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Krell amps and Tube Preamps - enemies?

Wow! I never realized how difficult it would be to add tubes with a KRELL amp. I'm no engineer, and, I don't pretend to be into the "technical" side of the audio world. So I'll try to explain.

It seems that tube Preamps create DC. I've been told that DC will dammage my Krell amp (FPB400cx), and possibly my speakers(Tyler Acoustics Linbrook Sig, System 1 piece). UNLESS, I open the amp up and do something to the "jumpers on the digital board" . This puts some protection into the signal path. The Bad thing is, I'm told, - it also colors or degrades the audible signal coming thru the speakers. So, if I want to use my SS set up, say for SACD or DVD-V/DVD-A, I would have to open the amp up again and reverse the proceedure. This would remove the "blockage" in the signal path. :-( This of course, would have to be re-done when I want to go back to the tube setup. WHAT A PAIN!

Needless to say, this has thrown the proverbial 'wet blanket' on my tube enthusiasm. Is this problem common to ALL SS amps? Or is it just a KRELL thing?

Any thoughts would be helpful.
(This is part of a thread i started on the speaker threads, but i thought i might have more luck here on the "amp' Threads)
Thanks
oldpet
oldpet OP
295 posts
 
Tvad - if it sounds the way it is described in the review i read - I'll live with out a remote. :-) Especially if i can grab one in the price range you mentioned. :-) The "wanted" is running.
ulf's avatar
ulf
103 posts
 
I asked Audio Research if I can use a Refr 2 mk2 pre to my Krell 450monos. They answered:
Teh ref2 mk2 has 4+MFD output capacitors, ie it is NOT direct coupling. We use it with our solid state power amps and have experinced no DC problems. They have direct coupling like the Krell amps"
So I can assume that it OK to use the Ref 2 without connect Coupling Capacitor in my Krells?
john_tracy
341 posts
 
I just finished building and "burning-in" a Raleigh Audio line stage kit that was featured in a series of articles in AudioeXpress magazine. The circuit was in part inspired by an article on parallel feed circuit topology by Lynn Olson that appeared in Vacuum Tube Valley. The relevance to this thread is this: it is transformer coupled on the input and output with Lundahl amorphous core transformers. If you haven't heard these trannies, don't let any pregedices you may have for transformers close your mind to this option. These amorphous core transformers have "magic" in them. And more to the point, no DC in output. Also, all your components will be galvanically isolated from each other. Since I have inserted this component into my system I have noticed a real lowering of the noise floor. This is one of the most open, realistic and revealing preamps I have ever heard. If you are looking for "natural presense" and "holographic" imaging check this preamp out.
oldpet OP
295 posts
 
John_tracy
I don't know anything about the amorphous core transformers, but if they work that's the only thing that matters. I'm curious as to where you got the pre amp, and the approx. price range. Thanks

pt
rwwear
2,867 posts
 
I have been reading that the VAC preamps use output transformers and really sound great. I would like to hear one with my Krell 600c but they are quite expensive if you want the top model.
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