2. amps-preamps
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tube pre amp and Krell FPB 600

Krell in its reference manual says : Tube pre amplifiers , by design, are capacitively coupled. For this reason, the benefit of a direct coupled amplifier can not be realized when used with a tube preamplifier. Additionally , many tube preamplifiers output a great deal of DC. This DC may exceed the servo of a FPB amplifier. Excessive DC level in a signal can damage amplifier , speakers , or both.
Can I use Air tight ATC 2 pre amp with Krell FPB 600 ?
Please advise.
Thanks
fpooyandeh

Showing 4 responses by rwwear

rwwear
2,883 posts
 
I've used lots of tube preamps with my 700c and never used the internal jumper and never have had a problem. The jumper defeats one of the better aspects of the amp by putting a capacitor in line with the signal. If a preamp leaks DC, I wouldn't want it. You can easily check the outputs of the pre by using a meter.
rwwear
2,883 posts
 
Thanks GR. I am no longer using a tube pre. I am also friends with the Krell service manager.
rwwear
2,883 posts
 
It is a well documented fact that the BAT VK-3 was a DC leaking fool. It shut down McCormack amps all the time at a store I was once associated with.
rwwear
2,883 posts
 

Are you having a problem? I would definitely turn the amp off before the preamp and wait for the preamp to warm up before turning the amp on. The 3 LEDs on the front of the amp will signify if there is a problem. Since your preamp is not balanced, I would put jumpers between pin 1 and 3 on the XLRs. I would contact Krell if you think you need to engage the internal jumpers. But they should be close to the rear inputs under the top cover.

 

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