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Is it hard on my amp to be driving 4 ohm speakers?

I'm a poor audiophile. My gear is very old. I have a Sugden A 28 amp and Epi M201 speakers. The speakers have a switch on the back that only gives you the choice between 4 and 16 ohms. The amp is class A, so it runs hot to begin with. The speakers don't seem to be very efficient, requiring lots of volume for best sound. I've searched for info on my amp with no luck. I'm guessing it's around 35 wpc into 8 ohms. AND I'm also assuming it would be a bad idea for the amp to set the speakers at 16 ohm. Am I right? Is my amp designed to handle driving 4 ohm speakers at high volume?
trapezoid
stanwal's avatar
stanwal
3,147 posts
 
No, that is not necessarily true; it is quite likely that the amp will put out as much or more power at 16 ohms. SS amps TRY to double their output every time the impedance is halved so the Sugden will struggle more with the 4 ohm load than higher ones as it does not have the power supply etc to double its power. Try setting the speaker at 16 ohms and listen beginning at low volume.
meiwan
399 posts
 
The Sugden is about 20wpc, but a strong 20. They can struggle with a 4 ohm load and will not likely play very loud with the easiest of loads. Try the 16 ohm setting but don't expect to rock the place. The Sudgen was made quality, not quantity.
trapezoid OP
6 posts
 
Thank you both for your help. I'll try the 16 ohm setting and go with it.
auxetophone
114 posts
 
I would listen to whatever setting sounds better. It's hard to predict what that will be, especially without knowing what circuit gymnastics are involved on making the 4/16 switch.

If you want to baby the amp above all, try measuring the heat sink temp after extended playing at each setting. I believe this uses a simple bias scheme not unlike Krell's sustained plateau bias, so it will run somewhat hotter at high volume by design.
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