Microphonic?

Deftone · 11-07-2009, 12:04 PM

I read here someone said you can tell if your tubes have gone microphonic by tapping on them with a pencil and hearing the tapping through the speakers....true?

I just tried on a couple of 12AX7 RFT's I just bought from Russia and I could definetly hear very distinct tapping through the speakers.

hipofutura · 11-07-2009, 12:56 PM

Mark, I think all of your preamp tubes will make a sound when tapped. What you're looking for is if any of them ring, not just thud.

Deftone · 11-07-2009, 01:06 PM

Quote:

Originally Posted by hipofutura

Mark, I think all of your preamp tubes will make a sound when tapped. What you're looking for is if any of them ring, not just thud.

I got a very clear ringing out of two of them.

Thanks, Don!

BillB1960 · 11-07-2009, 01:08 PM

From Eurotubes site:

#8. Are my tubes microphonic?

When you tap on a tube with the amp turned up you will hear the mechanical signal thru the speakers or the tube is dead. The definition of microphonic is that a tube when given a signal at a specific frequency will oscillate and carry on that tone by it's self like a ringing bell.

11-07-2009, 12:04 PM	#1 (permalink)
Deftone Senior Member Join Date: Feb 2008 Location: Rocklin, CA Posts: 2,733 Thanks: 185 Thanked 36 Times in 13 Posts	Microphonic? I read here someone said you can tell if your tubes have gone microphonic by tapping on them with a pencil and hearing the tapping through the speakers....true? I just tried on a couple of 12AX7 RFT's I just bought from Russia and I could definetly hear very distinct tapping through the speakers. __________________ -Mark '87 LP Custom Lite: Black '88 LP Custom Lite: Cherryburst '89 LP Studio Lite: Black W/ factory Floyd trem '02 SG Special Faded Krank Rev. jr. mini stack + Celestion V30 & G12H Marshall Lead 12 5w hand wired tube mini stack Phaez 18w Dasiycutter + efx loop + Avatar vert. 2X12 w/Eminence 100w

11-07-2009, 12:56 PM	#2 (permalink)
hipofutura Premium Member Join Date: Feb 2009 Location: Maine Posts: 1,580 Thanks: 12 Thanked 44 Times in 13 Posts	Re: Microphonic? Mark, I think all of your preamp tubes will make a sound when tapped. What you're looking for is if any of them ring, not just thud. __________________ Don Unencumbered by Knowledge Trapped inside this old man's body, is the mind of an old man 08 Classic Antique Wine Red Traynor YRM-1 (1x12 JBL) Phaez Daisycutter (2x12 Webers) www.dcsysinc.com www.seatrakinc.com

11-07-2009, 01:08 PM	#4 (permalink)
BillB1960 Senior Member Join Date: Jun 2008 Location: PacNW Posts: 413 Thanks: 5 Thanked 2 Times in 2 Posts	Re: Microphonic? From Eurotubes site: #8. Are my tubes microphonic? When you tap on a tube with the amp turned up you will hear the mechanical signal thru the speakers or the tube is dead. The definition of microphonic is that a tube when given a signal at a specific frequency will oscillate and carry on that tone by it's self like a ringing bell. __________________ Classic Antique Fireburst GOTW #2 Classic Antique Tom Morgan GOTW #5 Deluxe Antique Gold Top GOTW #8 ES-339 Caramel Burst Fender Limited Edition Strat Ibanez AR-250 Epiphone DR500M Masterbilt Crate Vintage Club 20 Mesa/Boogie F30 Fender Prosonic Zvex Nano *Al Gore didn't invent the Internet but he did make up Global Warming*

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