Audio Research LS27 & Krell Evo 400

[Ed944t]

In the Krell Evo manual is written that when connecting a tube preamp one must use the RCA inputs, not the xlr's.
The ARC LS27 is an hybrid preamp. Because I have pur silver xlr interlinks, I naturally prefer to use them if possible. Does anybody out there has experience with this? I asked Krells technical support but didn't get a reply.

 

[docvale]

In the Krell Evo manual is written that when connecting a tube preamp one must use the RCA inputs, not the xlr's.
The ARC LS27 is an hybrid preamp. Because I have pur silver xlr interlinks, I naturally prefer to use them if possible. Does anybody out there has experience with this? I asked Krells technical support but didn't get a reply.

“Must” is probably an excessive term.
My guess is that Krell commented regarding the typical higher output impedance that tube line stages have through their balanced outputs.

I don’t know what is the XLR output impedance from your ARC pre and the input impedance on the XLR input on the Krell, but if the latter were >10x than the former you should not have major problems. Otherwise you might experience some roll off on the higher frequencies.
You can always try to check for the most pleasing result.

ARC pre and Krell power amp were a popular audio show setup in Italy ~20 years ago, when the two brands had the same distribution (I don’t know how are things today). My guess is that balanced connections were used.

 

[docvale]

I checked the specs of both and the impedance figures should not pose any risk. The Krell manual refers though to protection from excessive DC from tube preamps.
Maybe ARC could give you a better answer is this.

 

[Ed944t]

It is indeed the problem of the excessive DC from tube preamps. The LS27 though has only tubes in the driver stage and mosfets in the power stage . I don't know which stage causes the excessive DC.

 

[trekpilot]

Shouldn't the output coupling caps take care of any DC?