US3538805A - Rc distributed filter for electronic organ - Google Patents
Rc distributed filter for electronic organ Download PDFInfo
- Publication number
- US3538805A US3538805A US738024A US3538805DA US3538805A US 3538805 A US3538805 A US 3538805A US 738024 A US738024 A US 738024A US 3538805D A US3538805D A US 3538805DA US 3538805 A US3538805 A US 3538805A
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- US
- United States
- Prior art keywords
- filter
- input
- tone
- resistance
- terminal
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- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H11/00—Networks using active elements
- H03H11/02—Multiple-port networks
- H03H11/04—Frequency selective two-port networks
- H03H11/12—Frequency selective two-port networks using amplifiers with feedback
- H03H11/1291—Current or voltage controlled filters
-
- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10H—ELECTROPHONIC MUSICAL INSTRUMENTS; INSTRUMENTS IN WHICH THE TONES ARE GENERATED BY ELECTROMECHANICAL MEANS OR ELECTRONIC GENERATORS, OR IN WHICH THE TONES ARE SYNTHESISED FROM A DATA STORE
- G10H1/00—Details of electrophonic musical instruments
- G10H1/02—Means for controlling the tone frequencies, e.g. attack or decay; Means for producing special musical effects, e.g. vibratos or glissandos
- G10H1/06—Circuits for establishing the harmonic content of tones, or other arrangements for changing the tone colour
- G10H1/12—Circuits for establishing the harmonic content of tones, or other arrangements for changing the tone colour by filtering complex waveforms
Definitions
- the conventional or normal RC ladder filter is composed of series resistances and shunt capacitors, the latter being connected between junction points of the resistances and ground. An input to such a filter may be applied at a resistance.
- a signal input resistance is inserted between each capacitor and ground, and the input signals are applied across these resistances. This implies that each input signal is applied in series with a shunt capacitor, which then becomes a blocking capacitor for undesired low frequencies which may be present at each input, but also becomes a shunting capacitor for harmonics applied to a lower frequency terminal. Since the shunt capacitors have increasing greater impedances at lower frequencies, the ladder may be extended to many sections with approximately constant peak responses. A specific embodiment employing eight sections is disclosed, but many more than eight may be employed, and the filter will retain approximately constant peak responses despite the large number of sections.
- the normal RC ladder network has no low frequency roll off, and no low frequency isolation exists.
- the presence of input resistances in series with the shunt capacitors of the filter radically modifies operating characteristics, by introducing low frequency roll off and isolation.
- each signal is subject to multiple attenuations, so that the filter cannot have many sections.
- the system includes an RC ladder filter, composed of series resistances and shunt capacities, each capacity being associated with a resistance connected in series with itself, across which input signal is applied. Output is taken from one side of the filter, the lowermost frequencies of a wide frequency spectrum being applied nearer the other end of the filter, and the higher frequencies nearer the output side of the filter.
- Complex tone sources provided by an organ tone generator are selectively connected by key switch means only, to each filter of a given footage, separate filter being provided for each footage of the organ. This implies that a single two contact switch is required as a tab switch for a flute tone coloring filter of a given footage. Adjacent groups of tones can be inserted at each input terminal of the filter, and a few sections added to the filter at the high end for which no input terminals are .provided. Further, each filter may be provided with an output amplifier which itself provides high frequency roll-off. It has been found that an entire manual 'of an organ, on one footage, can be efiectively filtered by one ladder network having nine input terminals, to provide flute tones when harmonic rich tones are applied as inputs.
- FIG. 1 is a schematic circuit diagram of a distributed RC tone color filter according to the invention.
- FIG. 2 is a graph showing the responses of the filter of FIG. 1, over its array of input points, as a function of frequency.
- terminal A indicates by its notation (1) by A that the lowermost group of frequencies to be filtered is applied to'this terminal and (2) by the subscript 12 that 12 tone signals are applied.
- these tone signals would be of square wave configuration, or some equivalent having harmonics which decrease in amplitude as l/n, where n is the order of the harmonic, and having only odd harmonics.
- a preferred wave shape employed is shown at 20, l/f being the period of the wave shape.
- the terminal A is connected to a terminal B by series resistance 21 and to ground lead 22 by a shunt resistance 23.
- the notation B indicates that the second group of tone signals, higher in frequency than group A, contains six tones.
- Terminal B is connected to ground lead 22 via resistance 25, and to series filter resistance R;, via filter capacitor C
- signal input terminal A B C D E F G,,, H, and I are provided and each terminal is connected by a signal input resistance to ground lead 22 and by a shunt filter capacitor, labeled C to C respectively, to a series filter resistance, these being identified as R; to R respectively.
- the highest frequency tone, applied to terminal 1- requires additional filter sections to attenuate its harmonics to acceptable level, the primary problem relating to the third harmonic. Therefore, additional filter sections are added on the high side of the filter, specifically composed of u, u, and C12, R12- Following R a load resistance R to ground is provided.
- the base-emitter circuit of an NPN transistor T is connected across R,,, and a collector load R, provided for 1",, a feedback circuit consisting of R, and C, in parallel is connected between the collector and base of T which provides roll off for the third harmonic of the highest fundamental frequency in group I7.
- the collector of T is then AC coupled to amplifier G, via tab switch TS, and via a conventional coupling circuit composed of series capacitor C series resistance R,, and shunt resistance R,
- the values of the circuit components employed in the filter of FIG. I depend on the frequency range of the tones to be filtered, i.e., the footages involved. Further, the system may be employed for producing other than flute tones, for example, diapason, which would use the preferred input 26 having all harmonics present at relative amplitude l/n, and the filter capacitor values may be scaled appropriately to the filtering problem to be solved.
- FIG. 2 is illustrated the response curves for the several input terminals.
- curve for example, the, double line represents the band of input fundamentals, centered on 600 cps.
- the third harmonic is then 1,800 cps. and its intensity is down about 17 db. below the fundamental.
- the filter is so designed that each set of fundamentals applied to an input terminal appears at the output of the filter at somewhere near l db. level, the average fundamental characteristic being indicated by line 51. It may be noted that the fifth harmonic for the F, band is down about 29 db. relative to the fundamenml.
- the characteristic of the filter of FIG. 1 is peaked, i.e. has low frequency roll off, so that subharmonics as well as harmonics of each input frequency are attenuated, each input terminal seeing a series capacitor as well as a distributed filter having shunt capacitive elements, in proceeding from an input terminal to the filter output terminal.
- An electric organ comprising:
- an RC ladder network having sections composed essentially of series resistances and shunt capacitors
- said ladder network having an output terminal
- connections of the tone sources to said junctions being arranged to assure that tones of lower frequencies pass through more of said sections than tones of higher frequencies.
- An electric organ comprising:
- said tone color filter consisting of capacitors and resistances arranged in a multisection ladder configuration
- a tone color filter for an electric organ comprising:
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- Engineering & Computer Science (AREA)
- Acoustics & Sound (AREA)
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Description
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US73802468A | 1968-06-18 | 1968-06-18 |
Publications (1)
Publication Number | Publication Date |
---|---|
US3538805A true US3538805A (en) | 1970-11-10 |
Family
ID=24966255
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US738024A Expired - Lifetime US3538805A (en) | 1968-06-18 | 1968-06-18 | Rc distributed filter for electronic organ |
Country Status (1)
Country | Link |
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US (1) | US3538805A (en) |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3960043A (en) * | 1974-06-24 | 1976-06-01 | Warwick Electronics Inc. | Filter circuit |
US4218950A (en) * | 1979-04-25 | 1980-08-26 | Baldwin Piano & Organ Company | Active ladder filter for voicing electronic musical instruments |
DE2911264A1 (en) * | 1979-03-22 | 1980-09-25 | Rainer Dr Boehm | Electronic organ loudness correction circuit - varies loudness over each octave to avoid jumps between octaves using capacitor and resistor |
US4409877A (en) * | 1979-06-11 | 1983-10-18 | Cbs, Inc. | Electronic tone generating system |
US4422360A (en) * | 1979-10-09 | 1983-12-27 | Carter Barry E | Device for improving piano tone quality |
US20120146717A1 (en) * | 2008-04-18 | 2012-06-14 | Madhur Bobde | Applying trenched transient voltage suppressor (tvs) technology for distributed low pass filters |
-
1968
- 1968-06-18 US US738024A patent/US3538805A/en not_active Expired - Lifetime
Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3960043A (en) * | 1974-06-24 | 1976-06-01 | Warwick Electronics Inc. | Filter circuit |
DE2911264A1 (en) * | 1979-03-22 | 1980-09-25 | Rainer Dr Boehm | Electronic organ loudness correction circuit - varies loudness over each octave to avoid jumps between octaves using capacitor and resistor |
US4218950A (en) * | 1979-04-25 | 1980-08-26 | Baldwin Piano & Organ Company | Active ladder filter for voicing electronic musical instruments |
US4409877A (en) * | 1979-06-11 | 1983-10-18 | Cbs, Inc. | Electronic tone generating system |
US4422360A (en) * | 1979-10-09 | 1983-12-27 | Carter Barry E | Device for improving piano tone quality |
US20120146717A1 (en) * | 2008-04-18 | 2012-06-14 | Madhur Bobde | Applying trenched transient voltage suppressor (tvs) technology for distributed low pass filters |
US8552527B2 (en) * | 2008-04-18 | 2013-10-08 | Alpha And Omega Semiconductor Incorporated | Applying trenched transient voltage suppressor (TVS) technology for distributed low pass filters |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: SECURITY PACIFIC BUSINESS CREDIT INC., 10089 WILLO Free format text: SECURITY INTEREST;ASSIGNOR:BPO ACQUISITION CORP. A CORP OF DE;REEL/FRAME:004298/0001 Effective date: 19840615 Owner name: GENERAL ELECTRIC CREDIT CORPORATION, A NY CORP., C Free format text: SECURITY INTEREST;ASSIGNOR:BPO ACQUISITION CORP., A DE CORP;REEL/FRAME:004297/0802 Effective date: 19840615 |
|
AS | Assignment |
Owner name: BPO ACQUISITION CORP., 180 GILBERT AVE., CINCINNAT Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:D.H. BALDWIN COMPANY AN OH CORP.;REEL/FRAME:004385/0934 Effective date: 19840615 |
|
AS | Assignment |
Owner name: BALDWIN PIANO & ORGAN COMPANY Free format text: CHANGE OF NAME;ASSIGNOR:BPO ACQUISTION CORP.;REEL/FRAME:004473/0501 Effective date: 19840612 |