Chopstick tube test

G

GuitarGuy08

Well-known member
Hey guys! I am wondering how to truly vet 'microphonic' tubes. Trying out different V1 tubes with my clean channel set to 10 and tapping the tubes with a wooden chopstick. Should I be hearing the tap through the speaker?

If I do, does this mean they are microphonic? I have some tubes that were definitely badly microphonic and are obviously bad but what about just hearing the taps with no ringing? Is this Normal or what is the best way to test? I heard noise when trying multiple NOS mullards, including a red tip and with modern JJs.


I have more to try but don't want to be chasing my tail about nothing.

I appreciate your expertise in advance!
 
headlessdeadguy said:



I use a pencil but you should be able to tell if you have microphonic preamp tubes by tapping on them.
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So what volume are you running when you tap? Are you maxed out on 10? When you tap, should you not hear any tap at all or are you looking for him/ringing/noise in association with the original 'tik tik' sound.
 
GuitarGuy08 said:
So what volume are you running when you tap? Are you maxed out on 10? When you tap, should you not hear any tap at all or are you looking for him/ringing/noise in association with the original 'tik tik' sound.
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If you turn your volume all the way up and tap on your V1 tube, your going to hear the tapping sound regardless.

A microphonic tube will usually be a high pitched/ringing sound that should be pretty obvious.

I’d say a chopstick is overkill. I just use my fingernail tapping lightly.
 
gtrwun said:
If you turn your volume all the way up and tap on your V1 tube, your going to hear the tapping sound regardless.

A microphonic tube will usually be a high pitched/ringing sound that should be pretty obvious.

I’d say a chopstick is overkill. I just use my fingernail tapping lightly.
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...and if the V1 is really crapped out,I have been able to hear the ding.high pitched ringing by rapping on the headshell with my fist.
Side of the fist works enough so you Bruce Lee fans dont have to Break the headshell in two.

Remember V1 is the closest tube to the input jack and with any good tube ,it will make noise.

TAD pre's and power are really really good tubes these days.
 
All 12AX7s are inherently microphonic. But once they reach a certain level of "bad", they will ring and oscillate if you gently tap on them. You might also hear rhythmic ticking/clicking coming through the speaker when the amp is just sitting idle. That's a sure sign of a bad preamp tube.
 
I think a chopstick is overkill because, as said, you are probably going to hear that tapping regardless. I just use my fingernail. Also, little known fact, maybe 46and2 can confirm - with a good glove you can swap preamp tubes while the amp is turned on, if you are trying to do some quick tube rolling. I wouldn't do that with power tubes obviously.
 
311splawndude said:
I think a chopstick is overkill because, as said, you are probably going to hear that tapping regardless. I just use my fingernail. Also, little known fact, maybe 46and2 can confirm - with a good glove you can swap preamp tubes while the amp is turned on, if you are trying to do some quick tube rolling. I wouldn't do that with power tubes obviously.
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Yeah you can, just put amp in standby. Not sure if it's ideal, though. I just did it with my Helios and preamp tubes weren't that hot.
 
Guys, this has been informative and entertaining! Definitely will change my standards while checking these tubes for noise/microphonics. If they all have it to a degree, I'll roll all I have in V1 and mark the quietest ones. I hear a slight 'ting' ring that last very shortly with a tube and 2 others where it sounds like you are tapping the Mic to check it. Those 2 are obviously noisy and will be kept as spares or replaced but the slight ting may be fine.

I popped some RCA output tubes and am shocked at how well they seem to work in this amp. That was during short testing but the tubes definitely make a big difference with this amp.
 
Yeah, tapping on a preamp tube won’t tell if it’s microphonic. Cuz some in certain slots you will hear the tap through the speaker, doesn’t matter what 12ax7 you put in.
 
crwnedblasphemy said:
Yeah, tapping on a preamp tube won’t tell if it’s microphonic. Cuz some in certain slots you will hear the tap through the speaker, doesn’t matter what 12ax7 you put in.
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I'm thinking I should pop them in a different slot and test while on the gain channel, just for fun. One of those tubes was definitely noisy because after swapping some in/out, I have noticed a reduction in noise. Will continue testing as much as I can.
 
311splawndude said:
I think a chopstick is overkill because, as said, you are probably going to hear that tapping regardless. I just use my fingernail. Also, little known fact, maybe 46and2 can confirm - with a good glove you can swap preamp tubes while the amp is turned on, if you are trying to do some quick tube rolling. I wouldn't do that with power tubes obviously.
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I'll be honest, I thought about that originally but did a lot of research and then walked away with turning the amp of between swaps. I'm broke and this is my only nice amp so I want to be extra careful but I also don't want to constantly turn the amp on/off and hit the tubes over and over...
So IDK anymore!
 
GuitarGuy08 said:
I'll be honest, I thought about that originally but did a lot of research and then walked away with turning the amp of between swaps. I'm broke and this is my only nice amp so I want to be extra careful but I also don't want to constantly turn the amp on/off and hit the tubes over and over...
So IDK anymore!
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No worries. Do what makes you feel right. I get lazy is all.
 
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