Tube got noisy? Why? Common? Failure immenent?


#1

I bet Paul loves these stories… hates those “fire bottles”.

I just had a Mullard NOS CV4003 / 12AU7 in my PrimaLuna HP integrated go noisy… sounds like static…fitzz… goes quiet … kinda random. Upscale Audio said the 6 month old tube was out of 90 day warranty and I needed to buy another. They asked for the test numbers on the box and they will match. $120 or thereabouts for one tube. I placed the order last night.

Questions
1- How common is this … any difference with new quality tubes and new old stock (NOS)?
2 - Why? What is happening in the tube?
3 - Is this the start of a failing tube that could damage my equipment?

I am not at all upset at Upscale… I have been using tubes for … since circa 1988 so I get it… tubes are a drug and a flaky one. However, I never did have one go noisy… usually they just stop working… or like all of them … the slow drip drip drip of neurosis inducing degradation.

Peace
Bruce in Philly


#2

How does the getter look? if it is white the tube has an air leak.

If the tube is glowing purple or cherry red it has died. This can happen if the bias is incorrect, but typically the tube is just dying.

I’m sure you know to clean the pins if a tube is noisy just to make certain the connection is good.


#3

Years ago I had this happen in an Atma-Sphere amp. I just replaced the tube and life was good. Sounds like a tube that is failing. As you know no one can really tell you how long a tube or anything for that matter is actually going to last.

I’m also a PrimaLuna HP Integrated owner and I love the amp!


#4

I had one Tungsram PCC88 just begin to get a bit noisy after 600 hours in BHK preamp. I used it as an excuse to try some Amperex 7308 and found them to be much quieter than the quietest Tungsram I had.


#5

The other tubes had been used for 6 months. Why they match the damn number on the box…Sounds…to me. And $120 is a lot of $$ for a CV4003. I will buy a 7316 tube instead.


#6

Getter is fine… shiny… no strange glow… just intermittently noisy… swapped channels… noise followed the tube.

These things have some sort of black magic in them.

Peace
Bruce in Philly


#7

Nah, once the cathode loses/uses too much of its emissive coating or properties…they ‘wear out’.


#8

Are you suggesting I buy two instead of just one to better “match” them? Or are you suggesting $125 per tube is outrageous and there are better values out there?

Tube rolling is an odd aspect to this hobby. For me, changing tubes is far more rewarding than all the other tweaks that you can spend a ton on and, frankly to me, not worth it. Just because you hear a difference does not mean it is an improvement nor that you will become emotionally closer to the music.

Changing tubes however, is different than typical tweaks such as power cords… they really do change the presentation of music. Even small changes can affect emotional outcomes. Tubes tweak the emotions. Equipment tweaks just tweak the wallet.

Having said all of this… The tube that went bad was new old stock … probably made in the 1960s. I suspect the differences between them are real but small… I dunno … well I just don’t care or chose to ignore it and haven’t suffered from this approach.

Could I find cheaper tubes than the NOS Mullards? Of course… but I don’t care. The original PrimaLuna-labeled Chinese 12AU7s that PL put in the thing are actually pretty darn good. I can live with them… I swapped out a few brands so that is how I learned these original Chinese are darn good… the Mullards were a tad nicer… worth it over the original Chinese? Probably not, but oh well, I had a few Pilsner Urquells in me and that darn internet ordering page…

PS Audio’s sales strategy should include sending each customer, six months after a sale, a free “thank you” case of beer. Then sit back and watch the drunken orders come in.

Peace
Bruce in Philly


#9

A wonderful statement.


#10

This is a good tube dealer at UK.

Good luck!

PS: According to the manufacture of the Preamp, “The two tubes in the center are the input tubes, and that’s where you want to have fun later if you wish by experimenting with different tube brands.”

You may want to use your best tubes for these two.


#11

I have the PL Dialogue Premium Preamp - I’ve tried the Brimar Telefunkun and just recently the Tungsram. All very good but the Tungsram’s got the most magic. Lots of texture - lush with detail - great bass - 3d soundstage and it’s the cheapest. Think the Tungsram gold 12au7 is around $65 at Upscale.It’s nice having a few different tubes available with this preamp. Can mix and match, tune and change as your mood dictates.


#12

You may very much like the Amperex 7308 in your pre. ~$95/each from RAM. Much quieter tube with all the magic of the Tungsram.


#13

I don’t think 7308 is direct replacement of 12au7. I could be wrong.


#14

Yea 7308 is a 6922\6dj8 variant - perhaps they have a 12AU7 version?


#15

Ah, ok. My pre accepts either voltage.


#16

#17

6DJ8 = 6 Volts and 12AU7 = 12 Volts. The first number indicates the Voltage. In a BHK Pre the Voltage is user selectible. I’ve purchased tubes from Langrex. They’re reputable and ship quickly.


#18

thx - I was just mentioning that the 7308 was a 6922 or 6dj8 type tube not a 12au7. My preamp uses 12au7’s only.