Re-tubing U47?

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MechaGodzilla
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Re-tubing U47?

Post by MechaGodzilla » Wed Feb 09, 2005 7:10 pm

So apparently our U47 needs to be re-tubed.
Any ideas on where to get said tube? I believe this one is still set up for a VF14.

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Re: Re-tubing U47?

Post by Professor » Wed Feb 09, 2005 7:28 pm

Might call Korby or Blue to see what they might have available or there's eBay.
You do know that the going rate for those tubes is up in the $1000-1500 range, right?

-J

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Re: Re-tubing U47?

Post by Family Hoof » Wed Feb 09, 2005 8:57 pm

Telefunken NA also sells VF14 tubes if you let them install it for you, but I wouldn't expect a good price. EF14s are MUCH cheaper and it's only a matter of swapping out two or three components to change for it. I have never heard any comparisons but I'd imagine there's got to be a sonic reason why one costs so much more.

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Re: Re-tubing U47?

Post by Frost » Thu Feb 10, 2005 12:14 am

Please do not ruin this mic by using anything other than a VF14 tube. Yes they are expensive but will last like 30 years on that tube. buy it and enjoy it. If you cant afford it, sell the mic and buy a soundelux and something else nice too.

Frost

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Re: Re-tubing U47?

Post by LRRec » Thu Feb 10, 2005 12:24 am


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Scodiddly
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Re: Re-tubing U47?

Post by Scodiddly » Thu Feb 10, 2005 12:37 am

Go over to Klaus Heyne's forum at Prosoundweb - http://recforums.prosoundweb.com

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Re: Re-tubing U47?

Post by dale116dot7 » Thu Feb 10, 2005 7:58 pm

EF14 isn't just a different filament voltage from the VF14. The cathode material is different, and there are some other differences to make the tube less likely to have grid leakage currents. There's a good writeup on Klaus Heyne's forum. Search for it, for sure. Apparently about one in 10 EF14's work ok for a mic. Also, the VF14's that passed the grade for microphone use are marked with an 'M'. Without the 'M' is a bit of a gamble. That being said, there's an original VF14 (likely not 'M' graded, mind you) on ebay right now.

Don't do the Nuvistor conversion. I've heard mixed reviews about Blue's EF86 conversion. Some places use different tubes - those submini tubes from Ratheon appear to be popular in this service.

A 30 year lifespan for a tube only really applies from when it was made. Air is slowly permeating into that tube, and eating away slowly at its guts from the moment it is sealed up. It is impossible to maintain a vacuum that good forever, so will a NOS tube last another 30 years? Maybe or maybe not.

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Re: Re-tubing U47?

Post by MechaGodzilla » Thu Feb 10, 2005 8:29 pm

Thanks for the advice. I had a feeling it was going to be in the $1000 range... yuck. I gather that anything involving some intensive surgery is going to be a no-go. Oh well - it's the studio's, so OPM, right? =)

One more question on this infernal money-sinkhole... the rubber-band shockmount for the tube - ours is quickly deteriorating. Is that part of the tube, or do I have another part to quest for, too?

Thanks,
A

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