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

Showing 3 responses by bifwynne

Mofi... you may have just provided your own solution. I just checked the specs of a number of ARC preamps on the ARCDB web site. None of the preamp's outputs inverted phase. I have absolutely no idea what that means, so I'm hoping Ralph or Al will chime in. But that may be the cause of the anomolie. I wouldn't use the Cary pre with the ARC amp until you sort this out.
Ok ... I admit not being a techie, so take this with a grain of pepper. If the problem with the amp is presenting in both channels, there could be a common power supply problem that is causing some type of oscillation (e.g., pulsing output power tubes). If all the output power tubes are affected, it seems more likley a problem in the power supply.

The problem is doubly weird because you say it does not occur if your Oppo 105 is directly hooked up to the VT100. Does the Oppo attenuate the signal presented to the VT100??

I have two suggestions. One -- if possible try to borrow another linestage/pre and see if the problem persists. Two -- even if the problem seems to resolve itself by changing out the linestage/pre, I would check in with Kal in ARC Customer Service. I think this situation deserves better advice than just a grain of pepper (or even a whole pepper shaker) from a know-nothing like me.

Please let us know how you make out.

Good luck.
Fantastic detective work Ralph -- many kudos!! I kinda figured that the problem related to a power supply oscillation of some type, but you took it 4 levels beyond. Who woulda thunk??