DCT
8:19-cv-00737
Cloud Microphones LLC v. Cathedral Pipes Microphones
I. Executive Summary and Procedural Information
- Parties & Counsel:
- Plaintiff: Cloud Microphones, LLC (Arizona)
- Defendant: Cathedral Pipes Microphones (California)
- Plaintiff’s Counsel: TechKnowledge Law Group LLP
- Case Identification: 8:19-cv-00737, C.D. Cal., 04/22/2019
- Venue Allegations: Venue is alleged to be proper in the Central District of California because the Defendant's principal place of business is in the District, and a substantial part of the events giving rise to the claims, including alleged acts of infringement, occurred there.
- Core Dispute: Plaintiff alleges that Defendant’s "Durham Mic Booster Preamp" infringes two patents related to phantom-powered preamplifier circuits for microphones.
- Technical Context: The technology concerns electronic circuits designed to boost the low-level signal from passive microphones, such as ribbon microphones, to make them compatible with modern recording equipment.
- Key Procedural History: The complaint alleges that the Defendant received a cease and desist letter on May 25, 2018, providing notice of the asserted patents and the alleged infringement, which forms the basis for the willfulness claims.
Case Timeline
| Date | Event |
|---|---|
| 2009-10-09 | Priority Date for U.S. Patent Nos. 9,167,327 & 9,888,315 |
| 2015-10-20 | Issue Date for U.S. Patent No. 9,167,327 |
| 2018-02-06 | Issue Date for U.S. Patent No. 9,888,315 |
| 2018-05-25 | Defendant's alleged receipt of cease and desist letter |
| 2019-04-22 | Complaint Filing Date |
II. Technology and Patent(s)-in-Suit Analysis
U.S. Patent No. 9,167,327 - "Microphone with Rounded Magnet Motor Assembly, Backwave Chamber, and Phantom Powered JFET Circuit"
- Patent Identification: U.S. Patent No. 9,167,327, "
Microphone with Rounded Magnet Motor Assembly, Backwave Chamber, and Phantom Powered JFET Circuit", issued October 20, 2015.
The Invention Explained
- Problem Addressed: The patent's background section describes the historical drawbacks of ribbon microphones, which, despite their desirable sound quality, suffered from low output signal levels that required cumbersome and specialized pre-amplification. (’327 Patent, col. 1:31-40). It also notes that conventional active microphones can introduce sound distortion. (’327 Patent, col. 14:25-30).
- The Patented Solution: The invention is a phantom-powered JFET (Junction Field Effect Transistor) preamplifier gain circuit that aims to solve these problems. It uses a specific four-transistor differential cascode design that can be powered by standard "phantom power" from a mixing console, boosting the microphone's signal cleanly and efficiently without requiring complex external power supplies or introducing distortion. (’327 Patent, col. 12:11-21, FIG. 11A).
- Technical Importance: This circuit design allows classic, passive microphones to be used more easily with modern digital audio equipment by providing a higher-fidelity, low-distortion signal boost directly at the source. (’327 Patent, col. 12:49-54).
Key Claims at a Glance
- The complaint asserts independent Claim 1. (Compl. ¶9).
- Essential elements of Claim 1:
- A phantom-powered JFET preamplifier gain circuit for a microphone.
- A first JFET with its gate terminal operatively connected to a positive signal input terminal.
- The first JFET is operatively connected to a second JFET in cascode, which has a positive signal output terminal.
- A third JFET with its gate terminal operatively connected to a negative signal input terminal.
- The third JFET is operatively connected to a fourth JFET in cascode, which has a negative signal output terminal.
- One or more resistors operatively connected to the first and third JFETs.
- One or more gain-setting feed resistors external to the circuit, operatively connected to the positive or negative signal output terminal.
- The complaint also asserts dependent Claim 2 and reserves the right to assert others. (Compl. ¶9, ¶13-15).
U.S. Patent No. 9,888,315 - "Microphone with Rounded Magnet Motor Assembly, Backwave Chamber, and Phantom Powered JFET Circuit"
- Patent Identification: U.S. Patent No. 9,888,315, "
Microphone with Rounded Magnet Motor Assembly, Backwave Chamber, and Phantom Powered JFET Circuit", issued February 6, 2018.
The Invention Explained
- Problem Addressed: As a continuation of the application leading to the ’327 Patent, this patent addresses the same technical problems: the low signal output of passive ribbon microphones and the potential for distortion in conventional preamplifier circuits. (’315 Patent, col. 1:26-40).
- The Patented Solution: The ’315 Patent claims a similar phantom-powered JFET preamplifier circuit. The core of the invention remains the four-JFET differential cascode topology, which is powered by an external phantom power supply to provide a clean signal boost. (’315 Patent, Abstract; col. 2:33-46). The claims are structured slightly differently, focusing on the configuration for receiving a "sound source signal" and coupling JFETs to positive or negative output terminals.
- Technical Importance: This patent protects a further iteration of the circuit, aiming to provide a robust, low-cost method for improving the performance and usability of high-fidelity passive microphones in modern recording environments. (’315 Patent, col. 2:17-23).
Key Claims at a Glance
- The complaint asserts independent Claim 1. (Compl. ¶21).
- Essential elements of Claim 1:
- A phantom-powered JFET preamplifier gain circuit for a microphone or musical instrument.
- A first JFET with its gate terminal coupled to a positive signal input terminal, configured to receive a sound source signal.
- A second JFET coupled to a negative signal output terminal, where the second JFET is also coupled in cascode to the first JFET and powered by an external phantom power supply.
- A third JFET with its gate terminal coupled to a negative signal input terminal, configured to receive the sound source signal.
- A fourth JFET coupled to a positive signal output terminal, where the fourth JFET is coupled in cascode to the third JFET and powered by the external phantom power supply.
- The complaint also asserts dependent Claims 2, 3, 4, 5, and 9. (Compl. ¶21).
III. The Accused Instrumentality
Product Identification
- The accused product is the Cathedral Pipes "Durham Mic Booster Preamp," also referred to as the "Durham." (Compl. ¶9, ¶11).
Functionality and Market Context
- The "Durham" is described as an in-line microphone preamplifier, or "mic booster," designed to be placed between a passive microphone and a mixing console. (Compl. ¶10, ¶15). A product screenshot describes it as a "simple micro amp buffer providing up to 25dB of ultra clean transparent gain to any passive microphone." (Compl. p.3).
- The complaint alleges the "Durham" contains a phantom-powered JFET preamplifier gain circuit that uses two LSK389 dual JFET chips, providing the four JFETs required by the patent claims. (Compl. ¶12, p.4). A teardown photograph in the complaint shows the internal circuit board of the "Durham," with components labeled to correspond to the patent claims. (Compl. p.5). The complaint alleges the product is sold for $65.00. (Compl. p.3).
IV. Analysis of Infringement Allegations
'327 Patent Infringement Allegations
| Claim Element (from Independent Claim 1) | Alleged Infringing Functionality | Complaint Citation | Patent Citation |
|---|---|---|---|
| a phantom-powered JFET preamplifier gain circuit for a microphone | The Durham is a phantom-powered JFET preamplifier gain circuit for a microphone. | ¶10 | col. 12:11-21 |
| a first JFET with its gate terminal operatively connected to a positive signal input terminal... operatively connected to a second JFET in cascode having a positive signal output terminal | The Durham allegedly includes two LSK389 chips, each containing a pair of JFETs. The complaint alleges one pair is connected in cascode to form the positive signal path. | ¶11 | col. 12:22-29 |
| a third JFET with its gate terminal operatively connected to a negative signal input terminal... operatively connected to a fourth JFET in cascode having a negative signal output terminal | The complaint alleges the second pair of JFETs within the LSK389 chips is connected in cascode to form the negative signal path. | ¶12 | col. 12:30-36 |
| one or more resistors operatively connected to the first JFET and the third JFET | A teardown photograph allegedly shows resistors connected to the JFETs on the Durham's circuit board. | ¶13 | col. 12:37-40 |
| one or more gain-setting feed resistors external to the... circuit, wherein the one or more gain-setting feed resistors are operatively connected to the positive signal output terminal or the negative signal output terminal | The complaint alleges the Durham includes external gain-setting feed resistors connected to the output terminals, as shown in a labeled teardown photograph. | ¶14 | col. 12:40-47 |
Identified Points of Contention
- Scope Questions: A central question may be the interpretation of "in cascode." The infringement analysis will depend on whether the specific arrangement of the dual JFETs in the LSK389 chips on the Durham's circuit board constitutes a "cascode" configuration as that term is used in the patent.
- Technical Questions: The complaint's infringement theory relies on teardown photographs. A key evidentiary question will be whether the components identified in the photos, such as the alleged "gain-setting feed resistors" (Compl. p.6), actually perform the function required by the claim language.
'315 Patent Infringement Allegations
| Claim Element (from Independent Claim 1) | Alleged Infringing Functionality | Complaint Citation | Patent Citation |
|---|---|---|---|
| a phantom-powered JFET preamplifier gain circuit for a microphone or a musical instrument | The Durham is marketed as a phantom-powered preamplifier for use with passive microphones. | ¶22 | col. 2:47-50 |
| a first JFET having its gate terminal coupled to a positive signal input terminal, which is configured to receive at least one sound source signal | The complaint alleges the Durham's circuit includes a first JFET connected to a positive input terminal for receiving a microphone signal. | ¶23 | col. 13:4-7 |
| a second JFET coupled to a negative signal output terminal, wherein the second JFET is also coupled in cascode to the first JFET and is powered by an external phantom power supply | The complaint alleges the Durham contains a cascode-coupled pair of JFETs, powered by phantom power, forming part of the signal path. A teardown photo shows the output terminals. (Compl. p.11). | ¶24 | col. 13:8-12 |
| a third JFET having its gate terminal coupled to a negative signal input terminal, which is configured to receive the at least one sound source signal | The complaint alleges the circuit includes a third JFET connected to a negative input terminal for receiving the microphone signal. | ¶25 | col. 13:13-16 |
| a fourth JFET coupled to a positive signal output terminal, wherein the fourth JFET is coupled in cascode to the third JFET and is powered by the external phantom power supply | The complaint alleges a second cascode-coupled pair of JFETs, powered by phantom power, is connected to the positive output terminal. A teardown photo shows the input terminals. (Compl. p.11). | ¶26 | col. 13:17-21 |
Identified Points of Contention
- Scope Questions: The term "coupled" is used throughout Claim 1. The dispute may focus on whether the electrical connections within the Durham circuit meet the definition of "coupled" and "coupled in cascode" as understood in the context of the specification.
- Technical Questions: The claim requires the JFETs to be "powered by an external phantom power supply." The complaint alleges this based on product marketing. (Compl. ¶22). The functionality of the power distribution within the Durham circuit will be a key technical question for establishing infringement.
V. Key Claim Terms for Construction
For the '327 and '315 Patents
The Term: "in cascode"
- Context and Importance: This technical term defines the core architectural feature of the claimed four-transistor circuit. The entire infringement allegation rests on the assertion that the two pairs of JFETs in the Durham are arranged "in cascode." Practitioners may focus on this term because its specific technical meaning will determine whether the accused circuit's topology falls within the claim scope.
- Intrinsic Evidence for Interpretation:
- Evidence for a Broader Interpretation: The specification does not provide an explicit definition, which may support using the plain and ordinary meaning understood by a person skilled in the art of amplifier design. The patent repeatedly refers to the arrangement of Q1/Q3 and Q2/Q4 as a "differential cascode" circuit. (’327 Patent, col. 12:15-16).
- Evidence for a Narrower Interpretation: The specific arrangement shown in FIG. 11A and FIG. 11B could be argued to be the only embodiment of "cascode" disclosed. A defendant might argue that the term should be limited to the exact schematic shown, where, for instance, the output of one transistor (e.g., Q3) feeds directly into the source of another (e.g., Q1). (’327 Patent, FIG. 11A).
The Term: "gain-setting feed resistors external to the... circuit" (’327 Patent, Claim 1)
- Context and Importance: This limitation distinguishes the invention from prior art where gain-setting components were integral to the main amplifier circuit. The claim requires the resistors to be both "gain-setting" and "external." The infringement analysis hinges on whether the resistors identified in the Durham teardown (Compl. p.6) satisfy both the structural ("external") and functional ("gain-setting") aspects of this limitation.
- Intrinsic Evidence for Interpretation:
- Evidence for a Broader Interpretation: The patent describes these as resistors "remotely located in another device" and part of the "phantom-power supply," which could be construed broadly to mean any resistor in the power path that influences gain. (’327 Patent, col. 12:56-62; col. 13:2-4).
- Evidence for a Narrower Interpretation: The specification explicitly links these resistors to an external "preamplifier (605)" shown in FIG. 11B, which is distinct from the core circuit (600). A defendant could argue that "external" requires the resistors to be in a physically separate device, not merely on the same circuit board as the JFETs. (’327 Patent, col. 12:40-47, FIG. 11B).
VI. Other Allegations
- Indirect Infringement: The prayer for relief seeks an injunction against "indirect infringement," but the body of the complaint does not contain specific factual allegations to support a claim for either induced or contributory infringement. (Compl. p.15).
- Willful Infringement: The complaint alleges willful infringement for both patents. The basis for this allegation is the Defendant’s alleged knowledge of the patents and infringement "at least as early as its receipt of the cease and desist letter on May 25, 2018." (Compl. ¶17, ¶33). This establishes a theory of willfulness based on post-notice conduct.
VII. Analyst’s Conclusion: Key Questions for the Case
- A central issue will be one of technical implementation: Does the accused Durham circuit, built with two LSK389 dual-JFET integrated circuits, actually operate as the specific four-transistor "differential cascode" circuit required by the claims? This question will likely be decided through competing expert testimony analyzing the circuit's schematic and operation.
- The case may also turn on a question of claim scope and function: Can the resistors on the Durham circuit board be considered "gain-setting feed resistors external to the... circuit" as required by Claim 1 of the ’327 Patent? The resolution will depend on the court's construction of "external" and the factual evidence regarding the dual role of those resistors in both providing power and setting the circuit's gain.