DIY Tube Microphone Part 3

Next is drilling the enclosure and wiring up the PSU boards.

On the left is the power switch, below that is an LED to indicate power.  On the right top is the 5 pin XLR which goes to the mic and below it is the 3 pin XLR output to the preamp.  On the far right you can see the audio transformer.  I scored a couple of vintage Jensens on Ebay.

I put a mic on each side of the box with a separate power switch and light for each mic.

Front of PSU

Back of PSU

I also had to make some tube mic cables.  Since tube mics require their own power supply, a regular 3 pin XLR won't cut it.  These require 5 pin.  I made them out of star quad cable.  See this post about making cables.

 How do they sound?   At first, they didn't work, but I had some conversations with the good folks at the Yahoo mic builders group, (especially Ricardo) and I was able to diagnose the problem and fix it.  It had to do with the wiring of the tubes in the microphone.

After I got them working, they sounded great except for  some minor hum or buzzing, which was really annoying.  I solved that problem by shortening all of the wiring in the PSU, keeping the audio cables well separated from the AC lines and some general clean up.  Result:  zero noise, pure tube goodness.

I am going to use these to record drums, hoping to get some vintage RVG drum sounds.  I will post something when I have it.

Update: see Sounds page.  The drums were recorded using these mics.

DIY Tube Microphone part 2

The build involves taking a cheap Chinese condenser and stripping it of everything except the case and the capsule:  All components were stripped off of the PCB and the 3-prong XLR was removed, leaving basically a hollow tube with a mic capsule on the end.  A 5-pin XLR is retrofitted into the end of the capsule and wired up directly up to the tube leads.  The original chassis ground of the mic is wired to pin 3 as per the schematic.

Not my prettiest work, but functional.

  By the way, check out these NOS tubes I scored on Evilbay:

RCA 5840

I used some perfboard to build the boards for the power supply. These are wired up just like the schematic.  Lots of good advice on the tape op message board and groupdiy.com .  This guy did this same build, but has quite a bit more skill than me.

Power supply boards front

Power supply boards back

More to come.

DIY Tube Microphone Part 1

My most ambitious mic project yet.  David Royer of Royer microphone fame published an article in Tape-Op magazine in 2003 about building a tube microphone from a cheap Chinese pencil condenser.  Here is the schematic for the build:

I thought I'd try to build one.  And, since I am definitely not an obsessive nut job, I figured if I'm going to build one, why not build two of them.  Here is some documentation of it.  I left out the hair pulling and cussing.  Fill that in wherever you see fit.

Another Mic Mod

Same cheap Chinese condenser (MXL 990), this time I used a different capsule, an Rk-7, also purchased from Microphone-Parts.com.  It's supposed to give a more vintage 47 type sound.  I'm looking forward to trying it out on the ole doghizzle (through a tube preamp).

MXL 990 Mod

I got a good deal on a cheap Chinese mic and upgraded using parts and a new capsule from Microphone Parts.  The capsule is an RK-47.  The mod went super quickly and I'm really happy with the results.  Matt at Microphone Parts is super easy to work with and I received the parts 2 days afer I placed my order. 

First some photos:

Front view

 

Back view

 I am eventually going to do a head-to-head with a stock MXL 990, but for now, here is a clip of me playing my bass recorded by the modded mic followed by Paul Chambers playing through what I assume is a tube U-47, just for comparison.  By the way, the drummer on my chorus is Billy Jones and on PC's it's Roy Haynes.

DIY Mic Cables

I made these xlr cables.

Same quality as Monster: nuetrik connectors and quad star cable, but at a fraction of the cost and in whatever colors I like.  You should make your own cables too.  This is where I got the materials.  You need to do a few at a time to make the shipping charges worthwhile.  Also, you need a soldering iron, some solder and a little bit of time (about 10 or 15 minutes per cable).