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Line Output Converter with Fisher 500c

Discussion in 'Tube Audio' started by friendlyvolc, Oct 12, 2018.

  1. friendlyvolc

    friendlyvolc Member

    Portland OR
    OK Braintrust: Let me know if this will work:

    I've got a Fisher 500c which has 2 sets of speaker outputs. I've got an Altec 604e that will be driven from Speaker 1. I'd like to drive a helper sub (Pure Audio/Eminence Neo15 Driver) from another amp. (I just built an open baffle for them)

    I could use a passive low pass on the Speaker 2, but I wouldn't have separate gain control. Also, the Altec is 16 ohms and the Eminence is 8 ohms. Both speaker outputs use the same 8 or 16 ohm output taps, so I can't do 16 on 1 and 8 on 2 for example.

    The receiver doesn't have a pre-out, just a tape out (line level), which doesn't have gain control.

    One suggestion would be to use the Speaker 2 output through a line output converter (like this one) to bring the high voltage of speakers down to the couple of volts for an amp input:


    I would then connect the LOC to an electronic crossover (Ashley in this case) set as a low pass and into some Heathkit WM5 mono blocks set to 8 ohms to drive the Eminence as a sub.

    1) What about impedance matching? Does the Fisher see the LOC as 8 ohms or 16 ohms or something else? These LOCs are normally used in car audio where solid state head units without RCA outs need to drive external solid state amps.

    2) Will this strain my receiver in any way?

    3) Are there any audio problems (distortion, loss of dynamics etc.) I need to consider?

    4)) Is this folly with a tube amp?

    I'm curious what you think might work best....



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  2. The Fuxtor

    The Fuxtor AK Subscriber Subscriber

    Calgary, Alberta
    I think the 500c has a center channel output? I know the 400 does, that can be used as a signal for your sub amp...
  3. friendlyvolc

    friendlyvolc Member

    Portland OR
    It does, but I was going to be driving stereo helper subs, not just a summed mono sub.

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