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In Reply to: RE: Nevr-Dull posted by erik on June 30, 2020 at 11:38:02
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?
Edits: 07/01/20 07/01/20Follow Ups:
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."
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!
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."
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."
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.
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