Loud tube noise on startup - advice needed

[shellylh]

I recently got a pair of NOS Tung Sol Round Plate 6sn7's for my Woo Audio WA5LE. Yeah, they were kinda pricey for NOS tubes, but I figured that you only live once right. I bought them from Paul Lindemann who I trust. I put them in the Woo and a little after the "initial warmup period" I turned up the volume (with no source playing) and I heard a loud scratchy horrible noise in the left channel. Then it was quiet. Shortly thereafter, I heard a similar sound in the right channel (may have been after the music started, can't remember) but it was much much quieter. I played some music and the music was playing, the amp/tubes seemed to be working fine and I didn't hear the noise again. I didn't keep the amp on very long, only for a couple more minutes (didn't want to press my luck plus I was tired).

Is this common to happen to a tube after shipping? Does this mean the tubes are bad? Since they were recently tested in Paul's Amplitrex, it seems unlikely.

I haven't heard this noise before but I usually* don't listen to the amp for noise when I turn it on. *The reason I was listening was that I first got these tubes from Paul a few weeks ago. At that time, I tested them in my B&K 747B to make sure nothing happened in shipping (no reason to think anything did though). Well, one of them was testing low (but no shorts or emissions) so I thought maybe the tester needed to warm up. After waiting for 5 minutes, I pushed the shorts button again (did not remove the tube in the meantime) and this time, the tester told me there was a short. I took them out, tested the next day for shorts and there were none. I also tried them in my amp at that time and they seemed fine (I don't remember if I listened to the tubes at startup though) but I was paranoid. I sent them back Paul who kindly retested them and told me they were "perfect." I tested a bunch of tubes in the tester and many are testing lower than they should so basically I don't trust my tester and will send it back to get recalibrated (which is annoying since I just recently bought it calibrated and tested and now I have to send it back. )

Does anyone know how often testers should be calibrated?

Anyway, Paul retested the tubes and sent them back to me with free shipping so now they have been tested twice and both times tested perfect. I am not going to test them in my tester because it is not reliable. Is there a chance that there is something wrong with the tubes (like an intermittent short)? Seems like no since there was a short burst of noise from both channels and it seems unlikely that both tubes are bad. However, I was alarmed at the noise from the tubes. If someone can tell me that this type of one time noise is common after shipping, that will make me feel better and maybe I will be able to enjoy the tubes.

Should I try them in the amp again today and see if the noise appears again or is that a stupid idea?

 

[cyd2025]

no, i wouldn't say it's common for tubes to be crackling and popping upon start up even
after a long shipping transaction. it's more likely that the 6sn7 is NOS and is known to
make noise initially. it should go away after several minutes but if not then you may have
a bad tube. it can also be that the pins and socket are not making a clean full contact,
but if your other 6sn7 tubes work fine, you can rule out the socket. it may be the pins
of the tubes.

*also, if your tube is mildly shorted it will glow more than normal due to higher amount of
current being discharged and you'll most likely hear humming... if it's a severe short it
should show on the tester and you'll see arching or flashing from the elements of the tube
when turned on followed by a loud popping sound. in this case you'll have to have the
tubes replaced.

a solid state tester shouldn't have to be calibrated very often, at least not as often as
tube-based testers. it really depends on how often you use it. resistors and transistors
will drift causing lower or higher readings but only after extensive use usually. and by
extensive, i mean hundred of tubes.

you may want to ask jack woo regarding the last question you posed. i don't think it'll
damage the amp but it may damage your headphone. what i'd try is to hold down the
tester button for longer than 1 min. on your tube tester as that should give a better
indication. any loud crackling or popping sound will show up as sharp unusual movement
of the meter in the tester. good luck.

 

[shellylh]

Hi takezo, thanks for the response. It wasn't really a crackling or popping sound. It is hard to describe, loud but not a whining noise either. Actually, it is getting hard for me to remember the sound. Anyway, I think I am going to send them back to Paul and stick with the RCA VT-231 grey glass for now. It is not worth the risk to me.

Quote:

Originally Posted by takezo /img/forum/go_quote.gif no, i wouldn't say it's common for tubes to be crackling and popping upon start up even after a long shipping transaction. it's more likely that the 6sn7 is NOS and is known to make noise initially. it should go away after several minutes but if not then you may have a bad tube. it can also be that the pins and socket are not making a clean full contact, but if your other 6sn7 tubes work fine, you can rule out the socket. it may be the pins of the tubes. *also, if your tube is mildly shorted it will glow more than normal due to higher amount of current being discharged and you'll most likely hear humming... if it's a severe short it should show on the tester and you'll see arching or flashing from the elements of the tube when turned on followed by a loud popping sound. in this case you'll have to have the tubes replaced. a solid state tester shouldn't have to be calibrated very often, at least not as often as tube-based testers. it really depends on how often you use it. resistors and transistors will drift causing lower or higher readings but only after extensive use usually. and by extensive, i mean hundred of tubes. you may want to ask jack woo regarding the last question you posed. i don't think it'll damage the amp but it may damage your headphone. what i'd try is to hold down the tester button for longer than 1 min. on your tube tester as that should give a better indication. any loud crackling or popping sound will show up as sharp unusual movement of the meter in the tester. good luck.

 

[Skylab]

It is definitely not unusual for NOS tubes to be noisy when first used. In fact, it's common. 6SN7's, IME, generally are not loud in their noise when first used, but I have had them make noise to be sure (some tubes, like the 6SJ7, will hum so loud it's horrifying for like 12 HOURS, but the 6SN7 does not do this).

If it's settled down, it should be OK as long as it tests OK, so now let's talk about that.

I bought some NOS TS RP 6SN7GT's from Paul, and they tested great. *Other*, used TSRP's I have gotten, however, take an unusually long time in test mode to get an accurate reading for whatever reason. It's not the only kind of tube I have experienced that with, but it a little unusual (I use a B&K 650).

One other thing regarding your tester - your AC line voltage will effect your test results. Since you live in Houston, I am sure your Air Conditioning runs a lot. Your test results will be different with the air on than when it is off. No kidding. I have a line voltage meter on my Monster Power line conditioner, and I have seen this happen (it's also a very well documented phenomenon). So your tester might be fine. Just turn of the Air when you want to test tubes. Try that before sending your tester off. My tester has been very consistent over the last 18 months, but I make sure I test when the line voltage is in the normal 120V area.

Back to the tubes - power them up with some cheap headphones if you have some. I keep the JVC RX900 ($50, and damned good for the money) around for just that purpose - watch carefully for any odd tube behavior like arcing on a lot of blue glow. But if they tested OK, you really should be OK.

 

[Pricklely Peete]

Every time Sky talks about tubes I learn something valuable and new...thanks man !

Aren't Tung Sols known to be noisy at first ? I seem to remember that from some earlier reading somewhere else. If they weren't that would mean they were used rather than NOS so maybe the noise is a positive but temporarily annoying sign of true New Old Stock condition. That's one way to look at it (if it's correct).

As always I could be wrong

Peete.

 

[shellylh]

The thing is that the loud sound only lasted a few seconds and then went away. It wasn't a whooshing or whining or popping sound though. I don't think it was static... well maybe a little. It is hard to remember what it sounded like now.

Interesting about the air conditioner. Thanks for the hint.

Do you know why the tester may have said there was a short if there was not a short?

Also, I noticed that the meter bounces around a lot with some tubes (maybe that is what takezo was talking about... will it bounce around whenever there are ). It bounced around a lot with the TS Round plates the first time I tested them. Am I not holding the test button down long enough or giving it enough time to warm up or both? I certainly never thought I should hold it down for 1 minute! I was afraid of holding it down too long.

By the way, what does arcing look like. Since the TS's are mostly covered, it is hard to see much.


Quote:

Originally Posted by Skylab /img/forum/go_quote.gif It is definitely not unusual for NOS tubes to be noisy when first used. In fact, it's common. 6SN7's, IME, generally are not loud in their noise when first used, but I have had them make noise to be sure (some tubes, like the 6SJ7, will hum so loud it's horrifying for like 12 HOURS, but the 6SN7 does not do this). If it's settled down, it should be OK as long as it tests OK, so now let's talk about that. I bought some NOS TS RP 6SN7GT's from Paul, and they tested great. *Other*, used TSRP's I have gotten, however, take an unusually long time in test mode to get an accurate reading for whatever reason. It's not the only kind of tube I have experienced that with, but it a little unusual (I use a B&K 650). One other thing regarding your tester - your AC line voltage will effect your test results. Since you live in Houston, I am sure your Air Conditioning runs a lot. Your test results will be different with the air on than when it is off. No kidding. I have a line voltage meter on my Monster Power line conditioner, and I have seen this happen (it's also a very well documented phenomenon). So your tester might be fine. Just turn of the Air when you want to test tubes. Try that before sending your tester off. My tester has been very consistent over the last 18 months, but I make sure I test when the line voltage is in the normal 120V area. Back to the tubes - power them up with some cheap headphones if you have some. I keep the JVC RX900 ($50, and damned good for the money) around for just that purpose - watch carefully for any odd tube behavior like arcing on a lot of blue glow. But if they tested OK, you really should be OK.

 

[Pricklely Peete]

Arc'ing is bright flashes (spark like short bursts).

Are the pins heavily oxidized ? You might want to clean them with Flitz or Caig Deoxit and then treat the pins after cleaning with Caig Pro Gold.

Has this noise disappeared and not manifested itself again ?

Peete.

EDIT: Have a look at the video (Yaquin MC 100B amp)..pay attention to the far right KT88. The blue flashing is arcing. video of tube arcing - Google Videos Note the additional glow at the base of the filament that is not present on the other 3 KT88's.

This video is a little more prominent (arcing and red plate glow of 7591 tubes) http://video.google.ca/videosearch?h...ng&hl=en&emb=0

 

[Skylab]

The other thing I forgot to say is that among the many great things in takezo's post, he mentioned tube sockets - in my DV337, if the tubes are not just exactly right in the socket, I get noise, but in the right spot, they are dead quiet. It would probably be best if I replaced those sockets, but the point is, the whole problem with the noise could have been seating in the socket. But it still could also have just been a one-time start-up sound.

Lastly, if the meter is bouncing around a lot, that is not good, no. I would let the tube warm up for at least 2-3 minutes before testing it. Then hold the test button down for more than just a few seconds (the nice thing about the 650 is there is no button to hold down, the test mode is a lever setting, so I will leave it in test more for a minute or more on each triode). If there is a lot of meter bouncing around SHARPLY during the test, and you don't have a lot of things happening at that time that would effect the line voltage, I would say these are not good tubes.

BTW I have bought a fair number of tubes from Paul Lindemann, including some NOS Tung Sol RP 6SN7GT's. They have all been good tubes. The worst problem I ever had was a tube with a loose base that he promptly replaced with no issue. The tubes I get from him all test very, very well on my tester.

 

[Rob N]

Could it just be bad contact with the pins and the socket?

I've had this with a Singlepower amp after warmup,if you move the tube in the socket while it's on does the noise stop?

If it is a bad contact I doubt it's the pins as the ones that Paul is selling have near perfect condition pins.

BTW I have used about 30 pairs of TS RP's from different sources and the only pair that was noisy had a low level constant hiss

 

[Rob N]

Quote:

Originally Posted by Skylab /img/forum/go_quote.gif The worst problem I ever had was a tube with a loose base that he promptly replaced with no issue. The tubes I get from him all test very, very well on my tester.

You can also get spilt or cracked bases sometimes,this isn't usually a problem

 

[shellylh]

Thanks for all your help. I ended up sending them back to Paul in the end but learned a lot from this discussion.

 

[nikongod]

Regardless of what the source of the noise is, I would be supercareful when noise suddenly appears. It is one of the signs that a tube may be on its last legs. My opinion is that life is too short to put up with tubes that are audibly noisy (not necessarily instrument grade, just noisy enough to actually hear.) and there are plenty of tubes that are not noisy even at reasonable prices.

It is possible that the sockets or pins are dirty or defective so thats def worth checking. If the amp is quiet with all your other tubes, and the tube you have is still noisy after a once-over on the pins with a fine wire brush move on to the next one...

Regarding the short that didnt show up short the second time you tested it:
Its possible that a little flake of something (the getter perhaps) rattled around in the tube and settled between the plate and grid. Short! Then you shake the tube around a little moving it in and out of the socket, and the flake moves around, and its no longer short. Then you shake it some more putting it in the amp and it goes short again.

Its very odd that it happened to both tubes. Perhaps they were slightly gassy. Sometimes the getter absorbs the gas as the tube warms up, but it only works for a little while. Its much better that you sent them back.

 

[shellylh]

Thanks nikongod, you are the first person to give an explanation as to why the tester might have shown a short one time and not another.

While we are on the topic of tubes:

I have a pair of RCA 6sn7 grey glass VT-231 tubes that I just got (tested NOS from Brent Jesse). One of them is really noisy (sounds like a loud hiss with some static) in the Woo. In my DV 336se, I can hear a hiss in one channel of one of the tubes very faintly if I use sensitive headphones. Brent says to let them run for 24 hours before sending them back. I am reluctant to do that in the Woo so was going to do that in the DV336se. Do you think the static could indicate the tube is on its last leg even though it tests new on Brents tester? Should I run both 6sn7 tubes in the DV336se for the same amount of time (independently) to keep them a matched pair or does this not matter for driver tubes. (Oh, and yeah, I haven't tried my tester yet becuase of the issues mentioned before with my tester).


Quote:

Originally Posted by nikongod /img/forum/go_quote.gif Regardless of what the source of the noise is, I would be supercareful when noise suddenly appears. It is one of the signs that a tube may be on its last legs. My opinion is that life is too short to put up with tubes that are audibly noisy (not necessarily instrument grade, just noisy enough to actually hear.) and there are plenty of tubes that are not noisy even at reasonable prices. It is possible that the sockets or pins are dirty or defective so thats def worth checking. If the amp is quiet with all your other tubes, and the tube you have is still noisy after a once-over on the pins with a fine wire brush move on to the next one... Regarding the short that didnt show up short the second time you tested it: Its possible that a little flake of something (the getter perhaps) rattled around in the tube and settled between the plate and grid. Short! Then you shake the tube around a little moving it in and out of the socket, and the flake moves around, and its no longer short. Then you shake it some more putting it in the amp and it goes short again. Its very odd that it happened to both tubes. Perhaps they were slightly gassy. Sometimes the getter absorbs the gas as the tube warms up, but it only works for a little while. Its much better that you sent them back.

 

[Skylab]

Wow...I am starting to worry about your Woo. Seems unlikely that all these NOS tested tubes from reliable sellers could be so bad. I buy untested tubes of unknown use level pretty frequently on eBay, and most of the time even they are completely quiet. I don;t think I have ever bought a real NOS tube that was noisy after burn in. And that you can only barely hear a faint noise with very sensitive headphones from the tube when used in your DV336, but that is is very noisy with the Woo, is a little worrisome. You did say you have some tubes that are totally quiet in the Woo?

And it is a good idea to run them in for 24 hours. do the noisy one first, but I definitely suggest to do them both.

And I hate to even say this, but I find the TS RP VT-231 far, far superior to the RCA. At some point you might want to try again with those. The RCA is a very lush tube, but lacks a little in definition in punch. It's a little syrupy.

 

[shellylh]

Skylab, I have a pair of Sylvania brown base 6sn7WGTA tubes that have worked fine from the beginning in the Woo. Perhaps with burn in the RCA tubes will be fine as well. I have a pair of basically unused Electro Harmonix tubes lying around that I can try in the Woo (not for listening but for testing purposes). As for the RP, I tried them again in the Woo this morning and one of the channels was barely audible so I am a little worried about that tube. I will probably get another pair in the future again. For now, I will stick with the Sylvania and RCA.


Quote:

Originally Posted by Skylab /img/forum/go_quote.gif Wow...I am starting to worry about your Woo. Seems unlikely that all these NOS tested tubes from reliable sellers could be so bad. I buy untested tubes of unknown use level pretty frequently on eBay, and most of the time even they are completely quiet. I don;t think I have ever bought a real NOS tube that was noisy after burn in. And that you can only barely hear a faint noise with very sensitive headphones from the tube when used in your DV336, but that is is very noisy with the Woo, is a little worrisome. You did say you have some tubes that are totally quiet in the Woo? And it is a good idea to run them in for 24 hours. do the noisy one first, but I definitely suggest to do them both. And I hate to even say this, but I find the TS RP VT-231 far, far superior to the RCA. At some point you might want to try again with those. The RCA is a very lush tube, but lacks a little in definition in punch. It's a little syrupy.