Anyone not sick of helping n00bs with Royer Mod?

[absolutebass]

Ok so I have been continuing my research, discovered a big problem I was not realizing there are two different mods for LDC and SDC. I have received some of the boards from blue jinn (thanks!) and was wondering if it was possible to make a single power unit with the transformer on a switch so I can use it with both LDC and SDC mikes? Could I just make the SDC PSU and mod my LDC mics with just the tube as per the royer2 mod? Or would I be better off just making 2 seperate PSU. I am planning on doing a pair of mxl 603 and a pair of mxl 2003 (which I am assuming are the same as the 2001 as far as the mod, please correct me if I am wrong!) Also when it comes to tubes, what is the difference sound wise (if any) between a Mullard or Raytheon or other 5840 compatible tubes? Finally, in reference to wiring the tube I was hoping someone could clarify what happens at the two marked points on the schematic. Do I simply bundle the 2,4,8 leads and 5,7 leads straight to the respective xlr pins? And what is the deal with the left fork of the 2,4,8 connection that just goes nowhere? Sorry if these are silly questions, I am just learning how to even read these diagrams. Thanks for any added info.

 

[audiophreak]

Ok so I have been continuing my research, discovered a big problem I was not realizing there are two different mods for LDC and SDC. I have received some of the boards from blue jinn (thanks!) and was wondering if it was possible to make a single power unit with the transformer on a switch so I can use it with both LDC and SDC mikes? Could I just make the SDC PSU and mod my LDC mics with just the tube as per the royer2 mod? Or would I be better off just making 2 seperate PSU. I am planning on doing a pair of mxl 603 and a pair of mxl 2003 (which I am assuming are the same as the 2001 as far as the mod, please correct me if I am wrong!) Also when it comes to tubes, what is the difference sound wise (if any) between a Mullard or Raytheon or other 5840 compatible tubes? Finally, in reference to wiring the tube I was hoping someone could clarify what happens at the two marked points on the schematic. Do I simply bundle the 2,4,8 leads and 5,7 leads straight to the respective xlr pins? And what is the deal with the left fork of the 2,4,8 connection that just goes nowhere? Sorry if these are silly questions, I am just learning how to even read these diagrams. Thanks for any added info.

  Hi absolutebass,
                              The PSU requirements for both mods are essentially the same , just some cap sizes are a little different.  I have been using the EDIT : LDC  PSU circuit for both with out any problems .. HOWEVER , in the LDC Mod all the audio circuit and audio transformer are IN THE MIC Body  , where as the SDC Mod C8 , R5 , and the audio transformer are physically too big to fit in the mic body.. so they are housed in the PSU enclosure ... so NO .. you cannot use the same PSU for both LSC and SDC -- but you CAN use the same PSU Circuit for both.

  I hope I didn't confuse you  ;D

  If you look at the Tube Data graphic Blue Jinn  posted on the first page of this thread, it lists the names of the structures within the tube and corresponding pin numbers - study that..then look at the Royer mod schematic and I think it will start making sense 

   

 

[Blue Jinn]

Hi,

+1 to the tube diagram and the schematic. It will make sense what is connected and why. As for teh PSU, I've thought about this, and I think becuase there is a separate output transformer (2:1) for the SDC mod, I don't see a way to have one PSU unless you also had a switch for say LDC/SDC to switch that trafo in out. I've thought of doing that way to have one PSU, and it seems a simple enough solution. Also, re-reading your post, the LDC mod has a 12:1 or so transformer, the SDC is a 2:1 so you can't use the same one. I suppose you could try the cathode follower on teh LDC? 

Note, the trafo isn't *necessarily required* for the cathode follower per the royer article, if the input it is going to drive is sufficiently high impedance.  I don't know the actual output impedance straight from the tube cathode follower, but I don't think my mic inputs are high enough.

Also, regarding the BigUgly boards, note that these are designed for the dual sided capsule. You have to move the location of a few parts to use for the stock Royer mod, and the part numbers aren't the same on the schematics. But it doesn't require cutting or jumpering anthing.

 

[tchgtr]

If you used one of the MXL mics that pretends to be a LDC, but is actually a SDC (like the 990, 440, etc.), it should be possible to get a transformer into the mic body (I think a Cinemag would fit easily), and as a result, have a SDC capsule mic that will work with the PSU for the LDC microphone.
Would probably sound a lot better than the original circuits, too...

 

[Blue Jinn]

NOTE:

I've been exchanging emails with riggler on this.

On the BigUgly PSU schematic there is a 190v in, and a 330R R1. 190v in with R1 at 330R is going to be way too high a B+ for a 5840 based circuit, and probably too high even for EF86 without changes to the polarization resistors. For the dual sided capsule, 100-135 (like the G7) is probably more appropriate.

FYI

 

[Blue Jinn]

BigUgly has kindly posted the schematics and BOM for his version as well as a comment regarding the power supply. The links and whatnot are in the black market thread, and I'm pretty sure those get deleted after a while, so I'm reposting that info in this thread:

Hey Everyone,

I'm truly happy to see so many getting some use from my silly mic hack. As far as where to set the B+, I would adjust R1 until I got between 120-130VDC. The reason for this is how the capsule polarizing voltage is derived. The capsule gets its voltage from a divider that is sourced from the B+. Mic capsules will generally get more sensitive with an increased polarizing voltage but beyond 70VDC the diaphragm can get sucked into the back plate. So I always shot for 60VDC. So I would always have to adjust R1 until I had 120VDC B+ under load.

cheers and have fun,

James

here's a link to the schems and BOMs for the PSU and mic PCB

http://www.mediafire.com/?1tjlbw7hf7ln7t0

 

[thatsaxyguymike]

I have some 991s and everywhere I go to look to find the direct schematics, BOMs, etc pdfs they don't seem to exist anymore. Does anyone have them?

 

[rock soderstrom]

I have some 991s and everywhere I go to look to find the direct schematics pdf they don't seem to exist anymore. Does anyone have them?

You are searching for the royer LDC mod info?

http://recordinghacks.com/articles/one-tube-microphone-from-berlin/
Info for Royer Mod SDC

https://tapeop.com/tutorials/34/david-royer/
This site claims the 603 is almost identical to the 991

https://audioimprov.com/AudioImprov/Mics/Entries/2013/2/4_MXL_990_Zener_Swap.html

 

[Flatpicker]

I drew that 603 schematic and posted it here around 20 years ago. Now I see it everywhere. Probably been to the moon and back.

 

[rock soderstrom]

I drew that 603 schematic and posted it here around 20 years ago. Now I see it everywhere. Probably been to the moon and back.

I would like to officially thank you in the name of the Audio DIY community!

You should do a 20th anniversary edition!