1x12 Combo "microphonic" rattle ?

[enigma]

When I play my 1x12 at a louder volume level (not overly loud) I hear what sounds like a microphonic rattle, or some "glassy" sounding rattle as if there are tiny broken glass inside the amp.

What could this be?

[tinkercity]

Most likely a pre amp tube. What kind of amp do you have and what tubes are in it? Power tubes can also be microphonic. A very easy way to diagnose is to gently tap each tube whilst the amp is on and see what makes the most noise

[enigma]

I just bought a used Dr. Z Stangray - the tone is fantastic and it seems to be independent of the microphonic rattle.

These tubes are held tight by wire-frame. When I rub the wire frame holding the Dario EF86 Phase Inverter I DO hear the microphonic sound. I'm assuming when the volume is up it vibrates the wire-frame which "rubs" against the tube. When I tap the tube I don't hear anything. The annoying sound seems to come only from this particular tube.

I wonder if this is enough diagnosis.

[mikedaul]

Another thing to check is the nuts holding the speaker to the baffle. They can work themselves loose over time from the vibrations...

[Nolatone Ampworks]

Originally Posted by enigma

I just bought a used Dr. Z Stangray - the tone is fantastic and it seems to be independent of the microphonic rattle.

I'll do just that, and see what happens. Thanks!

Sounds like a sympathetic tube rattle, and IME it's more often the power tubes. It's very tough to get rid of in a combo amp.

You can test it by grabbing the power tubes with a rag or glove (so as not to burn your fingers), and the damping of your fingers on the tube will usually suppress the rattle.

I use spring loaded tube retainers and thick rubber washers on top of the tubes to minimize it in my amps.

[Fauxkinbacker]

Tube microphonics. It happens - part of the nature of combo amps.

[enigma]

Paul, 4 EL84 Tubes have the dampening rubber rings. I tried the "rag-test" but it doesn't seem to be the power tubes. It seems that EF86 tubes are known for microphonics from what I read on the net. In fact, when I rub my fingers over the prongs on the EF86 tube (out of the amp) I can hear the microphonic noise.

Is there a particular brand you guys like/recommend? Paul, which brand do you use?

[Nolatone Ampworks]

Originally Posted by enigma

Paul, 4 EL84 Tubes have the dampening rubber rings. I tried the "rag-test" but it doesn't seem to be the power tubes. It seems that EF86 tubes are known for microphonics from what I read on the net. In fact, when I rub my fingers over the prongs on the EF86 tube (out of the amp) I can hear the microphonic noise.

Is there a particular brand you guys like/recommend? Paul, which brand do you use?

The rubber rings don't always take care of it IME.

I don't look at a rattle as a microphonic issue. A microphonic tube will generally squeel or whistle. Rattle is just a mechanical "looseness" inside the tube that's bad enough to be audible, and sometimes through the speaker. I guess it's all semantics.

What a tube sounds like outside the amp may or may not reflect to how it behaves inside the amp though.

The rectifier tube can cause this as well.

Do the rag test on all the tubes. Also, if you have more than one tube rattling, you may not be able to suppress it grabbing one tube at a time.

Also, make sure all the mouting screws are secure. I've heard the finish washers cause that sound. Also I've heard a loose chrome cap on a handle cause that.

[enigma]

Paul, thanks for the advice. I'm going to tighten everything that I see that might need tightening.

Oh, I do hear some "hissing" once in a while similar to a feedback, but very high pitch - almost like an amplified ice-picky tone.

[B_of_H]

i've gotten the 'sizzle' sound a few times out of combo amps that I thought might be a tube issue...both were just the tube sockets being too loose. I read up on the internet, asked a few friends about it and re-tensioned the sockets myself. worked perfect, no issues anymore. (and I bought a couple of extra sets of tubes thinking that was the problem so I have backups now for a while. :doh)

[sublimeaudio]

To check for microphonic tubes, tap on each tube with your fingernail while the amp is turned on. If you heard a noise when tapping (other than the noise of your finger tapping the tube) it is probably microphonic.

I also have had issues with rectifier tubes being rattly a lot. You can shake a tube to hear if there is any rattling.

[enigma]

I've tapped on the tubes, and no rattling. As Paul and others have suggested, it might be coming from the sockets, or other places.

[lux_interior]

Paul from Nolatone is absolutely right. I've come across this problem many times, not only in my own setups but from other people as well. As you know, combo amps have always been torture chambers for all tubes involved. Vibrations will always reach them, and this is a problem that is very likely to manifest itself sooner or later, unless the amp design is such that minimizes vibrations (for example, in my Koch Studiotone every tube was held in place very firmly by elastic rings, and I never had a problem).

Some tubes (even quality ones) are more likely to develop this than others, and it doesn't mean that they are bad and that should be discarded - they might be just fine in other combos. The only ones that are almost completely immune are Sovteks, but unfortunately usually sound very poor. I have seen this problem coming from power tubes much more frequently than preamps. It's not always detectable by the classic trick of tapping them with the eraser tip of a pencil while the amp is on. You can hear it not as squealing but as a small but audible annoying ringing noise on some specific notes (for instance, low D), and it comes from inner tube rattle. Some combos that don't have a design that minimizes vibrations as much as possible will produce this problem more often.

A technician once explained to me what Mesa is doing about it, and why my MKIIa is so problematic with some of the power tubes that I am using (the preamp ones were always fine). I asked him if I should install spring tube retainers, and he told me that this will probably make it worse due to the fact that they will transfer the vibrations to the tubes in a more intense manner. I didn't believe him at that point, but after experimenting I saw that he was indeed absolutely right. As a final solution, I was trying to decide between these two:
http://www.tube-shop.com/euro/store/...D=&RelatedID2=
http://herbiesaudiolab.net/guitar.htm
...and I chose the ones from Herbie's. I am waiting for them to arrive.

[soundchaser59]

Originally Posted by lux_interior

You can hear it not as squealing but as a small but audible annoying ringing noise on some specific notes (for instance, low D), and it comes from inner tube rattle.

Exactly what I thought. Mine sounds like a miniature hi pitched telephone ringing inside the center of the speaker, and it took me quite a while to realize it was the tubes reacting to resonance. No amount of tapping or pedal tweaking or knob tweaking could get rid of it.

I also realized it only does it on certain notes, and that was my first clue that it was a sympathetic resonance problem. Mine does it on the low (7th fret) B. And mine is not a combo, it's a small head.

But I had it sitting on a wood table a foot or two in front of the speaker. After almost going to the cuckoo's nest trying to stop it, I finally picked the head up to move it. As soon as I lifted it off the table the rattling noise stopped. The noise came back the moment I set the amp back on the table. If I switch speaker cabs the noise stops because the other cab is across the room.

This is one of the main reasons why I am moving away from combo amps, too many rattles and buzzes and resonances in the cabs, so many of which are made to sell to home consumers and not for real hi decibel guitar grinding. This must be why so many pros can be seen on tv and on stage using heads and speakers, and they dont always set the heads on top of the speakers.

I wonder if your noise stops when you pick the amp up and just hold it away from any surface? Maybe just setting it on a piece of foam or thick carpet would be enough to overcome the vibrator effect? What kind of surface do you set it on when you play? I've even found things like pencil/pen holders and cd cases buzzing in the room on certain loud notes. It's really cruel when it's the stand the amp is sittingon that is doing all the buzzing and rattling!

Maybe this is one reason why pro sound people started flying the big imperial star destroyer speakers at concerts?

[lux_interior]

Originally Posted by soundchaser59

This must be why so many pros can be seen on tv and on stage using heads and speakers, and they dont always set the heads on top of the speakers.

I wonder if your noise stops when you pick the amp up and just hold it away from any surface? Maybe just setting it on a piece of foam or thick carpet would be enough to overcome the vibrator effect? What kind of surface do you set it on when you play?

I have tried it on hard floors, on wooden stage floors, on carpeted floors, on its road case with wheels, on a special angled amp stand... it doesn't go away. This ringing sound is audible at quiet parts when I play by myself (for example in a song intro), and only when you leave a note to sustain... When the full band is playing, you don't really hear it at all. I could live with it, but I didn't want to have to deal with it in recording situations and when jamming at home.

As for the pros stopping the use of combos, I don't really agree... many pros still use combos, even in huge stages, and of course in studios. Again, if the amp is properly designed (use of soft vibration absorption materials? changing the cabinet resonance frequencies by making them heavier and more stiff? I don't know), there will be a minimization of vibrations. I don't think it's so serious to give combos a bad name, especially after 60 years of rock'n'roll!