The David Berning Company

Established in 1974, The David Berning Company manufactures tube audio amplifiers utilizing the patented^[1] ZOTL Impedance Conversion Technology that properly matches high impedance vacuum tubes to the low impedance realm of speakers without the use of traditional audio power output transformers or numerous paralleled output tubes common in traditional OTL designs.^{[2][3][4][5][6]}

The ZOTL Technology and David Berning's numerous other products have been reviewed over the decades by substantial publications including Stereophile Magazine, Audio Magazine, and The Absolute Sound. In continuous operation for over 35 years, the David Berning Company is among the oldest in audio manufacturing.

In its Issue #68 (October, 2009), Hi-Fi+ Magazine awarded Berning's Quadrature-Z "Power Amplifier of the Year 2009".

Other notable technologies pioneered and patented by The David Berning Company include Screen Drive ("Enhancement Amplifier")^[7] and Tube + FET Hybrid^[7] technologies.

In early 2009, The David Berning Company, in conjunction with Milbert Amplifiers, became an official mirror of Frank Philipse's massive (7GB+ as of September, 2009) Tube Data Archive.

In late 2009 the current product line includes the Quadrature Z vacuum tube power amplifier that is based on the ZOTL Technology. The current production Milbert BaM-235ab mobile vacuum tube amplifier incorporates Berning technologies and is specifically designed for 12-volt automobile and mobile use.

Past product offerings have included a push-pull dual 70 watt amplifier (ZH-270); a Single-ended, directly heated triode amplifier (Siegfried 2A3 and 300B models); a very low power tube amplifier / headphone amplifier (microZOTL) that can be powered by a 12 volt battery; a series of vacuum tube power amplifiers (EA-150, EA-230, EA-2100, EA-2101) and preamplifiers (TF-10, TF-12).

Patents

Patent # 5,612,646 - ZOTL Technology

U.S. Patent #5,612,646 Output Transformerless Amplifier Impedance Matching Apparatus^[8] - a method that properly matches high impedance vacuum tubes to the low impedance realm of speakers without the use of traditional audio power output transformers, yet also without numerous output tubes operated in parallel, the troublesome hallmark of traditional OTL designs.

Patent # 4,163,198 - Audio Amplifier

Patent # 4,163,198 Audio Amplifier^[7] - details a hybrid tube-FET amplification stage that forms the basis of the Berning TF-10 preamplifier. An important advantage of this amplification stage is the elimination of the parasitic feedback capacitance and thus providing a stage with improved transient response. This scheme was employed by several audio equipment manufacturers.

Patent # 3,995,226 - Screen Drive Technique - The "Enhancement Amplifier"

Patent # 3,995,226 Audio Amplifier - Tube Screen Drive Technique^[7] - details "screen drive", an important part of some tube amplifier designs. The screen drive allows tubes to be operated at much higher efficiencies, much higher power output, and at greatly enhanced reliability. Whereas the patent shows transistors driving tubes, the same principles apply to presently implemented versions of tubes driving tubes. This is also known as the "enhancement" amplifier.

Technical Papers

ZOTL Technology vs Audio Output Transformers - This paper demonstrates the electrical performance of an amplifier using the ZOTL technology versus the identical amplifier using a high-quality audio output transformer and presents these differences using oscillographs.

Electronic Devices and the Amplification Process - This paper shows how a curve tracer can be used to explore the attributes of the ZOTL technology and contrast it to the shortcomings of the audio output transformer. Also shown is how this tool can be used to optimally design an audio power amplifier.

David Berning, Design Engineer

David W. Berning was born in Cincinnati, Ohio, in 1951. He received the B.S. degree in physics from the University of Maryland, College Park, in 1973. In 1974, he joined the National Bureau of Standards (now the National Institute of Standards and Technology, NIST), in Gaithersburg, Maryland. Much of his career has focused on semiconductor device reliability, first using laser-scanning techniques to probe active devices, later on specializing in semiconductor power device reliability.

David worked for National Bureau of Standards (NBS, Gaithersburg, Md.), now National Institute of Standards and Technology (NIST), throughout the 1970s, 80s and 90s, was apparently the first person who combined vacuum tubes in amplifier stages with solid-state and microcomputer devices to maintain the operating parameters at proper, fixed points, and also regularly designed filament voltages to operate at below published specifications in order to extend tube lifetimes. Dave also built some unusual systems including a tri-amplified Magnepag Tympan III's with active equalization, a vacuum tube wristwatch, a vacuum tube D/A converter stage, and a valve front end for a Revox A77 (reel to reel) with techniques adopted from his production designs.

Independent Sources

Reviews of numerous products in respected, indepdendent publications.

• Quadrature Z (and ZOTL Technology) follow-up by Roy Greory, editor, Hi-Fi+ Magazine, Issue 61, November 2008
• Quadrature Z (and ZOTL Technology), Hi-Fi+ Magazine, Issue 60, October 2008
• Berning ZH-270 Review on Enjoy The Music
• ZH-280 Review by Rick Becker, Enjoy The Music, December 2006
• CES 2009 Show Report Part 5
• The David Berning Quadrature Z Mono Power Amplifiers @ AVguide
• Review of Berning ZH-270 by Positive Feedback magazine, Issue 5, 2002
• [1]
• The Zero-Hysteresis ZH270 amplifier by Gary Beard, Positive Feedback Magazine, Issue 5, 2002
• Audio Review
• Review by Dick Olsher, Enjoy The Music
• Review of Berning ZH-270 using ZOTL Technology by Charles Hansen, Glass Audio Magazine, vol. 12, issue 1-2, January, 2000
• Review of Berning ZH-270 using ZOTL Technology by Charles Hansen, Glass Audio Magazine, vol. 12, issue 3-4, February, 2000
• Review of Berning ZH-270 using ZOTL Technology by Martin Appel, Stereo Times, May 1999
• Review of Berning ZH-270 using ZOTL Technology, FI Magazine, Dick Olsher, March 1998
• [2]
• Berning's ZOTL Technology vs Audio Output Transformers
• Berning EA-2101 reviewed in Audio Magazine
• EA-2101 reviewed by Absolute Sound Magazine, vol. 80, June 1992
• Stereophile review of Berning EA-2101 power amplifier
• TF-12 reviewed by Absolute Sound Magazine, vol. 70, Mar/Apr 1991
• Stereophile review of Berning TF-12 preamplifier
• Stereophile review of Berning TF-10 preamplifier by J. Gordon Holt, May 1979
• EA-230 reviewed by Stereophile Magazine, vol. 5, no. 1

References

1. ^ USPTO patent 5,612,646
2. ^ Audio Magazine Review
3. ^ Review by Dick Olsher, Enjoy The Music
4. ^ Review of Berning ZH-270 using ZOTL Technology, FI Magazine, Dick Olsher, March 1998
5. ^ Review of Berning ZH-270 using ZOTL Technology by Martin Appel, Stereo Times, May 1999
6. ^ Review of Berning ZH-270 using ZOTL Technology by Gary Beard, Positive Feedback Magazine, Issue 5, 2002
7. ^ ^{a b c d} USPTO
8. ^ USPTO Patent Search

External links

• The David Berning Company website
• Milbert Amplifiers website
• Official mirror of Frank Philipse's substantial Tube Data Archive

Notes, See Also

• Milbert Amplifiers
• Julius Futterman
• Output TransformerLess
• tube amplifier
• high-end audio