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Whistling Tube Question

76.19.10.168

Posted on June 27, 2020 at 17:10:00
erik
Audiophile

Posts: 1077
Location: New England
Joined: April 3, 2000
Folks, got a pair of tubes, and one makes this whistling sound, like there is a huge mosquito in the tweeter. After 5-10 minutes of being on, that noise stops. Should I throw it away? Really love its sound, though.

 

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RE: Whistling Tube Question , posted on June 27, 2020 at 17:25:28
Jim McShane
Dealer

Posts: 5843
Location: Chicago
Joined: January 13, 2003
Clean the tube socket well. Look at the FAQ below for more info.

 

RE: Whistling Tube Question , posted on June 27, 2020 at 17:44:31
erik
Audiophile

Posts: 1077
Location: New England
Joined: April 3, 2000
Thanks, Jim, but I think it's the tube. When I switch the channels, the noise goes to the other side.

 

RE: Whistling Tube Question , posted on June 27, 2020 at 18:34:07
Jonesy
Audiophile

Posts: 2302
Location: Winnipeg, Manitoba
Joined: September 1, 2005
Contributor
  Since:
March 1, 2018
Unless you have already done this, I would still go with Jim's recommendations.

Cleaning tube pins and sockets. And in this case ensure the socket contacts are tightened.

I've had instances where pin size varies. And if a pin is just slightly narrower or dirty, contact will be inferior until things warm up and expand. Such as you are experiencing.

Worth a try.

Cheers!

Jonesy


"I know just enough to get into trouble. But not enough to get out of it."




 

RE: Whistling Tube Question , posted on June 28, 2020 at 04:07:02
bob_
Audiophile

Posts: 6
Joined: June 28, 2020
Hi,

I'vo got exactly the same problem. One of my NOS 12ax7 gives me the same squeaky noise with some hum. It lasts for about 10-15 minutes after powering the amp on, not the whole time, but is random sequence, like: 1 minute of whistling, than 10-30 seconds of silence, again few seconds of noise, and again few dozens of seconds - silence...and so on ...
I tried to clean the pins with isopropanol but that did not the job. Do you think it is a good idea to gently use a very fine sanding paper? Like 1000 or 2000 size?

 

An Update , posted on June 28, 2020 at 08:17:05
erik
Audiophile

Posts: 1077
Location: New England
Joined: April 3, 2000
So, folks, the preamp is fairly new, just a few months old, the sockets are clean as a whistle. Just in case cleaned them a bit. The pins on the tube are also cleaned (always do that), but this particular Soviet-made ones have thin pins, and they were very wobbly in the sockets. I bend the pins slightly outward, the noise is 99% gone, lasts just for a few seconds.

Still, I think there is some problem with that particular tube, since nothing in its place before made that noise.

Thanks everybody for the feedback.

 

RE: Whistling Tube Question , posted on June 28, 2020 at 10:14:12
Jonesy
Audiophile

Posts: 2302
Location: Winnipeg, Manitoba
Joined: September 1, 2005
Contributor
  Since:
March 1, 2018
I've never had a case extreme enough to use fine grit sandpaper or steel wool. But some here on AA have.

Others have successfully used De-Oxit.

My "goto" combination is "NeverDull" metal polish followed by a thorough rinse with Isopropyl alcohol. You can use cotton balls or swabs.

Or, if you break a cotton swab in half, you can insert it in a Dremel and get amazing results polishing and rinsing at the low RPM setting.

Just be wary to shield the spray when doing the polish and rinse. I even follow up with a dry swab in the Dremel to get any further residue off.

Needless to say you do go through many cotton swabs. Don't apply too much pressure and going around each pin once should be enough. Metal polishes are less abrasive than sandpaper, but should not be overused.

You should see immediate results, folling these steps.

Other metal polishes will work as well but tend to leave some dry residue behind.

And of course one must hold the tube carefully if you don't want to smudge any of the lettering.

Cheers!

Jonesy




"I know just enough to get into trouble. But not enough to get out of it."




 

RE: Whistling Tube Question , posted on June 28, 2020 at 11:10:49
bob_
Audiophile

Posts: 6
Joined: June 28, 2020
Thanks Jonesy, I'll give it a try. One more thing, can you tell what is the base ingredient (or even the composition) of "Never Dull"? Here where I live I cannot find the trade name...

 

Nevr-Dull, posted on June 28, 2020 at 11:54:43
Jonesy
Audiophile

Posts: 2302
Location: Winnipeg, Manitoba
Joined: September 1, 2005
Contributor
  Since:
March 1, 2018
Sorry, I had the spelling wrong.

The active ingredients are not on the can, but here is a link to their website. Along with explaining product use, there is a Safety Data Sheet (SDS) available for download. The sheet states the composition.

The product is made in the USA, but I've always been able to find it at the local hardware stores in Canada.

It does show up in Amazon and eBay searches, but looks like shipping may cost more than the product, depending where you live.

Hope you have good luck finding it. Not sure if there are equivalent products. Maybe Google can help.

The can contains a cotton wadding saturated with the ingredient. I sometimes pull off a small piece, or stick a cotton swab into the tin. The swab will absorb the ingredient.

The swab method takes a little longer but is less messy. If you do use a wad from the can, you really want to avoid touching other areas of the tube. It is an oily substance. I often use Isopropyl Alcohol for clean up. I think soap and water works ok too. When using a wad, you can't help but get it on your fingers!

Cheers!

Jonesy




"I know just enough to get into trouble. But not enough to get out of it."




 

RE: Nevr-Dull, posted on June 29, 2020 at 12:01:16
bob_
Audiophile

Posts: 6
Joined: June 28, 2020



Thank you for clarifying this and all the advices. Much appreciate it. I believe I can even get the exact same product here (see the image).
I need to take the shot and try because I was slowly loosing hope to determine whether to return the tube to the seller or not (and frankly said it would be a loss since they sound incredible in my system). After hours of testing and gently moving the tube when I first heard the whistle I was convinced it is totally random and must the some kind of internal flaw of the particular tube (as erik's case it goes from left to right when swapping the tube between channels)and I could not distinguish any clear differences in pin shape or diameter. I also tried to bend the pins slightly outwards - did not help. Would be also strange that this is some kind of bad contact between the tube pin (or pins) and the socket since it happens only with this one particular tube.

But finally, yesterday I started to push the tube firmly but slowly with a kind of circling movement (or maybe tilt it to a side better said) when squeaks appeared and it went away the very next second... Unfortunately it comes back right after few seconds more, but again giving a little bit of pressure when titling the tube solved the problem temporarily.. Not sure if this is only a coincidence but gives a little bit of hope that there must be something wrong with pins only and not the tube itself... We'll see...
erik - how about you? did you solve your case once for all?

 

Pins and Sockets, posted on June 29, 2020 at 15:19:49
Jonesy
Audiophile

Posts: 2302
Location: Winnipeg, Manitoba
Joined: September 1, 2005
Contributor
  Since:
March 1, 2018















Here are a couple of points with pictures that may help.

1st picture is of a Belton 9-pin tube socket. Extremely tight fitting such that you literally have to ease the tube in slowly and using a rocking motion.

2nd picture. As tight as the Belton's are, I still tighten them on occasion with a dental pick to ensure they are as tight as can be. Different pin sizes, as you may be experiencing, will enlarge them. Then when swapping in a tube with slightly thinner pins, contact will be weaker. I have found pin thickness discrepancies even of tubes manufactured in same plant. Though the date codes are often different. Both in 9 and 8 pin tubes.

3rd picture. Note that contact on the pin and socket can be at different points. Those contact points are the key areas of concern. Usually about a third of the way down. You can actually see a slightly darker area on the pins in the picture as to where they begin to engage and end up making contact.

4th picture. If you really want to clean those tube sockets, I find dental paper points to work best. I can actually "see" the dirt come off when I clean with the paper points and a contact cleaner. I've used a tube socket brush before, but I just don't know if nylon bristles are actually scrubbing.

5th picture is of the dental paper points that I buy. I usually watch for sales on eBay and stock up. Sometimes they come in variety packs. Sometimes you can just get the thicker ones. I believe I have enough to last a decade or two.

Note that the socket cleaning should be done before tightening. Sorry this is out of order, but I'm too far into writing this to start over.

Hope some of this helps!

Cheers!

Jonesy


"I know just enough to get into trouble. But not enough to get out of it."




 

Yup! That's a really microphonic tube that sings like that nt, posted on June 30, 2020 at 10:23:38
Ralph
Manufacturer

Posts: 3931
Location: Minnesota
Joined: April 24, 2002
-

 

RE: Yup! That's a really microphonic tube that sings like that nt, posted on June 30, 2020 at 11:22:20
erik
Audiophile

Posts: 1077
Location: New England
Joined: April 3, 2000
Thanks Ralph. Can it potentially damage the unit?

 

RE: Nevr-Dull, posted on June 30, 2020 at 11:38:02
erik
Audiophile

Posts: 1077
Location: New England
Joined: April 3, 2000
Bob, the sound is there when I turn it on, even though the noise level now is pretty low, but it quickly goes away, basically doesn't bother me at all, except for I don't know if it's safe to use :)

 

Seems unlikely- mostly an annoyance. nt, posted on June 30, 2020 at 12:35:30
Ralph
Manufacturer

Posts: 3931
Location: Minnesota
Joined: April 24, 2002
-

 

Appreciate your response , posted on June 30, 2020 at 13:53:23
erik
Audiophile

Posts: 1077
Location: New England
Joined: April 3, 2000
...it was great to know, I really like them, and it was quite difficult to obtain the version I have.

 

RE: Nevr-Dull, posted on July 1, 2020 at 12:40:33
bob_
Audiophile

Posts: 6
Joined: June 28, 2020



erik -> thanks for your feedback. In my case it is between 8-15 minutes during warm-up and then it goes away. Still not sure if this is related to pin-socket contact or not.
I have exactly the same feeling about it as you - I do not want to send them back, these are really hard to get and I love the sound and built quality...


Jonesy -> again, accept my big thank you for your help. I tried to follow all you advices, cleaned the pins as good as it was possible and this is the result (see the image). Haven't tried it out yet...

Ralph -> so you say it is the tube itself? I thought microphonics is caused by mechanical vibration, not a kind of self-resonance... Might be that I am wrong... Does this mean the tube is faulty then?

 

Microphonic vs Tube Pin Contact, posted on July 2, 2020 at 12:23:50
Jonesy
Audiophile

Posts: 2302
Location: Winnipeg, Manitoba
Joined: September 1, 2005
Contributor
  Since:
March 1, 2018
A tube either "is" or "isn't" microphonic (*see note at end of post). However, after it has been warmed up, a tube may physically seat itself better, literally "dampening", or "reducing", the amount of microphony.

Plus it is not just the tube that has warmed up, but the entire component. So now everything has tightened up. It's like a rough idle in a car that goes away after warm up. The tube is dampened, and the entire component is less prone to transfer mechanical vibrations to the tube. All good.

The dilemma is, did the tube noise disappear because the warmup/dampening reduced the microphonic, or did a better connection allow the tube to work as it should?

Once the component has warmed up, and the noise has disappeared, there is a test you can try. Gently tap the suspect tube with the eraser end of a pencil. If it "rings", it is microphonic. If it "thuds", it is normal.

Neither is a huge problem if you are happy with the overall sound in the end.

Some of the finest signal tubes are inherently microphonic. Yet they sound wonderful. Some, like Siemens, will even send a "ping" through your system when turning on/off a line selector or mono-stereo switch. Some dealers will even warn you of this, and that it is normal. In fact these tubes depend on their microphonics in a good way (not to the extent of whistling...:) Dampening them with rings does reduce the "ping", but it also takes away some of the magic.

If tapping with the eraser end you hear a "thud" after warm up, it means the tube is operating normally, not microphonic, but something was impeding the connection upon cold start. "Fixing" itself after warm up. You can leave it as such, or you could continue to try and address the situation so it is fine both on cold start or warm up.

My entire system remains on mute for a minimum of 30 minutes. It is dead silent upon unmuting in both the phono and line stages. If I didn't allow it to warm up, I would likely hear a cacophony of ticks, pops, hisses etc. Exaggerating a bit, but whenever I have not allowed a warm up, you can hear the equipment stretching before the race.

Sorry to be so wordy and hope some of this helps.

Enjoy those tubes!

Jonesy

(*all tubes are microphonic to some degree. For the sake of this discussion, we are using microphonic in the "extreme" sense.)










"I know just enough to get into trouble. But not enough to get out of it."




 

RE: Microphonic vs Tube Pin Contact, posted on July 3, 2020 at 02:50:01
bob_
Audiophile

Posts: 6
Joined: June 28, 2020
Nothing to sorry for! Your "wordy" is a valuable knowledge to me (and I believe to others).

Taking in consideration what you wrote above, mine is definitely not microphonic. I would not dare to tap it when hot and powered on (I've heard that you can even damage the tube doing it to strong or to often) but it is not ringing from itself and outside vibration.
Moreover, I want to thank you all for insisting to check and clean pins because it seems that at least in my case that was it. Two attempts (with about 50 minutes cool down between these cycles) of powering the amp on yesterday and total silence from start! I hope it will stay like this.
What I did more (apart of cleaning) was also gently straighten out this bended pin visible on my picture (left side).

What you wrote about 30 minutes warm up and lot of "strange" noises in the time sounds also reasonable. I remember that sometimes (especially) with new production tubes my amp performs the very same way - despite what you do, you need to wait till everything is decently warm and steady. After that you have a clean sound for hours... I was just afraid that with this particular tube I've got a broken one...

Once again - thank you and regards!

 

RE: Microphonic vs Tube Pin Contact, posted on July 3, 2020 at 06:22:36
erik
Audiophile

Posts: 1077
Location: New England
Joined: April 3, 2000
Glad you got your issue solved. Mine is gone too. What is interesting, that the noise developed gradually, after a week of using them. They are NOS (1962), never used before, except for testing/matching, so could've been a break in issue, but can't be sure.

In any case glad we're ok ;) and thanks again to everybody.

 

RE: Microphonic vs Tube Pin Contact, posted on July 3, 2020 at 08:50:43
Jonesy
Audiophile

Posts: 2302
Location: Winnipeg, Manitoba
Joined: September 1, 2005
Contributor
  Since:
March 1, 2018
Yes. Only tap if you are truly suspicious of microphony and are comfortable doing it.

Tubes are very robust and should survive the simple test. But it can get out if hand where people continually check obsessively or upon purchase from dealers/sellers claiming a tube is microphonic and want their money back.

I recall two personal instances where tapping helped me identify an issue.

One instance where a whistling sound was due to poor contact and not microphony. "Thud" tap.

Then another where a voice on an album I was familiar with developed a glare. By gently tapping the tubes in each channel, I found the microphonic tube and replaced it. Problem fixed. Was a "ring" tap on that tube only.

Otherwise I do not tap tubes as regular maintenance.

Also note that microphonic tubes can be used in other locations not susceptible to the issue. Do not through them out. Just put aside and label them as such.

Cheers!

Jonesy


"I know just enough to get into trouble. But not enough to get out of it."




 

Also good that you straightened the pin..., posted on July 3, 2020 at 11:19:41
Jonesy
Audiophile

Posts: 2302
Location: Winnipeg, Manitoba
Joined: September 1, 2005
Contributor
  Since:
March 1, 2018
I forgot to mention it!

The location of the pin bend socket contact area could very well have been a major factor.

Good catch!

Cheers!

Jonesy


"I know just enough to get into trouble. But not enough to get out of it."




 

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