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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
elb's avatar
elb
100 posts
 
Call up Krell and ask them.
rwwear
2,867 posts
 
Tube preamps can have DC leakage that's why they sometimes use coupling capacitors. And since Krell amps have no capacitors in the signal path, they can shut down when fed a signal that has DC present. This also occures with McCormick amps. I once worked at a store that sold BAT and McCormick and everytime we hooked a BAT preamp to a McCormick amp, the amp would shut down. The jumper inside the amp inserts a capacitor in the signal path with Krell. I used to use a Counterpoint SA-3 with my Krell and never had a problem without using the jumper.
drrdiamond
671 posts
 
I bought a "pre-owned" Krell FPB300 that had been used with a tube amp without doing any internal alterations.

It had to go back to the factory for repairs. Luckily, it was close enough to being in warrantee that Krell didn't charge me.

Richard
oldpet OP
295 posts
 
So to be safe the jumpers SHOULD BE MOVED. Right? How does this effect the sound of the amp? Anybody know of a SS preamp that sounds like a tube preamp?
thanks
Paul
newbee
4,767 posts
 
If there were such a beast as a SS amp which really sounded like tubes then the manufacturer would get a corner on the SS market (IMHO)! Some solid state amps that I have heard that come close that won't cost an arm and a leg are made by Muse and Plinius... I'm sure there are others. Personally, if I were going to have a SS amp in my system I'd find an older Threshold amp - the SA series. With your speakers the SA3 or SA2's would be great and they are not a problem with tubes - I used them for years w/o problems. I think they may well be the best amps Nelson Pass ever designed. By the way, I doubt that you will hear the insertion of the capacitor in the Krell unless you have everything else in your system optomized, with either a tube or SS pre-amp. Oh, an extra "by the way" DC offset from a CDP shouldn't be a problem - it should stop at your pre-amp, and even if it didn't the volume control would substantially reduce the signal if it did pass.
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