something to sotp tube rattling?

[xerxes]

basically, because there is nothing to contain the tubes in my amp, they rattle. anyone have a solution? ive heard someone makes like a "cage" type thing. anyone know where?

[TwilightOdyssey]

Re: something to sotp tube rattling?

I don't know of any cage-type devices to keep a tube from rattling, Xerxes, but there are companies that make different kinds of devices to keep tubes from rattling or becoming mircophonic. I've only tried one of them, but I've seen several. I don't remember who makes 'em, either, but an online audiophile site should have a tweaky mod like this, or perhaps even a tube manufacturer (Electro Harmonix, Golden Dragon, etc) would have this accessory.

The first one is a jacket that slips over the tube, and is made of kevlar (I think). These were in vogue in audiophile cirlces about 10 yrs ago, and haven't really seen them around in recent years.

Another one (and the one I tried) is a series of small rubber grommets that that get glued around the outer surface of the tube. This works very well, in my experience.

The 3rd one I've seen is a rubber damper that attaches to the top of the tube to keep it from resonanating.

I've had good results using method #2; but, I've only seen them for small power tubes (EL84) and input/preamp/driver tubes (12AX7, etc).

I'm unaware of a metal housing that wouldn't rattle as much as the tubes themselves. Hope you find this helpful.

[Wattage]

Re: something to sotp tube rattling?

Powerful combos are prone to that especially if they have el84's. TO gave you some good tips his #2 method is the best place to start. Playing loud will rattle tubes good and EL84'sare very susceptible to getting shook up. Once they really rattle a lot it is time to replace them.

[StefanM]

Re: something to sotp tube rattling?

Can someone tell me - when a tube goes microphonic, what does it sound like? Does it start feeding back of it's own accord at high gain - or is it more of a high frequency oscilation on high clean notes?

I get the latter; tried swapping in an AT7 (IIRC, a lower gain same pinout as 12axy) and got the former.

[xerxes]

Re: something to sotp tube rattling?

thanks twilight and wattage! appreciate the help. my classic 30 isnt that many watts, though. but im going to try out method 2. thanks. where can i get these gommets?

[TwilightOdyssey]

Re: something to sotp tube rattling?

Can someone tell me - when a tube goes microphonic, what does it sound like? Does it start feeding back of it's own accord at high gain - or is it more of a high frequency oscilation on high clean notes?

I get the latter; tried swapping in an AT7 (IIRC, a lower gain same pinout as 12axy) and got the former.

Don't know if you'll find this helpful, but I got this from the manual to my Rivera Knuckelhead:


Checking for microphonic tubes

As tubes wear, some problems can come up. One of the most common symptoms is a ringing sound. This is usually due to the tube becoming microphonic (like its name suggests, it's picking up sound and amplifying it).

With the amp unplugged and cooled off, examine the tubes to make sure they're in tight and straight. Never twist them! Gently grasp the tube and wiggle it into place. Because some of the tubes are inside of metal sleeves, you will have to remove the sleeves to check them for microphonics. Grasp the sleeve with your fingers and depress it (it's spring-loaded) and turn to the left (counterclockwise). Now pull it off; this may require a little wiggling action.

Preamp tube first aid

If you hear ringing (a feedback-like high-pitched sound) in your amp, it's probably coming from a preamp tube. Here's a procedure to find which tube is giving you trouble.

With nothing plugged into either the High Gain or Low Gain inputs, and the Master controls turned down to 5 or below, turn the amp on.

Turn up the Volume on Channel 1 and Channel 2. Now use the tip of a pencil to gently tap the end of each of the small tubes (V1 through V5) and listen for sustained ringing. Turn up the Volume and Master knobs and keep tapping until you find the tube that rings (or squeals).

Turn off the amp, and allow the tubes to cool. Now pull out the troublesome tube and replace it with one of the same value (that is, if you're pulling out a 12AX7, replace it with a 12AX7).

Make sure that the tube is oriented correctly when pulling it out or putting it back in. If you look at the end of the tube and the socket, you'll notice that the nine pins are arranged in an incomplete circle. Always make sure the pins are aligned correctly. Never force a tube into its socket.

Remember to put the sleeve back on after you check or replace a tube.

Power amp tube first aid

Like preamp tubes, power amp tubes can go bad or wear out. Your Knuckle Head has four power amp tubes, and if one goes bad, they should all be replaced. This assures optimum output and tone.

If a power tube shorts out, the HT Fuse will be blown. Remove power from the amp and replace the fuse before doing the following:

1. Remove the power tubes. Remember the way the eight pins are arranged, and note that the center hole on the socket has a keyway that matches the center post on the tube.

2. Replace one tube. Turn the amp on. If the fuse blows (or the tube glows cherry red, indicating an internal short), you've found the bad tube. Turn off the amp immediately. If the fuse doesn't blow, replace another tube and turn the amp on again. Repeat this procedure until you've determined which tube is bad.

3. When the tubes have cooled, remove them. Replace all power tubes. (Don't throw away good tubes from the old set, though--save them as spares!)

***
I found this info at http://rivera.com/rivera.khmanual.ht...crophonictubes

[TwilightOdyssey]

Re: something to sotp tube rattling?

thanks twilight and wattage! appreciate the help. my classic 30 isnt that many watts, though. but im going to try out method 2. thanks. where can i get these gommets?

No problem, Xerxes. Here are a few links for you to check out:

http://herbiesaudiolab.home.att.net/

http://www.0wned.org/~hstraub/damper.htm

(These are the ones I use)

http://www.audioweb.com/Ad/AdInfo.asp?adid=142936

http://cgi.ebay.ca/ws/eBayISAPI.dll?ViewItem&item=3084866980&category=50598

[xerxes]

Re: something to sotp tube rattling?

bumping just so in the morning i dont have to search for it, lol