] (v.10#3) pg. 70