Review: The Audio Research SP-8 preamplifier

 

History: Audio Research has a long and, dare I say, storied past.  Back in the era when vacuum tubes where being consigned to the ash heap of history, they, and a just a handful of manufacturers were still making gear that used these ancient amplification devices.  Even in 1990 I remember being at a used electronics company in Colorado and receiving less-than-kind words when inquiring if they had any tubes or tube gear.  "Vacuum tubes?  Why would you want to use tubes?  Are you fixing an old piece of equipment?"

William Z. Johnson obviously didn't get the message,  Like so many afterwards, he started out modifying Dynaco gear, and branched out making his own equipment under the banner of Electronic Industries.  This latter became Audio Research which started with the SP-1 preamplifier and the Dual 50 amplifier.  They really didn't have a hit on their hands until the venerable SP-3A preamplifier, and D-70 plus D-115 amplifiers (and the various following iterations) came and made them serious contenders in the audiophile world.  They also dabbled - and still do! - with solid-state equipment but are, of course, really known for vacuum tubes.

The Audio Research SP-8, first introduced in 1981, went through several minor redesigns.  I tend to think of the circuitry as being the ultimate Dynaco PAS or Marantz 7. For example the phono amplification is done through a pair of 12AX7s with a 6DJ8+FET cathode follower, RIAA handled via the negative feedback loop.  The linestage is similar with a pair of 12AX7s and a 6DJ8+FET cathode follower with loop feedback.  Where Audio Research shines is the power supply.  In this case a solid-state regulator makes sure the phono state receives a dead quiet high voltage.  And, oddly enough, a combination of a 12BH7 and 12AT7 provide the regulated supply for the linestage.

Controls are fairly simple but with some older ideas that have gone out of fashion.  ie, of course there is a volume but there is also the increasingly rare balance control.  And something else - there is a stereo, mono, reverse, left, and right mode.  Add in the switchable AC outlets for that extra vintage feel.  There is, however, no tone controls or a loudness switch.  But one can mute, select the phono or four other line sources, and switch between tape out monitoring or input.

This particular SP-8 under review is a Mark II, Revision 5, and has only had three previous owners.  When my friend offered to sell me this well-known classic, I jumped at the chance even though it needed to be repaired.  It turned out, due to years of being in storage, the power supply section that handles the muting and 12AX7 filament voltage was no longer working.  Instead of troubleshooting it myself, I sent the unit out to the Audio Research service department, who still does repair work on this 30+ year old gear.  They not only repaired the power supply in question, but also cleaned the volume pot, replaced all of the electrolytic capacitors, put on new feet, and found an additional issue with the linestage that needed to be fixed.  Now this SP-8 is ready to provide service for many more years of service.

 

First Impressions: After unboxing the returned SP-8, I first had to figure out where to place the eight different tubes.  It isn't obvious since the circuit board is not marked.  Instead one has to look at the manual, figure out what version you have, and then double-check your work.  I'm glad I did because I had to swap the location of the 6DJ8 and 12AX7 in the phono preamplifier.  Luckily I did not power on the unit!  After switching the location of my two turntables, due to the interconnect lengths and phono input location, I was finally able to sit down and do some quick listening.

With new electrolytics and NOS tubes that needed to be broken in, I found the bass rather lightweight.  The top end was also bright and the midrange was a bit muddled.  Nonetheless I could tell there was an increase in detail over the replaced Classe Five.  I let the preamplifier cook for a few hours and things started to snap in place.  For example, Chet Baker's voice on the title song from the album She Was Too Good To Me, was very emotional; perhaps the closest one could get to the now deceased trumpet player.  Pink Floyd - The Wall had fantastic imaging without any blurring of the instrumental or voice outlines.  The Classe Five, in comparison, sounded a little darker and less forward.  The SP8, at least with the excitement that new gear brings, seemed to be a real step up in fidelity.

Listening Test: After a few days of background music duty, it was time to put the "new" Audio Research through its paces.  I could tell right from the get-go that the bass had become more extended and some of the forwardness had been reduced.  Note that tube selection will, of course, change the sound.  ie, a set of new production tubes may not be as satisfying as some original 1950s Mullard 12AX7s that I was lucky enough to have on hand.

I have an interest in electronic instrumental music, to the point where I have made my own albums.  For this review I didn't have the ego to listen to my own work but instead picked out the soundtrack Beyond the Black Rainbow by Sinoia Caves.  This has a heavy Tangerine Dream influenced album with one or two sequencers often going at once.  The SP8 did an extremely good job capturing the attack of the electronically produced notes, putting them into their shifting artificial space in the soundstage width.  Bass was also deep without any "classic tube" coloration or overhang.  This is no golden-hued Dynaco PAS experience but instead has a speed that, until now, I thought was impossible with the 12AX7 tube.

 

Neil Young's Tuscaloosa is a live album from his Ditch Trilogy days, starting with two acoustic numbers before the whole band takes the stage.  With the Audio Research his voice had a real presence, the body and the diapraghm can be heard projecting much like the "real thing".  I've done sound for a few live shows and this albums captures that experience quite well, also with the proper amount of hall/stage reverberation, along with the oddly recorded, cardboard sounding drums.  Likewise with the dynamic shifts, which were recorded in a honest way, capturing what it must have sounded like being there; provided you had access to the soundboard instead of being in the back row!

Imaging and soundstage depth was among the best I've heard in my system .  An example of this is the song Warm Ways on the self-titled Fleetwood Mac album.  This is a busy mix but the outlines of the instruments and voices weren't slightly blurred like lesser preamplifiers.  This led to more detail, or, as Audio Research would say, High Definition.  I've owned plenty of other preamps in my life but none have quite approached the sound of the SP8, which, given it's rather pedestrian signal circuitry, a real surprise.  It's neither dark nor bright (tube dependent, of course!) but seems to pass the sound from the Thorens TD309 turntable along in a refreshingly honest way.

Dead Can Dance albums, by some strange miracle, are usually very well-recorded.  My original 1994 UK pressing of Toward the Within is no exception, capturing the vibrancy and the crowd excitement of this live recording.  The song Sanvean, with Lisa Gerrard's voice taking center stage, is a beautiful tear-inducing song.  I was swept away by the emotion of her voice, proving that the Audio Research is no clinical piece of gear.  The depth and power of the music was, once again, presented very naturally without any undue added coloration that one would find in a vintage "warm" preamplifier, but neither did the overall sound swing the other way towards hyper-detailed iciness. 

Parting Thoughts:  Given the age of this preamplifier, it may be a surprise to many that I find it quite neutral.  However I look at this era, the late 1970s to the late 1980s, as a golden age of audio reproduction.  Yes there were fewer companies back then, but they were really pushing the envelope of technology.  There are many examples of this - Krell, Mark Levinson, Threshold, and, of course Audio Research.  The SP-8 is the sound of a classic 12AX7 feedback circuit taken to the extreme.  And it pays off - given the right tubes! - with a very neutral, high definition sound that is also transparent.  If you can find one, and have the patience to have it properly serviced, then the Audio Research SP8 is worth the trouble, especially if you are into vinyl reproduction.

I had to add the caveat about vinyl reproduction because of the high gain nature of the linestage.  The average CD player or DAC with a healthy 2V output will give one a very limited volume control range.  An example of this, with my second turntable, a Dual CS5000 and the Schiit Mani phono preamplifier.  I had to set the latter to its lowest gain setting - 42dB - otherwise the SP8 at the bottom of the detented pot mean I was only two click away before the music became too loud.  And this with an amplifier that is not particularly sensitive.

Review System:
Thorens TD-309 turntable with Ortofon 2M Bronze
First Watt Aleph J clone amplifier
Cardas Iridium interconnects
KEF R500 speakers with Cardas Twinlink speaker cable

Review: B&W Matrix 805 loudspeakers

 Introduction
Bowers and Wilkins have long been audiophile darlings.  I'm no historical expert, but from my many years of reading the audio specialty magazines, it is the venerable 801 studio monitor that cemented their reputation.  Unlike many other speaker makers, they also produce their own drivers, and have an engineering staff on board to build excellent crossovers and cabinets.  This attention to quality is hardly extraordinary in the world of audiophiles, but like their British competitor KEF, it speaks of a long term love of the black arts of speaker design.

My own personal experience with B&W is very, very short.  The only pair I've personally heard was back in the 80s, when my best friend had a pair of stand mounted units of an unknown model.  I don't specifically remember much about the sound other than the speakers could take all the power that the Denon receiver could dish out.  This was, of course, before my audiophile days, when playing clean and loud was all that mattered to my teenage ears.

Time for a New Speaker?
Moving to a new house with a smaller listening space, and a Denon DL-103R cartridge that got damaged during the move, tempered my audiophile equipment craving.  Instead I pulled back on my expenditures, scaling back the size and quality of my system by going with a pair of KEF iQ30 speakers that I already owned, and buying a new Denon DL-110 cartridge.  I even stuck in some Chinese EL34 tubes for my Eico HF60 monoblocks, wanting to save my vintage Mullards for the day when I had a larger listening room.

However, fate being what it is, those plans of hanging back were thwarted by the purchase of a VPI Aries 1.  This was not a turntable purchase that I was planning to make, but it was such a hard deal to pass up - being local and priced lower than what I was seeing on Audiogon - that I took the plunge.  The resulting sound, even through the budget KEF monitors, was a major eye-opener.  I'll be reviewing this turntable in a separate post, but needless to say the overall sound, even with a budget priced Denon DL-110, became much more dynamic, involving, and was quite the step up in reproduction.  After hearing the Aries, I knew that to get the full effect I had to upgrade the rest of my stereo system.  I also knew that with my smaller listening space that approaching the bass and dynamics of the UREI would be near impossible, but perhaps I could be sated with a mini-monitor of high enough quality.

My initial thought was to go with KEF - specifically the KEF LS50, but the low efficiency of 85dB made me wonder if 60Ws of tube power would be enough.  The lower-end models of KEF had their own issues.  For example I wondered if the current Q300 model would really be a major upgrade versus the iQ30s currently in the system.  Browsing through Audiogon for monitors under one thousand dollars, I came across the B&W Matrix 805s, the baby brother of the famed 801s.  My interest piqued, I read the Stereophile review and this post by Ken Rockwell.  Both are excellent starting points if you wish to have a deeper technical description of these speakers.  Needless to say, I was thoroughly interest in this speaker now.  Though the efficiency is only a rated 87dB, it still seemed worth taking the risk.  I purchased the 805s and soon had them in my hands.

Initial Impressions
Opening the box and unwrapping the yards of bubble wrap, I was greeted with a very nicely built pair of mini-monitors.  The enclosure made of rosewood (veneer?) is very lovely.  Binding posts on the rear are recessed and gold.  The woofer is a 6.5" kevlar unit while the removable bullet tweeter on top is a metal dome that is time-aligned by a fourth-order crossover.  An extra feature is the optional outboard electronic crossover/filer the cuts bass off below 10Hz but firms up the response between 10Hz and 50Hz.  This could be useful to reduce turntable subsonics and improve the low-end for rock or symphony music.

Installation was on top of my UTI 29" tall stands, bi-wired with budget Kimber 8PR/4PR.  Distance between the speakers was some 7' from each other and perhaps 2' from the sidewalls and 3' from the rear wall.  Obviously not a cavernous listening area, eh?

Using the Denon DL-110 cartridge, along with Hitachi 5AR4s and Shuguang EL34s installed in the Eico HF60s.  The first record up on the Aries 1 turntable was Neil Young's "Live at Massey Hall".  This recording is fantastic - however with only one singer and guitar (or piano) it is by no means a complex or very dynamic album.  Nonetheless, it is a good album for picking out overall sound quality.  The treble sounded very clean and polite.  The midrange was clear with plenty of detail and space.  The bass, which isn't very deep on this album, had a slightly wooden character.

The next two albums: a German pressing of Pink Floyd's "Animals" and a Japanese pressing of Steely Dan's "Greatest Hits" showed the natural limitations of all small speakers.  As expected, ultimate dynamic range and the lower bass of the B&W 805s were limited by the small woofer size.  Yes, I'm being quite unfair comparing such a minute speaker to the massive UREI 813As, but I'm just reporting what I heard.  When the bass got really deep, the 805s didn't choke, but instead began to slowly compress, leading to the already mentioned wooden character to the bass.  However, throughout the dynamic swings, the sound still remained balanced and focused without getting gritty or uncontrolled like the KEF iQ30s.

Getting Deeper:
Now it was time to upgrade the rest of my system.  First it was a new cartridge: the Dynavector 10X5.  This is a good, dynamic high output moving-coil cartridge that works quite well with the Aries 1 turntable.  After that, it was time to bring out the best tubes I had for my Eico HF-60s.  Out went the Hitachi and Shuguangs, and in went my vintage Mullard tubes.  I also replaced the GEC CV4085s (EF86) with the very earliest and rare "long plate" versions that Mullard made.

These changes were proof positive that rolling in the right tubes can have a major impact on the sound.  Not only did the midrange become more relaxed, but the higher frequencies were even smoother than before.  The Dynavector 10X5 has always been a dynamic cartridge and partnered well with the B&W 805s.  Sure, the UREI 813As still hold sway in the explosive bass department, but for such a small speaker, the overall frequency response was much improved.

You Got to Equalize! 
B&W also included a small bass equalizer with the 805s.  Since I didn't have another pair of Cardas interconnects on hand, I opted to use some budget Canare wire to make the connection between the Quicksilver preamplifier and bass equalizer.  From the output of this little unit, Cardas Cross wire was used.

The change was immediately apparent - this small speaker now growled like a much larger speaker.  Again, it was nothing like a big speaker with multiple drivers, but it sure helped with rock 'n' roll music.  The wooden character of the bass was gone and instead became really firm and punchy.  However there was a bit of detail loss, but for the types of music I listen to, I definitely preferred the improved bass response.  Now I will have to go ahead and buy a short run of Cardas interconnects.  However purists or listeners of lighter fare may prefer the speakers without the additional wiring and active equalization.  Try it both ways.

Speaker Cable Upgrade:
The Kimber 8PR/4PR is great budget wire, but I was curious to hear how my vintage Cardas Hexlink speaker cable would fare.  So back in went the binding post jumpers on the 805s, and on went the Cardas.  The change was quite immediate - the slightly bright, polite sound became much more relaxed.  The top-end treble also smoothed out, turning the monitor into one warm, full-bodied speaker.  Wow.   I would never expect such a major character change from a few feet of cable.

Details R Us
Bass Response:  Hey, this is a small speaker with a relatively tiny woofer.  Expecting subterranean bass suitable for hard rock or organ music is just plain wishful thinking.  If you like that kind of music, you either need a larger speaker or an additional subwoofer.  However, with the B&W bass equalizer installed, lower frequencies are served well enough that I don't miss my big studio monitors (too much).  The sound became really punchy with good detail.  It wasn't all boom either, but instead the bass became very tight and controlled.  Obviously some thinking went into the speaker crossover design and the additional needs of the equalizer.  Again, very dependent on system and musical tastes.

Midrange: Compared to the UREI 813As, which are ruthlessly neutral as befitting a real studio monitor, the 805s have a slightly recessed sound when using the Kimber wire.  This was tremendously reduced by the Cardas cable.  When the music gets really busy or the dynamics really start swinging, it's almost as if the speaker is slightly "holding back" as the big peaks swell up.  Once again, perhaps this is just the effect of a small speaker being asked to do the work of a larger one.

Detail was exemplary - fingers on strings, studio effects, and overdubs were just that more obvious than many other (more budget) speakers I've heard.  The level of available information was much higher than my old Magnepan 1.6QRs, but not quite in the Quad ESL-63 league.

Treble:  The 805 tweeter ranks up there with some of the better I've heard.  It's clean but not totally antiseptic.  It's also very detailed  Sure, it doesn't quite strike in the electrostatic speaker or the plasma tweeter level, but it's no slouch either.  Admittedly there is a slight bump in the highest of frequencies, so some system matching is paramount here.  For example, the wrong solid-state amplification or an aggressive moving-coil or DAC could play havoc with the system balance.  Be also sure to play with speaker wire, as my Kimber vs. Cardas experiment proved.

Other: Even at loud listening levels, the 805s never fall apart.  That is to say the speakers never sound ragged or uncontrolled.  Soundstaging placement, width and depth are also very good, letting instruments and voices sit naturally within the space of the recording.  There was some minor shrinkage - as to be expected - of image size compared to larger speakers.

Conclusion:
Speakers in the less than one-thousand dollar range are a hard nut to crack.  My advice in this range is to buy the best used model you can afford.  The B&W Matrix 805 is one such model.  I'm sure there are many others, but few in this price range can match the engineering, quality, and performance of these top level speakers.  I expect the 805s to have a long shelf-life in my current system.  Highly recommended.

Review System:
VPI Aries with JMW 10.5i tonearm and SDS Power Supply
Dynavector 10X5
Cardas Quadlink 5C 1M interconnects
Quicksilver preamplifier with Mullard short-plate 12AX7s, RCA 12FQ7s, Raytheon black-plate 5814
Cardas Cross 1M interconnects
EICO HF-60 monoblocks with Mullard XF2 EL34s, EF86s, 5AR4s, and GE 6SN7GTAs.
Kimber 8PR/4PR 2M bi-wire cable or Cardas Hexlink
VTI UF29 stands
VTI BL503 equipment rack

The Most Important Preamplifier In the World: The Dynaco PAS

Introduction:
The venerable Dynaco PAS is perhaps the most famous stereo preamplifier of all time,  Much like the Dynaco ST-70, it introduced the magical sound of tubes to thousands of audiophiles throughout the past decades.  The PAS is still a popular model, both in stock form or as a platform to be tweaked and modified.  In this article, I will touch on a general outline of the circuit, the sonics strengths and weaknesses, some of the more popular modifications, and an idea of what to look for when rolling tubes. 

The Circuit:
So what is a Dynaco PAS?  There are three iterations.  The PAS-2, the earliest stereo version, with circuitry taken from the PAM-1 mono unit and a gold faceplate with brown knobs.  The PAS-3, with a more modern silver faceplate with matching knobs.  And finally, the PAS-3X with improved tone controls.  This is a full-function preamplifier with tone controls and inputs for phono, reel-to-reel, tuner, and others.  Gain, of course, is higher than modern preamplifiers since this was the days before high output CD players.

All PAS preamplifiers share the same circuit: For the phono stage, one 12AX7 per channel, each section in series, using loop negative feedback connected to a capactior and resistor network to provide the RIAA equalization.  For the linestage, a 12AX7 per channel, each section in series, utilizing loop feedback to lower distortion and provide a low enough output impedance to drive cables into a high impedance input of an amplifier.  Power supply rectification is handled by a 12X4 tube.  Filaments for the 12AX7s come from a voltage-doubler circuit, which - as the namesake suggests - doubles the supplied AC voltage from the transformer and smooths it out to DC.  Having DC on the filaments also helps to reduce hum.

Stock Sound:
My own experience with this unit started back in 1990, after the electrical failure of my first preamplifier, a solid-state SAE Mark XXX that I was using with my first ever amplifier, a Dynaco 70.  Compared to the SAE, the Dynaco PAS-3X had a more organic sound that was imbued with a mellowness that is often attributed to the term "tubiness."  Such a strong sonic fingerprint can mask detail and transparency, but the PAS never suffered from being unmusical.  Since that initial PAS, I've owned many other preamplifiers, each with different strengths and weaknesses, but none having quite the same magic as old vintage tubes.  Some of that is due to nostalgia, and the urge for musical enjoyment over technical perfection.  No, the Dynaco PAS is not a perfect preamp, but it sure is a fun one.

In the bass department, a stock PAS suffers from a little sloppiness and lack of control - usually a sign of aged power supply capacitors - but with a pleasant warmth reminiscent of a good tubed radio or an underdamped woofer.  Rhythm, which carries the beat and timing of a song, suffers compared to some of the better tubed and solid-state units.

The midrange is the Dynaco PAS strongest point.  There is a golden coloration throughout the music, which, though definitenly not neutral, is a pleasant addition for digital sources or hotly mastered albums.  This same effect shortens soundstage depth and width, diminishes transparency, and hides inner detail.  However, the listener may not care since the sheer musicality outweighs the apparent weaknesses.

Of course the treble follows the same character of the midrange: smooth and pleasantly colored.  Ultimate extension is limited, giving a rolled-off effect that may work to the benefit of the user, depending on source and material being played.  However, with some vintage speakers, the end result may lead to a rather dead sounding system.

The stock Telefunken smooth-plate 12AX7s are perhaps some of the better tubes for a stock Dynaco PAS.  The top end 'hotness' compliments the circuit limitations better than say, a Mullard long-plate, but still, the Dynaco PAS is remarkably tolerant of many different types of tubes from the lowliest Chinese 12AX7B to an expensive Amperex.

Modifications:
The number of changes that can be done to a Dynaco PAS are practically innumberable.  There are simple improvemnts on the stock circuit to full-bore modifications that use nothing but the chassis and power transformer.  Personally I prefer to keep the general character of the PAS intact, but improve the weaknesses to the point that the preamplifier can be used as part of a high-end system.  Some of these mods are simple to perform but many will require experience working with high voltage electronics.  Be warned!  If you don't know how to solder or understand electronic safety, please have the work done by someone who does.

Bypassing the tone controls [link] is an easy modification with a great improvement on transparency and detail.  Since the signal path is shortened and the effect of various capacitors are removed from the circuit, the overall quality take a jump for the better.  Bypassing the loudness switch is also a good idea since these older slider switches can be troublesome.

Signal capacitor replacement is another simple change that benefits detail. treble extension, and transparency.  The stock green paper capacitors are hardly high-end fodder.  As to what capacitor to use, that is up to the individual user.  However, space on the PCB is limited, so gigantic oil caps in metal cases may lead to troublesome short circuits.  For the budget-minded, any metallized polyproplene - Orange Drops, Panasonics, Russian military - will be an improvement.  Auricap, Obligatto, and Jantzen are well-priced improvements over the cheap units.  After that, the sky is the limit with some of the better Teflon, film and foil, and oil capacitors beckoning the well-heeled audiophile.  All have a slightly different flavor that will work better to varying degrees depending on other system considerations: type of amplifier, speakers, room, and signal source.

The next improvement can be a little more problematic.  Since the power supply capacitors - for both the main and the filament - are aged beyond any margin of safety, this should be a no-brainer.  However it will be noted that this step does heavily change the character of the Dynaco PAS.  Bass extension especially improves, but some of the golden glow is lost since the replacement electrolytics discharge faster and provide better regulation than the vintage pieces.  Replacing the stock selenium rectifiers with moderm diodes is a necessity.  If one doesn't want to source the can cap and two filament electrolytics, there are PCBs available - notably SDS and Curcio - that can be used. These boards also give the option of using solid-state diodes instead of tube rectification.  Personally I prefer the 12X4 rectifier, but some may prefer the solid-state replacement.  The end result is a more modern sounding preamplifier that can run with some of the entry-level pieces from Conrad-Johnson, Audio Research, etc.

The next modification isn't particularly difficult but requires some mechanical work to do it.  Replacing the stock carbon volume control with a Noble, Alps, or even a Goldpoint will lead to better channel tracking and improved transparency.

The final modification is one that won't necessarily change the sonics, but will stop the user from pulling out their hair in frustration.  You see the stock RCA jacks are cruddy little ceramic units that don't work particularly well with modern cables.  Various vendors offer replacements that bolt into the stock location.  This will require much wire tagging and soldering to accomplish, but the end result will be worth it.

End Result:
A fully modified Dynaco PAS loses some of the coloration, much of the excessive bass warmth, and the rolled-off treble.  Transparency and detail is much improved and is now a good match with many more amplifiers and speakers.  The phono and line sections, though still warm and full-bodied, now reveal more subtle differences between phono cartridges and DACs.  Though not quite top tier material, such a PAS can easily serve as the heart of a moderately priced or even a lower-priced high-end stereo.

Simple modifications after this are of a minor nature: better signal wire, source selector switch, tube rolling, and various damping and vibration control products.

Of course major changes are still possible - whole new PCBs and circuits - but be warned that these updates will drastically change the character of the preamplifier, making it sound much more modern but losing that vintage magic.  However, the amount of money one could throw into such a project may be better spent on buying a used but newer preamplifier from Quicksilver, Conrad-Johnson, Audible Illusions, or whatever your budget can afford.  After all, the Dynaco PAS is a fifty-year old unit that can now have several mechanical issues: switches, AC cord, and RCA and AC jacks that will need to be addressed if long-term service is of importance.  As is, the Dynaco PAS is much like a old car, requiring some work to run its best.

Review: Rotel RA-840BX3 integrated amplifier

When it comes to solid-state gear, I seem to be cursed.  Whatever used piece I buy somehow ends up having a problem.  Now I love my Audio Analogue Puccini amplifier for its smooth and warm sound, but the selector switch eventually became dodgy, often dropping the right channel of the phono, which is the one I use the most.  With that in mind, I decided to have it repaired but needed a short-term replacement since this stereo sees almost constant use.  I hunted around until I found a Rotel RA-840BX3 (what a mouthful of gobbedlygook) on Ebay. 

This is a budget amplifier from the early 90s that still features a phono preamplifier, and the normal CD, Tuner, and even video inputs.  Power output is an unremarkable 50Ws, plenty for your average speaker and small to midsized room.  Build quality is pretty good with an actual metal case and a mix of metal and plastic knobs.  It runs a tad warm and is a popular spot for my cat to hang out on the colder nights.

Sound quality:  I'm not going to wax overly poetic on this little budget integrated, but in comparison to the Puccini, it did not fail on it's face.  Bass seemed a tad deeper with the Rotel and on one of my favorite albums, Mirrors - Lights and Offerings, I would swear I heard more detail than before - a bit of hidden synth that changed the overall mood of the songs.  The 840BX3 is exceedingly polite in that British way but still not dark.  It certainly is not an overly "fast" sound unit either, but with the KEF iQ30s speakers the sound is very easy on the ears.  For a budget piece, I couldn't be much happier.  Highly recommended - within the confines of a low priced system.

The Most Important Amplifier In the World: The Dynaco 70

 

The Dynaco 70 is the most important tube amplifier ever made.  Sure, some may quibble at that characterization, but I can’t think of any other amplifier – at least within North America – that has turned on more audiophiles to the possibilities of tube amplification.  Like countless others, it was the amplifier that turned me on to an alternative way of listening to music. 

Back in the late 1950s, the stereo wars were heating up.  Many audiophiles had invested in the expensive monoblocks or stereo amplifiers from Marantz, McIntosh, and Fisher.  The smaller players – Heath, Dynaco, EICO, and Pilot were nipping on the heels of their more upscale brethren.   David Hafler made the right move at the right time by introducing a $99 stereo wonder – the Dynaco 70.

Sure, this little budget amplifier couldn’t compete with the big boys at a performance level, but it was such a bargain that no one seemed to mind.  The sales numbers certainly back this up.  Yes, the power transformer was woefully underrated for supplying the current to four EL34s, and yes, the 7199 tube is not an ideal driver/phase-splitter, but whatever failings the Dynaco 70 has is ameliorated by the warm forgiving sound that throws a big wide soundstage.  This is an amplifier made for playing music, and if paired with good tubes, the performance is damn well good enough to have made me a tube convert for life.

I bought my first Dynaco 70 at the tender age of nineteen.  I was heading off to college and needed a stereo system.  At the time I didn’t know anything about tube amplifiers but came enamored with them after hearing a McIntosh 240 over at a friend’s house.  I loved the black transformer and chrome chassis look and lusted after the glowing tubes.  When he asked if I wanted a tube amp, I readily agreed.  However, I will admit that I had to hide my disappointment when he brought out the brown caged Dynaco 70.  It certainly couldn’t compare to the McIntosh in the looks department.  But little did I know how this little tube amplifier would change my life.

The amplifier started stock with Siemens EL34s, a Mullard 5AR4, and RCA 7199s.  After a few weeks of that, the same friend suggested running an outboard tubed regulator to supply the front end.  With the shortage of 7199 tubes – this was before the Internet, mind you – I converted the PCB, through the use of a RCA manual and my first soldering iron, to use 6GH8As.  After that, it was modified to run the EL34s in triode.  After that, it was sadly sold to another friend who began his own audio journey with tubes.  At that point I was running modified Scott or EICO integrated amps, a small step before my DIY journey.

A few years ago, I exchanged emails with the fellow who bought the Dynaco 70.  He still had it!  We did a swap and I had my very first amplifier back in my possession.  The original circuit board was long gone, the tube sockets were shot, and the can cap had been replaced by a giant oil power supply capacitor.  This old amplifier was due for a rebuild.

In order to stay true with the spirit of the Dynaco house sound, my restoration was fairly limited in scope.  The input circuitry was replaced with a PCB from Triode Electronics that utilizes a pair of EF86 tubes and a single 12AU7.  The power supply can-cap was replaced with a SDS circuit board that fitted underneath one of the output transformers.  A bit of wire and solder, some new output tube sockets, and the amplifier was ready to sing again.  

For tube selection, I went with some budget Russian valves – EH EL34s, Sovtek EF86s and a 5AR4.  The sole American tube was a late production Phillips 12AU7.  The sound, as to be expected, was a little on the harsh side.  This was due to the “solid-state in a bottle sound” that afflicts many of the lower-end Russian tubes.  So it was time for a spate of rolling.  In the end, the amplifier finished with Matsushita EL34s, Dutch EF86s, a Hitachi 5AR4, and a 1950s-era RCA blackplate 12AU7.  This change made for a much smoother and cohesive amplifier that was quite enjoyable to listen to.

But, I’m not the sort of chap who wears rose-colored glasses.  The Dynaco, even with an improved power supply and new input circuit, suffers from several flaws that stop it from being a truly great amplifier.  

First of all, the power transformer is helpless underrated in the current department which will cause the voltage to sag at higher output powers.  Another issue is the use of a single 5AR4 rectifier to handle all four output tubes.  Sure, it’s within the specification of that tube, but still it is hitting the top of the envelope.  Of course these two problems can be rectified (ha! – editor) by an aftermarket power transformer and a different rectifier or even the use of solid-state diodes (which have their own issues).

However, even with those changes, I believe the fatal flaw of the Dynaco 70 rests with the A-470 output transformers.  Like many things Dynaco – especially on their budget gear – this output transformer was built to a price point.  At higher output levels, the amplifier sounds like the core is saturating, giving that pleasant “tube-like” compression.  It sounds like the images are on springs, causing the soundstage to shrink in size as large dynamic swings occur.  Why do I pin the blame on the output transformers?  I’ve heard the same effect on the Dynaco Mark IV, the monoblock version of the Dynaco 70 that have a much beefier supply that isn’t shared between two channels.

So yes, the Dynaco 70 – and all the new kit versions now available – is still a great introduction to the world of tubes, but it isn’t the end game.  There are much better - and admittedly more expensive – amplifiers that really lift the veil over the music and provide the sort of output that an audiophile wants to hear.

Review: Spica TC-50 speakers

A new house has forced me into a smaller listening room.  Since the full-range sound of the UREI 813A speakers would overwhelm this new space, I decided for an interim, ultimately deciding on a pair of mini-monitors placed on stands.

The Spica TC-50 was a popular budget mini-monitor speaker from the 1980s.  Featuring a sloped 45 degree front, a 6.5" woofer and a small tweeter, it is renowned for it's imaging capability.  Part of this performance is from the time-aligned drivers (from the sloped front) and the special crossover with matched drivers.  Of course such now vintage units suffer from aging components and drivers that are long out of production.

I bought my pair via Ebay for $250 and purchased the 29" VTI speaker stands via an online seller.

Going from a massive full-range speaker - sporting a time-aligned 604 driver combined with a 15" woofer - to a small mini-monitor takes some time getting used to.  Of course the majority of this change is the considerable lack of dynamics and bass extension with the smaller speaker.  It's simple physics - a 6.5" woofer just can't move the same amount of air as two 15" drivers working together.  In comparison, this lack of "slam" and macrodynamics makes the Spica sound rather thin.  For example, on Pink Floyd - Dark Side of the Moon, the sense of urgency as the music shifts into overdrive is essentially lost.  Simpler recordings, like The Immortal Otis Redding fare much better.

However, there is one area that both the UREI and Spica meet - it's the driver consistency - that sound of being cut from the same cloth.  Much of that has to do with the time-alignment since the output of the drivers meet the ear at the same time.  It's a hard effect to describe, but you know it when you hear it.  This is part of the reason that I enjoy KEF Q series speakers.

Anyway, at reasonable levels treble extension is fairly non-irritating though lacking in the best shimmer and detail.  The Spica does sound slightly tilted in this range, though part of that could be the comparison to my previous speakers.

The midrange is the strongest point - though not quite in electrostat territory, it's also no slouch in this department.  I tend to think "Poor man Quad ESL-63" performance.  This leads to good soundstage width and depth, though my old Magnepan 1.6QRs and even the UREIs, with their massive box, had a more realistic scale.  Vocal presence is quite good, though not scaling the heights of the best I've heard.  However overall coloration is still quite low - low enough to be called 'audiophile'.  A good example of the soundstaging depth and relative neutrality can be heard on Willie Nelson - Stardust where the location of the instruments and the vocalist are easily determined.

Bass, as to be expected, is the weakest point.  A decent subwoofer here would improve the sound, freeing the woofer from doing the heavy work.  Stock, it's sort of there, not going particularly deep.  I've heard more extension from the little, but thoroughly modern, KEF iQ30, which coincidentally also sports a 6.5" driver.

So what to think of the Spica TC-50?  It's a good little budget design that may have been a real champ in earlier days.  If you come across a pair for a good price and they haven't been modified, then go ahead and take a chance.  Having said that, a few more dollars will get you a KEF (or other) monitor speaker that will have a warranty, new capacitors, and drivers that can be replaced if you get a little out of control with the volume levels.

System
VPI HW19 Mark III with SDS Power Supply
Rega RB300 with Cardas wiring
Denon DL-110
Quicksilver preamplifier with Mullard short-plate12AX7s, RCA 12FQ7s, Raytheon black-plate 5814
Cardas Cross 1M interconnects
EICO HF-60 monoblocks with Mullard XF2 EL34s, GE 6SN7GTBs, Genalex CV4085s
Cardas Hexlink 2M speaker cables
Spica TC-50 with VTI UF29 stands
VTI BL503 equipment rack

Review: Eico HF-60 tube monoblocks

Introduction
EICO, unlike McIntosh, Marantz, or Fisher, isn't quite spoken with the reverent tones with discussing the best of the vintage amplifiers, but to do so would be a mistake.  From their budget units, up to the the flagship model, the HF-60, they represented a serious competitor to Heath and Dynaco, offering good value for the hobbyists of yore.  When I had the rare and unexpected chance to buy a pair, I went for it, knowing I would be hearing with one of the best EL34s amplifiers around.


The Amplifiers
So what is an EICO HF-60?  It's a monoblock amplifier - requiring two for stereo - featuring 5AR4 tube rectification, the classic Mullard 5-20 circuit with an EF86 and 6SN7 driving EL34 output tubes in Ultralinear, fixed bias, and the legendary Acrosound TO-330 output transformer.  There's nothing tricky going on here circuit-wise: current sinks, current sources, regulators, dc filaments, etc are non-existent, but component quality is still quite high with wirewound resistors, good tube sockets, and a really nice hunk of iron.  Biasing is through two pots: one to balance between output tubes while the other is raw bias.  These came as very basic kits with no circuit boards: the end-user was expected to be experienced enough to do point-to-point wiring.

Another thing to note is the high plate voltage and bias, making the HF-60 run steep Class A.  500VDC on the plates with 65mA means the EL34 output tubes are running 32.5Ws (plate + screen) of dissipation, right on the bleeding edge of their maximum rating.  If the lights are off, a faint red glow can be seen on the plates(!) which, according to the manual, is considered normal operation!  Back in the day, this was no big deal since you could pop down to the local store to pick up your new set of Mullard EL34s, but now with the high price of quality old-stock tubes, a user of this amplifier may want to dial back a few milliamps.

Not Quite Stock
Before I go and describe the sound of these amplifiers, I would like to mention that mine aren't exactly stock.  Of course these days it's hard to find a vintage tube amplifier that sports its original power supply capacitors, but my set of EICO HF-60s came with some additional modifications that will effect the sound.  First off was the addition of a small choke in the power supply.  The original just used 40uF of electrolytic to clean up the voltage.  Instead, I have a 25uF electrolytic bucket, followed by a 1.5H choke, and then a large 40uF Suzuki polypropolene capacitor.  This change gives a clean and fast power supply.  The second modification is to the EF86 input tube which now uses a battery to supply the bias.  This was done by the local "tube guru" and is purported to clean up the treble and whatnot.  Original coupling caps have also been replaced with MIT RTXs and some Jantzen Z-Superiors.

Tubes used for this review: Genalex CV4085, GE 6SN7GTBs, Mullard XF2 EL34s, and Hitachi 5AR4s.


First Impression
Expectations were high when I dropped the needle on Side 2 of Supertramp's Crime of the Century.  I've often been disappointed by audio purchases since the hype doesn't often live up to the reality.  In this case I had nothing to fear - within seconds I recognized that the EICO HF-60s are something special.  They really gripped the UREI 813A speakers hard, delivering power in an effortless way, all while casting a big, deep and detailed soundstage.  It thoroughly demolished the budget wunderkind Yaqin MC-10T, and my memories of other tube amplifiers - the Dynaco 70, Dynaco Mark IV, Dynaco Mark III, Harman Kardon Citation V, Heath UA-1, various Scott, Heath, and EICO integrateds, and anything else that I missed over the years of this crazy hobby.  The EICO also beat out my now departed Threshold S/500 or any other solid-state amplifier I've owned (which hasn't been many).


Listening Notes
Okay, enough gushing already, eh?  In order to give some further insight into these amplifiers, I invited a fellow longtime audiophile friend over to listen, hoping a second set of ears would keep my effusive praise somewhat in check.  After spending a chunk of cash it's easy to get carried away with new gear, missing the warts and blemishes of music reproduction.  We listened to a number of records and this is what we heard:

Steely Dan - Aja:  Recorded by Roger Nichols, Aja's technical prowess - both musically and sonically - is laid out perfectly with the UREI speakers.  The bouncy dynamics are engaging and fun, with plenty of little details to keep the brain locked into the music.  At no time do the amplifiers run out of power - delivering the power effortlessly. 

Grateful Dead - Terrapin Station:  Side 2 of this album is a sorta short rock opera with bits of Renaissance-inspired flourishes and backup vocals.  Yeah, it's a little cheesy at times, but still well-recorded with big dynamic shifts that sound diminished with lesser speakers and amplifiers.  Needless to say, the EICOs passed with flying colors, keeping everything locked into place without ever sounding strained. 

Faces - Long Player (German pressing):  Not exactly an audiophile recording, the Faces good-time boozy musical party record sounds better than I ever heard it.  Every instrument is audible, standing by itself in the soundstage without getting lost in the thick mix.  

Supertramp - Crime of the Century (British pressing): before I got the UREI speakers, I always considered Supertramp to be lightweight rock 'n' roll music.  But with the right system, the darkness of the music becomes more apparent.  Once again the dynamics and bass impact was amazing, as was the midrange and treble detail.  Soundstaging was deeeeeep, making my listening space sound like a larger than the confines of the walls.

Fleetwood Mac - s/t: Back when I was a kid, I pretty much loathed this 1975 album whenever my parents would play it.  But changing tastes and Stevie Nick's wonderful voice on Rhiannon changed my mind.  On this system, the high production values were evident, along with various multi-tracks used to create this sonic gem.

 
Sonic Scorecard
Bass: For the longest time, the king of bass reproduction was my Threshold amplifier.  250WPC with a huge amount of available current and the high damping factor helped to give some of the most fluid and detailed bass response I had ever heard.  A known limiting factor of tube amplifiers has always been - at least in my experience - the slightly sloggy and underdamped bass.  But somehow through the Acrosound TO-330 output transformer, those normal limitations are no more.  Low frequencies are extremely accurate, controlled, and easily equal that of the massive solid-state Threshold.  Amazing for a tube amplifier.

Midrange: They actually reminds me of an DIY amplifier I built a few years ago - a SE 300B design with a hefty SV83 pentode driver.  The same kind of speed and snappiness, along with a natural reproduction of vocals, guitars, and everything else that dominates the most important part of the frequency range.  No fine sand or loss of detail, but just a natural but uncolored presentation.

Treble: At my age, my hearing of highest frequencies isn't what is used to be, but still there was no sign of harshness or glassiness.  I may niggle here and there and say that I've heard better - the above mentioned SE 300B design comes to mind or my SE EL156 amplifiers - but this is very fine hairsplitting indeed.  Cymbals have a nice shimmer with natural decay while synthesizers snap and howl like the real thing.

Soundstaging: Deep, wide, and layered with everything sitting properly in it's place.  At no point did the sound ever collapse or shorten like I've heard with several other amplifiers with undersized power supplies and output transformers.

Detail: I'm no hyper-detail freak, but the EICO HF-60s certainly didn't fog over the sound with a "tubey" mush or give fake information by cranking the upper-mids on up.  Also different recordings sounded, well, different instead of congealing into the same tonality.  I've heard plenty of tube amplifiers that suffer from "too much character", making every record sound as if it was recorded in the same studio.

I'll also note that I did some brief listening on the Magnepan 1.6/QR speakers and got great results, but the maximum volume was limited.  Those speakers love to suck current and even 60Ws of tube power wasn't enough unless you enjoy baroque/folk/light rock music at moderate levels.


Conclusion
Okay, I hate to enthuse too much about just an amplifier since getting here has been a long journey.  That's to say that an amplifier is only part of the chain of electronic reproduction.  It took several other dead-ends and paths to finally come to this point.  First of all, it helps to have a solid front end.  Though not the best in the world, the VPI HW19 is still a solid performer, as is the Rega arm coupled to the Denon DL-103R and Cinemag transformers.  The Quicksilver is really a nice bit of kit, and none of what I'm hearing would be possible without the amazing extension, speed, and explosive dynamics of the UREI 813A speaker.  This same pair of monoblocks, especially stock, may not be quite so amazing with a lesser combination of gear.  Back in the past, I used to be amp crazy, thinking "just the right amplifier" would catapult my system from mediocre to greatness.  I've since learned that a solid front-end along with a good pair of speakers should be your first step before embarking on a path of expensive amplification upgrades.

Even though the EICO HF-60s are just a part of an overall, what I did hear from these amplifiers was a revelation.  The most amazing part was the way they delivered power.  I've owned some heavy-hitter gear in the past, but it's almost like the HF-60s "know" beforehand what wattage to deliver to the speakers.  This sense of ease in reproduction just makes you forget about the amplifiers and instead just revel in the music experience.  Yes, I've owned amplifiers that can deliver much more power, but they could never do with the finesse of this electronic antique.  Much of this has to do with the Class A biasing, but also the Acrosound TO-330 output transformers.  There is definitely something special about these hunks of iron.  It's too bad that their design blueprint has been lost in the mists of time, though I'm sure some of the best offerings from Tamura, Magnequest, Tango, etc could match their performance.

It's been a long journey but I'm happy to say that I've finally found a pair of "keep for life" amplifiers.  Until I hear something better at his price point - which may be possible - I will instead turn my attention to improving my turntable, stock up on my system's tube needs, and keep buying records.


Main System:
VPI HW19 Mark III with SDS Power Supply
aluminum rebodied Denon DL-103R
Rega RB300 with Cardas wiring
Cinemag CMQEE-3440A in custom aluminum box
Cardas Cross 1M interconnects
Quicksilver preamplifier with Mullard short-plate12AX7s, RCA 12FQ7s, and a Raytheon black-plate 5814
Cardas Quadlink 5C 1M interconnects
EICO HF-60 monoblocks with Mullard XF2 EL34s, GE 6SN7GTBs, Genalex CV4085s
Cardas Hexlink 2M speaker cables
UREI 813A speakers
VTI BL503 equipment rack

Review: Quicksilver full function preamplifier

Introduction
Quicksilver has been around for quite some time, but their products are often overlooked for the more flashy Conrad-Johnson, Audio Research, or whatnot.  However, much like VTL, Quicksilver instead concentrates on simple but solid tube circuitry, robust old-school construction, and moderate - at least for audiophile gear - prices.  The full function preamplifier in question is the earliest incarnation of the product having first hit the street in 1988.  Price back then was a princely $1995, making it roughly in the same price range as the famed Audio Research SP-8 or the slightly later Conrad-Johnson PV11.

I bought mine from a seller on Audiogon.  Shipping was prompt and I received a very heavy duty preamplifier that doesn't quite have the same ooze of quality that ARC or McIntosh has, but certainly is no slouch in fit 'n' finish.  Cracking open the top plate grills, you will see that the power supply and signal path are separated by a thick steel wall.  Very nice.  Component quality is also good though hardly esoteric.

Circuit and Controls
A quick look over the tube complement and circuitry:  Some of this is based on guesswork since no schematic could be found.  The power supply uses a large power transformer, a pair of 6X4s which are still widely available NOS, a small choke and a number of large Mallory capacitors to provide the DC smoothing, along with some regulation for what I assume are the tube filaments.  The line stage uses one 12AX7, one 12AU7, and one 12FQ7.  Since the reported output impedance is so low, I'm assuming the 12FQ7 is being used as a cathode-follower with some negative feedback wrapped around the entire circuit.  The last bit is the phono stage which only uses a single 12AX7 and a 12FQ7 with some sort of green LED biasing.  Coupling capacitor quality is in the meh range, but hardly out of place for the era.  The big 2uF capacitors on the output stage are some REL Polyesters (ughh).  The smaller signal caps are branded Quicksilver though also look to be REL made.

Front controls are fairly standard though a little dated: No remote here!  Lighted power, AC rear receptacle switch, and a mute button make up the left hand of the faceplate.  The right side has a tape monitor switches, a reduced (20dB) gain switch, a selector switch, and a stereo/mono/etc switch.  Volume control is dual mono with one stepped Blue Alps per channel.  These actually work better than expected - with the numbered volume steps it's very easy to match levels between channels.

Rear panel is the usual assortment of nice gold-plated RCA jacks and a grounding post for the phono stage.  Power cord is captive.  Fuse Holder holds a 1A unit.  AC receptacles are a nice throwback to the days when the user would power up his amp and sources with one flick of the on button.

The Sound
Okay, enough introductions - how does it sound?  Well, since this is an older unit, the stock tubes are long gone.  For the purposes of this review I used some really nice NOS tubes from my stash, so results will vary to a certain degree depending on what is plugged into the sockets.  In my case I used early 1960s short plate Mullard 12AX7s, a late 1940s black-plate RCA 12AU7, and 1960s-era side-getter RCA 12FQ7s.  Rectifier tubes were Tungsol 6X4s.  Some generic tube damping rings came with the unit, so I kept those in place.

It's been my experience that ultra-regulated, current-sourced, current-sinked, and whatnot circuits are very detailed, but also suffer from sounding slightly unnatural.  Note that tube regulators are usually better than solid-state, while shunt suffers from less sterile sound than series.  My own DIY experiments with a simple linestage showed that pulling regulation out of the circuit actually improved overall musicality and enjoyment.  Sure, some of the last bits of inner-detail are missing, but the music usually sounds more relaxed with a looser power supply.  This type of sound was very evident with the Quicksilver preamplifier which just uses chokes and caps to provide a clean source of DC.

Compared to my old Threshold FET-10/HL linestage and Audio Sector Phono Stage, the Quicksilver (with Cinemag step-up transformers) has a relaxed presentation that draws you into the deep soundstage.  It's almost like unclenching your teeth after a roller-coaster ride, or taking a good solid gulp of your favorite adult beverage: the muscles relax and you sit back with enjoyment, washed away by the sonic swirl of the music.  A good stereo should be a psychedelic experience - an unregulated and legal high - that lets you forget the troubles of the world.  With the Quicksilver preamplifier, I feel as if my entire audio experience has been improved.


Listening Notes:
I used my turntable exclusively for this review, but the linstage by itself is no slouch either.  The Audio Sector phono stage combined with the Quicksilver was a pleasant surprise, but the Cinemag and native phono section got the nod in sound quality.

The Who - Tommy (W. German Polydor):  The Quicksilver has very excellent detail and speed, keeping up with Keith Moon's manic drumming without breaking a sweat.  Small individual instruments - like a small bell - maintained their place in the soundstage while still being audible in the wash of thundering bass and guitars.  Depth was deeeeep, making my room seem bigger than reality.

The Beatles - Rubber Soul (Japanese Parlophone): This particular cut of this famed album has been described as bright and bass heavy compared to the original British pressings, but to my ears it sounds like it was eq'd flat.  With the Quicksilver, treble is extended and detailed with out any forwardness or grit.  There is lots of nice detail with John's wonderful voice cutting through the primitive stereo mix.  It's harder to get closer to the Beatles than this.

Tom Waits - Closing Time (80s Asylum): Perhaps I'm a sentimental slob, but I love this album.  However, the Quicksilver revealed the limitations of this later pressing.  Some detail, compared to some better versions, was missing, as if the music was hiding behind a thin gauze.  Tom Waits voice, however, was still wonderful, leading to some near tears while listening to the bittersweet song Martha.

Record after record revealed a preamplifier - and stereo system - that was very analog sounding.  Perhaps somewhat lacking in some of the hyperdetailed / transparency of more modern pieces, the Quicksilver was still no slouch.  When it came to musical enjoyment, I give it an extremely high ranking since it never sounds bleached out or unnatural, even with less-than-perfect recorded music.  If you want a preamplifier that speaks to the mind instead of the heart, you may want to look elsewhere.  I've gone down that road with my foray into solid-state gear, but I'll take naturalness over artificial effects any day of the week.


Overall:
Soundstaging:  Deep and Wide, imaging goes beyond the boundaries of the speakers and even the walls of my listening room.

Treble: Airy and extended, but also pure and detailed.  Compared to the darker Threshold/Audio Sector, it seems there is even more overall treble, but yet it never is harsh or unfaithful to the record.  A strange effect and not at all what I expected from tubes and a step-up transformer.

Midrange: Glorious, but not overly slow or "tubey" in the classic sense.  The Quicksilver certainly doesn't sound like a soggy Dynaco PAS.

Bass: The 12FQ7 output tubes can swing some current while delivering a low output impedance.  This translated into control.  I certainly didn't miss the solid-state drive of my last preamplifier combination.

Speed: (or PRAT) Good tube gear isn't supposed to be sloggy 'n' slow.  The Quicksilver preamplifier and Yaqin amplifier combination certainly doesn't sound like an aged tube integrated or a Dynaco 70 in need of a rebuild.  Instead, the music transients started and stopped on a dime with no overhang.  With the UREI loudspeakers, this led to a very dynamic, exciting, but yet unfatiguing sound.

Detail: As mentioned above, the Quicksilver is no king at wringing out the very last drop of detail from the music.  No, it isn't flat or uninvolving, but the very last bits of information are perhaps less apparent than some other units I've heard.  Some of this may be due to the large Polyster output capacitors.  An upgrade is due for some of the parts - notably some new polypropolene capacitors - so it will be interesting to see what effect this has on the sound.  But really, I'm not complaining because I'll take all of the positive attributes over hearing the squeaky chair of the violinist in the third row.of the orchestra pit.


Conclusion
For a going used price of $850-$1000, the Quicksilver full function preamplifier is highly recommended.  It's extremely well-made and is very natural sounding.  Errors - and I mean minor - are ones of omission with a high scale of musicality.  The simple circuitry will minimize future troubles since there are less "moving parts" once you get rid of the solid-state and regulation support circuitry often found in modern tube preamplifiers.  I expect to increase the audio grade of this unit with some coupling and electrolytic capacitor replacement, so stay tuned!


Main System:
VPI HW19 Mark III with SDS Power Supply
aluminum rebodied Denon DL-103R
Rega RB300 with Cardas wiring
Cinemag CMQEE-3440A in custom aluminum box
Cardas Cross 1M interconnects
Quicksilver preamplifier with (real) Mullard 12AX7s, RCA 12FQ7s, and a RCA 12AU7
Cardas Quadlink 5C 1M interconnects
Yaqin MC-10T amplifier with black-plate RCA 12AT7s and (real) Mullard XF2 EL34s
Cardas Hexlink 2M speaker cables
UREI 813A speakers
VTI BL503 equipment rack