Spatial Audio Raven Preamp

@marantz2270 

No.  The Revelation preamp and the Blackbird amps both preserve phase.  So just hook them up straight.

Thank you, Don. 

Both the preamp and power amp are so symmetric we have to take extra care during assembly to make sure the phase is correct at the output. Multi-color wire comes in handy here.

For that matter, the circuit is so robust it still amplifies with one side non-functional. Distortion is higher, of course, so it’s another thing to be checked during assembly and test. Both phases need to be present and accounted for, polarity correct in every stage, and both channels pair-matched.

The Raven requires a 6sn7 tube on each channel that has matched sections.  Really, a difference of 1 mA is no big deal, but tubes with wildly mismatched sections will not have good bass response.  Any modern 6sn7 you buy will have sections within 1 mA of each other.  The two channels don't have to be matched to each other, just the tube on each channel needs proper section matching within that tube.   The Blackbird amps require similar matching between pairs. 1 or 2 mA difference is fine.  Any more than that and bass response will suffer.  Of course both units are supplied with matched tubes and it is not hard to buy them.  

If you want to run NOS tubes or ANOS, you should ensure the matching is as above.  Smoke won't come out of the preamp or amps, they will work with mismatched tubes, but they won't sound as good.

@donsachs @lynn_olson I have been looking at maybe purchasing the  preamp for a couple months and have a few questions. I have a nice SS state amp but it is not balanced or have zero feedback.  What will be the benefit of the Raven Preamp if  the amplifier is not balanced or has zero feedback.  Does this negate all the benefits of the Raven or is it a cumulative thing?