I have an old sony str-d911 some pics

I know the str-d911 is a receiver and not an amp but the specs say 100 watts per channel I tried using a 40 watt and 100 watt light bulb (as a test/dummy load) connected to the left speaker channel playing 60 Hz but it doesn't seem to be putting enough power out to light it. What am I missing?

Here's The Spec sheet



Video of using a light bulb as a load below.

  • You're missing about 100 volts.
    – Tetsujin
    Nov 12, 2020 at 8:59

1 Answer 1


What am I missing?

Use a 24 V lamp instead.

Back of an envelope calculation. The formula I use is P = U * U / R.

Your amplifier: 100w in 4 Ohms --> cirka 20V output. Put 20 V into a normal 110V / 100W lamp (around 110 Ohms) gives you about 4 W = not enought to light it. Even worse with a 40W lamp (about 320 Ohms) --> about 1.3 W.

The Peavey in the video gives 650W in 4 Ohms --> about 50V --> 20 W or so = enough to light the lamp. Or they might have it bridge coupled, which would give about 100V across the lamp.

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