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Help required on Logitech Z-2300 toroidal transformer

Discussion in 'General Electronics Chat' started by RishiGuru, Dec 23, 2010.

  1. RishiGuru

    RishiGuru New Member

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    Here is some pictures of the 8 inch bass driver. It is made by TangBand and is based on their model W8-670Q. But as Logitech says these are custom designed from that model. While W8-670Q is capable of 70W, Logi's modified version W8-670C is capable of 100W. I think now they are also overrating this drivers too.

    I provide the link to their website below:
    TangBand W8-670Q

    Some pics of my subwoofer:
    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    Do you think this sub is okay. TangBand quotes FREQUENCY RESPONSE -->38-500 Hz
     
    Last edited: Jan 4, 2011
  2. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Manufacturers of cheap audio products lie about output power.
    They talk about turning up the volume control too high so there is horrible 10% clipping distortion to make the power number higher. But nobody listens to audio when the amplifier is clipping like mad.

    They don't say "continuous power". Maybe the power is produced for only a moment? Maybe it is "peak power" which is simply double the amount of real power. Maybe it is momentary peak power which might be 4 times the amount of real power.
     
  3. RishiGuru

    RishiGuru New Member

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    Z-2300 uses 2.5 inch polished aluminum phase plug drivers in their satellites. The 12W satellite drivers of Z-2300 are again custom designed & is based on 3 inch Tang Band (W3-594SB) having frequency response capability between 100Hz-20kHz.
     
    Last edited: Jan 4, 2011
  4. dave

    Dave New Member

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  5. mvs sarma

    mvs sarma Well-Known Member

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    yes
    modern world, created a new term called PMPO which, as you once rightly commented, is not defined anywhere If i remember.

    @Rishi guru,
    nice pics
    of late speakers come up with transparent polyurethane based cones. Everything looks transparent.

    We used to have woofer, mid range and tweeter. you cant perhaps have 100Hz to 20KHz same speakers?

    Perhaps the need for 5+1 system is different, as they are able to orient the sound as per original recording- may be what is called surround sound effect.
     
    Last edited: Jan 4, 2011
  6. RishiGuru

    RishiGuru New Member

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    You are absolutely right, they do not quote about "continious power". This is what I found in the Z-2300 manual:

    Total RMS Power : 200W
    Total Peak Power : 400W at < 10% THD
    System THD: Better than 0.05% before clipping
    Subwoofer: 120 W @ 8 ohms @ 10% THD @ 100Hz
    Satellites: 80 W (2 X 40 W) @ 8 ohms @ 10% THD @ 1kHz

    Can you describe what "Total RMS Power" means? And also peak power is rated less than 10% THD. But th question that eludes me the most, what is "System THD"? All this terms suddenly looks very mysterious to me.
     
  7. audioguru

    audioguru Well-Known Member Most Helpful Member

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    "Total RMS Power : 200W"
    They don't say that the volume control is turned up too high so there is horrible 10% distortion. They also don't say continuous or momentary. It is probably only for a moment.

    "System THD: Better than 0.05% before clipping"
    THD is Total harmonic distortion. Any modern amplifier produces low distortion when its volume control is turned down so the amplifier is not clipping.

    "Subwoofer: 120 W @ 8 ohms @ 10% THD @ 100Hz
    Satellites: 80 W (2 X 40 W) @ 8 ohms @ 10% THD @ 1kHz"
    10% distortion is when the volume control is turned up too high so there is 10% terrible clipping distortion to make the power numbers appear higher.
     
  8. mvs sarma

    mvs sarma Well-Known Member

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    at 230VAc, it is (20.1*1.414)-one diode drop. this value with no load.
    once loaded copper loss etc come up and rectified voltage falls to almost 21V or so DC.
    while so the design works anywhere between 18 to 25 but the output changes for the final stages of amplifier.
    pre-amplifiers would have regulated power derived from the 20V DC line.
    even power amps too may have stabilized biasing within the chip
    which power amp chip is used and what is its spec?
     
    Last edited: Jan 4, 2011
  9. RishiGuru

    RishiGuru New Member

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    So, it all comes down to a 80W "continuous power" 2.1speaker system which will provide moderately good distortion free sound under half volume.

    Also, never to turn the volume more than half, or else the transformer will blow!!!!!!!!!!!

    These crappy computer speaker companies......can go and F%@K themselves.
     
    Last edited: Jan 4, 2011
  10. RishiGuru

    RishiGuru New Member

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    Z-2300 uses Class-AB amplifiers from STMicrolectronics.

    The amplifier uses:
    i) Two STMicroelectronics Class-AB, 80W, TDA7295 amplifiers bridged together for the subwoofer.
    ii) Two STMicroelectronics Class-AB, 60W, TDA7296 amplifiers powering each of the satellites.
    iii) Two ripple filters SamXon/ CapXon 10,000 uF, 35V capacitors for smoothing the DC output.
    iv) A Japan Radio Corporation’s JRC-4565 operational amplifier required for the headphone socket in the control pod.
    v) Two voltage regulators a 78M18 and a 79M18, making positive and negative 18 volts respectively to feed the JRC4565 op amp.
     
    Last edited: Jan 4, 2011
  11. mvs sarma

    mvs sarma Well-Known Member

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    thanks Rishi jee
     
  12. audioguru

    audioguru Well-Known Member Most Helpful Member

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    The power transformer is rated to have an output of two times 20.1VAC when it has its rated load. So its resistance has already dropped the open circuit voltage and its peak will be 1.414 times higher which is 28.4V peak. The single rectifier drops it to 27.4V and the ripple drops it to 26VDC. A very poor quality transformer will have its core saturate a little which "squashes" the sine-wave and reduces the peak voltage.
     
  13. audioguru

    audioguru Well-Known Member Most Helpful Member

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    The Tangband 8" Taiwan woofers have paper cones not poly.
     
  14. mvs sarma

    mvs sarma Well-Known Member

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    they made a full wave rectifier with centre tap, thus it is dual output.

    ps:
    the music power was defined by ST micro in their datasheet for TDA7296 as
    " MUSIC POWER is the maximal power which the amplifier is capable of producing across the rated load resistance (regardless of non linearity)1 sec after the application of a sinusoidal input signal of frequency 1KHz."
     
    Last edited: Jan 4, 2011
  15. RishiGuru

    RishiGuru New Member

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    From the Logitech website i found out that Z-2300 have two model generations
    1) M/N: S-0118A
    2) M/N: S-0118B

    This numbers are printed at the back of the subwoofer. There are rumors in the web that the second model consist of 4 X TDA7296. One of the members of Logitech Forum confirmed me that he has got the S-0118A model and they have 2X TDA7295 (for sub) and 2X TDA7296 (for satellite).

    I have the S-0118B model.

    Now having a new model may have two implications:

    1) To rectify some problem in hardware that may have existed during the development of the product and later been reported by the customers after prolonged use.

    2) As a cost cutting measure. With time the minimum offering price(MOP) of a product comes down so the company is no longer able to keep the same margin in profit that it garnered on new release of that product.

    Now 4 X TDA7296 is more than enough for the 150.9VA transformer. And there is no need of TDA7295 since the toroid is incapable to extract the full performance from it.

    @mvs sarma & @AudioGuru

    How much power you TechGurus think will be distributed to the subwoofer & to each satellites?
     
    Last edited: Jan 4, 2011
  16. mvs sarma

    mvs sarma Well-Known Member

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    A WORD OF CAUTION TO RISHI GURU
    the fuse inside the transformer would not blow for no reason.
    Thus it is important to check for short circuits on load of either main or satellite amplifiers before really switching on the system with serviced transformer. OTHEWRWISE THE FUSE WOULD BLOW AGAIN.
     
  17. mvs sarma

    mvs sarma Well-Known Member

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    From a distance we cant comment.
    as it is already owned . there should be no regrets. human years need a few watts to be able to listen
    all other power only to disturb people surrounding you. thus , use it at a level where distortion is less
    but take caution not to energize unless any possible short circuit by any section of amplifier is tested deliberately and satisfied.
     
  18. RishiGuru

    RishiGuru New Member

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    Actually, I was blasting the Z-2300 at nearly 90% volume at my house party when it stopped working. It blasted for nearly two hours at 90% volume when suddenly everything stopped. I came and inspected the subwoofer & found that the heat sink is as hot as a frying pan & the LED on the control pod is not glowing. Also I checked the fuse at the back of the subwoofer & it was ok.

    Later as we found the internal fuse of the transformer blew. I am now astounded how that punny toroid could manage to withstand for almost 2 hours.
     
    Last edited: Jan 5, 2011
  19. mvs sarma

    mvs sarma Well-Known Member

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    If nothing else failed, you would be lucky !!!
     
  20. RishiGuru

    RishiGuru New Member

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    Tomorrow will be the day to find out whether every thing will pan out perfectly or not. Wish me luck!!!
     
  21. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Thank you for explaining that your house party had the sound system playing much too loud (you said it was blasting) which luckily blew up only the fuse in the transformer and not the entire circuit and speakers.

    Don't forget that it is a computer sound system, not a home sound system.
     

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