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

Project: Restoring a Audio Research SP-8 preamplifier

 A recent purchase was this Audio Research preamplifier that sadly is in need of repair.  All original early 80s, it will need a cap job, a new volume control, and a solid-state regulator supply fix.  More later!

Short Review: Lepai LP-2020TI amplifier

I'm in the midst of building a small home studio for recording synth and guitar.  My plan for monitoring was to use a pair of KEF Q350 speakers with a small amplifier.  With my past love of the Charlize and other Class T amplifiers, and a low budget, I decided to give the Lepai LP-2020TI, available from Parts Express, a try.  For $25 it is hard to go wrong.  If I didn't like it, no big hit to the pocket book.

This thing is tiny - like the size of two packs of cards.  It is also extremely light; helped by the 12V outboard power supply.  Build quality is just okay.  I'm not a big fan of the spring clip speaker wire connectors or the tone controls; which can thankfully be bypassed.  The light-up volume control is gimmicky too but no real major complaints given the silly low price.

In my garage system - replacing the venerable Adcom 545 - I was surprised how good CDs from the old Pioneer DVD player sounded.  There was a toe-tappin' excitement to the music with plenty of kick.  The Wharfedale Denton speakers are a good match with this amplifier, making more volume than I expected.  There was a nice speed to the sound too.  Over all I would give the slight nod of the Lepai over the Adcom, but we are talking a garage system so let's not get too carried away!

I originally wasn't thinking of plonking this little amp into my main system, but given the amount of free time I have due to being furloughed, I decided to give it a try.  Initial impressions were rather eye opening.  This is one very nice sounding amplifier.  But a few minutes of listening, even with my Dual CS5000 and Schiit Mani phono, I could hear a loss of detail and blurring compared to the Aleph J.  Bass of the Lepai was also a little rolled off and there was some solid-state grit and forwardness on top.  But to be fair, the Aleph cost in the neighborhood of $900 to build; a far cry from the dinner-for-one price of the Lepai.

Conclusions?  It's a good amp for cottages, garages small apartments, dorms, or where critical listening is not of upmost importance.  I could easily imagine a system with a Rega RP1, Schiit Mani, the Lepai, and your favorite budget mini-monitors.  Such a stereo would best a lot of ones that I've heard (or even owned!). 

Garage System:
Pioneer DV-V7400 DVD/CD Player
Schiit SYS passive linestage
Adcom 545
Wharfedale Denton 80th Anniversary
Belden 9497 speaker cable
generic interconnects

Main System (second turntable)
Dual CS5000
Schiit Mani
Classe Five preamplifier
DIY First Watt Aleph J amplifier
KEF R500 speakers
Cardas Twinlink speaker cables
Cardas Neutral Reference and Iridium interconnects

A Very Brief Review of the Schiit SYS

I bought this little $49 passive preamplifier to use in a CD-only garage stereo system.

For fun I plugged it between the Schiit Mani phono preamp and the Aleph J amplifier, using the cheaper of my turntables, the Dual CS5000 as source. The SYS sounds really nice. There is that slight lack of drive I've heard before with passive preamps but detail and transparency is extremely good.  None of that (minor) JFET darkness of the Classe either. I should try the Schiit Mani/SYS combination out with my Thorens TD309 but that will have to wait for another day.

For the price, it's a steal and would work wonders in simple system.

Review: KEF R500 loudspeakers

Introduction: Last month I bought a pair of KEF Q350 speakers. I liked some of the attributes over the Wharfedale Denton speakers - mostly the sense of speed and some better detail. My plan was to eventually replace the Q350s with a pair of KEF R3s, speakers that were being sold via Accessories4Less for a very nice price. Things, however, began to move a little faster than I expected.

Fate stepped in: the Walnut R3s were no longer available. With my wife's blessing I instead purchased a pair of reconditioned R500s, the previous generation of the current production R5. It's been a few years since I've owned "full range" speakers so I was curious to see how these would sound in my narrow mid century listening room.

Shipping was fast with a Sunday (!) delivery from Fedex. I managed to unpack and setup the speakers without any help but be warned, the cabinets are heavier than they look. My weekly workout plan paid off! I also liked the spiked feed and the cups to stop damage to the new cork floors.

First Impressions: Where did all that bass and body come from? The two 5.25" woofers move a lot more air than I expected but perhaps I've been living in mini-monitor land for far too long. Sure it's not quite in the old UREI 813A territory with 15" woofers but the KEFs acquit themselves well with most rock music. The blending of the drivers - bass, uni-q midrange and tweeter - is also seamless.  Even though I only have 25Ws of Class A Aleph J on tap I had no urge for more power with the small listening room.

My friend rolled over and we listened to a few favorite records. It was obvious that these speakers still had some breaking in to do since changes were audible even in the middle of an LP side. After a few hours it seemed as if the treble had become more extended and the drivers even faster than before. Forwardness and depth changed with whatever turntable / preamp was being used. ie - the Thorens TD309 / Classe Five gave a "back in the hall sound" while the Dual CS5000 / Schiit Mani was more forward "mixing board" approach but with a little less resolution and bass depth.

Listening: After a week of daily use, it was time for a solid listening session with notebook in hand.   Turntable used was the Thorens TD309 paired with the Classe Five.

The Who - Tommy (Tracks) is an odd little album that I like but only in small bursts.  It is also an album I've heard on several of my systems.  The first side of this German pressed double-LP album has a lot of dynamics and a wide soundstage with a lot of things going on.  The KEFs did a very admirable job here; the firm foundation of Keith Moon's drumming and John Entwistle's bass was some of the best I've heard; only beaten by the massive UREI 813A speakers.  Where the R500s really shined was the attack of Pete Townshend's guitar work, sounding detailed and full of body.  There were a few times where my jaw literally dropped with surprise by the sheer dynamics of the album, not to mention the soundstage height(!) which is something I usually only hear on very expensive speakers.

Dead Can Dance - Into the Labyrinth (4AD) has a lot of acoustic instruments in a wide, sometimes shifting soundstage.  My original 1993 British pressing sounded marvelous.  On the song The Ubiquitous Mr Lovegrove, Brendan Perry's voice had real weight and presence.  The fleshy finger strikes on the heads of the drums was readily apparent..  Dynamics, once again, were excellent as was soundstage depth and width.  Just a stunning album, one that I would use to demo any excellent hi-fi system.

Hiroshi Suzuki - Cat (Coumbia) has recently been re-issued on very clean and quiet Japanese vinyl.  The color of the Suzuki's trombone is vivid with astounding dynamics shifts.  The rest of his bandmates sound as if they are sitting in a living real space.  An example of ths is the song Walk Tall which begins with hand claps that echoed with a natural decay.  The treble is fast and transparent, especially for a metal tweeter driver.  The high end detail doesn't quite match the best I've heard - QUAD ESL-63s or Ionovac plasma tweeters - but still has less aggression than the horn tweeter of an Altec 604.

Creedence Clearwater Revival - Bayou Country (Liberty) is a classic rock 'n' roll album.  This original British pressing somehow bests the American copies I've heard with a cleaner, more see-through midrange.  The attack of the guitar has real body and presence; unlike the past mini monitors I've reviewed.  Once again the dynamics were impressive, especially the harmonica playing which had a real raw and dirty swamp sound.  It sounded as if a whole lot of air was being moved!  The instruments were each locked into their own space, separate but joined in the musical whole. 

 

Conclusion: As you can tell, I was taken away by the presence the KEF R500s could project.  The body of instruments and vocals were especially enjoyable.  These speakers seemed to sit in a middle ground between the UREI 813As and the Magnepan 1.6QRs, which is to say they could swing dynamically, soundstage quite well both in width and depth, and still provide musical enjoyment.  But they also didn't have the aggressive warts and all sound of the horn speaker, or the dark graininess of the planars.  After living several years with the limitations of small monitor speakers it will be difficult to go back; the ability of the larger KEFs to provide life-like body is something I cannot forget now.

In the future I will be playing with some wiring changes, a different cartridge, and maybe even a more powerful amplifier.  For now, however, the speaker quest is finished.

Review System:
Thorens TD-309 turntable with Ortofon 2M Bronze
 Classe Five preamplifier
First Watt Aleph J clone
Cardas Iridium interconnects
Cardas Twinlink speaker cable