Spatial Audio Raven Preamp

@terrapin77 Probably more than a few Don Sachs preamp owners waiting on the sidelines. No pressure!  Don't try to write a professional review, just your honest thoughts will do as it's all subjective anyway.

@donsachs My system might respond well to the Linlai tubes.

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?🤔