Sec Form 4 Filing - FICHTHORN JOHN @ QUANTUM CORP /DE/ - 2025-09-23

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person FICHTHORN JOHN 2. Issuer Name and Ticker or Trading Symbol QUANTUM CORP /DE/ [ QMCO] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O QUANTUM CORPORATION, 10770 E. BRIARWOOD AVE. 3. Date of Earliest Transaction (MM/DD/YY) 09/23/2025 (Street) CENTENNIAL, CO80112 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 15,271 D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Warrant (right to buy) $ 8.81 ( 1 ) 09/23/2025( 1 )( 2 ) J 2,653,308 ( 1 ) ( 2 ) 09/23/2025( 1 ) 09/23/2032( 1 ) Common Stock 2,653,308 ( 1 ) ( 2 ) ( 1 ) 2,653,308 ( 1 ) ( 2 ) I by Dialectic Technology SPV LLC ( 3 ) Convertible Notes ( 4 ) ( 5 ) 12/18/2025 J 0 ( 4 ) ( 5 ) 12/18/2025 12/18/2028( 4 )( 5 ) Common Stock ( 4 ) ( 5 ) ( 4 ) ( 5 ) 0 ( 4 ) ( 5 ) I by Dialectic Technology SPV LLC ( 3 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other FICHTHORN JOHN C/O QUANTUM CORPORATION 10770 E. BRIARWOOD AVE. CENTENNIAL, CO80112 X X Signatures Tara Ilges, attorney-in-fact for John A. Fichthorn 12/29/2025 Signature of Reporting Person Date

Explanation of Responses:

( 1 )On September 23, 2025 ("Issuance Date"), the Issuer issued to Dialectic Technology SPV LLC ("Dialectic") a warrant (the "Forbearance Warrant") to purchase 2,653,308 (as may be adjusted pursuant to the Forbearance Warrant) shares of common stock, par value $0.01 per share of the Issuer (the "Common Stock"), at an exercise price equal to $8.81 per share (as adjusted from time to time in accordance with the Forbearance Warrant) on or after the Issuance Date and until the date that is seven (7) years from the Issuance Date. ( 2 )The Forbearance Warrant is subject to a 4.99% beneficial ownership limitation and cannot be exercised in excess of such ownership limitation without waiver by Dialectic. On December 22, 2025, Dialectic provided notice to the Issuer of the waiver of such limitation, which will be effective February 21, 2026. ( 3 )These securities are held directly by Dialectic, a 10% holder of the Issuer, and indirectly by John Fichthorn. Mr. Fichthorn is the Manager of Dialectic Technology Manager LLC, the Manager of Dialectic. The Reporting Person disclaims beneficial ownership of these securities, except to the extent of the Reporting Person's pecuniary interest therein, if any. ( 4 )On December 18, 2025 (the "Closing Date"), the Issuer issued senior secured convertible notes (the "Convertible Notes") in the aggregate principal amount of $54,718,114 to Dialectic. The Convertible Notes mature on December 18, 2028 (the "Maturity Date") and have an interest rate of 10.00% per annum, payable in kind, compounded annually. The initial conversion price of the Convertible Notes equals $10.00 per share (the "Conversion Price") of Common Stock, subject to adjustment, and includes antidilution protections in favor of Dialectic as set forth in the Convertible Notes. The Conversion Price is subject to adjustment on the last day of the three (3) calendar quarters immediately following the Closing Date (each, a "Reset Price Date") to the greater of (a) $4.00 per share and (b) the lesser of (i) the then Conversion Price and (ii) the 30-day daily VWAP of the Common Stock immediately preceding the Reset Price Date. ( 5 )Based on the Conversion Price as of the Closing Date, the Convertible Notes were convertible into 5,471,811 shares of Common Stock. At the Issuer's option, all outstanding principal amount, accrued and unpaid interest and premium, if any, of any Convertible Notes outstanding on the Maturity Date will be exchanged into shares of Common Stock at an exchange price equal to 80% of the market price as set forth in the Convertible Notes. Following the six (6)-month anniversary of Closing Date, if certain conditions are met, the Issuer may elect to require the exchange of a portion of the total outstanding amount of any Convertible Notes into shares of Common Stock at the then outstanding Conversion Price.

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