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Is It Safe to Warm Up Power Amps Without Speakers Attached

A friend brings his amp over to try with my speakers. We listen to my amps first. He plugs in his amp and powers it on to warm up for an hour before we power down my amps and move the speaker cables to his amp. Is this potentially harmful to his amp? I recall reading in a manual or an online post that someone suggested never running an amp without a speaker load. Does it depend on ss vs. tube...SET or push-pull...etc.? Cheers,
Spencer
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swampwalker's avatar
swampwalker
5,138 posts
 
+1 polk432  In actuality there are some tube amp designs that can deal with being powered up w/o a load, but most cannot.  So best not to try to find out. 
dentdog's avatar
dentdog
473 posts
 
Be glad you asked.

tpreaves's avatar
tpreaves
2,682 posts
 
If it happens to be an Octave Audio amp, sure you can.
gammajo's avatar
gammajo
843 posts
 
Some class D amps will go into oscillation without load
thom_at_galibier_design's avatar
thom_at_galibier_design
723 posts
 
For tube amps, pick up two 8 ohm resistors with at least a 5 watt rating. Quality doesn’t matter - only value and power dissipation.  Those rectangular, sand-cast resistors typically available at Radio Shack are fine for this purpose.

Put one across each binding post and you now have a friendly load presented to your amp.

The exact value doesn’t matter, but keep it in the 8 ohm range which will work irrespective of which tap your transformer is set to (4, 8, 16 ohms).

Cheers,
Thom @ Galibier Design
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