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KT-88Z Treasures in VRDs


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The Penta Labs KT88 I was referring to is the KT88SC. I have not used the Penta Gold Aero so I cannot comment on those....nor have I used the Penta KT88-98 (didn't know that existed).

My comments on the KT88SC as my favorite out of Shuguang is based on use of Valve Art KT100 (second favorite by Shuguang but not produced anymore) and Shuguang KT88-98/Valve Art KT88 (both top/side gettered as well as top only getter.....the "value" tubes). The Valve Art KT100 and Penta KT88SC both are more stable tubes (especially at higher plate voltages)....biasing at install exhibits MUCH less wobble/flutter, very stable and steady, with only a few "dial ups" of the bias through breakin.....the value priced Shugs arent as stable out of the box (in fact the bias voltages are much more up and down when observed on the meter and take more breakin time to "hold steady", and aren't always tolerant of higher plate voltages.

I read somewhere that the VA KT100 used more or better cathode material which made it a stouter tube electrically. I cannot vouch at all for the Penta KT88SC, but it acts just like the VA KT100...very stable out of the box. NONE of the value priced Shugs I tried acted well in this way. I spent the better part of a year investigating these KT88s in VRDs to get good tubes for them, and then stocking up on the "good" versions.

Sonically, the Penta KT88SC is my favorite, as it is very smooth and with very good detail. The VA KT100 is a bit more tipped toward the upper mids but still has the Shug family sound.....the Penta KT88SC is just more refined and smooth through the midrange. The KT88-98 (Shug and Valve Art) are OK sounding (again, that Shug family sound, but not as detailed/refined), but I had such variance in the electrical viability that I moved on to tubes that were better electrically.

Not all Shuguang KT88 are created equal. The problem is that there are no "set standards" between these different tubes....one just has to try them. The way some of the larger purchasers of Shug tubes talk, it's akin to getting something "black market". It's all dependent on a buyer's ability to negotiate good product out of Shuguang, and sometimes these buyers get what they want.....and sometimes they don't and have to go back and have them "run again". Even amongst the "value line" KT88 (like the VA, Ruby, and standard KT88-98) there have been inconsistencies over the years....it seems you have to find the right tube during the right stage of the production cycle to get what works. I found very good results with the Penta SC and the VA KT100 and stocked up (and TESTED IN AMP) every one of those tubes to assure I had a stock that I trust. If you buy Shug tubes in three years? Who knows what you'll get....the cheaper ones might be OK and the pricey not so OK, that's par for the course with that plant.

The value priced Shugs were pretty good in '05-07....but it seemed about then (when I got my own VRDs) that the lower cost versions weren't very good, so I went through an array of KT88 in search of a viable "house tube". I went through KT88-98 (both side and top getter only), Genelex reissue (which went blue light sparkshow within 500 hours although I'm assured they are better now), then finally Valve Art KT100 and Penta KT88SC to find consistency and stability.

I can understand EVERYONE's frustration with Shug tubes because there are no set standards and little consistency with them. You might look, for example, at a Valve Art KT100 and a Shuguang KT88-98 and think they are the SAME, but in circuit, they are anything but.

It's all about finding a good "run".

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Hi Audible,

Thanks for the post and explanation. As I said,
given your assessment of them I will have to get a quad of the KT88SC.
As Craig said, I haven't found anyone other than Dougs tubes or Penta
themselves who sells them. Penta does not show them making a KT88-98.
See product list here.

However, Dougs tubes sells a Penta labeled KT88-98 they say is the Shuguang KT88-98
which Craig apparently disputes. You can find the Shuguang labeled
version at multiple places but the Penta labeled version I have only
seen (no actual image however) at Dougs.

To complicate things,
Penta does admit way back when that when they ran out of stock of SC's,
they substituted the 88-98 for the SC's for a short while so maybe this
is where Dougs got them. So much rebranding going on, who knows.

the label disputes and branding and purchase of branding rights, it
boils down to Chinese or Russian primarily and which Chinese or Russian
tube after that. I will try the Penta solid plates though and
probably the Tung-Sol's. As you said, these 88-98's are ok - they were
always stable in my amps - but they don't blow my mind.

I know
some others who run the Genelex and they all talk about the pretty blue glow of the tube... I have read that is a gaseous tube or some such thing and
you mentioning them going up in smoke on you in a pretty blue lightshow
isn't very reassuring for $200+/quad.

I am still interested in
seeing if anyone leans on Craig to boost the VRD's to 150 watts a
channel using the Tung-Sol 120's. Niche market there. 150 watt tube
monoblocks to power a home theater. Sell 7 at a time. Big money.
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You won't see me asking for the KT120 "upgrade". I have no use for that much power....I barely use what the VRDs have (in fact I rarely if ever take them out of class A....about 18 watts or so). And I certainly wouldn't have a set of amps like VRDs altered until I knew the tube itself was worth "building around". I'm not really thrilled with the sonics of most russkie tubes, as they tend to have an inner "wooliness" and "edge" that I don't care for much. Then again, some of those tubes might do better at operating points different than what my amps use.

As for the "pretty blue glow" of the Genelex, that might LOOK "cool", but it's NOT "cool". Blue glow is a sign of gas or lesser quality vacuum. The Penta KT88SC exhibited NO blue glow on install, and that goes for my entire stash that was tested in amp. Neither did my VA KT100. I did notice a bit of blue glow "fragments" in my one quad of VA KT100 after a couple thousand hours, and I see just a hint of it in two of my four currently used KT88SC, but it's minimal even after some extended use.

The "value" Shuguangs, like the VA KT88/KT88-98 exhibited much more blue glow when new....that was another difference I noted vs. the better Shugs.

I am told that the quality control of the Genelex reissues are much better than when I had them (which was about a year into thier production) but since I have had good luck with my current Shug batches I have had no reason to try the Genelex again.

As for the Penta KT88-98, I have no idea about those. It is interesting that Doug lists them at a much lower cost than the Penta KT88SC, but having never seen or worked with them I wouldn't know what they are like in actual use or how they would differ from the others. I hesitate to say they aren't good based on the price alone, as my VA KT100 cost $124 per matched quad from AES three years ago, which is one of the better tube buys I've made and are worth every penny.

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The Penta KT88-98 is not the same tube as the Shugaung KT88-98. The Penta KT88-98 actually is what Shugaung calls the KT-100.....(and no it is not the same as the Valve Art KT-100)

OOOOHHHH.....ooooookay, that KT100 is the "flat topped" one with the dual side and top getter with the rectangle supports on the top micas, right? I do recall that tube. I never did try that one...seemed to me the reviews of that tube weren't so hot. Seems I have had several tell me here to avoid that one, but can't attribute it to anyone in particular from memory.

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Doug will be sending a quad of SCs.

After this past week pretty convinced there is no best tube, only tubes that are better than some poorly done tubes.

The 88Zs have the nearly the warmth I like when paired with Amperex 7316s in V1 and 7025s in the V2 Slots.

Rate them 49, if 50 was perfect, 0 was ear splitting harshness and 100 would be mash potatoes packed into the horns.

The Genalex Reissues were a little harsh around, 46 on the same scale, but the low and mid bass were much better, stronger and tighter.

Note: Solid State Amps, Adcoms were about 40ish, caused headaches after 45 minutes or less of listening with stock horns.

So which Output Tube is better?

Niether really, depends on what you like.

But both sounded way "Better" than 98s (Not the SCs)

Some short plate 12AX7 Mullards showed up as a gift earlier this week.

I gave some similiar Mullards away because the sounded way to warm in my Mc Intosh MC-240.

With the Amperex 7316s and Mullards in the 12AX7 Slot, KT-88Z were way way to warm, 60ish on the scale.

When the Amperex 7316s, Mullards and Genalex are combined I got all of the warmth of KT-88Zs and then some, about 52 on the scale but kept about all most all of Low end and Mid Bass strength of the Genalex Reissues. Maybe I have to readjust my scale, 52 is the new 50.

So I have a new view on tubes, not better or worse individually, but how they fit into the system they are in.

If the Stock K-401 Horns were back in my system instead of Tractrix Horns, Fastracs, the KT-88Z and Mullards may be just right in the warmth department.

So far I like two "Tube Systems"

1) Amperex 12AU7s, Amperex 12AX7 with KT-88Zs

2) Amperex 12AU7s, Mullard 12AX7 with Genalex Reissues.

Next up some 6550s and 98SCs.

Two combinations I could listen to for the rest of my life, going for three or four. . .

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Synergy has MUCH to do with it. And yes, you are correct, there's no best tube, much like there's no best bottle of wine. Choose your "flavor", vinyard, and vintage[H]

My Mac gear is a good case in point: They just LOOOOOOOOVE Telefunken 12AX7 tubes. In that gear, they are just soooooo right. But in other gear, not always so much. I would say, however, that the Amperex/Philips 12AU7/12AX7 and 6DJ8 family of tubes are as "universally good" as any tubes given the broad range of gears they sound good in.....that's a good starting point for those tube types. But as good as the Amperexes are, I still would never say they are the "absolute best"....too many GOOD choices out there, and too many circuits and operating point combinations!

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I wouldn't be shocked if a quad of those Z's mysterously arrived for me to give a whirl not long after I ship a certain set of Tungsols ship out [;)] hint hint

By the way I've been setting up a new PC and just went to look for your email with that swanky Beverly Hills address and can't seem to find it... Please resend the email with your shipping address.

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There is always a catch. . .

I would not be surprised either, might come in same boxes as some Tung Sols.

Birmingham, MI is the Swanky Address.

Beverly Hills, MI Is the affordable housing address in Birmingham Schools.

Google my address just sent, use the little guy and see all sprawling 2,100 square feet on a 100 foot lot.

In 1952 they built the first 1,000 square feet. . .

Some idiot saved some money adding 1,100 square himself except for the framing and shingles.

I heard the @#$whole saved enough cash to buy a really cool stereo.

(Also saved enough to DIY heated floors, also very cool during Michigan Winters)

In case you are wondering there are 68 cuts, mostly miter joints,
on each one of those 8 Cedar Columns.

The semi neat thing about the address is when I travel and people ask were I am from I can answer:

"I live in Beverly Hills near Time Allen."

Tim is actually from Beverly Hills, Michigan, still has house here, and friends of my wife went to Seaholm High School with him.

His Tool Time Show took place by Woodward Ave which we walk to for ice cream, Dream Cruise etc.

Any Forum Dude, Dudettes will need my wife's approval, coming to Michigan for the Dream Cruise can shoot me E-Mail if they want to hear what VRDs and La Scalas sound like, really close together in a Basement.

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Your house is gray one right? If so very nice I like it! I hope you know I was kidding I'm familiar with Beverly Hills, MI. I was kind trying to impress everyone and maybe get them to think your a celebrity. I lived in Ferndale back in the early 80's and grew up until I was 12 in St. Clair Shores (the poor middle class area).


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Only thing flashy around here is an ocasional Golf trip and even those usually envolve my favorite sandles.

This should help find it -- Cedar Columns.

Our goal was to add a Dormer/Second story but make it look like we did not add a second story.



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One of the guys I fly for and a friend of mine took the roof off Friday afternoon, framed it on Staturday and Sunday. One of his friends gave one day cushion, that was not required, before he came over on the following Tuesday and finished putting all the shingles on.

Framing Crew:

6 Foreman and 9 Carpenters.

Paid them cash and got the materials for my friends cost, Lumber yard billed me direct my friend did not want a penny - just overtime for his crew.

What a guy.

They also added Store Room on the Back of the Garage and resided the whole Garage that same weekend.

(I watched one his Foreman open a Code Red Mountain Dew Drink half of it, pour in an Energy drink into the half empty bottle then finished the mixture off and go right back to work.)



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  • 1 month later...

Well received the KT-88Z treasures and I hate to report that "to me" these tubes look, sound and test identical to the Valve Art, Ruby or Shugaung KT-88-98...... 3 hole plates and dual top getters... The smoked glass looks great but I seriously doubt it does anything magical to make the tubes perform better.

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I have tried:

Gold Lion Reissues

NOS Tung Sols



Ranked above in order how I liked them.

NOS GE 6550 are breaking-in right now.

What have I descovered about Output Tubes?

That I like Amperex in the 12AU7 slot Mullard in the 12AX7 slot and the ouput tubes only makes a slight difference.

Regardless of cost or NOS or New I like the Gold Lion Reissues.

Since the Reissues are more reliable and cost a lot less takes any coolness of using vintage tubes away and makes it a no brainer so far.

SCs, GEC and GE to try still but I am not anticipating much of a difference.

I will try Craig's Penta SC recommendation next.

Then I will have enough Output tubes to last the rest of my life. . .

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  • 2 months later...

I have a really hard time spending $500 on current production KT88, and quite frankly have a hard time paying market prices for Tung-Sol 6550. I have found great success with the Penta Labs KT88. The Penta isn't your normal Chinese made KT88....it bests the standard Shuguang KT88s pretty easily. Clear, warm, nice detail, and act VERY stable in circuit. I have about 7 quads of these, as well as a similar stock of VA KT100, another "beefed up" Shuguang they had out a couple/three years ago that's another very stable tube in circuit - albeit not as smooth and detailed as the Pentas are.

I also prefer the Pentas over the Genelex reissues, although I'll vouch that the Genelexes are a good current effort.....but I definitely like the Pentas better in my rig (JM>VRDs>Heritage).

I have read others say that they like the Treasures over the Pentas, but I'm having doubts as to whether they are worth almost triple the $$$. I figure it's the typical "10% improvement for 300% of the cost". And given what I know of the VRD's, more bang for the buck comes from the front end tubes, and since I have two of the top four recent production offerings well in stock, I'm not grippin' over my output tubes much.....and I can run the hello out of them and not worry about running out of tubes.

That said, I'm glad Shuguang is trying to push the envelope. That's good for us tubers.

I have tried all the vintage GE 6550 (Boxes and extra tube signed by B. Carver), Tung-sols and Gold Lions, plus KT-88z, Chinese KT-98s and Gold Lion Reissues.

Right now I have Gold Lions Reissues in the Left Channel and Gold Lions NOS in the right I will have to plug in the C26 to do a proper side by side this weekend to see which one wins between those two.

Then a Side by Side with Pentas latter this year to determine the best output tube for me.

From what I can tell so far it will be almost imposible for there to enough difference to justify NOS Gold Lions vs Reissues.

Recently I had the Chinese 98 (Not Penta) in the right channeI, could really hear the difference to compared to the Left Channel Reissue Gold Lions.

Reissue Gold Lions had much more base and warmer vocals.

But comparing NOS Gold Lions to Reissues I will need to do a true side by side comparsion with the C26 playing the same channel through both to hear if there a significant differance my tin ears can detect.

Note: Gold Lion Reissues in right channel just blew with less than 2,000 hous since new, from a good source.

At least they provided some family entertainment when they arced, crackled and in general created a lot of excitement.

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Audiable Nectar nailed it as usual.

Hooked up the C26 and there was not a signifcant difference between NOS Gold Lions and Reissues.

NOS were no different on the lows just very slightly warmer in the mids but so close I might fail a double blind test. I could not hear a difference.

The biggest difference was I did not slide the speakers all the way back to their normal resting place, bid improvement in sound stage by getting them more even with end of short walls, closer to my sitting position/less recessed.

Eliminated for my ears:

NOS Tungsols

NOS GE 6550


So now all that is left is to compare Pentas to Gold Lion Reissues.

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Craig of NOS Valves swapped Tungsols for KT-88Zs.

I bought the Gold Lion Reissues, Quad but one blew last week, a pair of NOS Gold Lions, and GE6550s from Bob Carver.

Chinese came with the amps.

I will get the KT-88Z back this weekend, you are welcome to try them or the GEs anytime I am driving through. . .

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  • 3 months later...

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