Spatial Audio Raven Preamp

The Raven has split windings on the output transformer so both RCA and XLR’s can be used at the same time (the RCA output uses one-half of the secondary winding). So feel free to use to use the RCA output to power the active subs.

@lynn_olsen This suggests that there is a grounded center tap of the output transformer. Normally a balanced line output (if it supports AES48) is floating (this practice is to prevent ground loops). Did you provide a switch to break the center tap's ground connection if the RCA is not used? I don't see it in rear panel photos.

I received my Raven preamp a week ago.  I've got about 80 hours on it now.  

It's great!  I'm really digging the expanded tone colors, instrument textures, sense of space, and natural non-mechanical sound.

My system is all digital using a Holo May DAC into the Raven.  My main amplification is via a pair of DIY First Watt M2 monoblocks.  I also own a pair of Hypex Nilai 500 monoblocks that I have been using with the Raven.  I am running balanced from Holo May to preamp, and then out single-ended out to the M2 monos.  With the Nilai monos the system is fully balanced.  My speakers are Pure Audio Project Quintet15 open baffles.

I'm finding that I'm listening more to whole albums, or parts of albums, instead of jumping around to different selected tracks and playlists of selected tracks.  The music on the album sounds excellent, so I just keep going.  This is how I used to listen to vinyl before I developed my unfortunately terminal record mold allergy.

I found out about the Raven from this thread a few months ago.  I've had a checklist of features, getting larger over the years, that I wanted to see in a commercial vacuum tube preamp.  The Spatial Audio Lab Raven amazingly met my requirements.  I immediately ordered one.

More in my next post...

Is the Oregon Triode meetup still in the plans? I live in Portland, for now, and I'm interested in the Raven pre and maybe the amps at some point. Hoping to still be in Portland if this meetup happens.

My (opinionated) tube preamp checklist:

* Must take full advantage of balanced DACs

* No Balanced to Single Ended input transformers

* Must support XLR balanced out and RCA single-ended out for use with balanced amps or single-ended amps.

* Balanced XLR out and single-ended RCA out must have equally good sound quality

* Not capacitor coupled

* Much prefer 6SN7s. Would consider 6SN7 family or DHTs. But balanced DHT preamp is large, heavy, pricey, with possible microphonics, etc.  

* No small signal tubes

* Stepped attenuators with a good remote. No potentiometers. No TVCs or AVCS. (I do like autoformers combined with transistor buffers. I think resistor attenuation is a better match with vacuum tubes)

* Must look good in living room. Prefer wood chassis. Conversation starter preferred.

* Tubes proudly displayed, not hidden in chassis

* Medium voltage gain

* Damper diode or solid state rectification. Damper diodes preferred. (I bought a bunch of 6AX4 damper diodes in 2015 in anticipation)

* State of the art power supply regulation

* Must be good value for money

More in next post...

Nice that the Raven ticks all the boxes! Seriously though, you’ve pinpointed (better than I could) what separates the Raven from a conventional Marantz 7C re-creation.

The preamps from the Fifties and Sixties followed a pattern of 2-stage 12AX7’s for lots of gain, a 12AX7 or 12AU7 cathode follower to knock down the output impedance, and plenty of feedback around the whole thing. Look at an Audio Research SP-3A or SP-6 and you see the same circuit. This is what most audiophiles think is "tube sound" for the simple reason that hundreds of thousands of preamps and integrated amps were built just this way, so it’s a very familiar sound.

But there are other ways to build a preamp, borrowing from studio electronics going back to the 1930’s. That’s the Raven, with no coupling caps, zero feedback, and a fully balanced circuit all the way through.

More technically, when the Marantz (or similar) circuit is compared to the Raven, there are 1, 2, or 3 coupling caps in the signal path. "Tuning" the sound of a classical preamp is usually little more than a cap swap, leaving the circuit itself untouched. The classical preamp is single-ended, relying solely on feedback to get distortion down to acceptable levels. And the sonics of cathode followers remain controversial, depending on the nature of the cathode load (resistive, inductive, active current source, etc.).