[st4r0c3an]

The two big tubes that came with my MKII do not look the same.

tube 1

tube 2

One of them do not have the "nn" shaped wire that glows red when powered on. It instead shows glowing from the inside. Are they the same tubes? Could this (using different tubes) damage my MKII?

 

[Pricklely Peete]

Can you provide what is printed on both tubes themselves, the printing may be pronounced to slight, to none at all. The previous two situations are the norm with most tubes I've come across.

Peete.

 

[st4r0c3an]

One of the tube says 02 T on the front and 6N6 on the back. Tube 2 has no writing on it at all.

 

[Pricklely Peete]

Hmmm.......are you experiencing any channel imbalances , SQ issues ?

Peete.

 

[st4r0c3an]

Actually just recently I am starting to experience hissing in one of the channels. I think it may be caused by the tubes, but it only occurs a while after I turn the unit on after switching the tubes, so I haven't determined what's causing the problem. The hiss did change to the other channel after a switched tubes around... But I've switched too many times without documenting it to know if that is the real cause. Thanks a lot for the help.

 

[Pricklely Peete]

You may have a bad tube, make a note of the tubes position and do the switch, if the hiss follows the unmarked or marked tube you have a valid concern IMO.

Peete.

 

[st4r0c3an]

The hissing changed channel when I switched both the big ones and the small ones. But when I only switched the big ones, the hissing became worse and happened in both channels. I've had this amp for just a bit over a week and it has been perfect until yesterday. Could anything else be the problem? Oh yeah, the hiss is still there with no source and volume turned to zero. Also when I used RCA out at the rear, the hiss is still present.

 

[Pricklely Peete]

Try cleaning the pins of all the tubes if you can. It seems odd that things are getting worse. Be sure to let the amp cool down for at least 5 minutes before swapping tube around, start with one pair only. The power tubes please. Mark one with felt tip, just a tiny dot will suffice. The same can be done with the driver tubes.

Do you have any spare tubes to try ?

Peete.

 

[st4r0c3an]

Quote:

Originally Posted by Pricklely Peete /img/forum/go_quote.gif Try cleaning the pins of all the tubes if you can. It seems odd that things are getting worse. Be sure to let the amp cool down for at least 5 minutes before swapping tube around, start with one pair only. The power tubes please. Mark one with felt tip, just a tiny dot will suffice. The same can be done with the driver tubes. Do you have any spare tubes to try ? Peete.

No spare tubes. I switched the amp to another wall outlet and the hiss is a lot better but still present. Will swap tubes now.

Edit: by the way, is it normal to hear cracking sound when I power off my amp?

Edit 2: switched the big(power tubes), and the hissing is still present in the same channel as before. still very subtle compared to the other power outlet.

 

[st4r0c3an]

Okay, I switched the small tubes... And surprisingly, hiss is now happening in the other channel. Does this mean my tiny tubes are at fault? How does this explain the improvement with switching outlets? Could my main system be faulty? I would hate to do a warranty repair because shipping to China is pricey.

 

[fraseyboy]

About the big tubes, it's the same with my little dot. The logo is in a different place on each one. No problem.

As for the hissing, mine did the same when I got it too. I cleaned the pins on the offending tube with a microfiber cloth and the little bit of electronic cleaning solvent and that seemed to solve it. I also found that during the first 20 hours or so the tubes made various strange noises. They just need to burnt in properly I think.

 

[Dept_of_Alchemy]

It's quite a time consuming process to properly 'match' the power tubes (they're the big ones) because they're dual triodes and matching a pair means matching all four sections which logically I doubt LD would take the time to do so considering the price range these products are selling in. The same can be said about the driver tubes (the small ones), it's quite a common complaint from LD users that one of the channels on their amps are 'noisy' and it turns out that the pins need cleaning etc, which tells me that LD doesn't thoroughly test and match the tubes before shipping them.

On the one hand it's an understandable practice since most LD users end up tube rolling anyway and the stock tubes end up as back-up tubes. But I think since balanced and matched tubes do make a big difference in terms of sound quality that I wish LD would take the time to test them.

Anyway, if you're looking to upgrade your tubes I recommend checking out Yen Audio on ebay (eBay Store - Yen Audio: Little Dot Upgrade Tubes: GE mil-spec JAN 5654W Little Dot Amp MkIII MkIV EF95), all of their tubes are matched and would be a good step up from the stock tubes especially the 6H6P-I power tubes which I think makes a big positive difference in the overall sound.

- DoA

 

[jordanross]

Sorry to hijack but do you think they match the tubes on there upper amps (mkIVse)? Just wondering.

 

[st4r0c3an]

So I should get new power and driver tubes? Thanks. Time to save money once again only to empty it out for headphone equipments. XD

By the way, micro-fiber cloth is the ones you use to clean glasses right?

 

[Pricklely Peete]

Quote:

Originally Posted by jordanross /img/forum/go_quote.gif Sorry to hijack but do you think they match the tubes on there upper amps (mkIVse)? Just wondering.

Good for question for David I would think.....ask him I say

Peete.