<PAGE>   1
                                                                  EXHIBIT 10.43


                        [CITY NATIONAL BANK LETTERHEAD]


                             REVOLVING CREDIT NOTE


$10,000,000                                                   Irvine, California
                                                                    July 6, 1999


     FOR VALUE RECEIVED, the undersigned, SRS LABS, INC., a Delaware corporation
("Borrower"), promises to pay on the Termination Date to CITY NATIONAL BANK, a
national banking association ("CNB"), at its Office located at Irvine,
California 92618, the principal amount of TEN MILLION DOLLARS ($10,000,000) or
so much thereof as may be advanced and be outstanding, with interest thereon to
be computed on each Revolving Credit Loan from the date of its disbursement at a
rate computed on the basis of a 360-day year, actual days elapsed, as set forth
that certain Credit and Security Agreement dated as of July 6, 1999, between CNB
and Borrower, as it may be amended from time to time (the "Credit Agreement").
Capitalized terms not defined herein shall have the meanings given them in the
Credit Agreement.

     All or any portion of the principal of this Revolving Credit Note ("Note")
may be borrowed, repaid and reborrowed from time to time prior to the
Termination Date, provided at the time of any borrowing no default exists under
this Note and no Event of Default or Potential Event of Default exists under the
terms and conditions of the Credit Agreement and provided, further that the
total borrowings outstanding at any one time shall not exceed $10,000,000. Each
borrowing and repayment of a Revolving Credit Loan shall be noted in the books
and records of CNB. The excess of borrowings over repayments as noted on such
books and records shall constitute presumptive evidence of the principal balance
due hereon from time to time and at any time.

     Interest is payable monthly on the first day of each and every month
commencing September 1, 1999.

     If payment on this Note becomes due and payable on non-Business Day, the
maturity thereof shall be extended to the next Business Day and, with respect to
payments of principal or interest thereon shall be payable during such extension
at the then applicable rate. Upon the occurrence of one or more of the Events of
Default specified in the Credit Agreement, all amounts remaining unpaid on this
Note may become or be declared to be immediately payable as provided in the
Credit Agreement, without presentment, demand or notice of dishonor, all of
which are expressly waived. Borrower agrees to pay all costs of collection of
this Note and reasonable attorneys' fees (including attorneys' fees allocable to
CNB's in-house counsel) in connection therewith, irrespective of whether suit is
brought thereon.

     This is the Revolving Credit Note referred to in the Credit Agreement and
is entitled to the benefits thereof and may be prepaid in whole or in part only
as provided therein.

     Any change in the Prime Rate shall become effective on the same Business
Day on which the Prime Rate shall change, without prior notice to Borrower. Any
principal or interest not paid when due hereunder shall thereafter bear
additional interest from its due date at the rate of five percent (5%) per

                                       1
<PAGE>   2
annum higher than the interest rate as determined and computed above, and
continuing thereafter until paid.

     This Note shall be governed by the laws of the State of California.


"BORROWER"                         SRS LABS, INC., a
                                   Delaware corporation


                                   By: /s/ THOMAS C.K. YUEN
                                       -----------------------------------------
                                       Thomas C.K. Yuen, Chief Executive Officer


                                       2