How Do You Change Out a Mic Tube?

[Eric Wylie]

I am a long-time lurker on this board and have benefitted from the expertise that is freely shared here. In the last year I've made several purchases for my studio based on the advice of some of the great contributors to this board.

In particular, I have purchased items based on comments from Jeff Laurence (for whom I have - like many others - developed a great respect for both his work and advice --- I just got my Wharfedale monitors about a month ago -thanks, Jeff!) as well as Emmett (I've got an E-mu 1212m in my PC, thanks for the tip!) and other good folks.

In a recent post on good-sounding, lower-cost mics (Best Condenser mic for $200 or under??? http://www.radio-info.com/smf/index.php/topic,99287.0.html) was a reference to changing out the tube in a mic. How is this done? I can't find a post on any board or a Web page/site that explains the process. (I just purchased an MXL 960 this afternoon based on Jeff's comments in the above noted post and would like to pop in the Telefunken or Mullard tube mentioned.)

Is there a Web site or board post with step-by-step instructions (and maybe photos) to show how this is done (assuming it is a similar process with most brands of tube mics)? Although I'm more producer than engineer, I'm technically savvy enough to do the work, but just don't care to dig into a brand new (working!) mic without a little guidance. I've not owned a tube mic before -- maybe it will be obvious how it's done once I have one in hand?

Many thanks to all who share here! I promise to contribute as my knowledge allows.

Eric

 

[Chuck]

I'm not sure about the exact details of your particular mic, but it shouldn't be very hard to figure out. The tube is located under the metal can that is the lower part of the microphone (just below the grill). The main task at hand is to remove that cover. Before you take it apart be sure to unplug the power supply from it's AC source so you won't get a shock, or worse yet, damage the mic. ;D

Unplug the cable from the microphone. You will probably see a large knurled ring that surrounds the connector. It simply unscrews and will come off. That is what holds the metal cover in place and removing the cover will expose the tube. Usually the tube is in a shock-mounted socket with an elastic or spring mechanism that stretches over the top to hold it in place. You'll need to gently remove that from the tube, and then remove the tube from its socket. Because the socket is shock mounted, it will probably wiggle when you try to pull the tube out. That’s Norman. Just be gentle.

To replace the tube, simply reverse the process. Be sure to use a similar type tube as the one you took out. My mic used a 12AT7, which has a number of substitutes with different numbers. A tube substitution guide is very handy to have. You can probably Google that information. You might want to try several tubes to see which one works better. Some sound quite different from others, even if they are the same brand.

I hope that helps.

 

[Lee_Sackett]

I this one is like their V69, you'd unscrew the base of the mic body at the end where the connector goes, then slide the mic out of the metal sleeve. If you look at the underside of the grill basket, you'll see two screws; take those out and take the grill basket off.

There are brackets holding the capsule in place; there are screws on either side at the top of the brackets. Take those out, and carefully slide the capsule out from between the brackets. The rubber thing with the spring in it and the plastic thing that it goes into will fall out. Be careful with the wiring, and don't touch the diaphragm.

Grab the tube socket with one hand and the tube with the other, holding the tube at its center, not the tip. Pull the tube out and put the new tube in (you might want to clean the tube's pins with some type of contact cleaner and a Q-Tip before installing it).

Put the mic back together in reverse order.

If this doesn't do it, post back.

 

[jefflaurence]

Hi Eric:

YOW..with the 960..DON'T UNSCREW ANY SCREWS!

As Chuck mentioned..unplug everything..

Make sure you have a good NOS or tested quiet ECC81, or 12AT7 tube. Most of us like the Telefunken, or Mullard tubes, but Amperex works nicely as does Siemens.

At the bottom of the mic near the connector, you can simply uncrew the base...it will unscrew very smoothly. This will allow the "can" or the metal housing to just slide off (in the directioon of the connector..away from the capsule basket)

This will expose the printed circuit board, and the tube. It is indeed held tightly by a plastic ring at the top of the tube..Carefully push the tube and socket down toward the base away to pull the tube out, and replace the Chinese tube with your new tube..Then replace the plastic cap on the top of the tube and push back into place.

As always be careful of the delicate wiring

Put the metal housing back with the MXL logo on the same side as the "cardioid symbol" and replace the metal ring..tighten well, but do not over tighten.

I have some pics of a recent replacement I can e-mail to you..Let me know if you need em

[email protected]

 

[Eric Wylie]

Thanks Chuck, Lee and Jeff!

Armed with that info, I'm confident I can make the switch.

FYI - I looked at a bunch of tube sales Web sites and ended up ordering a pair of NOS Mullard tubes (hard-wearing, British Military stock) for $49 (including $5 shipping) from an Ebay store called BNB Tubes.

Of course, I'll be sure to record something with the stock tube before making the switch, so that I'll have some comparison files.

Thanks again, everyone!

Eric

 

[jefflaurence]

Eric..you'll hear the difference..let's hear some samples.

jl