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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
 
Will the manufacturers say if their products "leak" DC? It doesn't seem to be something a company would want to admit.
rwwear
2,868 posts
 
Well Newbee you got me on that one. But just because equipment is old doesn't mean it can't sound good. By the way, BAT has probably fixed the DC leakage problem that they had in their earlier preamps. I guess an SS preamp can leak DC but it is not as likely. You can easily measure for leakage with a voltmeter to the outputs of the preamp. I am pretty sure that Krell amps will only shut down when DC is present at the inputs. Once the problem is removed the amp will come back on without damage.
keis
176 posts
 
I've used a BAT KV-51SE, Calypso, and SF Line3 with a Krell KSA-200s with good results. (Also earlier a AR LS2B witched worked but the combo with THiel 3.6s drilled a hole in your ears.)
rooze's avatar
rooze
638 posts
 
I used an ARC LS 15 with a Krell FPB200 for a few months. Initially I didn't remove the jumpers in the amp, and I couldn't leave the amp switched on for any length of time, it would get hotter and hotter (without signal) then eventually shut itself down. I then swtched the jumpers and everything worked fine. It did not degrade the sound in any way that I could detect and it took less than 5 minutes to remove the jumpers and replace the lid.
I wouldn't let this put you off using FPB's with tubes....the FPB needs all the help it can get in the warmth and tonal balance departments.....go for it, it's a good amp and the LS range made a good match in my system.

Roozer
oldpet OP
295 posts
 
Rooze - Where did you get the instructions on how to do the operation? Why does Krell NOT ship the amps with the protection?
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