Tune rattle

[Headcoat]

Recently bought a pair of Mullard 6080 NOS tubes. Noticed that if I tapped the amp or the surface amp is on the right channel would ping in headphones. Switched the tubes and the ping moved to left channel. Contacted seller and he sent a new pair, I'm to return the originals. All good so far.

Just plugged in the new pair and am getting a similar pinging when I tap the amp, not certain if both tubes or just one. Need to verify that.

So... as both sets appear to have issues... am I right to think these are microphonic tubes or is such a rattle/ping normal with some NOS tubes? Can't say I've noticed anything similar with any NOS or new tubes priror.

I can't say I've noticed any issues when playing music, just when I tap the amp etc.

 

[MF 1000]

There are some reports of 6080 tubes going microphonic, but this would normally be pings/pops heard in your headphones. Obvious to say …just stop tapping your amp or the tubes too 😂😂

 

[Headcoat]

There are some reports of 6080 tubes going microphonic, but this would normally be pings/pops heard in your headphones. Obvious to say …just stop tapping your amp or the tubes too 😂😂

😂 I can't stop the tapping. But is it normal? No, not me tapping but the pinging noise, first set it only happened with one tube - switching channels tubes were in transferred noise to other side.

 

[MF 1000]

Does it settle down once fully warmed up ?

 

[rabski]

I don't use 6080s in anything, but the rule of thumb is that pretty much any valve is microphonic to an extent and some varieties are more prone than others, due to their internal construction. There are some metal-body pentodes where you're lucky to find better than 50% that aren't so microphonic as to be unusable.

Basically, if you have to hit it to hear it, then first, don't hit it, and second, don't worry about it. However, if it's quite loud when you tap the amp they're plugged into, I'd be a bit more concerned. It doesn't indicate likely failure, but it does mean that there is likely to be a degree of feedback, in that loud music will make the casework vibrate enough to affect the valve and the eventual sound.

One 'trick' is quite simply to leave it powered up for a few hours. Quite a few microphonic valves actually go a lot quieter when they're at proper operating temperature.

Other than that, I suppose return it or try a different make. There's loads around and they're not crazy prices.

 

[Headcoat]

Does it settle down once fully warmed up ?

First set got worse on warm up!

 

[rabski]

First set got worse on warm up!

Some microphonic valves start quiet, get notably worse as they heat up, then go a lot quieter. Run them for three or four hours and see. If they quieten down, they may well stay quieter.

 

[Headcoat]

I don't use 6080s in anything, but the rule of thumb is that pretty much any valve is microphonic to an extent and some varieties are more prone than others, due to their internal construction. There are some metal-body pentodes where you're lucky to find better than 50% that aren't so microphonic as to be unusable.

Basically, if you have to hit it to hear it, then first, don't hit it, and second, don't worry about it. However, if it's quite loud when you tap the amp they're plugged into, I'd be a bit more concerned. It doesn't indicate likely failure, but it does mean that there is likely to be a degree of feedback, in that loud music will make the casework vibrate enough to affect the valve and the eventual sound.

One 'trick' is quite simply to leave it powered up for a few hours. Quite a few microphonic valves actually go a lot quieter when they're at proper operating temperature.

Other than that, I suppose return it or try a different make. There's loads around and they're not crazy prices.

Cheers maestro Rabski. It's a rattle rather than ping. Light enough tap on amps casework. It's only a headphone amp so no issue with feedback.

I'll ponder but do like the sound of the Mullard so might well keep one or both sets.

 

[Lurch]

Buy some O rings (butyl I think for highish temperature) and pop a couple on each valve as dampening rings. Just match the ID of the O rings to the diameter of the valves.

 

[ChemMan]

Just recently I was hearing a slight ringing in the right channel. I assumed this was microphonic behavior and as such performed the perfunctory maintenance oft provided by the fellows in the know. I took all ten tubes out and checked the pins and gave them a very light brushing. I then manually biased the power tubes and all has been well for five days.