H03F 3/28
With tubes only
Official title: with tubes only
H03F3/28 (With tubes only) appears on 40 US grants and 17 published applications in this corpus.
Search patents in H03F- Granted patents
- 40
- Published applications
- 17
- Assignees
- 17
- Inventors
- 36
- Latest grant
- 13 Jan 2026
Filings by year
| Year | Granted patents | Published applications |
|---|---|---|
| 1978 | 1 | 0 |
| 1979 | 0 | 0 |
| 1980 | 0 | 0 |
| 1981 | 0 | 0 |
| 1982 | 0 | 0 |
| 1983 | 0 | 0 |
| 1984 | 0 | 0 |
| 1985 | 1 | 0 |
| 1986 | 1 | 0 |
| 1987 | 2 | 0 |
| 1988 | 1 | 0 |
| 1989 | 0 | 0 |
| 1990 | 0 | 0 |
| 1991 | 0 | 0 |
| 1992 | 0 | 0 |
| 1993 | 0 | 0 |
| 1994 | 1 | 0 |
| 1995 | 1 | 0 |
| 1996 | 4 | 0 |
| 1997 | 3 | 0 |
| 1998 | 1 | 0 |
| 1999 | 3 | 0 |
| 2000 | 3 | 0 |
| 2001 | 1 | 0 |
| 2002 | 0 | 0 |
| 2003 | 0 | 2 |
| 2004 | 1 | 1 |
| 2005 | 1 | 0 |
| 2006 | 2 | 1 |
| 2007 | 1 | 0 |
| 2008 | 1 | 0 |
| 2009 | 0 | 0 |
| 2010 | 0 | 1 |
| 2011 | 2 | 5 |
| 2012 | 0 | 2 |
| 2013 | 2 | 0 |
| 2014 | 3 | 0 |
| 2015 | 0 | 1 |
| 2016 | 0 | 0 |
| 2017 | 0 | 0 |
| 2018 | 1 | 0 |
| 2019 | 1 | 1 |
| 2020 | 0 | 0 |
| 2021 | 0 | 0 |
| 2022 | 0 | 1 |
| 2023 | 0 | 0 |
| 2024 | 1 | 1 |
| 2025 | 0 | 1 |
| 2026 | 1 | 0 |
By publication year. Applications have been published since 2001. 2026 runs to 8 Oct.
Recent patents
- Tube amplifier13 Jan 2026US 12,525,936 B2
- Valve amplifiers1 Oct 2024US 12,107,560 B2Blackstar Amplification Ltd.
- Audio amplifier circuit5 Nov 2019US 10,469,042 B1
- Incremental wattage reduction in a vacuum tube amplifier13 Mar 2018US 9,917,560 B1Mesa/Boogie, Ltd.
- Amplifier with selectable master control1 Jul 2014US 8,766,082 B2Mesa/Boogie, Ltd.
- Dual primary multi-coupled output amplifier architecture18 Sep 2025US 2025/0293644 A1
- Tube amplifier29 Feb 2024US 2024/0072742 A1
- Valve amplifiers1 Dec 2022US 2022/0385253 A1Blackstar Amplification Ltd.
- Audio amplifier circuit14 Nov 2019US 2019/0348957 A1
- Programmable Vacuum Tube Bias Control1 Oct 2015US 2015/0280667 A1
Most cited
By later US patents
- Variable control of electronic power supplies34US 5,635,872 AMaven Peal Instruments, Inc. · 1997
- Power amplifier capable of simultaneous operation in two classes24US 4,593,251 A1986
- Audio signal enhancement and amplification system20US 6,792,120 B12004
- Hybrid thermionic valve and solid state audio amplifier17US 6,140,870 A2000
- Variable control of electronic power supplies16US 5,909,145 AMaven Peal Instruments, Inc. · 1999