Spatial Audio Raven Preamp

I want to revisit what Lynn said about subtle content that is present in two channel recordings.  The content that gives the ethereal sense of space, and the very subtle reverb that is present from recording techniques or actually added by the producer.  I have owned really good stereos for years, both rebuilt vintage-based, and my own creations.   What the Raven (Revelation) preamp and the matching Blackbird amps do is to present this information.  It is not masked as in most systems, including some very good ones I have owned, and some very expensive ones I have heard at audio shows.  I am listening to the final versions of the Raven and Blackbird amps, and I hear these things that I have never heard before in recordings I am very familiar with.  It adds a whole new level of enjoyment and has been discussed, you can hear the intent of the musicians and the producer or recording engineer, and the room if the recording is from a live performance.   

The shoebox mono prototype amps mentioned by @sjsfiveo ​​​and ​@whitestix will give a portion of this effect and are very good.  The final version of the amps have it in spades.  We have improved both the preamp and amps just a wee bit since the Dallas show and I am looking forward to the next demo of the Revelation series so that others can hear what I get to enjoy in my living room daily.   I completely understand that a $19,995 pair of amps is outside the budget of many folks, but I do thoroughly enjoy playing them for people so that they can hear what is possible and what we have been up to.   Most people (myself included up to two years ago) have never heard this sort of presentation.  From a design standpoint, I understand exactly why all of our choices work well with this circuit idea, and why the system sounds as it does.  But hearing it is quite astounding to me.  It just vanishes and leaves the music hanging space for you to enjoy.

@sjsfiveo Yes, price has very little relationship to sound quality beyond a certain point.  One walk through an audio show will make that abundantly clear.  The Revelation series project was about designing the best sounding preamp and amps that we could using ideas that Lynn has been working on for decades, that have their basis in wonderful circuits and approaches developed a LONG time ago.  We implemented those ideas with modern power supply, filament supply, transformer, and attenuator technology that I had been using for a number of years prior to that.  The idea was to build the best sounding preamp and amps we could and then price them based on the build cost and required profit margin for the manufacturer to stay in business, while paying real technicians in Utah, real living wages.  You really cannot build gear of this quality on a shoe string budget.  That said, the gear does not cost six figures, nor does it have to!   

I have Don's 300b Shoebox Mono's and preproduction Raven and the combination is stellar. The music is authentic and rich and musical with the ability to listen to hours and hours without feeling tired or fatigued. It has everything I've always wanted in my system without overreaching. It has all the detail you could ask for without being analytical, clean but not to the point of being sterile, full without heaviness. I'm so happy with the sound that most if not all other systems I listen to anymore just don't do it for me even many multi 6 figure systems one of them being a $600,000 system.

I expect to be there for the Oregon Triode Society demo as well. Maybe I’ll meet some old friends ... I joined the OTS way back in 1990 or so, at the second meeting.

Way too far to drive all the way from the Denver metro area, so I’ll fly again, but take Business Class this time. My days of flying in Cattle Class are over, can’t handle the crowds or the itsy-bitsy seats the airlines use now. I do miss the Amtrack sleeper service from Denver to Portland ... that was a very nice train ride.

Looking back, I look at the incredible complexity of that Shadow Vector patent (which I invented solo, unlike the three-person CBS team) and how I really jumped in at the deep end of the pool when I joined the hifi biz professionally. Working as a commissioned salesman was such a horrific experience I was strongly motivated to get out of Los Angeles and move to Audionics in Portland, Oregon.

Although I had my differences with Audionics, they did believe in me enough to hire me to build the prototype, which took two years of hard work. That stretch was one of the biggest pushes I’ve done, along with finally completing my Psychology degree a few years later. Speaker design was considerably easier.

Shadow Vector Patent

Thanks for the kind words!   Working with Lynn has been a pleasure and I have increased my knowledge of tube circuits considerably since I met him..   He got me to consider "going outside the box".  The Raven and Blackbirds are about leaving the box.   Paradigm shifts are always healthy, or at least the consideration of them.  I have built or restored a LOT of tube circuits over the years and nothing I have ever heard or built or restored can touch the Raven and Blackbird sonically.  I think a lot of that is due to what Lynn discussed above about all the very subtle spatial cues that can be lost with lesser electronics and speakers.  I hear things with the Raven and Blackbirds that I have never heard in any stereo before.  Those who have heard them agree.  They don't sound like what you are used to hearing.  They push through boundaries.

As for reviews... we are working on it.  The final production versions of the preamp and amps are just finishing.  These include new cases from a different woodworker.  We didn't want to send out review units that did not look exactly like the final product.  Sonically the gear has been stable for a while, but the final cases had to be sorted out from a reliable supplier who could meet our demand.  That has happened and a set for review will be finished in the next month or so.  We have made arrangements with Positive Feedback to send them a set in the fall, and expect a review by the end of the year.  Of course we hope that owners will chime in as on this thread.   

Lastly, I don't know what shows we may attend, but I am pretty sure there will be a special demo in Portland for the Oregon Triode Society.  Maybe in August or more likely in October.  We will have a large room for two full days with the Raven and Blackbirds, and of course Spatial Audio Lab speakers.   I will be there along with the Spatial team.  So if you are in the Portland area, or perhaps want to make the trek from Seattle, you can hear the preamp and amps paired with top end gear in a good room without all the buzz of an audio show.  When we have a schedule we will let everyone know and hope to see some of you in a relaxed setting where we can all hang out and listen to music!

That's why I was pleased to collaborate with Don Sachs, starting a couple of years ago. I already owned his preamp, and I was quite impressed he had decades of experience on the insanely complex Citation I and Citation II preamp and power amps. Those products are not for the faint of heart ... Stu Hegeman was a seriously out-there guy, and a legend back in the Sixties.

Listening to my Raven and Don/Lynn's 300b monos, with my Cube Audio Jazzon speakers, is an experience that transports me to another realm... of pure musical enjoyment in an astonishing fashion.  I am not embellishing what I am hearing one bit.

I first connected with Don over 15 years ago when Jim McShane passed him the mantle of upgrading vintage Harmon Kardon amps and preamps, an almost insane task.  He upgraded my C-I, CII, and C-V to astonishing levels.  However, he thought about perfecting the Tubes4Hifi octal-based preamp with a more simplified topology and certainly took that inherently excellent design to masterful levels with his first preamp, his second preamp, and now the Raven.

My tubeoholics friends marvel at the sound of my system with his and Lynn's newest creations in my rack.  As you can see, both of these designers work tirelessly to provide gear to astonish listeners with vivid tonally pure sounds, where the music just seems to float between the speakers and invites me to enjoy my music to the maximum extent possible.  Don for sure listens to his system daily and hourly so he lives with his creations in his own systems and always has an eye towards subtle or significant improvements in his electronics.  I am a big fan and his preamp is simply outstanding.  I'd imagine his 300b monos, while pricey, would fair well against any of uber expensive 300b monos in the market.   Maybe one of the audiophile magazines will seek these units for review.  ;-)

I started my career in audio with the invention, patenting, and prototyping of the Shadow Vector quadraphonic decoder, back in 1973. That SQ/stereo decoder was specifically designed to preserve ambient cues and spatial impression, without adding anything like a reverb circuit, or taking anything away from the source material.

There’s a lot of content in a 2-channel recording that is destroyed on playback, or is below the threshold of audibility. This is not the fault of the recording, but the playback system. In general terms, this is low-level information with L/R phase angles between +/- 45 and 180 degrees. A (very good) quadraphonic decoder will route this information to the sides and rear, depending on phase angle, without affecting the frontal image or deforming it. Ideally, random-phase reverberation (from spaced mikes, reverb plate, or good digital reverb) should appear as an evenly weighted sphere around the listener, with no bumps, holes, or hotspots, just as it is in real, physical acoustic spaces. Again, this random-phase information is present on all stereo recordings with even a slight sense of space, because studio professionals consider "dry" vocals intolerable, so some reverb is added on just about everything. And the correct method of presentation is spherical, to match real acoustic spaces.

Unfortunately, 2-speaker playback abbreviates the most realistic spatial presentation, although some speakers preserve a vestige of it. Smooth dispersion patterns, freedom from resonant energy storage in the drivers, and freedom from diffraction artifacts (no sharp cabinet edges) can allow the sound space to leave the confines of the speaker cabinet (as it should in a good loudspeaker). Most listeners never hear this, but it’s still there on the recording, waiting to be heard. (And no, it doesn’t take 11 speakers to preserve spatial information. That’s for special effects in movie theaters.)

For some reason, electronics can also affect the spatial impression. I suspect that many electronics destroy, or alter, the low-level interchannel signals that convey this spatial impression, somewhat akin to MP3 lossy compression discarding "unnecessary" low-level bits. Nothing as violent as that happens in normal electronics, of course, but still, it subjectively sounds like bit reduction, with a loss or "air", spatial realism, and realistic tonality. I am not sure of the mechanism, but high-order nonlinearities, power supply switch-noise grunge, correlated noise, and odd, hard-to-pin-down capacitor colorations (possibly chemical reactions in the dielectric) all seem to play a role in shrinking the sound stage and destroying the ambient impression.

That’s why the Raven and Blackbird minimize energy storage in the signal path. There are no feedback loops, either local or overall. There are no coupling caps, on the input, between stages, or on the output. The balanced circuit presents a nearly constant demand on the power supply, which is further smoothed by the shunt regulator tubes in the preamp. The signal goes in, is fed to a Class A balanced pair of very linear vacuum tubes, and is transformer re-balanced on the way out. No signal recirculation, no phase inverters, no cathode followers, and no secondary side chains (DC servo circuits, dynamic loads, etc.), even at very low levels (which is why it is so quiet).

@donsachs You touched upon the primary reason I am moving back to tubes from solid state. No question there are very competent solid state electronics that can create a 3D soundstage.  My Ayre K-1xe does a better job at this than the Ayre K-5xeMP preamp, for example.  I have been able to attain a wide soundstage that extends beyond the speakers and has good depth and height on certain recordings.  What the Raven seems to deliver as described by yourself and other users is what I've been missing.  The wait is killing me.

@jc4659 I can assure you the preamp sounds believable.  The sound stage is entirely dependent on the recording.   On most every recording except mono ones, the image in my system using the Raven and the matching Blackbird amps will always extend several feet outside the speaker boundary with good depth.  Smaller sounds are physically smaller and things that are farther away are rendered that way.  On other recordings, the music will extend towards you and partially wrap around to the sides.  I use the analogy of omnimax theater for the ears.  Again, it is totally dependent on the recording.  I will get in trouble for saying this, but I will say it anyway.  My experience is that solid state amps tend to flatten the sound stage just a bit and make it more two dimensional.  I am sure there are great SS amps that don't do this, but most of the ones I have heard have this effect, at least to a degree.  A very competent tube amp generally is better at a 3D soundstage, provided the speakers are tube friendly.  Of course YMMV.

@terrapin77 Thanks for posting your early impressions of the Raven preamp. Happy to hear you're loving it!  I'm not sure I understand the meaning of "the music floating around me" but as long as it sounds real (believable) is what's important to me. Do you mean immersive?  I can't say I've experienced this before in my system where all music is spread out in front of me and in a plane behind the speakers. I'll just have to wait a few more weeks to experience it first hand.  I look forward to reading more comments from you and others about the Raven preamp from Spatial Audio Labs.

The Raven does get my curiosity going into overtime.

The idea of experiencing one in use is quite an attraction, the idea of one with the owned 845 mono's well that just double cool 😎😎.

All that I have come to know about the design intent to the working model has been a thoroughly good read, and the entirety of my local HiFi Group were supplied the Link, to share in the content of the Thread. 

@terrapin77 Thanks for posting.  To me, qualities of the Raven are transparency, tonal correctness of instruments and voices, and that ethereal sound stage.  The absolute blackness helps with all of that.  It doesn't really sound like anything except the music.  The Blackbird 300b amps have the same sonic signature, or rather lack thereof.  It is very different than what you are used to listening to, but you adjust very quickly and then nothing else sounds quite right:)  My old preamp and amps, which are quite good, sound veiled by comparison. 

After two weekend listening sessions, I now have about 25 hours on the Raven. I can honestly say this is my final preamp. On AudioCircle, sjsfiveo described the preamp as blacker backgrounds, greater detail, quieter and the sense that the music just floating around me." Him, like me, had a Don Sachs preamp before the Raven. I’m in 100% agreement with his review. In fact, the sense of the music floating around was the first thing I noticed when I played it in my system for the first time. I’m also in agreement with Don that the Raven is very transparent. It captures the nuances and subtleties of the music ensuring a lifelike and immersive listening experience. Even though I tell myself on a daily basis to stop spending money on audio gear, I’m 100% happy with my decision to buy the Raven. Now, I wish I had the funds to get the Blackbirds!!

Yes, that is how I currently run it.  I'll call David Whitt @ Spatial this week to inform him about the tube change.

@jc4659 I see your phono stage also has xlr output, so you can run a fully balanced system, even with phono into the Raven, which is great.  I would expect it to work well in your system.

Yes I think I would try the Linlai tubes.   Your system is fully balanced, so the Raven should shine there.  Please do post a review when you have put a few hours on it.

@donsachs Hi Don. Initially the Raven will be paired with a Pass Labs X350.5 power amp.  At some point I’ll need to downsize the amp but ithe Pass drives and controls my Verity Audio Parsifal Encores very well. The analogue side is a Linn lip-12 with a rebuilt Troika MC cart into an Ayre phono pre.  On the digital side I stream or play files from a MacBook Pro running Audirvāna and Qobuz which feeds a Musetec DA-005 DAC.  CDs are spun with a Meridian 508.24 used as a transport only. While I will likely make additional changes elsewhere in my system I am hoping the Raven preamp will be an end game component.  The Raven will be replacing an Ayre K-1xe preamplifier which is itself very good.  Overall, I would characterize my system as slightly on the warmer side of neutral.  I am wondering if the linlai tubes in the Raven might be a better fit.  Open to suggestions.

@jc4659  Yes, please do.  What amps and source(s) are you planning on using with the Raven?

I placed my order 2 weeks ago and chose the cherry base.  The build should be complete by the end of May according to Spatial.  I will post my impressions after about 20 hours of burn-in.

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.

@lynn_olson Fascinating but do you ever sleep?🤔

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.

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

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.

@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.

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.  

@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!

@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. 

@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.

@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

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

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

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)

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).

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.

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

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.

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

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

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

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 

is spacial audio the name of don sahcs work?

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

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.

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