SCHEDULE 13D/A 0001163368 XXXXXXXX LIVE 10 Common Stock, par value $0.01 per share 04/15/2025 false 0000709283 747906501 QUANTUM CORPORATION

224 Airport Parkway Suite 550 San Jose CA 95110

Pacific Investment Mgmt Co LLC (949) 720-6000 650 Newport Center Drive Newport Beach CA 92660 0001163368 N Pacific Investment Management Company LLC OO N 0 0 0 0 0 N 0 IA OO Common Stock, par value $0.01 per share QUANTUM CORPORATION 224 Airport Parkway Suite 550 San Jose CA 95110 This Amendment No. 10 to Schedule 13D (this "Amendment No. 10") amends and supplements the statement on Schedule 13D filed with the Securities and Exchange Commission (the "SEC") on March 28, 2022, as amended by Amendment No. 1 to Schedule 13D filed with the SEC on April 26, 2022, Amendment No. 2 to Schedule 13D filed with the SEC on August 12, 2022, Amendment No. 3 to Schedule 13D filed with the SEC on August 24, 2022, Amendment No. 4 to Schedule 13D filed with the SEC on June 14, 2023, Amendment No. 5 to Schedule 13D filed with the SEC on July 14, 2023, Amendment No. 6 to Schedule 13D filed with the SEC on August 15, 2024, Amendment No. 7 to Schedule 13D filed with the SEC on January 7, 2025, Amendment No. 8 to Schedule 13D filed with the SEC on March 21, 2025 and Amendment No. 9 filed with the SEC on March 31, 2025 (together with this Amendment No. 10, the "Schedule 13D") relating to the Common Stock of the Company, the principal executive offices of which are located at 224 Airport Parkway, Suite 550, San Jose, California 95110. Only those items that are hereby reported are amended; all other items reported in the original Schedule 13D, as amended, remain unchanged. Information given in response to each item shall be deemed incorporated by reference in all other items, as applicable. Capitalized terms not defined in this Amendment have the meanings ascribed to them in the original Schedule 13D, as amended. Enter occupation* Items 11 and 13 of the cover page of this Schedule 13D are incorporated herein by reference. Items 7 through 10 of the cover page of this Schedule 13D are incorporated herein by reference. On April 15, 2025, the Reporting Person sold 289,620 shares of Common Stock held by OC II and 672,507 shares of Common Stock held by OC III to an investment bank in a privately negotiated block trade at a price of $10.25 per share. Except to the extent reported in this Schedule 13D, the Reporting Person has not engaged in any transactions in the Common Stock during the past sixty days. 4/15/2025 Pacific Investment Management Company LLC /s/ Alyssa Creighton 04/17/2025