US & GB Audio Patents

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-correctionG = Class GIC = IC techNs =non-switchingP =Protection
MF = Motional feedbackD = Class-D

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

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