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

@mattw73 Thanks for your reminder about the sequence of powering on and off.

I have to admit, I sometimes forget and then end up crossing my fingers.  Not good.

Regarding the power going out or flickering during storms: I have both preamp and amp going straight into fresh/new sockets in the wall.  Whenever there is even the slightest prediction of a storm, I yank the power cables on both until the threat passes.  And if I'm away for a long time, I pull them just as a precaution.  

Like you, I also prefer some tubes in the chain.  The Krell paired with a SS preamp sounds a bit bright for my taste.  And there is nothing like high volume creamy distortion when driving a class D tube guitar amp. Buttery smooth and so fun to play.  But a vacuum preamp, for my taste, rounds out the brittle high end and adds a bit of warmth.

Interesting read. I used a tube preamp with a SS amp for a year without any issues, but reading all this, I will definitely stick to SS for both from now on. Tubes was not my thing. Too many updates temptations.

Hey @judsauce -

If a tube swap fixed your issues you have your answer. Any leakage at the outputs would not change based on the tubes, AFAIK. In either case, this problem is super easy to measure. Get a multimeter that measures at least down to 0.01 V and put it across the preamp outputs. You should measure very little, if any, DC.

I could imagine it is possible that swapping tubes caused oscillation though, which is a different issue than DC.  That's when the pre or an amp starts outputing very high frequencies (the very opposite of DC) which are inaudible, but still heat up the amp and voice coils.

There are some good reasons for mixing tube pre/solid state amp, such as wanting to drive very difficult speakers. Electro-statics for instance can really shine this way.

judsauce

You will get some great advice here, and many of us use tube preamps in front of our tube and solid state amplifiers......the combination can be a beautiful pairing.

I'd recommend reaching out to some of the best tube preamp manufacturers and have a conversation with them; most of them will give freely of their time.....as Lynn has done already. Ralph at Atma-Sphere and Aric Kimball of Aric Audio sometimes post here as Lynn has.

Some of those that I'd recommend are: Bob at Backert Labs (Rhumba Extreme & Rhythm preamps), Lynn Olson/Don Sachs (Raven preamp), Mick at Supratek, (several great preamps), Ralph at Atmosphere (MP-1 and MP-3 preamps), and Aric Kimball at Aric Audio (Motherlode II and XL and Super 6SN7 preamps).

I spoke with each of them before I purchased my Aric Audio Motherlode XL preamp, and they all were very giving of their time.....and you cannot go wrong with any of those preamps

Regarding the power going out or flickering during storms: I have both preamp and amp going straight into fresh/new sockets in the wall.  Whenever there is even the slightest prediction of a storm, I yank the power cables on both until the threat passes.  And if I'm away for a long time, I pull them just as a precaution.  

This is good practice, but about a third of the time I've seen gear go up it has been stormless.  About half of the power events at this location in SC were in clear blue skies, due to some transformer issue, and I'm often not even aware of a short intense storm about to roll through.  YMMV, but I've seen enough gear lost to something coming down the power or coaxial cable that I'm willing to "sacrifice" for surge protection.