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Last Updated
03/31/2019
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Detailed entries for one subject from the INDEX TO HOW TO DO IT INFORMATION. |
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AUDIO FILTER sa Q MULTIPLIER sa RADIO FREQUENCY INTERFERENCE FILTER x ACOUSTIC FILTER x NOISE FILTER (AUDIO) x SCRATCH FILTER (AUDIO) xx AUDIO EQUIPMENT xx AUDIO SIGNAL PROCESSING xx FILTER (ELECTRONIC) xx RADIO FREQUENCY INTERFERENCE FILTER 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. 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. 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). Op amps for audio. Active filters. Part 2. Multiple feedback filters (highpass, bandpass, etc) and super filters (biquad). A L.F. garbage filter. A 30Hz high-pass (rumble) filter with other uses. Constructing a general purpose VCVS filter card. Op amps for audio. Active filters. Part 3. The state variable filter and its applications. Adjustable audio windows. Fundamentals of audio filters and a practical 4th order bandpass filter you can build. Test report on Logical Systems' Model 318 Silencer dynamic noise filter kit. "A" weighting filter circuit is used to make weighted noise measurements of audio gear. 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. A continuous-time monolithic filter that is as simple to use as a monolithic sampled filter. Passive filters for digital audio. Design and build your own. Review of the Digital Antidote, a "black box" passive filter designed to correct the phase distortion inherent in CD reproduction. 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. 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. 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. 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. 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. Tilting with tubes. A previously published tilt control (filter circuit) is adapted to add a warm sound to a vacuum tube amplifier. 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. Circuit for an easily adjusted switched-capacator 60-Hz hum filter. 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. 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. Active audio filters for signal processing and control. How they work and how to use them in circuit designs. Twin-T notch filter circuit for use in a distortion meter to test audio amplifiers. A universal stereo noise filter and compressor will reduce noise and increase clarity of any audio signal. Est. cost: $95 (kit). Active hum filter is connected between tape recorder and amplifier to take out objectionably high hum level. 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. Audio crystal filter will improve selectivity and eliminate virtually all audio fuzz from your CW rig. Est. cost: $2. Adjustable speech filter. A 60-Hz reject network (attenuator). Combination test instrument is both a high-Q audio filter and a low-distortion sine, square or triangular wave generator. Est. cost: $35. Noise and interference filter for shortwave receiver. Active audio filter improves selectivity with a cutoff frequency of 3 KHz. Est. cost: $8. Filter removes the 60-Hz hum you get when using hi-fi headphones with a shortwave receiver. Circuit for a scratch filter to attenuate the surface noise on old 78-rpm phonograph records. Build a super audio filter. Capacitance multiplier reduces hum in hi-fi equipment by 80dB. Est. cost: $20. Circuit for filtering out interstation hiss on FM receivers. Build a dynamic audio noise filter. Cleans up radio, tape, and record signals from any stereo system. Est. cost: $129. Low-cost ultrasonic/infrasonic circuit (scratch and rumble filter) plugs into preamp's external jacks. Est. cost: $10. 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. Two circuits for active notch filters designed to filter out the 60-Hz hum caused by a power line. Scratch filter for a record player is built around a LM3900 quad op-amp. Tunable audio filter takes the incoming signal and amplifies it, while attenuating all other frequencies. 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. 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. Audio-enhancement circuits (filter circuits). (1) Bandpass filter. (2) Super bandpass filter. (3) Notch filter. 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). 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. Adaptive noise filter. Part 2. Build this combination hi-fi noise filter and dynamic range extender. Part 1. Build this combination hi-fi noise filter and dynamic range expander. Part 2. Build this low frequency filter for your hi-fi. Eliminates rumble and acoustic feedback without affecting the quality of the audio. Est. cost: $50. A look at digital filters and how they work. A simple solution to power-supply ripple (noise). Click and pop filter for your stereo. Build this inexpensive scratch filter. Est. cost: $80. Part 1. Click and pop filter for your stereo. Build this inexpensive scratch filter. Part 2. 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. Vocal stripper. Unique audio filter removes the lead vocals from a stereo recording, leaving just the background music. Est. cost: $50. 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. Notch filters. The theory and practical application of notch filters (frequency discriminating circuits). Fast and easy active filter calculations for electronic filters and crossovers. Includes a computer program to calculate values for Sallen & Key filters. Digital filters. Their use in high-quality audio applications is explored. | |||||||||
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