Left channel of power amp distorts, but only through 4 ohm speakers

[danr88]

I have a Fisher 500c power amp, rated at 8 ohms, and it distorts through the left channel when I play 4 ohm speakers through it. Even at a low volume, the left channel is pretty badly distorted. But 6 and 8 ohm speakers play fine at any volume and sound great. I have been able to deduce that my 4 ohm speakers (Klipsch KG4) are fine through other amps. I'm kind of new to this, I'm just trying to understand why only one channel would distort. Any help is greatly appreciated!

 

[adnick]

Welcome to AK......

Which speaker tap on the 500c are you hooking the 4 ohm speakers to?

There’s a Fisher sub forum with many 500c owners, and several experts in Fisher gear, you may want to post there....

VR
Andy

 

[sbcrockett]

I've experienced this behavior recently too but with a SS unit. I haven't done a full battery of tests, except that the slight distortion only happens with stacked Advents going through my Kenwood, which doesn't have taps for the different loads. The back of the unit just says 4-16 ohms. It's something that just started happening a week ago after using the Kenwood for weeks in this configuration. When I hook up the amp with just an 8 ohm pair of speakers there's no distortion at all. My initial suspicion was that the left channel transistor was not happy and borderline failing

Now that the weather has started to cool a little, I've rotated the Scott LK-72B in with the stacked Advents and it's been flawless and amazing with no distortion so I'm pretty sure it's nothing to do with the speakers but who knows...

-Steve

 

[Dave451]

Not sure about the 500C, but FYI my KG4's are marked 8 ohms and that's the terminal I play them from. Never had a problem. Welcome to AK!
Dave

 

[tonyg88]

500c should be 4 8 and 16 ohms

 

[danr88]

Thanks for the responses! I just posted in the Fisher subforum as well