Sep 092011
 

Shortly after receiving the StereoKnight Silverstone B&R passive magnetic pre-amplifier that I reviewed positively recently, its bigger brother the Enigma 1.0R arrived. The much larger box the delivery man brought to my front door gave the game away re the difference in size between the two pre-amplifiers; the Enigma is at least twice as big. How so you might ask as it too is a passive magnetic pre-amplifier? Put simply this pre-amplifier while a passive in essence has much more active circuitry in it than the Silverstone. Not only do you retain the remote control functionality of the Silverstone but you also gain a valve stage in the shape of a pair of 6922 and a pair of the 6H30 ‘Super Tube’ that Balanced Audio Technology made popular. This particular valve was brought/introduced to the west by Victor Khomenko of BAT and for quite awhile was only used in BAT products before being discovered and used by many other audio companies now days; including StereoKnight in their Enigma pre-amplifier.

However despite the active valve aspect of this design the Enigma 1.0R pre-amplifier still has passive magnetic technology at the core of its functionality. I will let StereoKnight explain how….

‘The unique design of this new tube preamp model “magnetic Engima-1.0R” can be implied from the prefix of the name: “magnetic”, which indicates the direct origin from StereoKnight’s other magnetic passive pre-amps. Not only does the Enigma-1.0R use 4 transformers for volume attenuation, but it also uses another 2 transformers for signal output and two more for the power supplies!’

These 4 transformers are used as part of the balanced input and 2 transformers used as part of the RCA input signal distribution, these then feed the signal to a volume control which attenuates in 33 steps which are connected to 33 digital relays. These relays are controlled by a CPU/IC that receives the signal from a digital stepper which is activated by either turning the volume knob or after receiving an instruction from the remote control.

StereoKnight go on to describe how ‘the remarkable level of performance’ they claim to have ‘achieved with an all new, audio and power supply circuits. The new audio circuit is pure tube, Class-A, with zero feedback, utilizing a total of four long-life tubes (2 6H30 as the drivers and 2 6922 as the amplifiers); and further, it is ture balance ciurcuit design in both input and output stage with the support of 4 volume control transformers. For balanced input signal, each channel has two oppsite signals: plus and negative one. Theoretically, it needs 4 transformers to attenuate 4 seperate input signals for a two channel source.

The magnetic Enigma-1.0R is direct upgrade from the StereoKnight Silverstone Reference version of the magnetic passive preamp by utilizing tube amplifiers and output transformers. One great advantage of this magnetic feature is its capability for optimal matching with any amps and interconnects while accepting any sources input at various impedance levels. With the least interfering audio consideration, the power supply is divided into two seperate parts: main power transformer used to power the audio circuit, a smaller power transformer is designed to support remote control and LED display functions. A MOSFET is just used for both voltage stablization and constant current supplying, which enhances the reliability and makes tube amplification linearly to the best.’

The Enigma as I have said earlier is about twice the size of the Silverstone Reference pre-amplifier, however it is visually the same, bar the diagonal slots over the valves for ventilation. It has 4 RCA inputs (to the SilverStone’s 3), 3 XLR inputs, 2 RCA and 2 XLR variable level outputs and exactly the same remote control functions as the SilverStone pre-amplifier.

External and internal fit and finish is to the same very high standard as the Silverstone B&R Reference. The internal space of the pre-amplifier is well laid out, with all cabling neatly routed within the pre-amplifier and there is also internal bracing which acts both for strengthening the case and as shielding between the various sections. The other notable aspect to this design is the number and quality of capacitors used.

One other thing of note is the slightly higher output voltage that the Enigma has over the Silverstone B&R Reference. However at no time was this an issue for me, in my review system and I only mention it here as for some it might be. I therefore suggest you avail of a home demonstration to fully check compatibility with your system.

As with the Silverstone B&R there were no times during the prolonged loan period that the Enigma pre-amplifier misbehaved, it always functioned flawlessly.

Warm Up

Unlike the totally passive Silverstone, the active circuitry in the Enigma did benefit from being powered up for about an hour or so before serious listening began. There is no standby option on this pre-amplifier, so leaving it on 24/7 will shorten the life of the valves dramatically and as I did try leaving it on for awhile and I heard no improvement doing this, I don’t recommend leaving it on.

One other area of interest, that can be a tad controversial is ‘how long does it take to run a new product in? Well in the case of the Enigma while I am pretty sure this will be vital (only borrow or listen to a well run in example if you are auditioning one) I can’t report on how the sound changed/improved during this ‘run in time’ as the Enigma I was loaned for review was already well run in.

Review System

Wanting to keep as much continuity as possible during my time with the StereoKnight pre-amplifiers (I had in for review), in order to get a feel for them as individual designs but also as part of a family of products, therefore I have mostly kept to the same system, to do these reviews i.e my downstairs reference system. However keeping in mind that as good as the Meridian G56 power-amplifier is and please make no mistake about that fact, I knew I needed to, at a later stage of the review, to up the ante by putting a more up market amplifier into the system; which is something I did, in the form of an Art Audio Diavolo; more on that, in detail, in part two of this review.

However before describing the rest of the review system I feel it worth saying that I would have loved to have tried the Enigma pre-amplifier with the sadly now gone AirTight ATM-300 as I feel the two would work well together but sadly I was unable to do that.

So, bar the addition of the Art Audio power-amplifier the system used for this review comprised of the Moon Andromeda CD player, Marantz SA7 and a Technics 1210, SME 5, Audio Technica ATEV33 MC cartridge, BAT VK10Se phonostage, Meridian G56 power-amplifier and the Anthony Gallo Ref 3.1 speakers.

All the equipment was housed on Clearlight Audio Aspekt racks, bar the power-amplifiers which sat on the top section of a Mana Reference table , which I used as an amplifier stand. This was fitted with the excellent Track Audio spikes as an interface between stand and the carpeted concrete floor. Interconnect cables were mostly Tru SoundZ and Atlas Mavros with speaker cables Atlas Mavros. Isolation products in the form of SSC platforms, Clearlight Audio RDC Cones and Sound Mechanics M8 cones were used and mains cabling was by Audience and Analysis Plus. No mains conditioners or filters were used during the review.

Music used

I mostly stuck with the same recordings for this review as I had with the Silverstone review, again to keep a degree of continuity, which I felt vital to establishing the ins and outs of this design compared to the Silverstone B&R passive magnetic pre-amplifier.

Thomas Dolby – Aliens Ate My Buick

The Dali Demo CD


Listening via the Meridian G56

After spending a little time listening to the Enigma casually and before getting down to some serious reviewing of the pre, I spent a few days trying various interconnects and isolation devices just to see if the choices I had made with the Silverstone B&R pre-amplifier were still relevant with the Enigma and for the most part they were. I kept the Tru Soundz interconnects as frankly they sounded excellent with the Enigma;  however unlike the Silverstone, the addition of an active circuit meant that I felt that mains cables did make a difference to the sound; as too did the use of isolation devices. I ended up sticking with Sound Mechanics M8 Cones under the Enigma and using an Audience AU24 mains cable as the best options in this current system configuration.

One other change I made to how I used the pre was by installing 4 Tube Shop Valve Damping Rings, one over each of the 6H30’s and also the 6922 valves, as using them, rather than the supplied valve dampers led to a slightly more open sound. I also used more of these valve dampers on the Art Audio amplifiers valves as well.

Once all the little details were dealt with and folks attention to detail in system set up is important, I began listening seriously and the initial treat casual listening had suggested I was in for was fully realised during later more prolonged listens. I had hoped the Enigma would slot into the reference system as easily as the Silverstone B&R had, in order to keep a review context and thankfully it did.

The Enigma has a beautiful open and detailed presentation, with just a hint of extra warmth to the sound but this was not the extra warmth that tubes bring to the party as such, but instead the extra warmth that having a fuller bandwidth brings. Don’t get me wrong here, the Stereo Knight Silverstone compared to the Enigma is not a lean upfront sounding pre, all detail and no subtlety, as its not, but comparing it to the Enigma revealed that it was just a tad leaner in the tonal palete unlike the slightly richer Enigma.

The Enigma also has a broader, deeper and slightly higher soundstage over the Silverstone, within proportion though, so not an overblown super magnified view of events. Instruments and vocals also had more solidity and weight to them, being more three dimensional and real to the slightly less three dimensional Silverstone and the much flatter sounding Meridian pre-amplifier.

The Enigma was also much better than the Silverstone in digging deeper into the recording, allowing the listener to hear everything but in a way that was musical and not destructive. Quite often in audio, equipment that allows you further into the recording does so in a way that pulls the listener away from the performance, the spirit/essence of the music and instead presents the music in a striped apart way that exposes all the flaws of the recording. The Enigma is transparent but manages a neat balancing act between musicality and detail retrieval. I much prefer this approach to music reproduction over the type of products that have hyper/ruthless/transparency as a design goal. If it’s not musical, frankly I find myself fatiqued and cut listing sessions short; at no time did the Enigma in the context of my system fall into that camp. I found myself sitting up late at night running through all manner of music as I had with the Silverstone. This is always in my view a good thing as a system or component that influences your music choices in one particular direction or another is usually doing so, as its flaws are influencing your choice; i.e to only playing what sounds good on it. Not so the Enigma pre-amplifier as it was sending me off in all directions to uncover and unlock the rich musical potential in all sorts of music.

Of course it was important for me to stick initially with the recordings I had used during the Silverstone review and I did so. On the Thomas Dolby album Aliens Ate My Buick, tracks like Pop Culture and Ability to Swing showed the Enigma to have the same ability to do pace, rhythm and timing but with a wee hint more than the Silverstone B&R. Bass was excellent, deeper and richer than the Silverstone but with no hint of it being stodgy or fat, in fact bass when the recording had it was highly nuance and articulate.

On comparing Budapest by Blimp via the Silverstone to the Enigma, the Enigma had better separation and detail on the massed choir voices. So in much the same way, as the Silverstone was more open and detailed than the Meridian G02 pre-amplifier the Enigma was over the Silverstone. Clarity and definition was also superior. Truth be told I sat through the whole album both off CD and on another occasion vinyl.

Another long used and trusted recording, Hugh Masekela – Stimela off the Dali Demo CD revealed that the Enigma was digging deeper into the recording in the area of acoustic space and extra clarity. The ebb and flow of the background instruments was portrayed in a beautiful gentle and sensual way with the rich timbre of the vocal being nuanced and full of emotion. All the noises the audience was making, was clearer, even down to separate voices.

The sounds of the drums, sax and percussion on this recoding were much more real sounding than the Silverstone and the Meridian pre-amplifier, with extra insight into the relationship between each other and their positions in the acoustic space of the venue, via the Enigma another veil had been torn down as the Silverstone had done previously over and above the Meridian G02 pre-amplifier.

Hugh’s trumpet playing was more palable and the actual breath behind each note was much clearer than via the other pre-amplifiers but as I have mentioned earlier this extra clarity and detail was achieved with no loss in musicality, none whatsoever. Percussion such as strikes on cymbals had more space and decay than before and the hits on drum skins were again more obvious than it had been before. With my eyes closed (something I always do while listening) I was more there than I had been with any of the other pre-amplifiers in the system.

However I had a nagging feeling that the Meridian G56 power-amplifier, as good as it is, and it is very good, that just maybe, I needed to use a more transparent amplifier just to see if there was more to be heard/had  from the Enigma. In order to do this I cast my net out to see if I could pull in an amplifier to do this and one was forthcoming in the form of an Art Audio Diavolo.

More Listening… The Diavolo cometh.

Towards the tail end of the main review period an Art Audio Diavolo single ended, 13 watt, class A, valve power/integrated-amplifier came into my possession and as I am always keen to try stuff out I hooked it into the main system not really expecting it to drive the Anthony Gallo speakers correctly and shock horror it did, although I felt that my Ruark Equinox’s were ultimately a better sonic match, so after listening for awhile with the Gallo’s I replaced them with the Ruark’s. However while still using the Gallo’s I felt that the Art Audio amplifier had opened up a whole new window onto the Enigma’s abilities that the Meridian G56 power-amplifier had been veiling to a certain extent and with the swap in speakers, while there was a slight trade off re the addition of cabinet coloration (something the Anthony Gallo speakers lack) the Ruark’s were still the better choice for continued listening.

As the cabling in the main part of the review, bar mains cables and speaker cables, was TruSoundz, I opted to hook the Diavolo up to the Enigma via a 1m length of RCA to RCA Revelation cable I had been sent for review (1) rather than use any other make of cabling for this part of the review;  though I should point out that I did try a few others before hand but as with the Silverstone I felt these cables were a more synergistic choice with the Stereo Knight components and the rest of my system.

The Diavolo was positioned on three M8 Sound Mechanics cones, on top of my Mana reference platform (initially) which has the bottom spikes replaced with Track Audio ones but after some time I opted to replace these with three Clearlight audio RDC cones. With the RDC under the Art Audio the sound was less forward and better balanced.  As I had with the Meridian G56 power-amplifier I continued to use an Audience AU24 mains cable with the Diavolo. Two unused RCA inputs were capped with Telos RFI caps.

After optimising the Art Audio within the system I relistened to the tracks and albums (and a few more as well) that I had before and as I have hinted at above I found that the Art Audio amplifier had removed a bottle neck and was now allowing  me to hear more of the StereoKnight Enigma’s abilities.

All the positive things I had heard and I mention in part one of this review where still there but with more beside. With the Diavolo in the system it was more obvious that the Enigma was letting more of the musical performance through, over and above the Silverstone or Meridian pre-amplifiers. The soundstage was now a tad deeper and wider and instruments and vocalists sounded more three dimensional but it was the way music now had a wee bit more poise and delicacy at times (when the recording possessed it ) and the whole performance, the message contained in the music, the emotional intent was now much more obvious than it had been before with the Meridian power-amplifier.

I am very conscious that at times writing about subtle changes in sound quality can appear over blown or very dramatic and while the jump in performance over the Meridian pre-amplifier and the Silverstone B&R the differences with the Art Audio Diavolo, were not to quite of the same magnitude but make no mistake here, the Art Audio Diavolo kicked open a door to allowing me to hear more of what the Enigma pre could do.

Conclusions

The Stereo Knight Enigma 1.oR pre-amplifier takes what the Silverstone B&R does well and ads to it by quite a big margin. The difference in price between the two pre-amplifiers is not inconsiderable but what your extra £1000 gets you is quite a big jump in performance in the areas of clarity, detail, greater frequency extension and insight into the spirit of the music. In a way I guess moving from the Silverstone B&R to the Enigma is a wee bit like going from a fantastic mini monitor speaker to a floor standing speaker; you get more weight and scale but in the case of the Enigma you don’t gain any stodge for your extras.

The Enigma pre-amplifier sits just to the warmer side of neutral and the Silvestone just to the leaner side of neutral and not by very much. I can see some preferring the Silverstone’s slightly leaner sound depending on system set up but as good as the Silverstone is you would in my opinion be missing out on the extra magic the Enigma can weave with your music if you were not to have a listen to this exceptional pre-amplifier.

I have enjoyed my time with all the StereoKnight products and look forward to hearing more of them in the future.

The StereoKnight Enigma 1.0R pre-amplifier is highly recommended.

Neil

Review product: StereoKnight Enigma 1.0R  ’copper’ passive magnetic pre-amplifier

Current UK Retail Price: £3499

Source of review loan product: UK Distributor http://www.lwaudio.co.uk/

Manufacturer: StereoKnight 532 Bedlington drive, Germantown,Tennessee, United States of America. Website:http://www.stereoknight.com/index.html


Feature summary of the Magnetic Enigma-1.0R line stage preamplifier

  • Fully differential circuit with balanced in and out
  • 4 transformers for volume attenuation with 33 steps
  • Transformer output
  • Pure tube, Class-A, with Zero feedback audio circuit
  • 2 X 6922 valves.
  • 2X 6H30 valves
  • Versatile to match all kinds of amplifier and interconects based on full magnetic or transformers implement design
  • Capable to drive two amplifiers or one amp + one subwoofer same time either through two balanced or RCA outputs
  • Full remote control on volume, source selection, output selection, balance adjustment, dimmer, etc.
  • MOSFET for voltage stabilization and constant current supplying
  • Hovland musicap capacitor in signal path
  • Detachable IEC power cord, high quality gold-plated StereoKnight custom binding posts and RCA jacks, TEFLON insulated wire and Japan made POCC rectangular solid core copper wire all the way
  • Full machined alluminum alloy chassis and remote wand for best vision and build quality

(1) I will be conducting a full evaluation of an entire cable loom of TruSoundz Revelation interconnects, speaker cable, power cables and mains distribution block in the not too distant future review currently under way. You can find more details on TruSoundZ here in the meantime http://www.trusoundz.com/indx.html

© Text and Photos Copyright 2011 Adventures in High Fidelity Audio…..except for StereoKnight product photos and album covers. Copyright belongs with their original publishers.

NB No part or portion of this article may be reproduced or quoted without written permission.

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