Genelex (New Sensor) Gold Lion KT88 failing?

Good evening Gents

(Well my evening it not so good)

One of the 4 KT88 (Genelex / New Sensor) tubes in my Mark III 'blocks seems "buggered" (to use a descriptive English technical term). It causes a static - like noise (think of rustling paper) on one channel, and I have isolated it to one specific tube - the "rustling noise will "travel" with the tube if you switch it to a different channel (yes, my NEW Mark III monoblocks :-(!! ).

Not only that, but it will not keep a bias setting - I set it, then five minutes later it is totally different and I have to set it again. The bizarre thing for me though is that in spite of this, it sounds as good as ever - sonically you can't tell anything is wrong, other than the static on that channel.

I guess it is a safe assumption to say that the tube is bad. Over the past 6 weeks the set has been running about 15 hours a day from being brand-new.... My question: Surely I should get a lot more than 500 hours out of it? I have heard some negative comments from the guitar playing community regarding this tube (whereas the same-brand KT66 Gold Lion seems to last much longer, if I understand correctly). Can you guys think of any tube that sounds as good but is more reliable?

'Jan
BC, Canada

Hi Jan,

Sorry to hear about your BUM luck with that Buggered tube---yuck yuck yuck. Sorry. Can't resist a korny joke.

I've been interested in this project of yours. Sorry I'm not here to offer a specific recommendation. Well, except to say that since you're already into this one to the tune of 7 KT88's, I'd be inclined to just get a stock of back ups for the next time this happens.

I guess your question is really more along the lines of whether it's better cutting your losses now, if this is gonna be a repeat problem.

How do you like the sound of those Genelex, when they're all working though?

And, oh, the question I should dare not ask . . . how do you compare the monoblocks against the ST 70?

Regards,
Brenton

Hi Tubenube - LONG time no speak, good to hear from you! :-)

OK, I don't have a reference point to measure the KT88s against, but seriously: Whether it has a longevity problem or not, they sound INCREDIBLY good, even to the point that unless I can find an affordable but sonically equivalent replacement (no, EAT KT88s not an option I'm afraid) I would probably replace the buggered tube with the same brand again while hoping that the replacement was not made on a Friday afternoon.

Yeah, a bum story aint it? (ROFL!)

-- 'Jan

Tube Nube wrote:...And, oh, the question I should dare not ask . . . how do you compare the monoblocks against the ST 70?

Ah, funny you should ask that - somewhere else I have posted to this regard. Problem really is that I used Auricaps throughout on this build, even on the input side (yes, wallet still smoking) and between the Auricaps and the KT88 tubes (plus Philips 12AT7s as opposed to JJ) the sound is sufficiently different but I don't know what to ascribe it to specifically.

Let's just say the Mark IIIs are more "In your face", and analytical / detailed to the point where you don't want to use low-end source material or components in the rest of your system. Comparatively, the ST-70 has a "laid-back" sound - which may be a characteristic of the sum of the different components used in its construction.

I prefer the Mark IIIs to the ST-70, actually. It makes good music sound so good that you want to get up and dance (hey, that's a big thing - I'm an old guy)

-- Jan

Hello,

I had the exact same problem a few mounts ago with a Gold Lion KT88, rustling noise also.

The tube had about 60 hours on it...

I replaced it with another one and no problems since, about 100 hours on it so far.

ixe13 wrote:Hello,
I had the exact same problem a few mounts ago with a Gold Lion KT88, rustling noise also.

Hi Ixe13,

Seems the guitar players love this tube's sound but hate its lack of longevity. I wonder if it comes out of a different factory than the KT66. I googled around a bit, there is a case out there where someone ended up having to replace EVERY tube over the course of a year.

Anyway, I contacted the supplier, they will replace the faulty tube. It still is a fantastic-sounding tube....


-- JunkyJan

You think that sucks? One of the NOS telefunken 12au7's in my sp8-se preamp went bad after only 200 or so hours of use. It went microphonic and after warming up it put out an awful high pitched droning sound. Now I've got two old philips tubes in the preamp and they sound alright, but have slightly more background hiss than the telefunkens.

Corona wrote:You think that sucks? One of the NOS telefunken 12au7's in my sp8-se preamp went bad after only 200 or so hours of use. It went microphonic and after warming up it put out an awful high pitched droning sound. Now I've got two old philips tubes in the preamp and they sound alright, but have slightly more background hiss than the telefunkens.

Hi Corona

I feel kinda bad for having complained about tube life publicly, I guess one have to remember that these things are consumables, a bit like a light bulb. In the case of the Gold Lions, I just wish it was a bit cheaper.

I have a pro guitar player friend of many years standing who will throw a troublesome / dead tube right across the room into his waste basket, without blinking an eye or even giving it a second thought. If it was a NOS tube like yours, he will add some spice to his language when he does that tho. Seems to me the guitar guys will thrash the living daylights out of their tubes and they just accept it will fail, sooner or hopefully later. It is Audiophools like myself who think our Beloved Tubes must live forever.

-- 'Jan

JunkyJan wrote:

Corona wrote:You think that sucks? One of the NOS telefunken 12au7's in my sp8-se preamp went bad after only 200 or so hours of use. It went microphonic and after warming up it put out an awful high pitched droning sound. Now I've got two old philips tubes in the preamp and they sound alright, but have slightly more background hiss than the telefunkens.

Hi Corona

I feel kinda bad for having complained about tube life publicly, I guess one have to remember that these things are consumables, a bit like a light bulb. In the case of the Gold Lions, I just wish it was a bit cheaper.

I have a pro guitar player friend of many years standing who will throw a troublesome / dead tube right across the room into his waste basket, without blinking an eye or even giving it a second thought. If it was a NOS tube like yours, he will add some spice to his language when he does that tho. Seems to me the guitar guys will thrash the living daylights out of their tubes and they just accept it will fail, sooner or hopefully later. It is Audiophools like myself who think our Beloved Tubes must live forever.

-- 'Jan

To be fair a properly made tube that's treated well should last at least a few thousand hours if it's a power tube like a el34/kt88/50c5/el84/etc. The little 12au7 tubes and the like should last well over 3000 hours. It's always a gamble with NOS tubes because you never know if they've been leaking air or if they have some inherent defect that will cause them to live a short life.

Anyway the troublesome telefunken ended up getting shot with a 22cal rifle for target practice.

I shouldna asked. Ohhh, I shouldna asked!

Thanks for that review, Jan. I also went looking for your discussion on another thread comparing the Mark IIIs to the ST70.

There may have to be a pair of mono blocks in my future!

JunkyJan wrote:

Tube Nube wrote:...And, oh, the question I should dare not ask . . . how do you compare the monoblocks against the ST 70?

Ah, funny you should ask that - somewhere else I have posted to this regard. Problem really is that I used Auricaps throughout on this build, even on the input side (yes, wallet still smoking) and between the Auricaps and the KT88 tubes (plus Philips 12AT7s as opposed to JJ) the sound is sufficiently different but I don't know what to ascribe it to specifically.

Let's just say the Mark IIIs are more "In your face", and analytical / detailed to the point where you don't want to use low-end source material or components in the rest of your system. Comparatively, the ST-70 has a "laid-back" sound - which may be a characteristic of the sum of the different components used in its construction.

I prefer the Mark IIIs to the ST-70, actually. It makes good music sound so good that you want to get up and dance (hey, that's a big thing - I'm an old guy)

-- Jan