2. amps-preamps
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Cary SLP98P not working with Audio Research VT100

HELP!

OK, a few months ago after doing a bunch of research to build a new system in a smaller room, I bought some Harbeth SHL-5's and an Audio Research VT100 MKIII amp to match with my existing Cary SLP98P F1 preamp.

When I first got the combo together they sounded amazing, but after a few hours of playing the sound started to degrade then it got really wierd:

The Audio Resarch amp started to pulse. The tubes would two at a time sequentially pulse lighter (losing thier blue hue) and the sound was terrible pulsing on and off as well. If I leave the system off for a long time then start again, the process starts again.

If the amp is attached only to the Oppo 105 I have on the rack, it has no issues. If the Cary is connected to the old Parasound amp I have on the rack, it works fine.

The Cary just came back from an update at Cary, it was doing this before the update, and this seems to have had no effect.

What could this be?

Some suggested DC from the preamp, but I just got it back, and would that build up?

HELP!!
macdadtexas
atmasphere's avatar
atmasphere
11,590 posts
 
If the preamp works with the Parasound, you just ruled out the preamp as the problem. Sounds like something is up with the ARC.
mofimadness's avatar
mofimadness
4,935 posts
 
Ralph...the OP does state that when he hooks up his OPPO 105 direct to the ARC amp, it works fine.

I think it has something to do with the output impedance of the Cary and the input impedance of the ARC amp and the cables used to attached them? It seems to me that it is causing an oscillation (the pulsing of the tubes in the amp).

Have you tried a different set of interconnects?

Maybe Al will chime in...
macdadtexas OP
1,794 posts
 
OK, when I remove both from the APC S15 and plug them both into a PS Audio Duet no problems for hours.

I'll try different cables, I still have my trusty Kimber Kable Hero's.

The impedence for the amp is the same as Cary's 120S, so I'm guessing that's not the problem.

My preamp is phase inverting, and I just read the manual again for the AR amp, and it states not to use a phase inverting preamp, but does not say why, and I can't find any info on the internet about that. Seems this would have come up previously with these two companies.

thanks.
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