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Path: utzoo!mnetor!seismo!gatech!mit-eddie!genrad!rep
From: rep@genrad.UUCP (Pete Peterson)
Newsgroups: sci.electronics
Subject: Re: need advice on TV sound amplifier
Message-ID: <1272@genrad.UUCP>
Date: Mon, 4-May-87 07:35:27 EDT
Article-I.D.: genrad.1272
Posted: Mon May  4 07:35:27 1987
Date-Received: Tue, 5-May-87 01:19:43 EDT
References: <578@stracs.cs.strath.ac.uk> <566@neoucom.UUCP>
Reply-To: rep@genrad.UUCP (Pete Peterson)
Organization: GenRad, Inc., Concord, Mass.
Lines: 30

In article <566@neoucom.UUCP> wtm@neoucom.UUCP (Bill Mayhew) writes:
>
>You can keep the volume at the TV headphone jack high enough for
>person with hearing loss and avoiding 60 Hz buzz by cutting down on
>the volume in the set's speaker.
>
>You might try using an operational amplifier chip to make a notch
>filter for the 60 Hz buzz for the ear phone listener.
>
The original request for this information didn't make it clear whether
the problem occurred at high volume settings (since he mentioned clipping)
or low settings which makes the residual hum ,at zero volume control setting,
significant.  In the first case, the attenuator on the output as mentioned
in a previous posting would make sense; if the problem is residual "buzz",
the attenuator on the TV speaker that Bill mentioned would probably help.

Two additional points:
    Trying to get rid of "60 hz buzz" (as opposed to 60 hz hum) with a 60
    hz notch filter will probably not work out too well since you would still
    be left with the harmonics, which are what makes it sound like "buzz"
    rather than "hum".  You could perhaps use a high-pass filter to cut off
    frequencies below 300 hz (telephone-quality sound).

    Hearing loss tends to be frequency-dependent; using an amplifier with
    some control over the frequency response (at least treble-boost if
    not an inexpensive graphic equalizer) might allow for greatly improved
    intelligibility without blasting the person's ears.

        pete peterson
        {decvax,linus,wjh12,mit-eddie,masscomp}!genrad!rep