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My 50W, 8ohm amp can't drive my 86db, 4ohm speakers? WTF??

OK, I am only writing this tongue in cheek.  Recently my integrated amp stopped working so while I wait for it to get repaired I just tried to use my 10 year old Sonos ZP-100, rated at 50W, 8ohms to drive my Sonus Faber Guarneri Evolutions speakers.  I knew the results  would not be stellar but I just love listening to music everyday I was hoping the Sonos would get me by for a few weeks.  Sonus Faber speakers are notorious for being power hungry and my Evolutions did not disappoint in this regard.  These speakers are rated at 25-200W, 86db, 4ohm.  At low volume the sound is alright but even at moderate levels, around 70-75db I start to hear what sounds like a slight buzzing/distortion at the upper mid range.  Its not really obvious unless you are familiar with the song.  In looking at the review Stereophile did of my speakers, the impedance does indeed drop to 4 ohm at 200hz and 4000hz so what I am hearing makes sense.  I assume this is my Sonos clipping?  If so, I am surprised that it would clip at such low volumes.  I thought clipping occurs at higher volumes?  I knew the Sonos wouldnt be able to really drive my speakers but I did not expect it to sound so bad at such a low volume.  Oh well...I will keep counting the days until I get my amp back.
128x128tboooe
bombaywalla's avatar
bombaywalla
1,958 posts
 
Shorted power rectifiers are a common problem in many amps. There is nothing surprising about this, nothing to do with any of the issues you mentioned (although they can be influences). Sometimes they just fail for no reason.
oh! ok.

I wonder if turning on and off my amp daily had a part in this. I think I will consider leaving it on all time, though I really dislike that thought since I only listen to my system 1-2 hours a night.
this could certainly have an effect - there’s a good reason why a lot of electronics (esp. IT related electronics & computers, laptops, external HDD, etc) are left on 24/7. Power cycling electronics does introduce a current surge each time thru the rectifiers & the power supply caps & the AC fuse. And, over time this will fatigue the said components causing failure.

There’s a lot written & discussed re. leaving s.s. electronics on all the time - just search the Audiogon archives & you should have plenty of good reading material.


atmasphere's avatar
atmasphere
11,973 posts
 
I wonder if turning on and off my amp daily had a part in this.  I think I will consider leaving it on all time, though I really dislike that thought since I only listen to my system 1-2 hours a night.  
In short (no pun intended), no. That has nothing to do with it at all. If properly rated the rectifiers should last decades with daily on/off operation.
czarivey
5,946 posts
 
I also tried to tow 27" Bayliner with Volvo 240 wagon, but shortly after I realized that my piston rings and bearings are gone...
I guess F350 is much better in this department and Pete 337 is even more better.
admranger
144 posts
 
Oddly enough, my Arcam P1000 (135w/ch x 7) soft on/off circuit took a dump so I had to drag out my 1982 vintage SAE 3100 (50w x2) to drive my ATC SCM 19 v2's.  So far I'm not experiencing any issues like tboooe has.  The ATC's are power eaters too, so I was worried about it.  I did notice that the LED power indicators light up a lot more with the ATCs than they ever did with the DCM Time Windows that it originally powered for me (back in college).

Glad you got your amp back up and running, tboooe.  I have to wait a few weeks before mine hits the bench to see the exact issues I have to deal with...
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