Since I often come across old Audiogon forum
posts while researching various questions on both A’Gon and Google, I thought I
should close the loop on this one in case anyone else has this same rectifier question
/ issue with their Cary SLI-80 integrated amp and stumbles upon this post:
Here’s the explanation as to how my Cary SLI-80
was working just fine with one of its two rectifier tubes being blown:
I finally contacted Cary’s tech department, and
spoke with Mark. Nice guy. I explained what had happened, that I just happened to
notice one of the 2 rectifier tubes in my SLI-80 was blown, and yet the amp was
working great, sounding great, and it may have been that way for several
listening sessions. What gives?
Well, I – incorrectly – assumed that since the
SLI-80 has 2 separate rectifier tubes, that one is for the left channel and the
other for the right channel. I was wrong (that’s OK, I usually am. Just ask my
wife ;-). Turns out, Cary runs the 2 rectifier tubes in parallel (and a
shout-out to fellow A’Goners almarg and GS5556 who mentioned this possibility
above). I’m not an electrical engineer, but I got the gist that – basically –
the one remaining good tube was doing the work of 2, and that’s why the amp
continued to perform just fine with one blown rectifier tube. Of course, that
also meant the remaining tube was working harder, and if I had left it that way,
it too likely would have blown prematurely.
I also – incorrectly – assumed that the HEXFRED
upgrade that my amp has in its rectifier stage was “taking over” most of the
work from the rectifier tubes themselves, and that may have explained why the
amp was working just fine on one tube. Again, I was wrong. According to Cary, while
the HEXFRED upgrade does “tighten up” and improve the rectification stage, the
amp still relies on the rectifier tubes themselves to do the actual work, and
the amp can still benefit from using higher quality rectifier tubes.
Cary also told me that part of their “ultimate
upgrade” package for the SLI-80 is to completely remove the tubes from the
rectification process and rely only on the HEXFREDs (and perhaps other magical
circuits, I don’t know). This explains the pictures I’ve seen online of some SLI-80
amps with no rectifier tubes at all, and just small black metal covers over the
rectifier tube sockets. So, if your SLI-80 amp – like mine – does have the
HEXFRED upgrade, but also still uses rectifier tubes, rest assured you’re still
running tube rectification, and can still benefit from rolling-in your favorite
tubes (like the now ubiquitous Philips 5R4GYS, they just look so cool ;-).
I hope that helps anyone with similar SLI-80 rectification
questions.
And with that, I rest my case, Your Honor.
From the sweet spot,
Mike (Mhwalker)
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