Another newbie building an MXL 2001 Royer Mod...questions within

Title says it all! I spent about a week reading and gather information about how to do the Royer Mod to an MXL 2001. Bought some stuff from Mouser and my local electronic supply store. Got a Jensen DB/E-U transformer for the mic output (still waiting for that as of writing this) and the Big Ugly PCB's from member Blue Jinn (only used the mic PCB). With the original Royer Mod schematics (from the pdf of the Tape Op article) and Big Ugly mic PCB sitting right in front of me, I was able to populate the PCB to my liking and create the circuit. At first I was planning on using perf board and wiring this point to point but I opted for a cleaner look.

My tube wound up being a Sonotone 5840 and herein lies my question: are the pin numberings/locations standard like other vacuum tubes say for guitar amps? Meaning, when looking at the bottom of the tube (with the 8 leads facing up toward your face and the missing pin or gap at 6 o'clock) is pin 1 located to the left of the gap? Then I assume they are sequential from there.

Also, I did a couple things that I think worked out pretty well that I thought I would share.

1) I put the 2 capacitors up from the bottom of the board. I left one lead of C1 sticking all the way to provide a contact point for the capsule lead that needs to attach to it and R4. I put some black insulation over the capacitor lead and left a small bare spot to connect the capsule lead to.

2) I left the pin 1 lead (or at least what I think the pin 1 lead is) sticking straight out of the tube like Royer describes instead of wiring it to the PCB. I put a little bit of insulation on that too and will connect the red capsule lead directly to it (the red capsule lead looks a little more brown than read in the picture).

Also, I built my PSU into a small Pelican case and it came out great. I started a separate thread for the questions I had relating to the PSU here http://www.groupdiy.com/index.php?topic=49273.0

I made a simple diagram of the tube leads so everyone is on the same page.

Is this the correct pin numbering / locations for the 5840 tube?

Google 5840 tube pinout. This will provide an answer for you. Also, isn't the big ugly royer a multi-pattern mic circuit? If so, the MXL 2001 is cardioid only, and may be under-utilizing the circuit.

-James

Also, isn't the big ugly royer a multi-pattern mic circuit? If so, the MXL 2001 is cardioid only, and may be under-utilizing the circuit.

Click to expand...

The boards allow for multipattern, but it isn't necessary. The tube circuit alone is a huge improvement on the mic. I did a modified / unmodified comparison with a pair. I did replace the capsules though.

Cool. At least the option is there, if the appropriate dual-diaphragm capsule is used. I did mine point to point on perfboard in an AKG Perception, so I can't comment on the big ugly boards.

Yeah the BigUgly PCB is a multi-pattern circuit but I just wanted to build the most basic mic mod that I could...or stay as close as possible to the original Royer concept. The circuit board is very well made and definitely has more capability than I am utilizing. This is just my first microphone mod. I have 2 MXL 991's and a 990 as well. I also have a Behringer B1 and that rounds out my low end mic collection. All my other stuff is stock tube and condenser mics and various of dynamic mics that I use in my studio.

My only real experience with electrical mods to my equipment has been with converting my vintage guitar pedals to true bypass, building a pedal board, changing/biasing tubes in my Marshall heads, & rewiring guitar circuits...but then I started building a professional level studio in my home about a year ago and that has brought on many projects. I have a Soundcraft 800B 32x8 console which I have been modifying and optimizing for recording (i.e. adding balanced line in/outs to each channel, recapping, changing op amps, & refurbing faders, etc.). I run that to 2 Lynx Aurora 16 channel converters for full 32 channel recording/mixing. I designed a patchbay system for that connection. Also have a Tascam MS-16 1" reel-to-reel that needed calibration and cleaning up. Wired my "family room" up with input panels for mic's and headphone returns.

I want to start building clones of old outboard gear...Universal Audio and Fairchild are coming to mind but that is just the dream at the moment.