<PAGE>   1
                       AMENDMENT NO. 5 TO LOAN AGREEMENT

     THIS AMENDMENT NO. 5 TO LOAN AGREEMENT (the "Amendment") is made and
entered into as a December 15, 1999, by and between LASALLE BANK NATIONAL
ASSOCIATION, f/k/a LASALLE NATIONAL BANK,  a national banking association (the
"Lender"), and KOSS CORPORATION, a Delaware corporation (the "Borrower").


                                  WITNESSETH:

     WHEREAS, Borrower and Lender entered into that certain Loan Agreement dated
February 17, 1995, as amended by that certain Amendment No.1 to Loan Agreement
dated June 15, 1995, as further amended by that certain Amendment No. 2 to Loan
Agreement dated May 20, 1996, as further amended by that certain Amendment No. 3
to Loan Agreement dated December 31, 1997, and as further amended by that
certain Amendment No.4 to Loan Agreement dated April 29, 1999 (collectively, the
"Loan Agreement"), pursuant to which Lender agreed  to provide Borrower with a
revolving line of credit up to $10,000,000.00 (the "Revolving Loan"); and

     WHEREAS, Borrower has requested Lender to extend the Maturity Date of the
Revolving Loan to November 1, 2001, and Lender has agreed to do so provided,
among other things, Borrower executes and delivers this Amendment.

     NOW THEREFORE, in consideration of the premises which are incorporated
herein by this reference, and other good and valuable consideration, the receipt
and sufficiency of which is hereby acknowledged, the parties agree as follows:

     1. Section 2.1(A) of the Loan Agreement shall be decided in its entirety
and replaced with the following new Section 2.1(A):

     Subject to the terms and conditions of this Agreement, on the date upon
     which all terms and conditions of the Documents have been met or fulfilled
     to the satisfaction of Lender (the "Closing Date"), the Lender agrees to
     make loans to Borrower on a revolving basis (such loans being herein called
     individually, a "Revolving Loan", and collectively, the "Revolving Loans")
     from time to time in such amounts as Borrower may from time to time request
     up to an aggregate amount outstanding of $10,000,000.00; provided, however,
     that (i) each borrowing by Borrower hereunder with respect to any Revolving
     Loan shall be in the aggregate principal amount of at least $10,000.00;
     (ii) the Lender's commitment to make Revolving Loans shall remain in effect
     for a period to and including November 1, 2001 (the "Revolver Termination
     Date"); (iii) notwithstanding any provision herein to the contrary (1) upon
     the occurence and continuance of any Event of Default, and in each such
     event, the Lender may, in its sole discretion, immediately
<PAGE>   2
          cease to make Revolving Loans; and (2) on the Revolver Termination
          Date, Borrower shall repay to the Lender all Revolving Loans, plus
          interest accrued to the date of payment; and (iv) for a period of at
          least 30 consecutive days during each fiscal year of Borrower, the
          amount of Revolving Loans outstanding shall not exceed $2,000,000.00.

          2.   Subsection 2.1(B)(b) of the Loan Agreement shall be deleted in
its entirety and replaced with the following new Subsection 2.1(B)(b):

          (b)  all Letters of Credit shall expire prior to November 1, 2001;

          3.   Borrower has reviewed the areas within its business and
operations which could be adversely affected by, and has developed or is
developing a program to address on a timely basis, the "Year 2000 Problem"
(that is, the risk that computer applications used by Borrower may be unable to
recognize and perform properly date-sensitive functions involving certain dates
prior to and any date on or after December 31, 1999), and has made related
appropriate inquiry of material suppliers and vendors. Based on such review and
program, Borrower believes that the "Year 2000 Problem" will not have a
material adverse effect on the Borrower. From time to time, at the request of
Lender, Borrower shall provide to Lender such updated information or
documentation as is requested regarding the status of its efforts to address
the Year 2000 problem.

          4.   Borrower shall deliver to Lender as a condition to Lender's
undertakings as provided hereunder, note amendments, a directors' consent,
secretary's certificate and such other documents as Lender shall request, each
in form and substance satisfactory to Lender and its counsel.

          5.   All references to "the Agreement" in the Loan Agreement shall
mean the Loan Agreement as amended by this Amendment. All references to "the
Loan," "the Loans," in the Loan Agreement shall include the loan amendments
made hereunder. All references to "the Documents" in the Loan Agreement shall
include this Amendment, the amendment to the Revolving Note and any other
instrument or document required hereunder, whether now existing or at any time
hereafter arising. All references to "the Revolving Note" and in Loan Agreement
shall included the amendments thereto.

          6.   All of the agreements, representations, covenants and
obligations set forth in the Loan Agreement are hereby reaffirmed and restated
as of the date of this Amendment. All representations and warranties contained
in the Loan Agreement remain true and correct as of the date of this Amendment.

          7.   Borrower agrees to pay all fees and out-of-pocket expenses of
Lender including, without limitation, outside counsel to the Lender in
connection with the preparation of this Amendment, and any and all agreements,
instruments and documents required or contemplated by this Amendment.


                                                                          Page 2
<PAGE>   3
          8.   Except as specifically amended and modified by this Amendment:
(a) the Loan Agreement shall remain in full force and effect and is hereby
restated and incorporated herein by this reference; and (b) all terms defined
in the Loan Agreement shall have the same meanings herein as therein.

          IN WITNESS WHEREOF, the parties hereto have caused this Amendment No.
5 to be duly executed and delivered at Chicago, Illinois, as of the date first
above written.

LaSALLE BANK NATIONAL ASSOCIATION       KOSS CORPORATION

By:    James J. Hess                    By:    Michael J. Koss
   --------------------------------        ------------------------------------

Title: Vice President                   Title: CEO/President
      -----------------------------           ---------------------------------


                                        ATTEST:

                                        By:    Richard W. Silverthorn
                                           ------------------------------------

                                        Title: Secretary and General Counsel
                                              ---------------------------------




                                                                          Page 3