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I have a 70V (Pyle PMX3500PH) connected to six speakers drawing 30W each connected through an OSD volume control (SVC 300). Since it's a transformer-based volume control, when you turn it all the way down, I am assuming that this appears to the amplifier as if there is zero load on the amplifier. With zero load, then you essentially have a voltage differential but no current coming out of the amplifier.

Is it bad for the equipment to leave the amplifier running with music playing through it, and have the volume all the way down (zero load on the amplifier) or should we turn off the amplifier every night? Does having the volume all the way down look like an open circuit with infinite impedance on it?

EDIT: For more clarity based on comments: The question is based around having a centralized amp in an inconvenient location, with a volume control knob placed in each room that can control the audio level. If all of the volume controls are set to zero, then there is effectively zero load and zero current. (obviously ignoring leakage here). So is there a fundamental problem with running an amplifier without a load (does it cause some sort of issue with the transformer on the amplifier itself).

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  • \$\begingroup\$ In general, you should turn stuff off if you aren't using it. \$\endgroup\$
    – JRE
    Oct 15, 2022 at 12:18
  • \$\begingroup\$ What precautions are written in the user guide for the amplifier? Have you heard of global warming? What is a transformer-based volume control? \$\endgroup\$
    – Andy aka
    Oct 15, 2022 at 13:51
  • \$\begingroup\$ The question is based around having a centralized amp in an inconvenient location, with a volume control knob placed in each room that can control the audio level. If all of the volume controls are set to zero, then there is effectively zero load and zero current. (obviously ignoring leakage here). So is there a fundamental problem with running an amplifier without a load (does it cause some sort of issue with the transformer on the amplifier itself). \$\endgroup\$
    – Taylor Hall
    Oct 15, 2022 at 14:18
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    \$\begingroup\$ Not sure what you care about. You will save power if you turn off the amp. The amp will have appreciable consumption while powered on, even if the output is silent. Some things may last longer at a constant elevated temperature rather than constant thermal cycling of being turned on and off. But other things (electrolytic caps) will probably last longer if they are kept at lower temperatures. On balance, I would say turn it off if you can, but if you can't I doubt it will cause a dramatic shortening of its lifetime. \$\endgroup\$
    – user57037
    Oct 16, 2022 at 6:49
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    \$\begingroup\$ Any well designed amplifier will be happy with no load. I have encountered one amplifier once which started to oscillate and run very hot once the speakers where disconnected which the manual warned about. Expensive “audiophile” amp with garbage circuit design. \$\endgroup\$
    – winny
    Oct 16, 2022 at 7:59

2 Answers 2

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The OSD volume control is a 12-step rotary switch / line matching transformer combination.

Here's the schematic of a representative 4-step control.

enter image description here

When turned all the way down, the transformer is disconnected from the line.

The line amplifier would be protected against open-circuit. Hence no damage would be caused to it when operated without a load.

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There are differences in "Volume Controls", you picked a good one. The SVC300 is an impedance-matching volume control that lets you adjust the volume of a pair of speakers independently of other speakers. It will keep a relative constant impedance load on your amplifier. The all resistor ones are in several configurations and many will not do that. Your choice of amplifiers is good, I could not find the idle power, it will only draw as much power as it needs. The higher the volume the more power it will use. The only thing I see missing is that it is not installed in my home.

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