2. amps-preamps
  3. 147940-3215

amp clipping earlier than usual?

I have a pair of mono amps with clipping indicator LEDs. One of the amps' indicators is lighting up for the first time. I've never been able to make them light up before. But it only happens on one of them. It lights up way sooner than as loud as I typically max them. I don't hear any distortion. So I'm thinking it's not an output transistor. These are LSR&D Superamp monos, 300wpch. Anyone? TIA
csontos

Showing 7 responses by csontos

csontos OP
1,311 posts
 
Hey Ralph. Actually, that amp seems to be down about 2db. I switched sides to check. I have several of these sets so I'm certain.
csontos OP
1,311 posts
 
Hi Elizabeth. I should mention the transformer in that amp is 120deg F while the other is 112deg at idle
csontos OP
1,311 posts
 
Thanks guys. No pre, Oppo CDP direct. So yes, switched ICs and speaker cables. These amps are completely rebuilt about 4 years ago.
Ralph- yeah, more like 3db, noticeable. But if there's no distortion, and not a blown output(maybe yes?), what could cause that? My main concern is the transformer.
csontos OP
1,311 posts
 
Right. They seem to be the ones that are usually kept in place during rebuild. I guess they are more robust than the smaller ones.
csontos OP
1,311 posts
 
Well, the only caps not replaced are the large ones in the psu which I just happen to have Kendeil replacements for. But is there a way to be sure?
csontos OP
1,311 posts
 
I have some limited skill in electronics, mostly with good direction. I can replace the caps no problem. I have LTP transistors on the way anyway. Offset is a bit high for my liking so I will take care of both issues at the same time. It's just that I would rather not change the big caps unless I'm sure they're the culprit.
csontos OP
1,311 posts
 
I set the bias to 120ma as per spec. However the late Dr. Marshall Leach was aware a hotter setting is preferable to some and did state it could be safely set as high as 200ma. So there is a wide safe margin. The psu caps are good quality Sprague and show no signs of malfunction. I have a hunch there's something else going on.
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