KT-88 advice

pelliott321 · « **on:** 1 Mar 2011, 08:35 pm »

I have a TAD-60 from Paul Grzybek (of Bizzy Bee Audio fame) since May 2006, and I am finally replacing the output tubes. The amp can handle anything from EL34 to KT88's
I am using the amp very successfully driving the mids and ribbon of my rebuilt Maggy IIIa's up until Sunday morning using JJ KT77's when one went pop. I have a spare set of EL34's that are old and will not last long which are in and working ok.
So I am shopping around. Paul suggests Valve Art KT88. I see too many choices and prices from $50 MP to $900 MP
Whats good, bad, and just plain ugly
Paul suggests Valve Art KT88

putz · « **Reply #1 on:** 1 Mar 2011, 08:48 pm »

Read this topic and you'll be enlightened/more confused than ever

http://www.audiocircle.com/index.php?topic=89859.msg886843#msg886843

richidoo · « **Reply #2 on:** 1 Mar 2011, 08:49 pm »

EL34 and KT88 require different bias current. You may have to change the setting for the different tube types. Usually putting an EL34 into an amp biased for KT88 will blow it pretty fast. EDIT: and KT88 in an amp biased for EL34 will sound weak.

Whenever changing tubes, even if they are same type, it is best to turn the bias adjustment down to zero, then change the tubes, then gradually bring the bias current back up to the specified value after reaching temperature.

The bias setting will change a bit during break in, so check it again after 10 hours, 50 hours and 200 hours. Then it should hold steady until the tubes start to wear out.

It is good to know how to check and adjust bias so you can get the best performance and life from the tubes, but some amps don't make it easy if the chassis must be opened up to access the test points and adjustment pot.

Ericus Rex · « **Reply #3 on:** 1 Mar 2011, 08:52 pm »

In this thread:

http://www.audiocircle.com/index.php?topic=90507.0

...AC member rpf had some Gold Lion KT77s for sale for $100. They should be far more reliable and possibly better sounding than the JJs you had. Price is a steal too, if he still has them.

Several members rave about the Penta Labs KT88 and the very expensive Shuguang Black Treasure. Haven't heard either yet. I'm currently running the Genelex Gold Lion KT88 reissue and I like them. Haven't heard the Valve Arts either, but I think those are just Shuguang tubes, yes?

Pez · « **Reply #4 on:** 1 Mar 2011, 08:56 pm »

I have used the Pentas, GLs and the treasures. The treasures are the best by a wide margin. The Pentas are very good, but cannot compete with the treasures. Other than thy I wouldn't consider any of the other tubes mentioned.

rpf · « **Reply #5 on:** 1 Mar 2011, 09:33 pm »

Quote from: Pez on 1 Mar 2011, 08:56 pm

I have used the Pentas, GLs and the treasures. The treasures are the best by a wide margin. The Pentas are very good, but cannot compete with the treasures. Other than thy I wouldn't consider any of the other tubes mentioned.

So you found the Pentas better than the GLs? How do they sound differently?

enzoducoing · « **Reply #6 on:** 1 Mar 2011, 10:39 pm »

Hi,
I have used in my amp several types of KT88s, among those a quad of NOS Genelex, a quad of EAT (Euro Audio Tube), a quad of Gold Lion re-issue, which I own and have still in use. These are among the best if not the absolute sounding KT88s you can get your hands on, but in all the best sounding KT88s I have heard in my amp were "Groove Tubes" KT88-C tubes. Groove Tubes is primordially a guitar amp tube since they make them in three levels of distortion (high, low and no distortion). Obviously for an audio amp you'll need the non distortion type, and they are readily available on different sites, mine were sold to me by Brent Jessee of www.audiotubes.com. I can't tell you anything about biasing since my amp has auto bias, but this has made it very simple to swap them around and verify this personal appreciation. They are not expensive, think middle of the pack, and they sing with a powerful and crystalline presence that equals the EATs (four times more expensive) and have the wonderful open throaty tone of the best NOS.
Give them a try, you'll not be disapointed.
M

bunky · « **Reply #7 on:** 2 Mar 2011, 01:37 am »

Quote from: pelliott321 on 1 Mar 2011, 08:35 pm

I have a TAD-60 from Paul Grzybek (of Bizzy Bee Audio fame) since May 2006, and I am finally replacing the output tubes. The amp can handle anything from EL34 to KT88's
I am using the amp very successfully driving the mids and ribbon of my rebuilt Maggy IIIa's up until Sunday morning using JJ KT77's when one went pop. I have a spare set of EL34's that are old and will not last long which are in and working ok.
So I am shopping around. Paul suggests Valve Art KT88. I see too many choices and prices from $50 MP to $900 MP
Whats good, bad, and just plain ugly
Paul suggests Valve Art KT88

Pez · « **Reply #8 on:** 2 Mar 2011, 02:39 am »

The Pentas are just more refined and nicer, way more articulate sounding overall while also warmer sounding and just a better tube overall.

rpf · « **Reply #9 on:** 2 Mar 2011, 02:56 am »

Thanks.

ken · « **Reply #10 on:** 4 Mar 2011, 12:14 am »

I believe Paul thinks the Valve Arts are one of the better tubes out there for the $ as he recommended the el34's to me as well for the 1000's and you can get a quad for approx $100.00 but if you can afford it by all means get the Treasures. I just priced some Penta 88's and they're going for $300.00 and change and I need an octet, and I believe the Treasures are even more. That kind of money for someone in my shoes is hard to justify (sorry dear we couldn't buy those airline tickets because I wanted new tubes, we can just go on vacation next year) All kidding around aside buy the best tubes you can afford, both the Treasures and Pentas will probably outlast the others by a wide margin just don't use KT 66 tubes I don't believe they'll work in the TAD 60 as they don't in the 1000's and I think the amps are more similar than different.

Good luck

Ericus Rex · « **Reply #11 on:** 4 Mar 2011, 12:49 pm »

Dougstubes.com = Pentas for $180 quad.

rbwalt · « **Reply #12 on:** 4 Mar 2011, 02:46 pm »

tubeaudiostore.com.

r.

pelliott321 · « **Reply #13 on:** 4 Mar 2011, 03:24 pm »

Asking for tube advice really brought out a lot of suggestions
doug's tubes is the first place I go when looking for tubes and if he has what I want I drop him an e-mail, and go with his suggestions, which i eventually did
thanks for all the responses

ken · « **Reply #14 on:** 4 Mar 2011, 04:50 pm »

Quote from: Ericus Rex on 4 Mar 2011, 12:49 pm

Dougstubes.com = Pentas for $180 quad.

I don't know where I remember seeing the Pentas for so much I guess I should have checked around a little more

ken · « **Reply #15 on:** 4 Mar 2011, 04:52 pm »

Quote from: pelliott321 on 4 Mar 2011, 03:24 pm

Asking for tube advice really brought out a lot of suggestions
doug's tubes is the first place I go when looking for tubes and if he has what I want I drop him an e-mail, and go with his suggestions, which i eventually did
thanks for all the responses

Which tubes did you finally decide on?

AudioSoul · « **Reply #16 on:** 6 Mar 2011, 02:15 am »

I bought a quad of Penta Kt88's from Doug's Tubes and I am very happy with the quality and the sound. Just for reference: I went from a 6550 tube to these and I have them in a AES Super amp........

Pez · « **Reply #17 on:** 6 Mar 2011, 02:18 am »

Agreed, Doug is great to deal with.

HT cOz · « **Reply #18 on:** 7 Mar 2011, 03:09 pm »

Quote from: AudioSoul on 6 Mar 2011, 02:15 am

I bought a quad of Penta Kt88's from Doug's Tubes and I am very happy with the quality and the sound. Just for reference: I went from a 6550 tube to these and I have them in a AES Super amp........

Which 6550 tube where you using?

Leadfeathers · « **Reply #19 on:** 8 Mar 2011, 01:47 am »

Quote from: AudioSoul on 6 Mar 2011, 02:15 am

I bought a quad of Penta Kt88's from Doug's Tubes and I am very happy with the quality and the sound. Just for reference: I went from a 6550 tube to these and I have them in a AES Super amp........

I'm curious too about which 6550 you went from, and which of the KT88's you went to......the 88-98, or the 88SC.......
But more importantly, tell us what you've noticed about the change in what you're hearing....

I've got Tung-Sol 6550's in my Music Reference RM-9, and have been considering the change to the Penta Labs KT-88SC, based on some earlier reviews......would love to hear what you think, even if they still have break in time left. Thanks.