Spatial Audio Raven Preamp

Yes, I’m curious too. Oddly enough, even though I designed the Raven in 1998, I never actually heard one until the Seattle show last June 2023.

Don and I agreed it was good to choose tubes that were (A) in current production from respected vendors with an excellent track record of reliability, and (B) offer the option of using classic vintage tubes for folks who want to do that. So no unobtainium surplus tubes like 12SN7, ancient 101D’s, or using power-tube DHT’s in a preamp stage that require exotic anti-microphonic isolation systems.

We want keep it simple and focus on the most linear circuit possible. The entire signal path is transformers, wire, and vacuum tubes, in a fully balanced configuration similar to Western Electric line amplifiers from the Thirties. It’s actually rather difficult to "tune" subjectively because there isn’t much you can tweak.

One thing I can say: when you get rid of the last coupling cap in the circuit, surprises await.

One of the points of inspiration: the late-Twenties Western Electric Model 43A amplifier, used in the WE Mirrophonic theatre systems.

Of course, things were a little bigger back then. This entire rack is one channel of amplification. Two racks were typically used, with instant changeover in case of failure while the movie was presented.

@lynn_olson Fascinating but do you ever sleep?🤔

What Lynn said about coupling caps is true.  I have gone through most of the best ones in various designs, and they can sound good to very good.  But the entire Revelation series we designed for Spatial has NO coupling caps from the input to the preamp to the output of the 300b amps.  When you eliminate all of them the sound is quite remarkable.  Provided you have REALLY good custom transformers, specifically designed for their application, and we do.  The Raven preamp will actually drive a 600 ohm load, so a 5K power amp is nothing to it.