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Tube Diagnosis

I am a bit limited in my experience with Tube quirks so looking for a bit of insight.

With no music playing I noticed a small amount of noise coming from the left channel of my system a couple weeks ago.

I isolated it to my preamp (Aesthetix Calypso - 12AX7 gain and a 6922 output in each channel) and then further to the left channel output tube. I did this by swapping the left and right output tubes and the noise moved with the tube.

I am running used tubes with a reasonably low but unknown amount of hours, all was silent until a couple weeks ago. Telefunken ECC803S for Gain and amperex PQ white 6922's for Output.

The 'noise' is a low level crackle that seems random. i.e. crackle crackle---silence for a random amount of seconds--crackle and so on. It is independent of volume and does not change if the tube is lightly tapped! The noise is low as I mentioned but can be heard during silent sections of music and is distracting enough for me to buy new tubes to get rid of it. The only other thing I have noticed is that the noise is a bit more pronounced when I first turn on the system, after it warms up things mellow but the noise does not go away.

I have experience with tube rush and what I would call microphonic noise - tube noise that increases with volume and responds to tapping of the tube. This is something different.

So, is this the sound of a Tube that is dying or just a tube that went noisy and will now stay that way?

Thanks
nikturner920
11 responses Add your response
larryi
3,715 posts
 
The first thing I would do is clean the pins on the tube and the socket. Poor contact sometimes causes that kind of noise.

Is it coming out equally from both channels or only one channel? If it is one channel, you can isolate the offending tube (if it is the tube) by swapping left and right tubes to see if the problem follows a particular tube.

I hope it is not the 803S. I run those in a phono stage and they are really big bucks these days.
riley804
1,224 posts
 
If it is one channel, you can isolate the offending tube (if it is the tube) by swapping left and right tubes to see if the problem follows a particular tube.

He did this and mentioned it in the thread :

I did this by swapping the left and right output tubes and the noise moved with the tube.


I am running used tubes with a reasonably low but unknown amount of hours,

You have done the process of elimination , so guess its time to buy some different tubes.
racamuti's avatar
racamuti
362 posts
 
Call Andy at "Vintage Tube Services", he can recommend some quite replacements that won't break the bank!.Good luck!
dan_ed
2,451 posts
 
Try Larry's suggestion first, it could be dirty pins. You can use a pencil eraser. If you have alcohol wipes use one of those after erasing the pins.
nikturner920 OP
144 posts
 
Thanks guys.

The noise follows the tube and thank god it is Not the 803S, it the amperex PQ. Still pretty pricey for low noise matched pairs.

The pins looked clean but worth checking that.

Used VTS in the past and like them. Thing is I love that sound of this tube other than the noise. Maybe Andy can track something that will sound the same.
larryi
3,715 posts
 
If you can find a vial of Caig Deoxit, that is a pretty good product for cleaning contacts, including tube pins and sockets. I like the super concentrated form of deoxit that is not in a spray can, but has a very thin needle like dispenser. A very small amount on a Q-tip that has been shaved down to fit between the pins works well. This gives a more heavy duty cleaning than the eraser, though I like that approach too.

For the tube socket, I use one of those specialty toothbrushes that are designed to go between the teeth. They look like they have only one fuzzy protrusion on a toothbrush handle.

Good luck on your noise fighting venture.
audiogalore
70 posts
 
I had the same problem with a Sovtek 6922. "A sporadic crackling noise" that was audio-able when idle from the left channel. Replaced all with JAN Phillips low noise 6922 and that corrected the problem.

Enjoy music!
dan_ed
2,451 posts
 
I don't believe I ever found much difference with 6922s back when I owned a Rhea, at one time, and later a pair of Rogue mono-blocks. They either had noise or sucked, or both. Or they didn't. Nothing that really stood out. Granted I never chased high $$$ tubes.

Anyway, hope the cleaning does the trick.
nikturner920 OP
144 posts
 
Tried cleaning the pins last night, no dice. Looks like I am going to try and get a NOS pair. Real bummer as it is just enough noise to annoy me but the tube still sounds great otherwise.

I was able to dig up another pair of 6922's to swap in for the time being. Noise free, but a bit of the magic gone that I had with the amperex PQs.

Looks like I will be calling Andy at VTS.
atmasphere's avatar
atmasphere
11,566 posts
 
Cleaning the pins will not do a thing- that was obvious when the problem moved with the tube!

The tube will be like this forever. If you don't mind tapping it occasionally, you might be able to use for quite a while longer, but you will find that when you get a quiet tube in there that it will be a real relief.

Vintage Tube Services was/is an excellent recommendation. Andy takes the time to delve into the circuitry of his customer's equipment; IOW he already knows what sort of tube you will need for your preamp.
nikturner920 OP
144 posts
 
Bit the bullet and called Andy. He is great. NOS set of amperex super low noise a-frames on the way to try and decided to test out a pair of Mullard cv-4004s for in the 12AX7 slots.

Tube rolling is fun, but damn I wish they were $10 like the old days.
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