Tube microphonics

Here's another tidbit of audio nervosa; never mover tube gear warm, it must be totally cooled down first. To do otherwise is to invite the tubes to become microphonic! 

and this is why i have daily deliveries of dry ice!!! 😂🤣😆😃

Here's another tidbit of audio nervosa; never mover tube gear warm, it must be totally cooled down first. To do otherwise is to invite the tubes to become microphonic! 

people posting their experience with microphonics.  The worst offender in my experience is OS (they are never really New) 6SN7.

Jerry

@carlsbad2 

Yes, I share that experience. Old GT series 6SN7 from the 1940s are notoriously microphonic. This is exacerbated by the fact that they're often shoved in high gain positions upstream (preamp), where their large plates are loosely held by tired micas and well - that's the inevitable result. However I've still had good luck with them in V1 amp slots, since they're far enough downstream at that point. That's really where I get the most benefit from my 1940s 6SN7 collection. You can still hear a little reaction if you ping 'em but not enough to worry about. 

I've not had a problem with mircophonics on the later (50s and 60s) old stock GTA and GTB series 6SN7. So if you have a problem slot and still want a vintage tube, use that. Sonically I prefer the tall bottle variants of these. 

1. Heat Dissipation: Vacuum tubes can get extremely hot during operation. An O-ring might inhibit the necessary heat dissipation, potentially leading to damage or reduced lifespan of the tube.

A ring on an audio tube is not going to be any problem for heat. Tubes are a lot better at self cooling than high power transistors. Just don't cover the majority of its surface or run them with a blanket on. 

A thought I have *may* reduce the cost of fighting microphonics. And ChatGPT seems to agree -- to an extent:

Is there such a thing as high-temperature O-rings, and could they be put around vacuum tubes in HiFi equipment, to suppress microphonics?

ChatGPT

Yes, high-temperature O-rings exist. They're often made from materials like Viton or silicone that can withstand higher temperatures. However, their use in HiFi equipment to suppress microphonics might not be entirely straightforward.

Microphonics in vacuum tubes refers to the phenomenon where mechanical vibrations within the equipment can modulate the signals passing through the tubes and create noise or sound distortions. These can be caused by various factors such as transformer vibrations, loudspeakers, or even sound waves in the air.

Theoretically, using O-rings as a dampening material around vacuum tubes could help reduce these vibrations. However, this might not be advisable in practice for several reasons:

1. Heat Dissipation: Vacuum tubes can get extremely hot during operation. An O-ring might inhibit the necessary heat dissipation, potentially leading to damage or reduced lifespan of the tube.

2. Material Compatibility: While high-temperature O-rings can withstand heat, they may still degrade over time due to prolonged exposure to the high temperatures of vacuum tubes.

Therefore, while it's possible that high-temperature O-rings could help dampen microphonics, it's important to consider potential problems. There are dedicated tube dampers available on the market that are specifically designed for this purpose and may offer a more reliable solution.

people posting their experience with microphonics.  The worst offender in my experience is OS (they are never really New) 6SN7.

Jerry

@curiousjim

yes

in the amps i have had that run them in the input and driver stages, arc put dampers on 6n1p as well as 6h30p tubes as well... and of course on older models, the 6dj8's

Arc puts damping rings only on the smaller tubes  (In my case they’re 6922’s.) for a reason.  They are the most sensitive to microphonics. Having said that,  all tubes are subject and it can’t hurt to try tube dampers on your other tubes.

All the best.

     Keep in mind: parked next to your speaker systems, your amp's entire chassis will be boogieing, in tune with the music.

    How much time, effort and dinero, have many of us spent, in an effort to eliminate undesirable vibes, from our components' (passive/active) electronics?

          Of course: one's listening habits (ie: SPLs) would be a major variable.

                                               Happy listening!

I was thinking the same from the very beginning

                            And: you were correct.

       ie: https://upscaleaudio.com/pages/microphonics

@onhwy61   I was thinking the same from the very beginning too. Plus my speakers are B&W 800 matrix. Top and bottom bass also. They act like having 2 subwoofers on ea speaker. 

If you think about how nearly all loudspeakers radiate bass pressure waves, then it really shouldn't make much difference if the power amp is behind or in front of the loudspeaker as far as exciting tube microphonics.

@mulveling @jjss49 @jetter  Thanks for clarity on tube dampers on tube power  amps. @mulveling  Hell no I’m not gonna spend almost 2k just for looks. Wouldn’t even spend 50$ just for looks on a tube damper without it doing nothing. 

In a "combo" guitar amp the entire amp including the tubes are in the same box as the speaker. Since the mid 30s. It works great. 

My experience echoes Mulveling's

Never had a power tube be microphonic in the slightest.

perhaps i wasn’t clear in my earlier post and created some confusion -- arc puts dampers only on low level tubes -- not the power tubes

IMO tube dampers on power tubes will have no effect unless you’re doing it for the look. Never had a power tube be microphonic in the slightest. I’ve also never had any damper solve a microphonic tube issue in a preamp -- the solution in that case is a new tube, or a different preamp with lower gain.

Update on tube dampers for KT150s. Herbie’s does make tube dampers for KT150s. They are $54 ea. So I will need a total of 16 x 2. Power output. And 2 x 2 drivers. For a total of 36 KT150s. -$1944 

Maybe. I’ve only rarely heard any tubes acting microphonics in power amps, and only for very old NOS tubes in the V1 / input slots. Amps are very far downstream in the gain structure, so microphonics are rarely an issue. Tube preamps and phono stages are a different story.

Anyways, I’ve had a few different tube power amps right besides my speakers. Never in front, but I’ve had them on bare floor, spikes, hockey pucks, isolation feet and even expensive $3K isolation shelves. Never heard that much difference from the isolation, sorry. I play loud too. Swapping the AMPS themselves, however, is always a hugely audible difference.

@tattooedtrackman So just test for microphonics in all your tubes as I described.

@carlsbad2   Kinda both. Because I really don’t want to move those amps with the full sets of tubes already in them. Don’t want anything happening to the tubes by a bump or so. I already had one tube arc on me the first time I tried my amps when they got delivered. And it took out a resistor and fuse also. Don’t want that to happen again.    @jetter That sounds like a good idea. I will definitely try it. And yes. I did carry them upstairs but like u said there were no tubes in them. @ghdprentice Right. They don’t have rubber dampers for the KT150s. 

These days ARC only puts dampening rings on small tubes. Not big power tubes. 
 

This does not take away from the argument that tubes can be microphonic. I suspect the large power tubes may run so hot, that they cannot use those dampeners.

i haven’t bought new audio research tube amp in a few years but i have over a half dozen of them, and in every case, the company puts thick rubber tube dampers on every low level tube when the amp is shipped from the factory, and when replacement tubes are shipped there are instructions to move the old dampers over to the new tubes to be installed

this shows that as designers/makers of the gear, they are definitely concerned about unwanted microphonics affecting the sound produced, and are making an effort to damp them out

so i think it is worthwhile for the op to make an effort to move the amps, as hard as that might be, away from the speakers, to see if a positive sonic difference results

Those Ref 750s have 16 KT 88s sitting on top of the amps with only air around them, right? You did not say what speakers you have.  If you have speakers that have large woofers pointed at your tubes, I think they could affect the sound. 

I suggest you move the amps around the speakers, to the sides, behind the speakers, etc. until you find where your system sounds the best, and that may be with the amps in front of the speakers.😁  Use some furniture sliders to move the amps around.  We don't want to hear about you ending up in the hospital.☹

Edit-It's a free exercise to move them, so try it.

Agree 100% in general, and while OP carried them up a flight of stairs, they do weigh 170 lbs each.  And I am pretty sure the more delicate tubes weren't in them as they are now. 

"Someone told me on another site that if I move the amps beside the speakers and not in front of them , my system will improve immensely."

Oh brother... to much audio internet info.

Not saying a tube can become microphonic, but that looks like perfect example of A.N.

I’d stay away from audio forums and just enjoy your excellent gear.

Edit-It's a free exercise to move them, so try it. Everything in audiophoolery is YMMV.

@tattooedtrackman 

I know this is kind of backwoods, but then again I live in Vermont.

If I had your beautiful setup, here is what I would do before moving your heavy amps around.  @jjss49 if you think this is a bad idea please chime in.

With your preamp, amp and CD player on, I would set the preamp to CD mode.  I would turn my preamp up to about 1/10th volume (any VERY low setting).  I would GENTLY tap on the top of the preamp cover, then CD player cover, and then sides of the amps.  If I did not hear the dreaded (thump) or a tube rush sound I would repeat this, increasing the preamp volume, in small increments until I was at about one half volume.  This should take in total about 25 seconds.

If you do not hear a "thump" through your speakers when taping on your units I would say you have nothing to worry about regarding microphonics.

In my layman's way of explaining it, microphonics are the result of anything vibrating a tube sensitive to microphonics, whether by picking up speaker vibrations, taping the top of the unit having the microphonic tube or any other movement.

Just because a tube pings if you tap it does not mean it will sound bad. Mild microphonics is not a problem. I’ve heard tube trials where the best sounding tubes happen to be microphonic (the tubes were 310A’s).

this is very true, and an important point to note in any discussion about tube microphonics in a hifi use context

thanks for reminding us @larryi !!

Just because a tube pings if you tap it does not mean it will sound bad.  Mild microphonics is not a problem.  I’ve heard tube trials where the best sounding tubes happen to be microphonic (the tubes were 310A’s).

It must be hard to try or the OP would have tried it rather than starting a thread.  but maybe his real question is "what is microphonics"....

I test all my tubes for microphonics and reject any tube that exhibits audible microphonics.  "Microphonics" is then the tube acts like a microphone.  when it is excited by sound or vibration, you hear it in the system.  Easy to test for, put the tube in, turn on the systme with nothing playing,  and tap it lightly with your finger nail or a pencil.  If you hear it (coming out of the speaker) that is microphonics. 

So if your tubes can be excited by sound, the music itself can cause noise.

Jerry

@jjss49  Ty. I will try it. Appreciate the feedback. 

yes indeed - don’t ask -- just try it!!!

here is an explanation

@fuzztone  What is tube microphonics ? Also I really don’t have that much room beside my speakers for these amps. That’s also why I wanted to know more about this before a keep moving them. 
 

It might improve immensely. Worth a try.