The Valve Art 6550A is a three hole, grey plate power tube with a single side getter positioned at the bottom of the plate structure, as was the case with the Valve Art KT88.  Also, just like the VA KT88, this tube has a chrome-colored collar with a brown base.

Although I believe the review sample was purchased about eight years ago from Tubeman, they are no longer listed there.  I did find them available from two other online vendors for approximately $110 per matched quad. 

Front view                                                                                        Close up showing the two top getter rings
      

The only other brand of 6550A that I have are made by General Electric.  As the GE 6550A have been used, the middle portion of the top flashing has become transparent, forming two hemispheres.  This hasn’t occurred as yet with the VA tubes which still have their full getter flashing atop each tube.  I have a quad set of Philips 6550 which appear similar to both the VA and GE 6550A, but are labeled as being simply 6550.

This set also showed considerable variation in tube height.  Notice how much taller the right hand bottle is, although the plate structure and plate size were identical in all four of them.
 

The quad did show a noticeable change for the better during break-in and that’s most likely due to its not having been used, other than to make sure the tubes worked properly, when I first purchased the set.  This review, unless otherwise stated, will describe the VA 6550A's characteristics after the quad was fully broken in.

Listening Impressions:

• Well-balanced sound across the frequency range with exception noted below
• Mids are somewhat hollow-sounding, less rich than the VA KT88s (or the GE 6550A, for that matter)
• Take considerably longer than most tubes to warm-up during each listening session before they come into their own
• Borderline excellent timbre (what I also call, perhaps mistakenly, “inner detail”) and decay although initial transients are lacking compared to their VA KT88 brethren
• Sound stage is wide, deep and populated by solid images

Generally speaking, these are very good sounding tubes and another excellent bargain.  They seem to occupy a middle ground sonically between the 6550 and KT88 types.  The VA 6550A also falls in the middle of my ranking for output tubes in this grouping of Chinese manufactured tubes.   

These are three-hole, grey plate KT88s with a top getter and single side getter, positioned (unusually) at the bottom of the plate structure.  The Vale Art tubes are labeled as manufactured by O & J Enterprises Co., Ltd., China and are said to be copies of the GEC (Genalex) KT88.  They are carried by Tubeman at a price of $74.95 per pair.  Cryogenically treated VA KT88s are also available for $99.90 from the same online dealer.

The VA KT88 has a chrome-colored collar and brown base.  The review set is well broken in and was purchased eight or nine years ago, most likely from the dealer cited.

Label side view                                                                                 Rear view with side getter flashing
      

Listening impressions:

• Borderline excellent detail, transient snap, and dynamics
• Bass lays a solid foundation and electric guitar sometimes has a growl to it which is not common in my system
• Treble is extended but not exaggerated -- cymbals have a metallic shimmer that slowly fades into the noise floor
• Accurate midrange that allows for clear, easy to follow dialogue and realistic vocals (mouth noises, etc.)
• Instruments occupy their own space and the acoustic is easily heard

The Valve Art KT88s are my favorite of the Chinese manufactured tubes reviewed so far.  This is due to the fact that they seem, at least to me, to combine the clarity and resolution of the 6550 output tube with the superior, transparent sound staging ability of the best KT88s.  This similarity to the 6550 may be what, in the final analysis, pushes the VA KT88 to the fore of the Chinese manufactured KT88 type output tubes.   

During the review process, I found myself forgetting to listen critically and became absorbed in whatever was playing on my stereo.  It’s hard for me to pay them a higher compliment than that.

The review sample was purchased from GD Audio (Good Components) where the price is currently listed as $29.50 per tube.  This KT88 tube has grey solid plates, two rather large (although the size varies from tube to tube) side getter flashings, and a chrome-colored collar with a black base.  The pins fit more snugly than I would have preferred both going in and coming out.  Be extremely careful with them.

On initial power-up, at the lowest bias setting on the Premier 11A, there was a momentary crackling sound emitted by the speakers which immediately stopped.  Although these tubes were brand new, the review sample was tested for over 30 hours and their sound did don’t change after 10 hours or so of cumulative playing time.

Label-side view of the GEKT88                                                                   The matched quad in the Premier 11A
             

The labels listing the matching information later detached themselves from the tubes and fell alongside the tube sockets inside the cover.  Be careful removing them if you are using metal tweezers to extract them.  

These tubes exhibited the typically rich and smooth sound of the KT88 family and, in particular, were extremely similar to the Shuguang KT 88-98 and Penta Labs KT88SC. 

For the first five hours the GEKT88 exhibited excellent high frequency detail and extension.  In this regard, they were most reminiscent of the New Sensor Gold Lion KT88, my current favorites of this type.  However, at around the 10 hour mark the highs lost that extra degree of sparkle as the tubes burned in.

Listening Impressions:

• Good to very good leading edge transients and same level of detail.
• Continuous sound stage with very, very good width, depth and height.  Solid images.
• Bass response is good although no more so than average.
• Midrange is good with a tendency toward warmth.

Overall, I would put these on par with the Shuguang KT 88-98 although they weren't identical in sound characteristics.  However, the Penta KT88SC/Mullard PCC88 combination was superior.  As good as the Shuguang GEKT88 were with sound staging, they weren’t a match for the Penta Labs KT88SC.  

These are Soviet made dual triode tubes with production years of 1979, 1980 and 1982 purchased from Upscale Audio about seven years ago.  Upscale still has them listed on their web site as the 3^rd type (or, “Type 3”) variant and they range in price from $20 each for the Driver Grade to $30 for Gold Grade to $35 for Platinum Grade.  Although I no longer am sure, I believe the review samples are Platinum Grade (“Lowest noise and microphony with the tightest triode balance we have available. This is typically 10% or tighter, but may be higher depending on available stock.”).

The 6H23π type is the Soviet equivalent of the 6922 dual triode and was designed, originally, for military and space use.  The “EB” variant is supposed to be the ruggedized version and is the more sought after variety.

Standard Arabic numeral designation:                                                 Other side showing month of production in Roman numerals (this was abandoned soon after)

The middle fellow in both shots appears to be a little tipsy. 

I had not listened to these tubes in my c-j Premier 16LS2 for quite some time and was quite pleased with how the sounded.  These followed on the heels of the Mullard PCC88/7DJ8, previously described, and was in many ways quite different sounding.  I’ve been using the Saratov 6H23π-EB initially with the vintage Tung-Sol three hole 6550 and currently with the Shuguang GEKT88 (review forthcoming) output tubes in my Premier 11A power amplifier.

Compared to the Mullard PCC88, I found these tubes to have a more natural presentation with an even, linear response across the frequency range.  Although the Mullard mated perfectly with the Penta Labs KT88SC output tubes, I thought they sounded tipped up and exaggerated in the treble with the original Tung-Sol 6550s.  So, if your output tubes are a little on the dark side, the Mullards are a very good choice in bringing more detail to the front.  However, their use with a neutral tube such as the original Tung-Sol 6550 is more iffy and with somewhat lean or analytical tubes such as the SED =C= 6550C or the Ei KT-90, I feel they are too much of a good thing and wouldn’t use them in those combinations.

Listening Impressions:

• The Saratov 6H23π-EB is a definitely more even-balanced sounding tube that lays a solid foundation in the bass.  Cellos have a woody quality that I find appealing. 
• It has a more subtle presentation of inner detail and, if anything, may be slightly warm in the upper bass and lower midrange.
• Treble presentation is neutral and without exaggeration.
• Lateral separation, height and depth are very good although not as immersive as the Mullard/Penta combination.

All in all, the Saratov 6H23π-EB tubes are a good choice for a neutral sounding tube and although not in the same league as the Lorenz PCC88 (and other vintage varieties such as Telefunken and Amperex) have the definite advantages of being both readily available and very reasonably priced.

NB:  These were mistakenly identified in the original posting as Voskhod 6H23π-EB when they are in fact from the Saratov factory.  Sorry for the confusion.  I do in fact have some Voskhod 6H23π-EB and may report on them in the future.

As I’d hinted with the final photographs in the previous installment, this preamplifier is clear and transparent.  Therefore, it takes on the characteristics of both the source components that are upstream and the type of dual triode tube that’s being used to “drive” the preamp.

As a reference point, when I use the word “clear,” I mean that the component under discussion portrays the details of the music in a way that is easily heard.  When I use the word “transparent,” on the other hand, I mean that it allows the listener to immerse himself or herself more easily into the sound stage as if it were an almost three-dimensional landscape, an acoustic diorama of sorts.

For the sake of this review, I’ll be discussing the sonic characteristics of the 16LS2 using the 1960’s vintage Lorenz PCC88/7DJ8 dual triode which were manufactured in their Stuttgart plant.  It appears, in the one case where I have both the 6DJ8 and the 7DJ8 version of the same tube and vintage (the 1968 Telefunken), they sound identical to me. 

I find the 16LS2 is very much like a chameleon due to its clarity.  Is it the last word in clarity?  I’m sure that it isn’t by any means.  However, I’ve found that almost every change I’ve made in my system, be it tubes, turntable, cartridge, CD player, universal player, music server, interconnects, speaker and power cables, has always made its presence known. 

Does my tubed Modwright/Music Hall CD-25 present the information on a Red Book Compact Disc differently than my Oppo BPD-95 universal player?  Most certainly, it does.  The Oppo seems to have more apparent detail while the CD-25 projects a more holographic sound stage inhabited by more solid images.  The Oppo is more impactful while the CD-25 is more musical.  Once we shift to SACDs, though, the gap between the two narrows and the BDP-95 now sounds as smooth as the CD-25 and the qualities of image solidity, sound stage width and depth are more evenly matched.  The key point is that the 16LS2 allows me to hear, what are at times, relatively small differences.

The 16LS2 is also extremely quiet.  There is none of the low level tube rush or roar evident with some preamplifiers.  Because of a discussion thread on the AudioAficionado board, I tried an experiment with the 16LS2.  I switched the source selector to the CD-25, which was on, and set the Level control to 66 (the unity gain setting on the preamp).  I never listen at this loud a volume during normal playback.  In any event, with my ear right up to my QUAD 989 speakers, I couldn’t hear any noise coming through the system.  Just to be certain, I moved my ear to various spots on the speaker:  the bass panels on top and bottom and also the middle portion of the speaker.  No sound was heard.

I did hear, even at a low (in the mid- to high-teens) volume setting, a hum coming through when the source was switched to my cable box.  So it’s not that the preamp is muting output when no signal is present.  I was eventually able to get the cable box to quiet down by finagling the position of the box although when I did increase the volume setting to around 50 or so, there was some residual hum heard.

The 16LS2 is an excellent performer.  Bass is handled tunefully and articulately while the treble portion of the spectrum shimmers.  I’ve never found the highest register to be rolled off, at least to my tastes.  Although, depending on ancillary equipment and the tubes used, I could see why this might become an issue.  A “palpable” midrange is a c-j hallmark and the 16LS2 doesn’t disappoint in this regard either.  Female voices, in particular, are realistic and occupy space in your listening room.

Dynamics is an area I have difficulty describing.  It may have to do with my system, as a whole.  Going from very soft sounds to soft or average are handled capably.  From average sound levels to loud or very loud is something else.  If there's a place where my system is lacking, I feel this is where it could use the most improvement.  This reticence to switch into high gear in a moment, a lack of impact if you will, what I believe is called macrodynamics, could use some help.  Now, how much of that may be the fault of the 16LS2 and how much could be left at the door of the rest of my system is something that continues to puzzle me.  But, if push came to shove, I'd have to say it's due to the rest of my system and primarily, the QUADs.  Extremely dynamic is not an expression that applies to them, in my opinion.  

conrad-johnson is reputed to have a house-sound, especially during its earlier years.  The Premier 16LS, introduced in 1998, and to a somewhat lesser extent, the 16LS2 do have the richness that c-j products are known for.  To some, this will be perceived as a drawback and, in fact, c-j’s more modern offerings have veered towards the more tonally neutral portion of the lean and analytical versus rich and lush continuum. 

What may sound polite and just a bit laid back to some, may be just right to others.  As with everything in our hobby, it always comes down to system synergy and personal taste.  In my not unbiased opinion and everything having been said, the conrad-johnson Premier 16LS2 strikes the right balance for me.

In preparing to write this entry, I realized that I neglected to mention the Mute button on the 16LS2 and its remote control.

Well, as the name implies, depressing this button sets the preamplifier’s Level control to 00.  Something that may be worth mentioning, however, is the fact that once the mute button has been engaged, you can’t change the Level setting.  You may, however, change the source setting even when the 16LS2 has been muted.  So the workaround is to change the source, then unmute the preamp, change the Level to something more comfortable and then switch back to the source you were drunkenly listening to.  Alternatively, you could stop after two glasses of Montrachet and not get into this predicament at all.

The default Level setting when the preamp is initially powered up out of the box is 20.  That’s also the Level setting the unit will default to after a power outage, power cord change, etc.

Speaking of power cords, here are a couple of photos of the stock 16 gauge power cord.  It’s sheathed in basic black (and who doesn’t like a basic black sheath?) and has the words “Hospital Grade” molded into the male end.  I don’t know what the green dot signifies.  Perhaps, that it has passed inspection. 

When I bought the 16LS2 from this lovely couple who lived in an even more lovely home in Hollywood Hills, he’d discarded the stock power cord so I had to order one from conrad-johnson.  I think it cost all of $25 and is worth every penny. 

I’ve since replaced the stock cord with a Shunyata Venom3 that currently retails for more than four times as much.  The Venom3 boasts “Medical Grade” connectors and “MASSIVE 12 Gauge OFC Conductors” according to the blister pack it comes in.  Photo below.

The Venom3 is not nearly as flexible as the basic black sheathed jobbie and its female end is kinda heavy and sticks out a little too much for my liking, but hey, to each his own.  What it does, however, is sound better than the stock cord.

The Venom3 allows for a more open high end and better detail.  The bass also has some more weight to it without being overdone.  The differences are noticeable but not night and day.

Okay, the next installment(s) will finally cover how the 16LS2 actually sounds.  Without giving too much away, I leave you with these final photographs.

Another reason I don’t use the o-rings is that it aggravates my audiophilia nervosa.  What if instead of putting the rings one-third of the way from the top and bottom of each tube, I bunched them together in the middle of each tube?  Or, what if I only used one o-ring per tube?  And if I did, where would I put it?  By the top mica ring or the bottom mica ring?  Or maybe in the middle like with the double rings bunched together?  Yikes.

I think you get the idea. 

Also, I failed to mention the External Processor (epl) button.  That’s because I don’t use any kind of home theatre preamplifier/processor.  But if I did, I could use the button on the preamp, or, the epl button on the remote.

One reviewer described the 16LS as giving 80% of the ART’s performance at a little more than 50% of the price.  Unfortunately, never having heard the ART myself, I can’t comment directly on his opinion but I did think it was a favorable comparison.  And the six tubes in the 16LS2 versus the 10 in the ART do mean it’s less expensive when it comes time to re-tube. 

Another area of practicality is the stock power cord that comes with the 16LS2:  it’s actually pretty good.  I’m using a Shunyata Venom3 with mine which is an improvement but if you have to stick with the standard cord, it’s not a bad choice.

According to the conrad-johnson web site the switching in this preamp is sealed and has gold-plated silver contacts.  The input and output connectors are machined from oxygen-free copper and are also gold-plated.

Here are two photos of the front and back of the remote control.  The Balance control takes a little getting used to but after a while I got the hang of it.  When you increase the right channel by depressing the right Balance button, the left channel goes one click lower.  The longer you depress the Balance or Level buttons, the quicker the 16LS2 ratchets through its settings.  It helps if you like clickety-clack noises because that’s what it sounds like. 

You’ll also notice that on the reverse side, the remote has four hemispherical thingys, one placed at each corner.  This prevents your remote from sliding around when your yacht is on the high seas.  This way you only have to hold on to your glass of Montrachet to make sure none of it sloshes onto your pants.  It probably also prevents you from scratching the teakwood coffee table in your cabin. 

Here’s a shot of the rear of the 16LS2.  No, this isn’t mine.  I cheated and got the picture off the Web because I didn’t want to unplug everything since that would’ve been a royal pain in the you-know-what.  

So, working from left to right because this picture sucks, we have:  The left channel RCA connectors (the ones with white rings and inserts) are on top and the right channel (the ones with red rings and four of which have red inserts, too) are on the bottom.  Also, from left to right, they are:  Aux1/Ph (red insert), Tuner, CD (red insert), Video, Aux2, EPL1 In, EPL2 In, EPL1 Out, EPL2 Out, Main Out (red insert), Main Out (red insert).

Those epl in-connections could also serve as just two additional inputs for a total of seven, if so desired. 

The two Main Out connections allow for biamping for those audiophiles who lean that way.

Then there’s the IEC connector for the power cord (photo of the cord to follow in another installment).

There’s a screw to the left of the power cord receptacle (that you really can't see) that may be for grounding, or, it could be just a scratch in the casing.  I can’t tell from the photograph and as previously stated, I’m not going to take mine apart to see. 

Next to the IEC receptacle is the usual Caution warning about frying your silly self if you’re adventurous enough to go poking around inside the casework. 

And at the far right of the picture, there’s the model and serial number plaque.

Here’s a gratuitous topless shot of the 16LS2 sporting the Voshkod 6H23-EB tubes I put in yesterday.

I’m not going to comment on whether the preamp sounds better with the tube cage or without.  But here’s a hint:  Say you’re driving down the Pacific Coast Highway on a nice warm, sunny day in the convertible vehicle of your choice.  Which way do you think you’re going to enjoy the experience more:  with the convertible top up or down?  I rest my case.  I was going to use a Scarlett Johansson in a bikini versus a just her bottoms’ analogy, but I didn’t want to offend anyone’s sensibilities.  Plus, it’s sexist.  

For those of you who entered the “How Many Screws Are There In The Tube Cage Contest?” we come to the final photographs.  The answer, in brief, is that I still don’t know. 

There are four plates as I described yesterday.  In the picture on the left, I flipped over the second plate from the right so you could see the cushions which I guess are for additional vibration damping.  The final (bottom) plate which is shown close up in the right hand photo is actually connected to some runners and I was too scared to take it apart because I thought the set screws might come apart and then I’d be, well, screwed.  So.  There appear to be eight Philips head screws (four that connect the top plate and four that connect the bottom plate to the runners), two set screws, and eight of these post-like thingys that connect the intermediate plates.  There are also four more of the post-like thingys between the bottom plate and the runners but they may be different from the other eight, I’m not sure and I’m not going to find out, either.    

Today’s entry is an introduction to the conrad-johnson Premier 16LS2 preamplifier.  conrad-johnson describes the Premier 16LS as a single unit version of their ART preamp and it uses the same parts quality as the more expensive unit.

The 16LS2 replaced a Premier 17LS in my system.  The 17LS is a very good preamp, also a one chassis “baby” version of c-j’s ART preamp, although designed to a lower price point ($4,500 for the 17 vs. $8,495 for the 16LS2 vs. $14,995 for the original ART).

For some in-depth analysis of the 16LS, the reader is directed to these reviews:  Stereophile reviews of 16LS and 16LS2.

I’ve taken the following description of the 16LS2 straight from the Stereophile review because it encapsulates the preamp's basic information as well as I ever could.

*************************************************************************************************************************************************

Description: Single-chassis, remote-controlled, tubed line-stage preamplifier. Tube complement: six 6922 dual-triodes. Inputs: five unbalanced (RCA), two processor loops. Outputs: two unbalanced (RCA) plus processor loops (RCA). Frequency response: 2Hz->100kHz. Gain: 26dB. Maximum output: 15V. Distortion (THD or IMD):

************************************************************************************************************************************************

You’ll note that the preamplifier inverts phase, which is the case with every line stage in their preamps that c-j has made since the PV-7 and Premier 7 models.  c-j states that each active voltage gain stage in a circuit inverts phase once and since their preamps only have one gain stage, they invert phase.  The solution is to switch the positive and negative leads of both speaker cables either at the amplifier end or speaker end and correct phase will result.

conrad-johnson believes that keeping circuits as simple as possible and parts quality as high as possible, will result in superior sounding equipment.  That is the reason that they also eschew balanced circuitry and connectors.  

Another factor to keep in mind is the 16LS2’s output impedance of 700 ohms.  While that’s not inordinately high, it is high enough that interconnects with the lowest possible capacitance and shortest lengths should be used for the best high frequency response.  Their most current model preamplifiers such as the ET5 and GAT have achieved output impedences of 100 ohms by using high output MOSFET buffers to drive the output stage.

Here are some photos of my 16LS2.

The preamp has a 100 stepped attenuator in 0.7 dB increments with unity gain at step 66.  I have upstairs neighbors, so depending on the source, I don't usually go above 40. The relays are microprocessor controlled and make a clacking noise which you get to like.  All functions may be accessed from the remote control which is machined from a billet of solid aluminum.  The remote is solid enough to be used as a weapon to club an intruder, or, an overly boisterous guest. 

A close up of the display and indicator lights.  You can toggle through the sources and raise or lower the volume with those buttons below the display.  You can mute the preamp also.  I always use the remote.  You can only turn the unit on or off with the Power button on the far right.  I don't know why that wasn't included on the remote.

Here are the unit's tubes, behind their protective cage.  I've replaced the Mullard 7DJ8 tubes with Voshkod 6H23 tubes.  I'll write about them in the near future.  The cage can be disassembled layer by layer with a Philips head screwdriver, for cleaning I guess.  There are four screws per layer and four layers counting the base, so that's 16 screws you have to contend with.  The entire cage can be removed by its two captive screws with a flat head screwdriver.  You could go topless but then the dust gets in there more easily.  The 16LS2 comes with 12 rubber-like (maybe they're silicone) o-rings.  They are used to reduce microphonics and you're supposed to put two on each tube.  You position the o-rings one-third from the bottom and one-third from the top of each tube.  I don't use them, I feel that they reduce image size, flatten the soundstage a little and suck out some of the air.  Other than that, I think they're fine.  Most people seem to use them, at least as far as I can tell from the conrad-johnson forum on Audio Aficionado.  All of the tubes are inserted into this plate that's decoupled from the rest of the unit.  When you first get the preamp, you remove four transit screws from the bottom of the preamp and that allows the plate to decouple from the rest of the works.  That's supposed to help with vibration-induced microphonics, too. 

I'll have more to say about the preamp in the entries to follow.

Here are some photos taken over the years of my system.

November, 1974:  (l to r) Cervin Vega 211R,                  December 25, 1985(?):  Same system, in our first home, with CD-4 demodulator serving  
Pioneer PL-61,Marantz 4300 and Dokorder 7140              as Santa's resting spot, speakers (out of shot) may have been Polk SDA 2B at this point
                  

c. 1995:  (third home) Martin-Logan Aerius, c-j PV-10AL,
Adcom GTP-400, Adcom GCD-600 and Adcom GFA-555         Later 1990's:  Golden Tube Audio SE-40

  September, 2011:  Entire system                                                                  January, 2012:  Premier 11A with vintage Gold Lion KT88s                 
                     

I thought some reader(s) might be interested in how my system has changed over time.  Dates, when given, are approximate and I'm also sure I've left out any number of items.  But this was generally speaking how it's evolved.

Any comments are welcome.  Thank you.