September 2017

World Premiere Review!
Raven Audio Silhouette MK 2 Reference Preamplifier With MM Phono Stage
A wonderful vacuum tube stereo preamplifier with the joys of tube swapping too!
Review By Ron Nagle

  The following review should be considered a continuation of the review of the Raven Reflection Mk 2 integrated amplifier that appeared in Enjoy the Music.com in September 2016. Since that time there has been an unfortunate series of natural climate related events that necessitated their move to a new manufacturing facility.

Unfortunate Trend
I touched on this same theme when reviewing the companion Raven Audio Reflection MK 2; it's about cutting corners. Nowadays you may find many expensive analog audio devices incorporating digital power supplies, but why? After all, linear power supplies do the same thing. You can pick up a catalog from a number of on line manufactures and order an inexpensive ready-made off the shelf digital power supply, one of hundreds of different types. Some of them in an effort to sound more linear (continuous) the designers increase the switching / sampling rate higher, to approximate radio frequencies. (Read: Noise and shielding). With this option does everything come down to money and profit? You can bet the house on it.

Some People Care
Over a space of forty three years I keep coming back to vacuum tube audio. It is there where we can still find smaller companies and a few people (like me) with hot solder burns on their hands. It seems to me Raven Audio a Texas Company is one of those companies that care. In part my conclusions are based on the fact that I can't find any corners that were cut in order to produce this Raven MK 2 preamplifier. To illustrate, Raven Audio builds their components in Texas and hand solders their amplifiers with point to point Teflon insulated wire. In addition Raven Audio developed and makes a separate line of state of the art Film Capacitors for sale to other manufacturers. At the top of the Raven line of Reference components. The CEO Dave Thomson provides from his own stash a selection of to die for near impossible to get no longer made rare vacuum tubes. This exotic mix of audio tubes includes three manufacturers I've heard of but never actually seen. There are three sets of spare tubes; among these are pairs of original, Tungsram, Brimar, and Valvo manufactured miniature dual triodes.

Nomenclature
The Silhouette MK 2 preamplifier is $15,995 and is CNC milled from a solid billet of aircraft grade aluminum as is the transformers cover on the top of the chassis. The remote control is also milled aluminum but with just two buttons that control volume up or down. The preamplifier measures 19.4" x 11.5" x 8.5" (WxDxH) and weigh 47 pounds. The MK 2 uses a total of ten vacuum tubes they are: OA3, 6SN7, 6B4G, 5Y3 two 12AT7, one 6922, and three 12AX7 tubes dedicated to the phono amplifier. . A less expensive line level version Silhouette preamplifier is available without the three 12AX7 tube phono stage. The front panel has three large control knobs. Left to right they are, Power, on /off, ALPS motor driven Volume control, and a Source selection knob. The Source selector switches between four unbalanced (RCA) positions. Three are line level inputs and the fourth is the unbalanced input for the Moving Magnet phono amplifier stage. Consequently at the back chassis are five sets of RCA jacks with one pair serving as an output to a power amplifier. And last two additional pairs of XLR jacks are intended for a balanced preamplifier input and an output to a power amplifier. There also an industry standard IEC power cord socket, plus chassis grounding stud for the phono stage amplification. There are two missing features that I wish the Silhouette MK 2 had. Both could be incorporated as functions of the remote control. The first would be a mute function and the second would be the expanded ability to switch between the four input sources.

Note: The amplifier literature states that the designers found no difference in sound quality between balanced and unbalanced connections. As a consequence the four input and output XLR jacks are optional. Of these the third XLR ground wire is made common to the negative leg thereby forming an unbalanced wiring configuration. And in keeping with that this MK 2 audition was accomplished with a one meter pair of unbalanced Analysis Statement Silver cables from the preamplifier to my Sanders ESL power amplifier.

Silhouette Sound
My ethics are such that it is always my goal to capture and describe the essential character / sound of a review component separately and independently from the components of that make up the remainder of my review system. Simple logic really, because if you don't have a reference system then how would you rally know how a component sounds? Upon tuning on the Raven Audio Silhouette MK 2 reference preamplifier with MM phono stage there's a 30 second power on delay as the tubes heat up. During this period there is a small blinking blue LED on the line select knob. It stops blinking when the amplifier is up to operating temperature.

The very first thing you will hear is an exaggerated tube sound; with the music sounding  a little too warm with a bit of augmented bass too. From among the extra sets of tubes supplied with the preamplifier I swapped the two Valvo line stage dual triode tubes and substituted two Tungsram 12AT7 black plates in the front row of the line stage positions (3 and 4). The result was a bit more speed and extension up top where dog whistle frequencies live. Somewhat better but still unmistakably tube sound. Even with broken in vintage tubes it takes about 20 minutes for the MK 2 to fully wake up. At that time the one note bass levels disappear and are replaced by a myriad of far more subtle harmonies. The result after everything settles down is the modern sound of tubes. That is the sound that I prefer. Knife edged transient attack is something I associate mostly with solid-state digital devices. The digital stop and start function even with higher bit rate devices. It does not allow for the time it takes for the complex interleaved tonal structures of music to decay naturally. The difference between the two becomes more apparent listening to something like the acoustic sound of a close mic'ed Cello. If you were sitting right next to that cello, you would feel the halo of air reverberating and surrounding the cello's wooden body. And you would hear the wood vibrating. It is a visceral wave front that impacts and sends vibrations to the surface of your skin. With a superbly captured close up recording the Silhouette MK 2 can get you there. The Silhouette Mk 2 conveys the overtones, timber and harmonic structures of the living event.

The Sound Of Vinyl
I saved the best for last; Raven Audio's Silhouette MK 2 optional phono preamplifier. The phono stage is designed for a high output moving magnet (MM) cartridges. The default cartridge loading is not adjustable and is fixed at 47kOhms. To do full justice to the preamplifier I purchased a new high output 0.5 mV limited edition Ortofon Silver moving magnet cartridge. I ran it for a while to let it break in. As is my ethic I do not list the records I sampled because you most certainly don't own the same recordings.

The MM phono stage of the Silhouette Mk 2 sounds even more like classic tubes. I did note a slight lack of high frequency extension. As a consequence it does imply a warmer treble. But understand, nothing is actually missing from the treble frequencies. This turns out to be a happy trade off. For it lends a warmer life like harmonic envelope to the sound of a human voice. There may be some person who can tell when a violin is a half note off. But my reference is the sound of a human voice this is something I know very well. Because of this I prefer to listen to a female vocalist. A perfect example might by Peggy Lee singing "Fever". It is here that subtle tonal inflections convey human emotions. The MK 2 paints the sound of a human voice and gives it meaning. That same tubular quality allowed me to hear some lower volume bass overtones that I never heard before. These are sub harmonics that are masked and ride along under the louder fundamental frequency.

Conclusion
I wish I could keep the Raven Silhouette MK2, but it is out of my reach. To me a natural sounding wide open soundscape is first and foremost on a list of must haves. I will remember the wonderful wide dimensional sound that fills my room. It is expensive, but it is so very hard to return to a lesser land of mere mediocrity.

Remember to Enjoy The Music and from me...

Semper Hi-Fi!

Reference System
Sources:
SOTA Sapphire turntable with Grado laboratory reference tone arm, Ortofon Silver MM cartridge.
Sony UHP-U1 Universal Disc player.
Music Hall upsampling DAC 25.3 with headphone amplifier, Yamaha WXC-5 Wi-Fi Blue tooth receiver.

Reference Amplification:
Sanders ESL power Amplifier

Speakers:
Aurum Cantus V30M, Mark Daniels Omni Harmonizer tweeters.

Speaker Cables:
Kimber Kable 12tc 11 ft. And a Kimber Kable 8TC 18" to tweeter speaker.

Interconnect Cables:
Monster Reference 4 pairs, two-0.5 meter, 1 meter and 1.5 meters, Nordost Red Dawn 1meter, Audioquest Cinnamon XLR 1 meter.
Chord Silver Siren 1 meter, Homemade Teflon RCA 1 meter, Autobahn 0.5 meter digital

Power Conditioning:
Wire World 10 gauge IEC line cord, Power Cords: Kaplan Cables 12 gauge IEC

Specifications
Type: Vacuum tube stereo preamplifier with optional MM phono stage
ALPS 20kOhm motorized volume control with +6dB gain 
Upgrade available to Tokyo Ko-on attenuator upon request
Input Terminals: One pair balanced XLR and three pair unbalanced RCA line level
Input Impedance Phono: 47kOhms
Output Impedance Line Stage: < 200 Ohms
Tubes:
    5Y3/5AR4/5V4/5V3A/5R4 - Rectifies tube power supply
    6B4G – Regulator
    6SN7 - Voltage adjuster
    OA3 - Reference voltage
    Two 12AT7 - First stage amplifier
    Two 12AU7 - Current supply for first stage 12AT7
    Two 6N6P/6DJ8/6922 - Preamp output stage cathode follower
    Three 12AX7 - Phono preamplifier section
Dimensions: 19.4" x 11.5" x 8.5" (WxDxH)
Weight: 47 lbs. 
Price: $15,995

Company Information
Raven Audio
6840 W. 70th Street
Shreveport, LA, 71129

Voice: (318) 703-4542
E-mail: info@ravenaudio.com
Website: www.RavenAudio.com