With apologies to David Bowie, my system has been going through some changes lately, so this gives me a reason for the latest entry.

My conrad-johnson Premier 16 LS2 preamp uses six 6922 dual triode tubes and in fact, any member of the 6DJ8/6922/7308 may be used.  Although not designed to use the 7DJ8 dual triode which runs on a 7 volt heater current (as opposed to the 6 volt 6DJ8), these tubes appear to work very well also.

Of late, my mainstay has been the Lorenz PCC88/7DJ8 in the Premier 16LS2.  It appears to do everything you want from a preamp tube:  it gets out of the way and lets the music flow through the system just as neutrally as you’d like.  In addition, it images like a champ with a fully fleshed-out sound stage. 

Recently, however, I received some Mullard 7DJ8 tubes and in order to make sure they had arrived in good shape, I plugged them in.

Here are a couple of shots of what they look like.  They were manufactured in Mullard’s Blackburn, England plant and if you look closely at the second shot you’ll see a sepia colored character imprinted on the bottom, right-hand corner of the tube which appears to be an “8” or perhaps a “B”.  It’s a “B” and it is in fact the plant designator for the Blackburn factory.  The second photo also shows the getter ring, just under the top flashing, both of which are angled.

I’ve kept the Penta Labs KT88SC output tubes in the Premier 11A in order to maintain some system continuity.  So what I’m reporting should be directly attributable to just switching out the Lorenz PCC88/7DJ8 tubes for the new kids on the block:  the Mullard PCC88/7DJ8.

Listening Impressions:

• A more open and airy treble presentation than the Lorenz
• Very dynamic sound with a peppy and sparkly presentation that seems to bring out a previously hidden quality in the Penta KT88SCs
• Midrange is not what I expected based on the Mullard reputation of a “rich” presentation – in fact, the mids are quite neutral
• Downside:  the bass doesn’t reach as far down as with the Lorenz tubes but is nevertheless impactful
• Sound stage is very, very good.  Perhaps as good as with the Lorenz.

I was pleasantly surprised by how well the Mullards acquitted themselves.  To give one example:  I was watching the movie Fast Five (okay, there’s no accounting for taste) and in one scene, a screw (or maybe a bolt) falls to the hard-surfaced floor in a garage and while I knew it was taking place in the movie, I still glanced at my own living room floor because that’s where it sounded as if it had fallen. 

These moments where the sound is utterly realistic are what we live for and while this was a sound effect and not music, I think it still speaks very highly of the Mullards. 

The change to the system’s sound with the new preamp tubes in conjunction with the Pentas has been analogous to the difference between Shunyata cables (Altair and Antares interconnects) and Nordost’s Red Dawn cables.  The Penta KT88SCs now sound much more like the New Sensor Gold Lion KT88s with more apparent detail while retaining their excellent imaging abilities.

I will be interested to hear whether the Mullard PCC88s continue to shine with other output tubes or if this is fortuitously a particularly synergistic match up.  

The tubes under review in today’s entry are made in China by Shuguang “exclusively for Penta Laboratories” who test and re-label the tubes under their own brand name.  Penta Labs is located in Chatsworth, California. 

Physically, the tubes have solid grey plates with a top and two side getters.  Interestingly, half of the tubes have a brown base and the remainder is black based.  They bear a date code of 0529 (29^th week of 2005).  This is most likely when they were processed at Penta Labs.

According to the Penta Labs web site:  “The KT88SC is made in China by the Shuguang factory exclusively for Penta Laboratories. It was designed to be equivelent (sic) to the original Genelex (sic) / M-O Valve KT88 in construction tecniques (sic) and cosmetic appearance.”  As you’ll read, these folks market a pretty good tube, but they really need to spell check their ad copy.

I remember purchasing the tubes directly from Penta Labs, but after visiting their web site, I’m not sure that can still be done.  Maybe contacting the company directly to order them is possible.  In any event, they are available from Doug's Tubes at $52 each.  The usual caveat:  I have no affiliation with either of these companies.  As a matter of fact, this is probably a good place to state that I do not have any affiliations with any of the companies mentioned in my blog entries.

Here are two photos of the black base version of the KT88SC tubes that were actually used in the review:

Although I’d thought that these tubes were fully broken in prior to my listening tests, I did notice improvements as time went on.  Most noticeable, their top end opened up but never to the degree I would’ve liked.

Listening Impressions:

• Typical smooth presentation that I’ve found to be, in general, characteristic of KT88 tubes with a relatively balanced sound across the frequency spectrum 
• There was one exception to the balanced sound, and that was a noticeable lack of upper frequency sparkle that I find the best of breed to possess.  They did not have the crystalline highs of vintage Tung-Sol 6550s or, even, the New Sensor Gold Lion KT88s
• Good inner detail and timbre
• Bass was good to very good and never drew attention to itself
• Midrange was good with female vocalists, especially, nicely handled
• Where these tubes really excelled, in my opinion, was sound stage.  The images were spread across the speakers, clearly defined and projecting well into the room and behind the speakers, as well.  The images also had a solidity that helped foster the illusion of reality 

There is an ease to the sound that is reminiscent of the original Genalex KT88s and in this regard, they are successful.  Their sound staging is exemplary and if this is high on your list of desirability, you might want to give these a listen.  I find I prefer these to the KT 88-98 type reviewed in part 2 of this second cycle but they are less satisfactory to me than the New Sensor Tung-Sol 6550s in this cycle and the two KT88s listed in the first cycle. 

Update:  I’ve received some Mullard PCC88/7DJ8 tubes and installed them in my c-j Premier 16 LS2 preamp.  While they break in, I’ve decided to keep the Penta KT88SC power tubes in the amplifier and will report on what changes, if any, there may be to the system’s overall sound. 

The tubes under review in today’s entry are the Chinese manufactured Shuguang KT 88-98 output tubes.  They are a three hole, grey plate variety with a brown base.  They were originally purchased from Upscale Audio but a recent perusal of Kevin Deal’s web site no longer lists this type.  I was able to find them at GD-Audio for the very reasonable price of $30 each.  I have no affiliation with either dealer. 

Here are a couple of photos of the KT 88-98 tubes that were actually used in the review:

A note on a generic and very subjective set of terms that you’ll see sprinkled throughout my listening impressions.  I will frequently use these words to describe my reaction to how the tubes sound, and they’re ranked in ascending order:  fair; good; very good; very, very good; excellent.  Stop sniggering.

Listening Impressions:

• Nicely dimensional and refined as is typical for a KT 88 type
• A little more rounded sound than the New Sensor T-S 6550 with very good treble response and good to very good detail
• Good transient snap but a notch below the New Sensor T-S 6550 in this regard.  This may be what I’m hearing as a “more rounded sound”
• Dialogue is very clear
• Chimes and bells are realistic, if a little distant
• Bass response is good

As I also found with the New Sensor Tung-Sol 6550, the Shuguang is a pleasant sounding and musical tube.  My listening preference is for a more detailed presentation than I found with this KT 88-98, so I’d have to rank this particular tube below the New Sensor T-S 6550.

I realized that although I’d provided a link to my system that lists what equipment and accessories are currently being used, I thought it’d be worthwhile to show the small signal tubes being used during the course of my power tube reviews.

conrad-johnson Premier 16 LS2 Preamplifier:

This preamp uses six (three per channel) 6922/E88CC tubes.  I’ve found that 6DJ8/ECC88, 7308/E188CC and 7DJ8/PCC88 tubes also work very well in this unit.

My current tube of choice is the 1960’s vintage Lorenz 7DJ8/PCC88 made in their Stuttgart, Germany plant.   Its sound is very similar to the Telefunken 6DJ8/ECC88 and 7DJ8/PCC types from the same time period, but I prefer the Lorenz by a small margin for its across-the-board excellence.  Of all the tubes that have been rolled through the 16 LS2, these get out of the way more than any other while still ticking all the audiophile approved boxes including sound stage palpability.  They’re clear and detailed without ever sounding sterile and are as close to not being there as any I’ve heard.

conrad-johnson Premier Eleven A Amplifier:

This amplifier uses a pair each of 6FQ7 (you can also use the 6CG7 type) and 5751 tubes.

I’m currently using GE tubes in both of these positions.  The Eleven A was originally voiced by conrad-johnson using GE tubes in all positions, including GE 6550A power tubes.

GE 6CG7

The tubes in the amplifier are actually the earlier model of the 6FQ7, the 6CG7, and include the central electrostatic shield that was later eliminated in the 6FQ7 model.  conrad-johnson doesn’t ground pin 9 which is connected to the shield so I guess, in theory, these two types shouldn’t sound any different in the Eleven A. 

This picture shows the central silver/chrome shield but because it's reflective, the shield appears to be the same color as the outside plates, dark grey.

This is a double mica tube, with one mica layer above and the other below the vertical plates.

GE 5751

These are GE triple mica, black plate 5751 tubes and date to sometime in the 1950’s.  The vendor I purchased these from has them listed as triple mica, grey plates but they certainly look black to me.  For that matter, although it may be difficult to tell from the photograph, they also appear to have double mica plates (therefore four in total) below and above the central, vertical plates.

Here are all the little guys lined up for the last shot.  To their right in the photo, you can see the Shuguang KT 88-98 power tubes that will be the subject of my next meanderings.

This is the first installment of the second round of my power tube reviews and will cover the New Sensor reissue of the classic Tung-Sol three hole, grey plate 6550.  These tubes were well broken in and were purchased in 2005 from an online tube vendor whose name I no longer remember.  They are Russian made and have date codes from November, 2004. These could very well be from some of the initial production runs and may or may not be different from current production.

Listening impressions:

• Punchy bass with very good dynamics
• Very good transient response and clarity
• The sound stage has very good lateral separation and depth with clearly defined images although the images themselves are somewhat two dimensional
• Evenly balanced midrange

Overall, their sound is similar to vintage Tung-Sol three hole grey plates although not quite as refined or dimensional.  Still, they're very musical and I could live with these quite happily.  They are an excellent value given their quite reasonable prices.

    New Sensor KT120                                                             Ei KT-90                                                 

 I hope you liked the photos.

I've started the next phase of the review and I'm currently listening to the New Sensor Tung-Sol 6550 reissue tubes.  I'll report back as the review progresses.

Philips ECG 6550 ST shape          Philips ECG 6550 straight bottle                            GE JAN 6550A                                      SED =C= 6550C

Here are the two KT88 tubes in the survey.

 New Sensor Genalex KT88                  Genalex GEC KT88

I thought some readers might like to see photographs of the power tubes described in Part 1 of the Power Tube Mini Review.

Note:  These tubes are not depicted actual size nor are their relative sizes accurate.  I've tried to get them all basically the same size for purposes of this layout, but not always successfully.

  Tung-Sol black plate, top getter only    Tung-Sol solid grey plate         Tung-Sol three hole grey plate

I seem to be only get a few photos in at a time, so I'm going to have to do this piecemeal.

The tubes comprising this review were auditioned in my system which was previously described in my February 29, 2012 entry.  Although I’ve made three cable changes to the system since, that was subsequent to the subject of this entry.  The various tubes are listed in descending order:  that is, from favorite to less liked.  I should note, however, that I consider even the last one on the list to be better than most current production tubes.  The New Sensor Genalex KT88 and KT120 and the SED =C= 6550C being the only exceptions as they are all currently manufactured.  I have not listened to the New Sensor Tung-Sol 6550 in too long a time, so it isn't included in this list.

Please bear in mind the usual caveats that while this is how they sounded to me, it is of course system-dependent and subject to my own personal tastes.  You will most likely find different results if you audition these tubes. 

“COO” refers to the tube’s Country Of Origin.  Finally, the “Comments” section is just a thumbnail description.

Within the last five years, perhaps a little longer, tubes of Chinese origin have come into their own with greatly increased reliability and sound quality.  Some brands, such as the Shuguang Treasure series and PSVANE, have been very well received by audiophiles and their sonic characteristics well-documented in some of the forums.

Although I do not have either of these brands in house, I do have a fairly extensive collection of other Chinese power tubes by Valve Art, Penta branded KT88SC, and “plain vanilla” Shuguang.  I have not listened to these tubes in my present system and have excluded them from this review for that reason.

Although I do not have any plans at present, they may be the subject of a future review.  Perhaps with the New Sensor Tung-Sol 6550 as an outside control.