Spatial Audio Raven Preamp

@fthompson251 I pulled the trigger yesterday.  If it all works out as it should this will be my endgame preamp.

I would appreciate your findings if you don't mind when you get it settled into your rig, thank you! It would also be the end gamer for me as well.

Don Sachs is awesome, man. Met him for the 1st time in Dallas. Very knowledgeable. 

is spacial audio the name of don sahcs work?

Mine is delivering on Tuesday.  I sold my Dons Sachs preamp to partially fund the purchase.  Don has retired from building so the only way to purchase the Raven is through Spatial 

@terrapin77 Please post your impressions after the new preamp has settled into your system.  Thanks!

The Don Sachs and Lynn Varley Revelation (Raven) preamp and Blackbird 300B amps seem extremely interesting. I've followed their 300B thread here on Audiogon (where Ralph from Atmosphere has added a ton), and it is a master class in tube amp and preamp design and theory. I've learned a ton; it's a long detailed read.....and above my level of knowledge, but I've learned a lot.

I'd love to read your experiences

It is very good to see the Raven Pre Amp has began to get a following and committed purchases. 

I await in eager anticipation the user reports from adding this design into their home systems

I expect my Raven will be delivered in about 5 or 6 weeks. I already have Don's dual mono 300b amps and the newest rendition of his Model 2 preamp, so I will get to compare them side by side.

That should be a synergistic combination so I’m anxious to hear your thoughts as well as the comparison between preamps.  Thanks!

I hope you folks like the Raven (which are built and sold by Spatial Audio Labs). It’s a miniature version of the power amp, with one stage of gain instead of three. It has both RCA and XLR inputs, with the balanced input going straight to the 6SN7 grids, and the RCA going through a studio-quality input transformer (which converts the signal to balanced). The volume control is a special-order Khozmo dual mono unit, with volume and L/R balance on the remote control. The output is also transformer coupled, with both RCA and XLR balanced outputs.

Don Sach’s previous preamp had a special SRPP circuit, which used clever noise-cancellation techniques to reject power supply noise. The Raven similarly uses inherent circuit balance to also reject power supply noise ... although there isn’t much, since the power supply regulator itself has 130 dB of noise rejection.

Probably the biggest sonic difference is the previous Don Sachs preamp used a cathode follower and a very high quality coupling cap in the final stage, while the Raven uses transformer coupling to accomplish the same thing.

They are custom-design Cinemag, optimized for our circuit. They are not off-the-shelf parts, which have bandwidth problems with the output impedance of the 6SN7.

The 6SN7 is one of the best tubes ever made, but is not easy to match with most transformers. That’s where Cinemag came in, who saw the 6SN7 as a fun challenge. Several prototypes later (design, computer model, build, measure, listen, and repeat the cycle), we arrived at the production models we’re using now.

The Khozmo volume control is also optimized for this preamp, with a different signal path than most preamps. The Raven is balanced throughout, from input to source selector to volume control to vacuum tube to output.

One nice thing about transformer coupled balanced construction is the risk of sending DC pulses to a delicate transistor power amp are greatly reduced. (Even when a transistor amp is switched off, a DC pulse of more than a few volts can damage the input transistors.)

P.S. How does the output transformer protect a power amp? First, there’s a 4.5 times step-down ratio, reducing unwanted transients by a similar ratio. Second, the circuit itself is balanced, instead of a single-ended cathode follower exposed to a hundred volts or more. Circuit balance is typically 3% or better, reducing potential transients by a similar amount (about 30 dB). Third, and most important, transformers can never pass DC, unless the windings themselves have failed. By contrast, capacitors may pass "leakage current" and gradually short out as they age (a well-known problem when restoring vintage electronics).

The Raven has delivered.  About to get it hooked up and do some listening. I'm not very good at describing audio playback, but I will do my best.  The preamp is absolutely beautiful!! My full system is below.

Lumin U1 Mini streamer

Audio Mirror Tubadour V DAC

Spatial Audio Raven preamp

D-Sonic m3a-1200s amp

DIY Gunned MMGs (have a set of the Caladans on order)

That’s great news!  What were you using for a preamp before that you will be comparing the sound to?

@jc4659 I was using Don Sachs preamp that had his last updates.  I sold it to partially fund the Raven purchase 

@terrapin77 

Yes, please let us know how the Raven mates with your system and your impressions.  It will help others get a data point on a new product that is finally reaching production after 2 years of development.  Spatial is starting to crank them out now.  They are all hand built and point to point wired and they do take time to build.  I believe they will have a 45 day return policy, with little or no restocking fee if you pay the shipping.  So I suppose one could try one relatively risk free.

I use one, and I find it is totally transparent, but I am totally biased:)

cheers,

Don

@donsachs Curious if you are using your pre with stock tubes or not.  I am expecting to receive my pre by the end of May but since I chose the cherry base perhaps a little longer. On one of the other forums someone who received their preamp commented "OMFG" upon first hearing it.  Waiting rather impatiently for the follow up.

@jc4659 That was me who commented OMFG.  I'm planning a writing a review after I get some more hours of listening.  I've never reviewed audio equipment so I'm planning on writing down some notes over the next 3-5 listening sessions. 

@jc4659 I am using the Shuguang flagship WE6SN7plus in mine.   They are finally back in production.  That will be the base tube going forward.  The hand selected Linlai E-6SN7 is more expensive and the upgrade option.  I would say they are both just superb tubes.  The Shuguang is a bit warmer and has almost all of the detail and air of the Linlai.  The Linlai has a tad more air and is a tad more neutral.  That isn't to say the Shuguang is syrupy or the Linlai cold.  You would be happy with either, but if  your system is a bit bright, then pick the Shuguang, and if your system could perhaps use a bit more air, then use the Linlai.  Both are just wonderful tubes.

You have to realize that I have a Lampi Pacific 2 DAC, the matching Blackbird 300b amps, and some amazing open baffle speakers so my system allows me to hear even subtle differences between tubes.  If you had a more pedestrian DAC and amp and speaker in the chain, then the differences would be masked.  The point is that the Raven is totally transparent to my ear and will let you hear everything in a way that most preamps cannot.  My 2 cents, and yes, I am totally biased since Lynn and I designed it!

I have had the pre-production "shoe box" 300b monos as well as the Raven for several months and have owned all Don's earlier preamps and the Kootenai.  They mate very will with my Cube Audio Jazzon speakers.  Outstanding gear, no question.  

@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?🤔

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.