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Hi-Fi speaker volume control question

Discussion in 'General Electronics Discussion' started by quantumtangles, Apr 25, 2013.

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  1. quantumtangles


    Dec 19, 2012
    I would like independently to control the volume output of two pairs of speakers connected to the same stereo power amplifier.

    Can I interpose potentiometers between the +ve and -ve speaker cable outputs, which is to say, can I plant four pots in between the amp and the speakers whose output I want to control?

    The plan is to balance volume from speakers at the far end of the room with speakers to my right and left that are closer to me. I want more volume from the speakers that are further away.

    So can I use pots? If so what pots would appear suitable? Is there a circuit I can build that would make for a nice project?

    The system is as follows:

    Technics Stereo Power Amplifier SE-A1010
    Technics Stereo Control Amplifier SU-C1010
    Yamaha Model NS-500 speakers x 2
    Yamaha Model NS-200 speakers x 2

    Stereo power amplifier specifications:
    Output power 100W+100W (4 ohms, 1kHz, 0.05%)
    80W+80W (6 ohms, 20Hz - 20kHz, 0.02%)
    70W+70W (8 ohms, 20Hz - 20kHz, 0.015%)
    THD 0.015% (-3 dB (20Hz - 20kHz), 8ohms)
    Frequency characteristic 5Hz-100kHz+0 -3 dB
    Dumping factor 70 (8ohms)
    SN ratio 98dB(EIAJ)
    Input sensitivity/impedance 1V/20kohm
    Meter indicating range 0.001W-200W (8ohms)
    Power source AC100V, 50Hz/60Hz
    Power consumption 210W

    Stereo Control Amplifier Specs

    NS-500 Specs:


    NS-200 Specs:


    Should I bite the bullet and get an appropriate graphic equaliser/surround sound unit?
    Last edited: Apr 25, 2013
  2. davenn

    davenn Moderator

    Sep 5, 2009
    you are going to struggle trying to find pots that can handle 100W
    when I was in the PA game I used to use switched attenuators that handle to ~ 40W
    havent seen anything rated for more than that

  3. shrtrnd


    Jan 15, 2010
    I would worry about differences in power outputs.
    Are you planning to independently control each PAIR of speakers, or each of the
    four speakers INDEPENDENTLY?
    It sounds simple to think in terms of the different speaker volume levels, but altering
    the load (which is what a speaker is), has an effect on the amplifier output circuitry
    itself. If you're not careful in balancing the amplifier output loads, you can damage the amplifier
    output circuits inside of the amplifier chassis.
    Something to consider.
  4. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    Nov 28, 2011
    As Dave said, the problem is power dissipation. Any power that is not sent to the speakers must be dissipated somewhere, and that place is the series resistors.

    If you're not changing the settings often or quickly, you could do something with an array of relays, like a discrete DAC built with high-power resistors, but you'd probably need a microcontroller to control it all.

    Also anything you connect between the amplifier and the speakers will affect the damping factor and the frequency response.

    A variac would also work... for frequencies below a few hundred hertz!

    I would buy a small power amplifier module and slave it from the line outputs of your main amp. These are available as kitsets and pre-assembled for reasonable prices. Google is your friend.
  5. quantumtangles


    Dec 19, 2012
    Many thanks you guys. As always, you are really helpful and it is much appreciated :D
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