Apex 460 mod with some Telefunken ELA M 251 influences

[HellfireStudios]

Which capacitor is hooked to plate out/Pin 1 of the tube? Is it the big PIO or the electrolytic at around C8 on the PCB?

 

[saxmonster]

James,
The 47uf 50V Nichicon Muse is attached in the C7 spot.  I don't know what that does it terms of the mic.  Maybe Jim or Langston could chime in.  I also don't see a 100pf in there.  I don't know enough to say this is what they did to it.  I wouldn't mind taking it apart to see for myself but I don't want to break anything.  Just going to leave it alone, hahahahah.

Thanks
-Scott

 

[saxmonster]

Looks like the wire runs from pin 1 (green wire down to the big cap that the t14 transformer is glued to).

no Name on that cap but it says

MP 1uf/160V

 

[dmp]

C7 is the cathode bypass cap. And they used a really nice, high quality one (MUSE series)
The big one down by the transformer does indeed look like a PIO.

I am really interested to know if they changed the capsule biasing to allow omitting C4 (as in a 251). A C12 design would have C4

I only see two signal caps up at the top (silvery) which I'm guessing are C3 and c5, I don't see a C4!!!!!!!

 

[saxmonster]

It looks like C4 in under the pcb, in between the two pcb.  It looks like a styrene, maybe this is the 100pf one?  HTHS

-Scott

 

[HellfireStudios]

No, C4 is not the smoothing cap. It is rated at 1000pF. C4 should connect to the backplate. On the ELA M 251 schematic, C8 is the cap I'm refering to. I doubt your mic has the smoothing cap. This capacitor is one of the ways AKG (the designers of the 251) was trying to reach their design goals. They were trying to build a competitor for the U-47, for which Telefunken had lost American distribution. The cap shaved off the high end to make it more tonally akin to the U-47 with the much brighter C12 capsule.
In your case, the cap could be on a switch for the brighter horns that come your way. Nice mic, though. If it sounds great to you, the switch might be more trouble than it is worth, but trying out the cap would be easy enough.

 

[saxmonster]

Has anyone ever altered the length of the original 460 Capsule mount. The black rubbery section.

I used Tim's Mount but the part that it attaches to seems high.  If I could cut that down a bit to lower the capsule under the ring at the top of the mesh on the original 460.  This way the capsule would sit right in the middle between the bottom of the mesh and that ring at the top of the mesh.

Does that make sense to do or should I just leave it?

Thanks

-Scott