I have an old pioneer amp (pic related) and I've been using it for many years with two speakers with compatible power/impedance.

I have an old pioneer amp (pic related) and I've been using it for many years with two speakers with compatible power/impedance.
I've just bought a new (active) subwoofer for some extra woof woof action during movies and plugged it to the sub pre-out.
When I enable the sub (especially above -50db), I lose audio on the right speaker or it goes to a way lower volume than the other! As soon as I disable the subwoofer, the audio comes back. Actually plugging in the woofer or not doesn't make a difference, the settings do.
This happens regardless of the (analog) input or length of the (analog) cable but doesn't happen if I'm using the optical input.
Any clues? I often heard about replacing capacitors on old amps but I have no clue about the "symptoms" of old caps.

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  1. 1 year ago
    Anonymous

    Does your woofer have its own crossover? I understand many people go L R channel to the sub then out to the speakers from there.

    • 1 year ago
      Anonymous

      Woofer doesn't have its own crossover. I've also tried changing the crossover freq in the amp just for lulz but obviously it has no effect (regarding the problem, it does change the actual freq).

      I'm not sure I understand what you mean, but the amp has a dedicated sub pre-out (which I use) and as far as I know, it shouldn't be related to a channel. Obviously I don't know if it is connected to a channel on the actual pcb.

      https://i.imgur.com/KqdtKqW.jpg

      Also caps can often be visually inspected

      sounds like its fricked.
      first step would be open it up and see if theres anything looks fricked, skid marks, leaky caps etc.
      the symptoms of a fricked cap is first of all it leaks all its fluid which will either cause it to go open circuit or poossibly short out and then all the fluid eats the copper tracks on the pcb causing absolute havok.
      it all really depends on where the cap is in the circuit and on the board to say what the effect would be.
      that it doesn't happen on optical in is an interesting clue.
      first step open her up, if its not immediately obvious then break the pcb down into what each area does and concentrate on relevant sections.
      obviously if you can get a service manual would be great ideally a circuit diagram but getting more and more unlikely with new stuff.

      I've had a quick look through the openings on the top, big ones are ok but tomorrow I'll open it up.

      If you're using speaker output A, try switching to speaker channel/output B (or vice-versa) and see if it still happens.

      It also may be a case where the subwoofer pre-out is only active for surround mode(s) so switching the sub on may change the sound mode from stereo to surround? I've had a couple of old Pioneer surround receivers similar to the one in your pic, but I had always only run them in surround mode for home theater so I don't know if this is actually the case.

      I'll try speaker B first as it's quick.

      Sub preout definitely works for stereo, it all works fine using the optical input, the problem appears only with the analog inputs.
      Enabling surround kind of makes the other speaker go to the same volume as the R channel while on stereo (low/no volume). I haven't tried anything else because I don't have surround speakers and want just "straight" amplified audio, no dolby bullshit.

      Thanks all for the ideas

  2. 1 year ago
    Anonymous

    Also caps can often be visually inspected

    • 1 year ago
      Anonymous

      that picture is incorrect. all three caps are bad, ifany are swollen, and the others are the same brand they all need to be replaced.

      • 1 year ago
        Anonymous

        While recapping a whole board is good practice it's definitely not necessary for the equipment to function. If the cap isn't swollen then it probably still works, albeit probably not for much longer.

  3. 1 year ago
    Anonymous

    sounds like its fricked.
    first step would be open it up and see if theres anything looks fricked, skid marks, leaky caps etc.
    the symptoms of a fricked cap is first of all it leaks all its fluid which will either cause it to go open circuit or poossibly short out and then all the fluid eats the copper tracks on the pcb causing absolute havok.
    it all really depends on where the cap is in the circuit and on the board to say what the effect would be.
    that it doesn't happen on optical in is an interesting clue.
    first step open her up, if its not immediately obvious then break the pcb down into what each area does and concentrate on relevant sections.
    obviously if you can get a service manual would be great ideally a circuit diagram but getting more and more unlikely with new stuff.

  4. 1 year ago
    Anonymous

    If you're using speaker output A, try switching to speaker channel/output B (or vice-versa) and see if it still happens.

    It also may be a case where the subwoofer pre-out is only active for surround mode(s) so switching the sub on may change the sound mode from stereo to surround? I've had a couple of old Pioneer surround receivers similar to the one in your pic, but I had always only run them in surround mode for home theater so I don't know if this is actually the case.

  5. 1 year ago
    Anonymous

    What model subwoofer do you have?
    If it has high-level (speaker-level) inputs, I'd just forget about fixing the sub output on an old (practically obsolete) receiver, and just run speaker wire from the front speaker outputs to the sub.

  6. 1 year ago
    Anonymous

    Dirty switch contacts. Bang that switch on and off about 50 times and see if it starts to come back. If yer good, get inside with some contact cleaner. Fricking caps. You guys overthink this shit.

    t: Tech since 1984.

    • 1 year ago
      Anonymous

      Do not listen to this guy. That stuff destroys caps.

      • 1 year ago
        Anonymous

        Not true. Why do you lie?

  7. 1 year ago
    Anonymous

    is it a powered subwoofer or do you have a power supply for it?

    • 1 year ago
      Anonymous

      >is it a powered subwoofer
      OP referred to it as an active subwoofer.
      That implies that it has its own amplifier.
      >or do you have a power supply for it?
      what are you talking about?

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