megaworks THX 550 loud hiss, brand new. Faulty?

Discussion in 'NZ Computing' started by Joshua Wood, Nov 9, 2005.

  1. Joshua Wood

    Joshua Wood Guest

    Hi all,

    I've just purchased the Megaworks THX 550 (with free DDTS-100), and
    from all the satelites there is quite a loud hiss. This is by far the
    loudest hiss I've heard from a speaker system, and certainly not
    something I would have expected from something that has passed THX
    standards. I'm wondering if my unit is faulty.


    Here is what I've investigated so far:
    I've tested the following setups:

    Xbox -> DDTS100 decoder -> Megaworks 550. Connected using BOTH coax
    and optical digital. Tested 5.1 DVD and stereo MP3.

    PC - > DDTS100 decoder -> Megaworks 550. Tested stereo MP3.

    In all cases the hiss is still present. If I was to plug the 550
    directly into my PC it would still be there. The hiss is present when
    there are no inputs plugged into the amp/sub unit, not even the input
    plugs. The hiss is present even when mute is pressed on the wired
    remote! The hiss level does not noticably change volume when the
    master volume is altered. All volume settings (ie specific speaker,
    treble, bass etc) are at their default levels.

    Even when I mute the speakers using the speaker wired remote, the hiss
    is still present, again indicating that it's not from an external
    (audio) source.

    It will not be interference from monitor/ac since my stereo in exactly
    the same place (which is currently NOT powered) did not have this
    issue. I have even tried an alternate power cable to the speaker
    system, with the same hiss issue present in both cases. (I was sent
    the 550 system with both an Asian power cord and what I would guess to
    be a European power cord. NOT a New Zealand power cord despite it
    being purchased in NZ. I did however get sent a NZ power cord by the
    computer company when I asked about it).

    I cannot try unplugging the wired remote as this powers on the system.
    However, I decided to go all out testing. I tried my Senheiser
    headphones, which are reasonably expensive and good quality, in the
    wired remote headphone jack. NO HISS. Sound was fine. This would seem
    to indicate that it's not the amp or wired remote or any external
    input - but possibly
    either:
    1) bad speaker wiring
    2) bad/damaged speakers (all 5 satelites, highly unlikely).

    I then unplugged all inputs and all speakers from the amp/sub, except
    the centre speaker & wired remote. The hiss was present. I then made a
    quick wire allowing me to connect my stereo speakers to the amp via
    the centre speaker RCA connection. I removed the 550 centre speaker
    and plugged in my stereo one. The hiss was THERE!!! So it's NOT the
    speakers or their wiring (I also played around with the wiring and it
    made no difference - it was either hiss or no connection).

    I then decided to take it 1 step further, and attached my headphones
    to this quick wire in the centre speaker. I also get hiss! Whereas
    with the same headphones in the headphone jack of the wired remote, I
    get nothing!! I tested all 5 RCA outputs (for the satelites). ALL gave
    hiss!!!

    So it's pretty much narrowed it down - the hiss is coming from the RCA
    outputs which goto the satelites. The amp is probably not to blame
    since headphones via the headphone jack work fine. However something
    between the amp and these outputs might be.

    Can anyone tell me - should I be hearing audible levels of hiss from
    this speaker system when there is no sound playing? And even when
    there is sound playing! The

    Further - try this. Setup a 550 system using just one (or all)
    satelite connected to the sub/amp with no inputs plugged in. Turn the
    system on. Do you get hiss? Do you get hiss when it's muted? You
    should be able to replicate my issue like this. If there is no hiss,
    it would signify an issue with my system.


    It's a long post and I'd like to thank those that read it, but it's
    bit of a hassle RMA'ing it if I don't need to. Although frankly, I'm
    so far disappointed with this system. Mostly because of the hiss, I
    wouldn't have thought it would be there. I've tried emailing
    creative's tech support, that was a joke and waste of my time.

    Hoping someone here can help! Many thanks in advance.
    Josh
     
    Joshua Wood, Nov 9, 2005
    #1
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  2. Joshua Wood

    Roger_Nickel Guest

    Joshua Wood wrote:
    > Hi all,
    >
    > I've just purchased the Megaworks THX 550 (with free DDTS-100), and
    > from all the satelites there is quite a loud hiss. This is by far the
    > loudest hiss I've heard from a speaker system, and certainly not
    > something I would have expected from something that has passed THX
    > standards. I'm wondering if my unit is faulty.
    >
    >
    > Here is what I've investigated so far:
    > I've tested the following setups:
    >
    > Xbox -> DDTS100 decoder -> Megaworks 550. Connected using BOTH coax
    > and optical digital. Tested 5.1 DVD and stereo MP3.
    >
    > PC - > DDTS100 decoder -> Megaworks 550. Tested stereo MP3.
    >
    > In all cases the hiss is still present. If I was to plug the 550
    > directly into my PC it would still be there. The hiss is present when
    > there are no inputs plugged into the amp/sub unit, not even the input
    > plugs. The hiss is present even when mute is pressed on the wired
    > remote! The hiss level does not noticably change volume when the
    > master volume is altered. All volume settings (ie specific speaker,
    > treble, bass etc) are at their default levels.
    >
    > Even when I mute the speakers using the speaker wired remote, the hiss
    > is still present, again indicating that it's not from an external
    > (audio) source.
    >
    > It will not be interference from monitor/ac since my stereo in exactly
    > the same place (which is currently NOT powered) did not have this
    > issue. I have even tried an alternate power cable to the speaker
    > system, with the same hiss issue present in both cases. (I was sent
    > the 550 system with both an Asian power cord and what I would guess to
    > be a European power cord. NOT a New Zealand power cord despite it
    > being purchased in NZ. I did however get sent a NZ power cord by the
    > computer company when I asked about it).
    >
    > I cannot try unplugging the wired remote as this powers on the system.
    > However, I decided to go all out testing. I tried my Senheiser
    > headphones, which are reasonably expensive and good quality, in the
    > wired remote headphone jack. NO HISS. Sound was fine. This would seem
    > to indicate that it's not the amp or wired remote or any external
    > input - but possibly
    > either:
    > 1) bad speaker wiring
    > 2) bad/damaged speakers (all 5 satelites, highly unlikely).
    >
    > I then unplugged all inputs and all speakers from the amp/sub, except
    > the centre speaker & wired remote. The hiss was present. I then made a
    > quick wire allowing me to connect my stereo speakers to the amp via
    > the centre speaker RCA connection. I removed the 550 centre speaker
    > and plugged in my stereo one. The hiss was THERE!!! So it's NOT the
    > speakers or their wiring (I also played around with the wiring and it
    > made no difference - it was either hiss or no connection).
    >
    > I then decided to take it 1 step further, and attached my headphones
    > to this quick wire in the centre speaker. I also get hiss! Whereas
    > with the same headphones in the headphone jack of the wired remote, I
    > get nothing!! I tested all 5 RCA outputs (for the satelites). ALL gave
    > hiss!!!
    >
    > So it's pretty much narrowed it down - the hiss is coming from the RCA
    > outputs which goto the satelites. The amp is probably not to blame
    > since headphones via the headphone jack work fine. However something
    > between the amp and these outputs might be.
    >
    > Can anyone tell me - should I be hearing audible levels of hiss from
    > this speaker system when there is no sound playing? And even when
    > there is sound playing! The
    >
    > Further - try this. Setup a 550 system using just one (or all)
    > satelite connected to the sub/amp with no inputs plugged in. Turn the
    > system on. Do you get hiss? Do you get hiss when it's muted? You
    > should be able to replicate my issue like this. If there is no hiss,
    > it would signify an issue with my system.
    >
    >
    > It's a long post and I'd like to thank those that read it, but it's
    > bit of a hassle RMA'ing it if I don't need to. Although frankly, I'm
    > so far disappointed with this system. Mostly because of the hiss, I
    > wouldn't have thought it would be there. I've tried emailing
    > creative's tech support, that was a joke and waste of my time.
    >
    > Hoping someone here can help! Many thanks in advance.
    > Josh

    The headphones probably have their own amplifier. Occasionally
    this type of hiss is due to high frequency instability caused by
    deteriorated power supply decoupling capacitors allowing unwanted
    interaction between the power output stages but my first suspicion
    would be a leaky electrolytic capacitor or maybe a noisy IC
    somewhere in the low level filtering/signal processing stages
    between the volume control and the output amplifiers. The specs
    claim 99dB s/n ratio so any hiss should be, at most, barely audible.
     
    Roger_Nickel, Nov 9, 2005
    #2
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  3. Joshua Wood

    Dave Taylor Guest

    Joshua Wood <t_h_e_king@h_o_t_m_a_i_l.c_o_m> wrote in
    news::

    > Hi all,
    >

    SNIP
    >
    > Hoping someone here can help! Many thanks in advance.
    > Josh


    Is it a computer?

    Try nz.tech

    --
    Ciao, Dave
     
    Dave Taylor, Nov 10, 2005
    #3
  4. Joshua Wood

    Joshua Wood Guest

    Thanks, but it would appear this is a common issue, to which Creative
    don't care. I'ev already had a few emails to tech support who are just
    monkeys. I'm gonna try for an RMA but not holding my breath on a new
    one being any better. I'm thinking about returning it, as it certainly
    doesn't do what it advertises it does.

    I'm pretty disappointed with it all.
    Josh

    On Thu, 10 Nov 2005 00:06:32 +1300, Roger_Nickel <>
    wrote:

    >The headphones probably have their own amplifier. Occasionally
    >this type of hiss is due to high frequency instability caused by
    >deteriorated power supply decoupling capacitors allowing unwanted
    >interaction between the power output stages but my first suspicion
    >would be a leaky electrolytic capacitor or maybe a noisy IC
    >somewhere in the low level filtering/signal processing stages
    >between the volume control and the output amplifiers. The specs
    >claim 99dB s/n ratio so any hiss should be, at most, barely audible.
     
    Joshua Wood, Nov 10, 2005
    #4
  5. Joshua Wood

    XP Guest

    On Thu, 10 Nov 2005 21:59:05 +1300, Joshua Wood
    <t_h_e_king@h_o_t_m_a_i_l.c_o_m> wrote:

    >Thanks, but it would appear this is a common issue, to which Creative
    >don't care. I'ev already had a few emails to tech support who are just
    >monkeys. I'm gonna try for an RMA but not holding my breath on a new
    >one being any better. I'm thinking about returning it, as it certainly
    >doesn't do what it advertises it does.
    >
    >I'm pretty disappointed with it all.
    >Josh




    Get the Logitech


    The Creative stuff is way over priced and does not get good reviews unless you
    buy the very Top model..


    >On Thu, 10 Nov 2005 00:06:32 +1300, Roger_Nickel <>
    >wrote:
    >
    >>The headphones probably have their own amplifier. Occasionally
    >>this type of hiss is due to high frequency instability caused by
    >>deteriorated power supply decoupling capacitors allowing unwanted
    >>interaction between the power output stages but my first suspicion
    >>would be a leaky electrolytic capacitor or maybe a noisy IC
    >>somewhere in the low level filtering/signal processing stages
    >>between the volume control and the output amplifiers. The specs
    >>claim 99dB s/n ratio so any hiss should be, at most, barely audible.
     
    XP, Nov 10, 2005
    #5
  6. Joshua Wood

    Andrew Guest

    Dave Taylor wrote:
    > Joshua Wood <t_h_e_king@h_o_t_m_a_i_l.c_o_m> wrote in
    > news::
    >
    >> Hi all,
    >>

    > SNIP
    >> Hoping someone here can help! Many thanks in advance.
    >> Josh

    >
    > Is it a computer?
    >
    > Try nz.tech
    >

    Most definatly computer related though
     
    Andrew, Nov 10, 2005
    #6
  7. Joshua Wood

    Dave Taylor Guest

    Andrew <> wrote in news:43735013.2020107
    @wetaeffects.co.nz:

    > Dave Taylor wrote:
    >> Joshua Wood <t_h_e_king@h_o_t_m_a_i_l.c_o_m> wrote in
    >> news::
    >>
    >>> Hi all,
    >>>

    >> SNIP
    >>> Hoping someone here can help! Many thanks in advance.
    >>> Josh

    >>
    >> Is it a computer?
    >>
    >> Try nz.tech
    >>

    > Most definatly computer related though


    oh, I thought is was an amp of some kind for a stereo...

    --
    Ciao, Dave
     
    Dave Taylor, Nov 10, 2005
    #7
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