Updated:
27 Jan 2010
Loudspeaker & crossover patents added
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Audio Patents: chronological order.
This is a so far incomplete guide to USA power amplifier and loudspeaker patents; there must be thousands of them. It excludes any that are (in my opinion) of no interest, but certainly does not have all of the interesting ones at this point. Anything relating to valves has been ignored; this is the 21st century, after all. Titles have been compressed in some cases.
Where the patent is known to be assigned to an audio manufacturing company, this is indicated.
| E =error-correction | G = Class G | IC = IC tech | Ns =non-switching | P =Protection
| MF = Motional feedback | D = Class-D
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AUDIO POWER AMPLIFIER RELATED PATENTS
7 053 705 Mixed mode current voltage amp Z-synth Hench May 06 Tymphany
6 646 508 Wide bandwidth current sharing MOSFET amp Barbetta Nov 03
6 584 204 Loudspeaker system with feedback Al-Ali et al Jun 03 MF
6 441 685 Amplifier circuit and NFB thereto (Class-D) MacMillan Aug 02 D
6 434 243 Power Amplifier Read Aug 02 A+
6 268 770 Wide Bandwidth MOSFET Power Amplifier Barbetta Jul 01
6 262 633 High Current OpAmp Output Stage Close Jul 01 IC
6 255 907 Power amplifier Alexanderson Jul 01
6 215 356 Power Amplifier Arrangement Servaes Apr 01 G
6 160 455 Derived Power Supply for Composite Bridge Amplifiers French Dec 00
6 144 256 Wide bandwidth, current sharing, Mosfet power amp Barbetta Nov 00
6 127 888 Power Amplification Device Kokubo Oct 00
6 016 079 Power Amplifier Device Reffay Jan 00
5 973 563 High power output stage with temperature Seven Oct 99
5 903 189 High Gain Low Distortion Bridge Amp with Feedback Huijser May 99
5 892 398 Amplifier Having Ultra-Low Distortion Candy Apr 99 E
5 815 040 Wide bandwidth current sharing MOSFET amp Barbetta Sep 98
5 796 305 Amplifier arrangements with high Damping Factor Sondermeyer Aug 98 MF Peavey
5 764 781 Speaker and amplifier system Ding Jun 98
5 710 522 Amplifier Having an Active Current Source Pass Jan 98
5 705 951 Method for correction of error signals Hakansson Jan 98 MF
5 387 876 High Efficiency Amp w Reduced Switching Distortion Sondermeyer Feb 95 G
5 383 083 Protective apparatus for power transistor Shinoda Jan 95 Pioneer
5 369 355 Compensation circuit for transformer linearisation Roe Nov 94
5 343 166 Efficient High Fidelity Audio Power Amplifier Pass Aug 94
5 337 012 Amplifier having temperature compensated bias Dijkmans Aug 94
5 276 394 Compensated transformers Mayfield Jan 94
5 268 527 Audio Power Amplifier with Reactance Simulation Waller Dec 93
5 245 296 Audio amplifier circuit and method Miller Sep 93 MF
5 179 352 Amplifier with distortion reducing NFB Inohana Jan 93 Pioneer
5 097 223 Current Feedback Audio Amplifier Alexander Mar 92
5 086 473 Feedback system for a sub woofer Erath Feb 92
5 070 308 Working point adjusting circuit for power amp Padi Dec 91
5 057 790 High efficiency class A amplifier Landi Oct 91 NS
5 055 797 Bias control for power amplifiers Chater Oct 91
5 019 789 Adaptive bias circuit for preventing turnoff Graeme May 91 NS
4 991 916 Automatically Biasing a Push-Pull Amplifier Deaver A Feb 91
4 990 863 Amplifier Output Stage Susak et al Feb 91 IC
4 980 920 Negative impedance driving temp compen Noro et al Dec 90 MF Yamaha
4 922 207 So-Called Bridge Audio Amplifier Botti May 90
4 868 870 Servo controlled amplifier Schrader Sep 89
4 814 723 Integratable Class-AB Output Stage Botti Mar 89
4 758 796 Bridge Amplifier Verhoeven Jul 88
4 752 745 Opto-isolated Bias Circuit for Push-Pull Power Amps Pass Jun 88
4 721 919 Class-G Bridge Amplifier with Unipolar Supplies Rosa et al Jan 88
4 688 002 Audio Power Amplifier Wingate Aug 87
4 688 001 High Efficiency Low Distortion Amplifier Dijkmans Aug 87 G
4 638 260 Audio amplifier Hamley Jan 87
4 614 914 Low distortion transformer coupling Hofer Sep 86 AP
4 611 180 Grounded bridge amplifier protection thermal Stanley Sep 86 Crown
4 607 233 Push pull amplifier circuit with stable Class AB Tuijl Aug 86
4 595 883 Emitter follower type single ended pushpull Nakayama Jun 86 NS
4 558 288 Emitter follower type SEPP circuit Nakayama Dec 85
4 555 674 Power audio amplifier with automatic adj Palara Nov 85
4 520 323 Emitter follower type SEPP circuit Nakayama May 85 NS
4 511 857 Output Following Intermediate Cascode Circuit Gunderson Apr 85
4 502 020 Settling time reduction in wide band dir Nelson Feb 85
4 491 804 Bias Circuit Independent of Device Characteristics Main et al Jan 85
4 489 283 Power Amplifier Ishikazi Dec 84
4 484 151 Series amplifier circuit Nijman Nov 84
4 476 442 Amplifier With Distortion Cancellation Iwamatsu Oct 84 E
4 467 288 Distortion-Free Complemented Error-Feedback Amplifier Strickland Oct 84 E
4 464 634 Audio Power Amplifier Velazquez Aug 84
4 458 284 Method for electrical and thermal protecn Otala Jul 84
4 439 743 Biasing circuit for power amplifier Schwarz Mar 84
4 431 972 Push pull amplifier Ishii Feb 84
4 430 527 Loudspeaker crossover delay equaliser Eberbach Feb 84
4 424 493 Cross coupled complementary power amplifier Schroeder Jan 84
4 422 050 Single ended push pull amplifier with two Suzuki Dec 83
4 415 868 Audio Power Amplifier Gross Nov 83
4 404 528 Output amplifier Yamaguchi Sep 83
4 403 198 Biasing Circuit for MOSFET Power Amplifiers Muller Sep 83
4 401 954 Power Amplifier Suzuki Aug 83
4 401 951 Bias circuit for use in a single ended pushpull Tanaka Aug 83 NS
4 395 588 MFB system with bypass network Franssen Jul 83 MF Philips
4 393 353 Negative feedback amplifying cct Minagawa Jul 83 JVC
4 387 270 Method of harmonizing the impedances Sakano Jun 83 MF
4 367 442 Distortion Correction Circuit for A Power Amplifier Tanaka Jan 83
4 356 452 Class A push pull amplifier with bias control Iwamatsu Oct 82
4 355 341 Power protection circuit for transistors Kaplan Oct 82 RCA
4 345 215 Audio frequency power amplifier circuit Amada Aug 82
4 342 966 Power amplifier circuitry Tamura Aug 82
4 334 197 Power amplifier circuitry Otao Jun 82
4 331 930 Bias Circuit for Power Amplifier Shibata May 82
4 321 554 Time Delayed Variable Output Current-Limiting Quilter Mar 82
4 317 081 Single-ended Push-Pull Amplifier Kobayashi Feb 82
4 316 149 Power Amplifier Yamaguchi Feb 82
4 306 199 Push-Pull Amplifier Kondou Dec 81
4 302 727 Power amplifier having bias circuit Iwamatsu Nov 81
4 276 516 Thermal stress reduction in IC power transistors Congdon Jun 81
4 274 059 Single ended push pull amplifier Okabe Jun 81 NS
4 260 954 Amplifier load correction system Crooks Apr 81 MF
4 254 379 Push pull amplifier circuit Kawanabe Mar 81 NS Pioneer SA-9800
4 241 313 Audio Power Amplifier Takehara Dec 80
4 237 425 Automatic bias adjusting circuit Spiegel Dec 80
4 236 118 Stabilized remote sensing high fi (cables) Turner Nov 80
4 229 618 High fidelity speaker with NFB Gamble Oct 80 MF
4 223 273 Power amplifying device for driving loudspeakers Yokoyama Sep 80
4 220 930 Quasi linear amplifier with feedback control Ahmed Sep 80
4 215 318 Push-Pull Amplifier Circuit Kawanabe Jul 80
4 180 706 Loudspeaker motional feedback Bakgaard Dec 79 MF B&O
4 178 559 Amplifier distortion reduction apparatus Nichols Dec 79
4 176 323 Transistorised Power Amplifier Odell Nov 79
4 167 708 Transistor amplifier Goto Sep 79
4 165 494 Bi state linear amplifier Becker Aug 79
4 160 216 Eliminating transitional gain variations in Class AB, B, C amps Thornton
4 146 845 Audio Amplifier Output Circuit Lunquist Mar 79
4 135 162 Power amplifier circuits Takahashi Jan 79
4 121 168 Optically Coupled Bias Circuit Stitt Oct 78
4 107 619 Constant-voltage Constant-Current Amplifier Pass Aug 78
4 100 501 Audio frequency power amplifier Nakagai Jul 78
4 087 761 Audio Power Amplifier Fukumoto May 78
4 077 013 Audio Power Amplifier with Automatic Bias Control Morez Feb 78
4 031 482 Bias circuit for FET Tsurushima Jun 77
4 027 270 Class ABC amplifier circuit Class-G Pitel May 77
4 001 707 Amplifier circuit Class-H Iguchi Jan 77
3 995 228 Active Bias Circuit for Push-Pull Amplifiers Pass Nov 76
3 970 953 Distortion-Free Amplifiers Walker Jul 76 E
3 961 280 Amplifier circuit having power supply voltage Class-G Sampei Jun 76
3 808 545 High Power Bridge Audio Amplifier Stanley Apr 74
3 866 134 Power Amplifier with Self-Biasing Higuchi Feb 75
3 821 656 Driver Stage of a Class-B Amplifier Takeda Jun 74
3 808 545 High Power Bridge Audio Amplifier Stanley Apr 74
3 772 606 Multi-Level Power Amplifier Waehner Nov 73 G
3 622 899 Series amplifier circuit Eisenberg Nov 71 G
3 500 218 Transistor Complementary Pair Power Amp Burwen Mar 70
3 493 879 High Power High Fidelity Solid State Amp Stanley Feb 70
2 751 442 Distortionless Feedback Amplifier Ketchledge Jun 56
2 748 201 Multiple Feedback Systems McMillan May 56
AMPLIFIER INPUT STAGES ETC
7 053 705 Z-synth patent
5 512 858 Amp stage w low thermal distortion (i/p stage) Perrot Apr 96
4 748 420 Quadcomp amplifier Metz May 88
4 528 517 Overdrive thermal distortion compensation for Cascomp Schlotzhauer Jul 85
4 322 688 Cascode feedforward amplifier input stage Schlotzhauer Mar 82
3 938 055 High performance differential amp Buhler Feb 76
3 936 725 Current mirrors Schneider Feb 76
POWER AMPLIFIER PROTECTION
6 927 626 Thermal protection system for amplifier Stanley Aug 05
5 847 610 Protection Circuit for an Audio Amplifier Fujita Dec 98 Yamaha
4 330 809 Thermal protection circuit for transistor Stanley May 82 Crown
3 526 846 Protective Circuitry For High Fi Amp Campbell Sep 70
PHONO (RIAA) INPUT STAGES
4 470 020 Virtual ground preamplifier for MM cart Mohr Sep 84
4 293 823 Balanced input phonograph preamp Hochberg Oct 81
4 139 825 Audio frequency amplifier L in RIAA NFB network Inoue Feb 79
4 032 855 Phonograph Preamplifier with infrasonic cutoff Holman Jun 77
CROSSOVER NETWORKS
7 085 389 Infinite slope loudspeaker crossover Modafferi Aug 06
6 707 919 Driver control circuit Koval Mar 04
5 930 374 Phase coherent crossover Werrbach Jul 99 Aphex
5 568 560 Audio crossover circuit Combest Oct 96
5 185 801 Correction circuit and method for 2-way spkr Meyer Feb 93
5 129 006 Electronic audio signal amplifier Hill Jul 92
4 771 466 Multidriver loudspeaker apparatus Modafferi Sep 88
4 769 848 Electroacoustic network delay HF Eberbach Sep 88
4 589 135 Zero phase shift filtering Baker May 86
4 525 857 Crossover network & clipper Orban Jun 85
4 430 527 Loudspeaker crossover delay equaliser Eberbach Feb 84
4 282 402 Design of crossover network for hifi Liontonia Aug 81
4 229 619 Method and apparatus for driving multi way spkrs Takahashi Oct 80
4 198 540 Compensated crossover network Cizek Apr 80
2 771 518 Frequency Band Separation Amplifier Sziklai Nov 56
LOUDSPEAKERS
4 015 089 Linear phase response multi-way loudspeaker Ishii Mar 77
BRITISH PATENTS
GB 2439983A Inclusive compensation Whatley Jan 08
GB 2424137A9 Class-XD power amplifiers Self Sep 06
GB 2242089A Padless mic amp Self Sep 91
GB 2214372A NIC panpot Self Aug 89
