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Vacuum tube tinkling noise when turn on/off.

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DraKnight13

Active Member
Hello everyone, I have a quick question that I can't seem to find answer on Google and it is bothering me quite a bit. I have a variety of tube amplifier. 2 of them are next to my desk, and they both doing the same thing. Upon starting up, or shutting down, the tubes would have these tinkling sounds like metal rods hitting the glass of the tube. During operation (after it has been turn on for a while), I don't hear the noise anymore, but the noise is bothering me cause I am afraid something is wrong and it may damage the amplifiers. (the tube I am using are vintage EL-34 for the Dynaco ST-70 clone and vintage 6L6GC for Mcintosh MC240). I have properly bias the current on the Dynaco ST-70 and it has been working without any hum or problem so far. Is this something I should be worry about???????
 
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The noises you describe are normal, in my experience. The operating temperature created by the heating elements inside the tubes causes expansion, and the noises occur when the constituent parts of the tube expand or contract at different rates. The effect is similar to the "ticking" that often occurs in an automotive exhaust system when the engine is shut off.
 
My very first tube amps, Dynaco Mk III, were rebuilt and I used inexpensive Chinese 6550 tubes, without knowing much about the tubes at the time. Turns out those tubes sounded really great, I still have a pair. But those tubes would make the same noises you describe, upon startup and power down. It gave the amps some character, I enjoyed those sounds. The tubes also had a certain smell about them after they ramped up to operating temp, not an overheating smell, but an industrial smell that I found pleasing (I suppose I am a little weird).
 
Normal. :thumbsup:

Think of the sound metal makes as it heats up (expanding) and cools (contracting). Same thing!
 
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yep, expansion, bigger bottles seem to do it more but I've had even EL84 types make noises. Ever hear a rectifier buzz? 5U4's sometimes have a noticeable rattle of the filament, particularly when cold.
 
Maybe I am just a bit too cautious. These amps are so close to me that the noise is very obvious, and I had a 6550 in an audio research amp arced on me for the first time 2 weeks ago that worry me. Thanks everyone for chiming in!!!!!!!!!!!!
 
Some tubes are louder than others when it comes to the cooling-off noises they make. All of the different EL34s I've used in my ST-70 have always made lots of loud 'tinkling' noises as they cool, while the EL84s in my ST-35 are much quieter. The reissue Tung-Sol 6550s in my Mark IIIs are somewhere in the middle loudness-wise, I think.
-Adam
 
I've always thought this was just one more of those subtle "cool factors" of tube amps.

For me, tube amps are not just about the sound (from the speakers). Perhaps this is partially due to poor modern sources, including compression and lossy formats. Poor speakers on the other end, too. I'm sure some that know me would add poor musical choice to this list.

But tube amps look cool.

I also add the filament glow, and sometimes other good or bad color emissions.

I would even add the smell to this list.

The metal/glass sound post shut down is just one more.

Many "high performance" systems make a "clinking" sound post shut down. As someone mentioned, cars do it. It can be heard after even "meh" cars are shut down, but it is more pronouced with a high=performace engine/exhaust system. It is very pronounced on an old radial aircraft engine. I'm pretty sure I have heard the same thing after shutting down a model airplane with an actual turbine engine.

Commercial jet aircraft will make a similar (and I think cool-sounding) noise after shut down, but it is for a different reason. The fan blades are not rigidly attached to the hub in most larger passenger jet aircraft. If there is a breeze blowing through the engine, it will spin, and as each blade rotates around the hub, it will shift position due to gravity, and make a clanking sound. On a 4 engine jet, with the right breeze it could be quite a symphony.

Another similar sound is the halyards clanking against the mast of sailboats in a marina (again, light breeze required, and not temperature related.)

So... Hook up a dummy load, disconect the input, and enjoy tube amp ownership!
 
The only time it's not normal is if you hear a bunch of tinkling sounds while the amp is still powered up. It may be a sign that the tubes are getting too heated, up to and including red-plating. :eek: Not sure if it always happens, but it did happen when the EL34s on my ST-70 red-plated awhile back.
-Adam
 
Same thing happens when you shut off a car engine on a quiet night as the engine and other parts begin contracting as they cool.
 
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