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Thread: DBX problem

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    DBX problem

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    Hi,
    I have 2 Yamaha 4-track cassette recorders, the MT120 and the MT2X, and both have a problem with the DBX noise reduction:

    when I put the DBX on, the sound of the 4th track of the MT120 completely disappears while the others are fine, and for the MT2X the sound disappears on all tracks at once;

    I wonder if this problem is common?

    I went to the repair shop with the MT120 but the guy couldn't find the problem.

    Now, I think Yamaha, like Tascam, probably use the Type II DBX right?

    I have a few DBX NT40 and DBX 154 units, are these DBX Type II units?

    If yes then I could probably use them through the output of the tracks, I only need to transfer the tapes on the computer.

    TIA for your help.

    Sincerely,

    Me-Uzik

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    Check that this machine does not have a dbx by-pass on channel 4 for the recording of time code. If it does it could be a faulty by-pass switch / circuit.

    Cheers

    Alan.

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    Quote Originally Posted by Me-Uzik View Post
    Hi,
    I have 2 Yamaha 4-track cassette recorders, the MT120 and the MT2X, and both have a problem with the DBX noise reduction:

    when I put the DBX on, the sound of the 4th track of the MT120 completely disappears while the others are fine, and for the MT2X the sound disappears on all tracks at once;

    I wonder if this problem is common?

    I went to the repair shop with the MT120 but the guy couldn't find the problem.

    Now, I think Yamaha, like Tascam, probably use the Type II DBX right?

    I have a few DBX NT40 and DBX 154 units, are these DBX Type II units?

    If yes then I could probably use them through the output of the tracks, I only need to transfer the tapes on the computer.

    TIA for your help.

    Sincerely,

    Me-Uzik
    dbx is level sensitive on playback. If there is dirt on the play head or anything that weakens the playback from its original level, switching in the dbx can really drop the sound level severely.
    What I'm saying is, there may be nothing wrong with the dbx electronics of your Yamaha. You need first to establish the machine is playing back correctly. Just cleaning the play head may be all that's needed.

    But these are old machines now. It may need some refurbishment even just to play your tapes back correctly.

    Also, correctly decoding dbx and Dolby cassette tapes for transfer to digital is not always smooth sailing, and that's with the correct gear in the best condition.


    Cheers Tim

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    Hi,
    thanks for your replies;

    There's no DBX by-pass for a time code on the MT120;

    As for the heads they are clean.

    The circuits might need to be cleaned, I know that when I haven't used the DBX NT40 units for a while I need to open the units and spray cleaning stuff and play with the switches a few times before the sound gets back, so it might be the same for the Yamaha machines.

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    OK. How about the cassette? Is the small pressure pad intact that pushes the tape onto the head?
    Cheers Tim

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    Quote Originally Posted by Me-Uzik View Post
    Hi,
    I have 2 Yamaha 4-track cassette recorders, the MT120 and the MT2X, and both have a problem with the DBX noise reduction:

    when I put the DBX on, the sound of the 4th track of the MT120 completely disappears while the others are fine, and for the MT2X the sound disappears on all tracks at once;

    I wonder if this problem is common?

    I went to the repair shop with the MT120 but the guy couldn't find the problem.

    Now, I think Yamaha, like Tascam, probably use the Type II DBX right?

    I have a few DBX NT40 and DBX 154 units, are these DBX Type II units?

    If yes then I could probably use them through the output of the tracks, I only need to transfer the tapes on the computer.

    TIA for your help.

    Sincerely,

    Me-Uzik
    Cassettes used dbx II. The NT40 is that type. The 154 isn't. All 150 series units were type I.
    Rick Ruskin
    Lion Dog Music - Seattle WA
    http://liondogmusic.com

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    Tim,
    yes the pads are ok. I doubt the problem is with the tape though.

    RRuskin, thanks, if can't fix the problem I might try with the NX40 units.

    Thanks.

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    Alan (witzendoz) said:

    "Check that this machine does not have a dbx by-pass on channel 4 for the recording of time code. If it does it could be a faulty by-pass switch / circuit."

    Hi Alan, sorry I was wrong in my other reply, there is a sync switch on the MT120, I just never used it and didn't see it as the unit was at the repair shop;

    I think that yes it could be the problem, however I don't know if these circuits are available nor are they changeable. Probably, but I don't know much when it comes to this. I could ask the technician, and if someone here knows please let me know.

    I noticed though that when I record music on track 4 using DBX the sound on playback has been recorded way too loud and it distortionates a lot (when DBX is switched off, compared to the other tracks).

    I checked the calibration and it's fine (rec and pb) so it probably is the circuit like you said.

    I'll see what I can do.

    Thanks,

    Me-Uzik

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    I can't find it, so I'm assuming the post was lost in the database crash earlier (along with mine about finally fixing my A807), but someone said something very important:

    Make sure that if you record with DBX on, you always play it back with DBX on. If you record with DBX off, play it back with DBX off.

    Apologies if it seems obvious, but just to be sure you're doing it right :P

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    Yeah, I noticed that a bunch of my posts are not here anymore. Thanks for re-posting jp and yeah it seems the OP's problem is not using the dbx correctly.

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