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I recently bought a Sony STR-DH800 from eBay and to cut a long story short I'm getting different volume levels using the same speakers across the various speaker terminals.

I have a multimeter and I was wondering if there is a way I can check the output from each speaker terminal so that I can do a comparisons.

The amplifier has a bi-amp feature to allow you to connect the Front A and Front B speaker terminals into a single pair of speakers. However, if you decide not to use the bi-amp you can use Front A and Front B speaker terminals independently to drive two pairs of stereo speakers. This then gives you three modes from a button on the front of the unit to change the speaker configuration:-

  1. SP A
  2. SP B
  3. SP A+B

Sadly the Front A speakers terminals are extremely quiet compared to Front B. I'm not here to further diagnose why it's quiet or whether I've configured something wrong as I've already done all of that, I just need some readings so that I can prove that there is something electrically wrong the amp and try and get my money back or get it repaired.

UPDATE I connected the two pairs of speakers to the Front B terminals and it drove all 4 speakers at full volume. From a good judgement I would say I was over 90dB. But there is something wrong here as I haven't set the Surround Back (aka Front B) terminals to bi-amp. In fact there doesn't seem to be any difference setting Front B or bi-amp.

I should note that I connected both pairs of speaker to Front A and they significantly drop in proportion to Front B. In other words both pairs of speakers connected to front A aren't the same volume but are very low compared Front B.

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  • \$\begingroup\$ As the two sets can be used independently, the four output terminals must be fed by four separate amplifiers. Hard to believe that the two A channels can have an identical fault and that it's nothing to do with the setup. Is the same problem present in bi-amp mode? \$\endgroup\$
    – Finbarr
    May 16, 2020 at 16:30

1 Answer 1

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Audio amplifiers basically produce a voltage output. The current out depends on the speaker connected. Lower impedance speakers will make for more power out.

Usually, you can connect speakers in parallel to the amp outputs. This will draw more current from the amp, and will increase distortion some. If you don’t overload the amp, no harm will come to it.

Also, different speakers will have vastly different volumes for the same power input.

With a voltmeter, you can see the voltage across the speaker. With a second meter, measuring current, you could determine the current and so compute the power. If you know for sure the impedance of the speaker, you can compute the power from the voltage, but real speakers have a varying impedance with frequency. If you replace the speaker with a power resistor, then you can compute the power output from just the voltage, since the resistor impedance is constant and known.

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  • \$\begingroup\$ You'd need a multimeter that can handle audio frequencies. Many cannot. \$\endgroup\$
    – JRE
    May 16, 2020 at 18:12
  • \$\begingroup\$ You'd also need a continuous test tone to get a steady reading on a meter. Normal music varies way too much to provide any useful values. \$\endgroup\$
    – Finbarr
    May 16, 2020 at 19:01

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