23 May 2020

6AK5 Microphone build thread

I'm not a professional blogger, doing some organizing posts here. I think maybe somebody might find this helpful.

MXL V89MBP donor body for RoyerMod/BigUgly/G7'sh mic update 21-July

Picked up one of these that was not working on battery. Had the hole already cut and a switch so thought to make cardioid/omni version of the Schoeps circuit. (I am not interested in doing any metal work)  Upon a brief inspection, some of the circuitry is on the main board on a smd circuit board, and some on the board containing the switch. Seemed too complicated now.

But there is about the same amount of space as found in the MXL 9000/76t; so I thought I could just gut the thing and do a point to point SELA/Royer'sh with a 6AK5 instead of a 5840 and a dual sided capsule. I have some generic K47 clones so will use that. Will post some pics of the internals soon. One more project on the table. This should be relatively simple though.

Have taken apart mic partially, removed XLR plug (which was in pretty tight) remembered this time that the screw is threaded counter-clockwise and tight is up not down. The switchcraft I have will go in much easier. Need to solder the wires to it next. I've sketched out a schematic and a parts placement guide. Plan to leave the switch board in place as it already is lined up, and just remove all the other parts on it. Here is my schematic, the circuit is pretty much the Royer/SELA with an added grid resistor (I have a 2G to try out, with longer leads than the 1G's from the original mic) also an omni/card pattern switch. I want to keep my PSU's consistent (for no good reason, I'm not going to have that many....) so will use the  100/60 voltage divider as in the Royer rather than the  120/60.

 Here is my proposed layout, basically following the schematic:

The transformers are noname appr 11.5:1 or so. I used one in my other RoyerMod 2001, and in the "U87 Front End" mod I did to another 2001. I got several of these off Ebay and in a trade.