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moresound
Loud Sun Studios
As we all know... we are not to hot plug in a tube microphone. But is it ok to unplug the tube microphone hot?
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Richard Monroe
Well-known member
10 characters be damned-No.- Richie
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moresound
Loud Sun Studios
Why not? Isn't that the same as turning it off?
Dogbreath
Im an ex-spurt
Ya know? I've never really thought about it but I just never do it.
I figger it's like on my old Sunn tube head, it always sits on standby for warm up and cool down for at least 10 minutes before I shut it down so I do a similar approach with my mics. Kill the line/mic, flip my input from A (mic) to B (usually nuthin) and then kill the 48v.
But I pretty much have a set regimen I do for firing up and shutting down all my gear. Making sure the power up n down is as smooth as possible. No problems in over 10 years...(knocks on forehead)
I figger it's like on my old Sunn tube head, it always sits on standby for warm up and cool down for at least 10 minutes before I shut it down so I do a similar approach with my mics. Kill the line/mic, flip my input from A (mic) to B (usually nuthin) and then kill the 48v.
But I pretty much have a set regimen I do for firing up and shutting down all my gear. Making sure the power up n down is as smooth as possible. No problems in over 10 years...(knocks on forehead)
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Richard Monroe
Well-known member
Why not? Isn't that the same as turning it off?
No. My tech is limited, but not all of the multiple pins disconnect simultaneously and a transient short circuit can result. I'm no tech- the electronic details of it are beyond me, but it's what I've been told by at least 2 competent techs. The same goes, in theory, for any hot mic, tube or not. Even if you are disconnecting, say an SM57 from a PA, you hear that *POP*? That's surge, and turning the volume down so you can't hear it doesn't make the surge go away. It might save a tweeter, but it's still not so hot for the preamp. In the case of a tube mic, I'm told it's more of a danger to the mic. IMHO, you should never disconnect any hot mic.-Richie
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moresound
Loud Sun Studios
Ya know? I've never really thought about it but I just never do it.
I figger it's like on my old Sunn tube head, it always sits on standby for warm up and cool down for at least 10 minutes before I shut it down so I do a similar approach with my mics. Kill the line/mic, flip my input from A (mic) to B (usually nuthin) and then kill the 48v.
But I pretty much have a set regimen I do for firing up and shutting down all my gear. Making sure the power up n down is as smooth as possible. No problems in over 10 years...(knocks on forehead)
DB..thanks.. I suppose your right. I pretty much follow the same regimen as you do on firing up and down a system, be it live or in the studio. With no problems as well for maybe twice as long!----knock on your forehead.
mshilarious
Banned
I have no comment about tube mics--seems to me the only area of concern is the filament, the rest is pretty severely current-limited, but it's not my area of expertise--but regular phantom-powered mics and preamps should be able to tolerate a hotpatch. If they can't, they were not properly designed. My preamp has to endure up to 50 hotpatches a day, a year later and probably 2,000 hotpatches it's just fine.
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moresound
Loud Sun Studios
Thanks Richard. I only ask cause my associate told me that he had in fact pulled one of the tube microphones while hot.
I checked the microphone to make sure that nothing had happened to it and luckily it is fine. I guess a one time mistake like that may be a 50/50 chance of a failure but I can see where repeat offenses could spell disaster.
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moresound
Loud Sun Studios
Thank you MSH ..Now when you say filament are you referring to the filament with in the tube of the microphone?
I'm one for always just turning down or muting the channel of the mixer/preamp or channel strip to change out a dynamic or any condenser microphone and your saying that should be alright?
And one other aspect that hasn't been addressed and that being.. the power supply of a tube microphone. Could this as well be damaged?
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Richard Monroe
Well-known member
Thanks Richard. I only ask cause my associate told me that he had in fact pulled one of the tube microphones while hot.
I checked the microphone to make sure that nothing had happened to it and luckily it is fine. I guess a one time mistake like that may be a 50/50 chance of a failure but I can see where repeat offenses could spell disaster.
Hell, I'm more inclined to believe MSH. He *is* an advanced mic tech, and has the advantage of empirical (he's done it) evidence. It may be that your 50/50 is really 100 to 1, but *I* am the lucky SOB that would make that 00 dice roll and fry some NOS Mullard tube. I also note that his experience is more limited with tube mics. I believe that the manual of my NTK (sorry, my only tube mic) advises specifically not to connect or disconnect it hot. This leads me to believe that where there's smoke, there's fire.-Richie
mshilarious
Banned
Yes. Filaments have a strange property; they are a sort of positive varistor. That means their resistance is much lower cold than hot. When you plug in a cold mic into a switched-off power supply, then turn on the power supply, presumably the power supply will have some sort of soft-start for the filament, at the very least it needs to charge its filter capacitors. That will ease the inrush current to the filament, which should help preserve its life. On the other hand, if you hotpatch the power supply, its fully charged capacitors will be capable of flooding the cold, low-resistance filament with current. That's probably bad.
Unplugging the PSU hot isn't as bad for the filament; it is hot and high resistance (just as light bulbs die when you switch them on, not off). Now, guitar amps have their standby mode; that switches the plate voltage on and off independently of the filament. But guitar amps have power tubes which are running much more plate current than a mic tube, so I'd expect much less of a problem with the mic. For example, I don't know of any tube mic preamps with a standby, but honestly I don't pay a lot of attention to them, so maybe there is one.
Well I won't say that it is OK, but if the design is competent, then it is OK. If your gear breaks because of it, it was going to break eventually anyway. A preamp doesn't know if an input surge is due to a hotpatch, or because you stuck your mic inside of a kick drum.
Even a passive component can trigger a pop when patched, for example, a guitar into an amp. No current of any significance there. If you have the amp dimed, sure you could trash some ears--probably not the woofer, those are pretty robust. But a DI'ed guitar through monitors, yeah you could destroy a tweeter. But if the preamp stage of amp or DI was damaged by that, it's a piece of crap, so killing the gain before the patch should work fine. It costs about $0.05 in components to have adequate surge protection on inputs and outputs. There are many pro studios where the console phantom power has never been switched off . . .
It shouldn't be, obviously any power supply part has to be rated above the voltage it supplies.
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moresound
Loud Sun Studios
I agree Richard ....I feel fortunate that accident didn't let the smoke out of that tube microphone.
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moresound
Loud Sun Studios
Thank you MSH... As always great advice and is much appreciated. I will heed your advice.
PhilGood
Juice box hero
The main reason for not unplugging a tube mic right after powering it off allows the capacitors in the power supply to fully discharge. There are some large values in there, especially on the filament side, that hold their charge for quite a while. If you were to plug a mic back in without those capacitors being discharged you would get that same flooding that mshilarious mentioned.
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