Vacuum Tube preamp with my KRELL KAV 250a, a no no......WHY?

@atmasphere  there were many krell amps damaged from BAT tube preamps, they got a bad batch of Jensen capacitors. If it would have only been one amp damaged, krell wouldn't have went to the trouble of putting capacitors on the input of their amps with jumpers to bypass the caps if not needed.

FTR:  When I mentioned that film caps get leaky, I meant the DC voltage leaked.  This may have no visible effect.

Electrolytic caps OTOH can literally leak, or blow open from internal gasses.

"The cap failure you experienced might have been caused by not speccing the cap right. If its connected to a plate circuit, it must be rated at a value 15% or so above the no-load DC Voltage of the power supply in the preamp! If not, it can short on turn-on.  I have seen some oil-filled parts that have developed 'leakage' but its worth noting that they are not considered to be 'film caps'."

It's possible that I cut it a bit close, with a 300VDC rated cap in a circuit that, worse come to worse, might see 300VDC before settling to 150VDC--though I took plenty of precautions.  I'm certainly more prone to err on the side of caution since then. ;-)

I had a krell ksa-100 that I used with a don sachs pre for 3 years and no issues. I now bought a simaudio 760a and it goes into dc protection mode within 10 min of operation. The sachs does leak some dc at the outputs. Some amps just don’t jive with some tube preamps due to dc leakage. We just put the sachs internally and everything is fine. A transformer coupled tube pre is the safest bet. Krell usually respond very well to tube preamps. It might be that since the recap your amp is now too sensitive. It’s a journey man, it can be frustrating but it sure is fun. 

I've used tube preamps with many a Krell amp over the years with no problem.If there is a problem the amp should detect it and shut down until the fault is removed. Years ago when I sold BAT and McCormack. The VK-3 would always shut down the McCormack amps as soon as they were turned on. Removing the pre from the circuit rectified the problem.