So, WTF?

treitz3

Hello all. I had a GTG this weekend and I knew a tube was going bad within my Canary pre (preamp portion of the pre, not the power supply)

I powered it down last weekend and to make a very long story short, never powered the system back up until this morning.

When the tube went bad, it produced what I can only describe as a "whistle" or a high pitched whine in the R channel.

It was very bad last weekend and I almost called off the event, but I did have a workaround that doesn't matter for this post, so I won't bore you with the details.

We had the event and it went well but with this unwanted artifact kept rearing it's ugly head from song to song. Sometimes it was noticeable and other times, it was very distracting. So much so, that I wanted to resort to plan "B", which was to lose the pre altogether. Basically bypass it.

It never got as bad as it did last weekend but it was still testing my patience duri g the GTG.

When the event was over? I powered her down. After about 30 minutes and a "Fonzie" style whack on the side of the pre? I powered her back up.

Walla!

Noise gone.....and I do mean GONE! Like, nothing....as if I installed new tubes.

Prior to that, Iightly tapped on the pre and you could hear the microphonics amified over the speakers. It was undeniable to all in the room.

While said tube(s) are still microphonic (as evidenced by tapping on the case of the pre itself), there is no longer any whine or whistle.

I have heard that "droppings" within the tube can be corrected but in all my years, I have never experienced this.

Can anyone explain, in rational and layman's terms what in the F just happened? No matter how loud I turn it up right now? There is zero whine or whistle. It's as quiet as the day I bought the quad. Go figure.

What gives?

Tell me about your experiences with something like this, if you have ever experienced it before. I am perplexed.

If only the crew that was here today could hear what I (don't) hear now....

Tom

F1nut

Whack it again to see if the whistle comes back.

audioluvr

Tom,
That has always been my go to approach for fixing almost anything. Unfortunately it is a temporary fix and will probably just return in spectacular fashion.

Emlyn

Some of the two box tube preamps are so complex that there could be a number of problems that have nothing to do with the tubes. In the past I've had to self diagnose that the tubes aren't the issue by replacing them with cheap but robust Russian ones that I know are not microphonic. The problem was still there and it turned out a couple of times to be a problem in the external power supply for one channel only. Static has also been a problem that could be remedied by powering down and back up.
The problems tend to be electronic gremlins rather than physical. Tubes are really pretty simple devices that don't tend to fix themselves. They only get worse as they wear which is why I mostly gave up on them.

In this case could it have been an issue with powering the preamp back up and it not settling in right?

mhardy6647

Could be a cold solder joint or even a passive component (resistor, or even capacitor).
I'd guess that a whistle/whine is symptomatic of oscillation -- might even be ultrasonic oscillation (i.e., an issue in a feedback loop) with a heterodyne ("beat") frequency that's audible.

Throwing an oscilloscope on it when it's whining would be a good way to find out.

treitz3

@Regan ran across something the other month that brought me to trying the "Fonzie" move. While it wasn't an optimum move, I figured, what the heck.....I'll try it. Unconnecting everything with my space available in the rack can be....well, a chore, complete with unnatural bending and contortions of the body that are not comfortable at all.

What he ran across was a statement from Brent Jesse's website that perked my ears when it comes to noises within tubes. Here is what is found on his website...http://www.audiotubes.com/tubetap.htm



I don't know if you will be able to read this screen capture or not, so I will also quote him below, for easier reading.

Brent Jesse Recording Studio wrote:

Now, what if I heard something? For noise, at normal listening volume at your listening position you will clearly hear hiss, pops, crackles, rumble, whistles, or any combination of the above. For microphonics, at normal listening volume you will clearly hear tapping through the speakers as you tap on the unit. In the case of noise, you may be able to fix it yourself. First, locate which tube is noisy. You may have to substitute one tube at a time and try the unit out until the noise vanishes, indicating the last tube you took out is the one. If you don't have spare tubes, just swap the tubes one at a time from the left channel to the right channel and listen after each tube swap. The noise will follow the noisy tube to the other channel. Take that tube out of your unit and tap it on its side firmly on a table top. Then, hold it upright and tap it firmly with a wooden pencil. This will nearly always knock the offending flake of material out of the grid where it will cause no more noise. Reseat the tube and give it a good 12 to 48 hours of burn in time and the noise should be gone for good. I know it sounds extreme but in at least 85% of noise cases, this resolves the problem. Some audiophiles have said tapping a tube can CAUSE it to become microphonic. I totally disagree. I have tried this trick for 25 years with mostly successful outcomes, and never once has a tube become microphonic after tapping it.

The highlighted in bold is the juicy stuff. Instead of taking everything apart, I tried the "Fonzie" move first, to see if I could knock the flake off of the grid. Well, last night, it worked.

I do not think it's the external PS, as I tapped on that portion and zero noise. The microphonics only appeared when tapping on the case of the pre-part of the pre-amplifier (selector/volume knob portion of the pre, not the PS section).

We'll see if this permanently fixes the tube. If this noise rears it's ugly head again, I will definitely take everything apart and try to locate the issue. If it ever does turn out to be an oscillating issue, I'll just send it back to Canary for professional repair. It's been so long since I have used an O-scope, that I probably have forgotten how to use one.

In the meantime, I'll try to look for a matched quad of VT231 military stock 1950 Raytheon tubes, although they are as rare as hen's teeth nowadays.....not to mention, the price has flown into the upper stratosphere. That, and look into getting some tube dampers.

Anyone have a good suggestion for a tube this size? (all mine are for 12AX7 type/size tubes)

Tom

bcwsrt

I’ve got a microphonic 12au7 in the trio of them I was using in my amp before @pitdogg2 let me test drive some absolutely amazing vintage Teslas a few weeks ago. I need to make time to find it and try this fix on it. Can’t hurt anything and if it works, that’d be great.

bcwsrt

I wouldn't call what I just did a "Fonzie" move since it was just a little light tapping around the top and sides of my amp with my fingers as I began to swap one tube at a time out to see if the problem remained, but #&^$ if that didn't cure my microphonic issue, at least for the time-being. After the first couple of taps, the microphonics became less and less until they totally went away.

Tubes are cool. But weird.

Thanks for the thread.

heiney9

I've had some finicky tubes in the past. Unless it's a new production tube, these wonderful glass bottles filled with magic are 40-50-60 years old. Sometimes this happens. That's why I have multiples of my favorites.

It is a sign a tube is probably going bad, but I personally have solved many a noise issue by cleaning the pins and socket and re-applying De-Oxit. That has helped in many cases.

Tubes can be finicky, sometimes there is no logical reason. I am still amazed these little glass bottles still perform after all this time.

H9

invalid

It is a sign a tube is probably going bad, but I personally have solved many a noise issue by cleaning the pins and socket and re-applying De-Oxit. That has helped in many cases.


H9[/quote]

I know Andy at vintage tube service says even if the pins don't look dirty they should still be properly cleaned or they can't be tested for noise issues.

pitdogg2

Exactly Brock.
At this point in time even NOS tubes can and do give up the ghost. What the unknown is just how those little fire bottles had been handled the last 6-8 decades. I'm sure for their early lives they were plentiful and easily replaced so they may have been bounced around pretty good. Seven decades later they're very pricey and we handle them much more carefully.

treitz3

https://herbiesaudiolab.com/collections/tube-dampers/products/hal-o-iii-stabilizer



Not a flattering photo but this is the best that I have searched for so far when it comes to temp resistance and damping the microphonics of a tube my size (get your head out of the gutter).

It seems as if the best place to place them is at the top 3/4 of the tube itself. Does anyone have any experience otherwise....or any other suggestions?

Please advise and thanks.

Tom

pitdogg2

I tried several of the Herbie's, they've been riding in a drawer for several years now. I didn't find them a worth while investment.

treitz3

Your findings do not mimic those whom I have spoken too...

Over damping is one thing....getting rid of micro phonics? Another

But thanks for you thoughts on this. Much appreciated.

Tom

heiney9

I've used them in the past with mixed results. I've used 2 on a single tube in many cases. It worked for a few to tame the microphonics. On others it was a mixed bag of slight reduction, but still there just less obtrusive to almost no effect

I am in the camp that it's worth a try and I think Herbies are about the best at what they do. IIRC, the investment isn't huge so why not give it a try. Like I stated I ended up using 2 on a small long plate signal tube that was known to have microphonic issues and it did help.

H9

55SLA70

Take that tube out of your unit and tap it on its side firmly on a table top. Then, hold it upright and tap it firmly with a wooden pencil. This will nearly always knock the offending flake of material out of the grid where it will cause no more noise.s

This just worked for me. After reading the above a couple hours ago, I took a NOS USA Amperex 7308 White Label I had laying around, that crackled in the left channel, followed Brent Jessee's advise and, low and behold, fixed it. Not only is it dead quiet, it's one of the better sounding tubes in my arsenal.

Thanks for posting that Tom!

Emlyn

treitz3 wrote: »

Not a flattering photo but this is the best that I have searched for so far when it comes to temp resistance and damping the microphonics of a tube my size (get your head out of the gutter).

It seems as if the best place to place them is at the top 3/4 of the tube itself. Does anyone have any experience otherwise....or any other suggestions?

Please advise and thanks.

Tom

I tried several different types of tube dampers and settled on the Herbies with the silicone pads. My tube preamps with small signal tubes didn't run hot. That was the best solution for me in terms of not over dampening compared to others. I don't have any experience with the expensive metal ones from Herbies but they look good.

F1nut

I tried the Herbie dots...sent them back.

treitz3

Never even heard of the Herbies dots....but duly noted. Thanks.

Tom

mhardy6647

treitz3 wrote: »

Never even heard of the Herbies dots....but duly noted. Thanks.

Tom

Sounds like a popular, if slightly risky, accessory for a Grateful Dead concert BITD...

txcoastal1

Quinn the Eskimo was popular during the late 80's early 90's Grateful Dead Tours...so I have been told

mhardy6647

txcoastal1 wrote: »

Quinn the Eskimo was popular during the late 80's early 90's Grateful Dead Tours...so I have been told

"When Quinn the Eskimo gets here, everybody's gonna want a dose."

(actually, I think the line is "When Quinn the Eskimo gets here, everybody's gonna wanna doze"... but either one works)

https://youtu.be/K13hH0pJx5s

Needless to say, no Eskimos Inuit named Herbie, or Hermey, for that matter...
Which is not to say that there are none in the Arctic, though, of course.

bcwsrt

Took me a while to find this thread again, but I was able to recall most of what is in the Brent Jesse quote above when I had some hissing and crackling in one of my favorite 12AU7s in my amp for a few days leading up to last weekend. A few firm tabletop taps followed by a pin cleaning with the (red) DeoxIT D100L and the noise was ~80% gone. Now, a good 12+ hours later, it's back to its previous eerie quietness.

Just thought I'd bump this back up for anyone that hadn't seen it.

I've bookmarked it this time. Lol

treitz3

Good deal! I am happy that this thread has helped a few folks out.

FWIW, the very same tubes that were whistling? Well they are still playing, sans whistle ever since then.

Tom

dromunds

On the other issue, I’m not a fan of tube dampers. I found they muffled (or veiled) too much of the sound to make them beneficial. I tried various and like Rooftop said previously they are now in a drawer.

GlennDog

bcwsrt wrote: »

Just thought I'd bump this back up for anyone that hadn't seen it.

I haven't seen it . . . very good to know. Thanks!