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  1. #1
    AR Newbie Registered Member
    Join Date
    Aug 2007

    Unhappy Erratic volume on Technics SU-X911 amplifier ("New Class A")

    Hello, was wondering if someone could advise on this problem ...

    Background: My midi Amp (SU-X911) is part of a Technics system (CD player, Tuner, Cassette Deck, Equalizer). The system was bought sometime in the late 80's (yes it's old).

    Problem: Amp volume (controlled by electronic dial) DANGEROUSLY ERRATIC - suddenly silent for 2-3 seconds, before jumping to almost max! Adjustment to volume control brings it back to normal volume. During the silent and max jump, the volume level display (eg. "-44dB") does not change.

    Consequences: My precious speakers risk being blown up!

    Remedy attempts so far: Following advice from an electrician colleague, I've pulled apart the amp, pulled out the volume control potentiometer and spray cleaned it (with electronic spray). I must say the amp was generally very very clean inside.

    Success? - No, problem returned after one day of amp operation.

    Other Notes: My colleague now suggests it could be the amp itself playing up (ie. not the volume pot). I listened to a whole CD (45mins) last night but it was via headphones, and did not encounter the problem - interesting to see if the problem occurs using headphones as well as the speakers themselves (the Aaron ATS-1 speakers are 8 ohms, and the amp speaker output itself is rated 8-16 ohms)

    Any ideas anyone? Would greatly appreciate advice - perhaps there's one bit of the amp I need to look at / replace.


  2. #2
    Forum Regular royphil345's Avatar
    Join Date
    Apr 2002
    Sounds like a problem with an IC (computer chip that controls the volume setting). Whatever it is... It would to need to be diagnosed / repaired by someone with the knowhow and equipment to do so.... if parts are even still available...

    Sounds like it would be cheaper to just replace it. Just the way things are these days...
    You got quite a few years out of it. Onkyo makes some nice 2-channel receivers at reasonable prices... Maybe shop for an inexpensive pro audio setup that better fits your application?...

  3. #3
    Audio Hobbyist Since 1969 Glen B's Avatar
    Join Date
    Dec 2001
    New York
    I second Royphil's advice to just deep six that old Technics amp and get an Onkyo 2-channel. I'll even help you out and provide a link to the Onkyo TX-8222 for $179.99. You may be able to find it cheaper if you look around.

  4. #4
    AR Newbie Registered Member
    Join Date
    Aug 2007


    Thanks guys - yes it appears I will just have to ditch the thing.

    It's likely though I will upgrade to (shock horror) a 5.1 system, because I already have two good quality Aaron surrounds that used to utilise the Technics' "virtual surround".

    So far, I'm still able to listen to the Technics despite the faulty IC, because even when it jumps to the high volume, it appears it's not high enough (about -18dB) to cause damage, but hey that's a risk isn't it? So yes I shall be shopping around for a 5.1.

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