As the subject says, I have a bad case of Tube Rattle.
Is annoying, I cant play the -2 on many of my harp whit out that sound, and is loud.
I read on a google search that this is a common problem on the combo amps.
I have 2 questions: - A tube damper is a good idea? (sub question: there is something like a DIY damper?)
- Is this rattle bad for the tubes?
I have a Jan Philips 5751 and a Buguera EL84 (I used to have a EH EL84, but it turn out to be a microphonic one)
Last Edited by on Nov 30, 2012 4:21 PM
I've never heard it called "tube rattle" but the video demonstrates a microphonic tube. That means the tube will generate sound associated with vibration. To find it, take a wood stick (chop stick works great) and tap each tube while the amp is on. A microphonic tube will create sound through the speaker when you tap it.
Tubes should not be microphonic. Replace the tube that is. ---------- /Greg
I've had tubes straight from the factory that were microphonic. Others popped the first time I fired them up. Tubes are a crap shoot, but when you get it all right they are magic.
@Rogonzab - When did this rattling start? If you can determine that, undo the last change you made before it started & see if you can eliminate it.
The video may be the same issue that you have...then again, it's a 35yr old amp in the clip & could be a totally unrelated issue. There are many causes of rattling sounds and it can be virtually impossible to determine the exact cause of similar sounding rattles that have different causes.
So it's a process of elimination (do Greg's chopstick test - I do this with no instrument plugged into the amp and all controls fully up - any tube that makes unusual pops, crackles, whines, or rattles goes. Preamp tubes will often make some dull mechanical noise from the disturbance, but this should stop when you stop agitating the tube...any persistent ringing, whistling, whining is a "no-no")...don't forget to eliminate the harp too...you say your 2 draw is affected badly, try the same note on another harp just to make sure there is no reed rattle.
The vast majority of combo amps don't rattle with good tubes...on the other hand some specific models of amp ALL rattle under the same circumstances. This is sometimes down to design & layout (oscillations that are purely elctrical in origin often sound like mechanical rattles), reducing preamp gain can help in these cases.
1 means power tube taping 2 means preamp tube taping
One question: yesterday I play for a while and the only noise that I hear (besides the notes) was the "rattle", I diddint hear this kind of sound at all. Can a tube became microphonic from one moment to another?
Last Edited by on Dec 01, 2012 10:40 AM
Very hard to say. First turn the amp down until it isn't generating feedback from the phenomenon - THEN tap the tubes.
P.S. If that is a brand new amp it is clearly defective and should be exchanged for one that works. It isn't your job to diagnose a problem with a new amp!
P.P.S. - the offending component (probably a tube) has a resonant frequency "just right" to work with other components resonant freq's (the speaker) to generate feedback. A tube damper is usually a piece of rubber tube placed over part of the vacuum tube to add weight/change its resonant frequency. A few o-rings can be used for this purpose.
Doesn't sound like the tubes are the underlying issue. Some may make it worse/better (use what gives you the least problem, also consider 12AY/12AU7) but the amp seems somewhat unstable. This may, or may not, be normal for this model.
I had a look at the schem - normally, for a cleaner/lo gain/harp friendly sound you would run the master ("volume") up high and the "gain" low. But the V5 uses an unusual master circuit value - I'd suggest keeping the "Volume" between 9'o'clock & 12 o'clock, (use the "gain" as the volume control)...as when the "volume" is fully up it shows the EL84 a huge 1Meg grid load (a design that was dumped in the early 50's by most manufacturers).
If you can get reasonable volume before feedback, without the loud humming/throbbing sound, the amp may be fine. If you bought it from a shop, or have access to new models in a local shop, see if they do the same, as Greg says if there is an issue (like a bad ground) it's the seller's responsibility to ensure it works as "normal" (being aware that if they all do it, then that is "normal").
Good luck & keep us posted....
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Last Edited by on Dec 01, 2012 12:43 PM
4 months ago: I bought the amp. (this is a second version of the same amp, the first was the one whit the blue light, mine has a orange one) The stock tube where ok (the brand on it was Bugera), but the distorion that they give I didnt like, so I bought new tubes.
3 months ago: The new tubes arrived. I try a Tung Sol 12AT7, EH Tung Sol 12AT7 and a EH EL84. I kept the Tung Sol 12AT7 and the EH EL84.
2 Month ago: Start hearing some craking and a kind of feedback noises. Replace the EH EL84 for the Bugera EL84 and the sounds where gone.
1 Month ago: No problems.
Last week: I took my amp to the house of a guy who sell me a Jan Phillips 5751. We test the tube, and it was ok. Couples day later, the rattle start. I take of the Jan tube, and put it again on the amp in case that it came loose or something. This reduce the rattle for a while. Then the rattle became more and more loud. Then I made this post.
I replace the Jan Phillips 5751 whit the Tung Sol and the sound on the video disapear. I still have a litle rattle, but only when I play a deep bend on the -2 whit an A harp.
@5F6H, You are right, I did play whit the volume knob on 10 and use the gain knob for volume control. I am going to test the way you told me.
There could be lots of explanations. There could be a bad solder joint - most likely going to one of the tube sockets, but could be anywhere. The wire may have been making partial contact and that can indeed be microphonic due to the vibration from the speaker. It may have finally broken free.
If you decide to check this yourself - know that there is DEADLY high voltage DC running around in your amp, and it can remain for hours, even days, after you shut your amp off. If you don't know how to discharge the power filter capacitors, I'd leave it to an expert. ---------- /Greg
