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Can phantom power destroy inputs?

Discussion in 'Recording' started by vwerner, Nov 16, 2003.

  1. vwerner

    vwerner Guest

    Have a problem on my Tascam US 224 where I suddenly lost all input signal on my XLR and line inputs.

    This hapened right after I connected my Rode NT1 to the unit, via an external phantom power supply that was already switched on.
    The volume ouput on the soundcard was set at zero, but one trim pot was set at maximum.

    Could this have dammaged something on the input circuit? The unit is operating fine otherwise, has power and plays back without problems.

    How can I prevent a repetition in the future?

    Also does anyone know what repair costs for this kind of dammage on these units might run to? ie would it be better to fix, or buy a good used unit on E-bay?


    PS: I am currently working in Korea, so getting feedback on these issues is not as simple as running out to the nearest Guitar centre... any help is appreciated.
  2. knightfly

    knightfly Active Member

    Jan 18, 2002
    Phantom power is applied to both of the balanced inputs equally, so that there is no difference of potential caused. The ground lead is the return for it. The problem comes when you plug things in with power applied - it's likely that you can make contact with one of the 48 volt lines (mic cable) before the other, which would put a 48 volt difference across the input. This could easily damage input circuitry in some units.

    Normally, the way around this is to never connect phantom powered devices when they are powered up. Many of these devices further safeguard equipment by "ramping up" their 48 volt supply so there is no sudden surge. Plugging them in while they're powered defeats this feature.

    Phantom power normally won't hurt either inputs or non-phantom powered mics, but a sudden surge like that, as well as the possibility of only ONE of the two balanced inputs seeing that high voltage, certainly can.

    Tascam's BBS has been down for months now, so getting in contact with them from Korea may be tough. You could try going to Tascam.com and looking for support options, I'm pretty sure their repair facility is still available thru Email.

    Not sure what the 224 costs, but it's definitely possible that getting a used one might be cheaper than repairs, considering most shops charge at least $50 or more per hour plus parts... Steve
  3. vwerner

    vwerner Guest

    OK. Thanks for the reply Knightfly.

    Maybe this gives me an excuse to get the M-Audio 410. :)

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