A couple of mic and G7/BigUgly questions

[Blue Jinn]

Hello,

OK this may be a lame question, but what exactly is the purpose of the teflon standoffs to wire in the capsule? I've seen it recommended in a few threads, seen them in an MXL mic, but don't really understand the reason.

Second, I just did a Royer Mod on a MXL 2001, with BigUgly's boards. (Just need to put the PSU in his house and I don't have the teflon posts...) I noticed that the BigUgly and the G7 are fairly similar, except BigUgly's circuit doesn't have the bypass capacitor(s) in the cathode resistor, nor does the cathode resistor float above another resistor.  I re-read analag's r8 thread, but don't really understand this

Quote from: "skipwave"

    I just realized I am still wondering what purpose that 1k resistor in series with the transformer winding serves.

    It is also in series with the Rk, so that totals 2.82k, and the polarization voltage divider (virtually no effect there), and all those 0.1uF bypass caps around the capsule circuit. Hmmm......



A quick study of the classics will aid you in deciphering this piece.
The 1K that is floating Rk and the tranformer above ground creates a partial cathode bypass, which drives up the tube gain without the derogatory sound effect of using a cap to achieve this result. 2.82k is supposed to decrease the current flow through the tube to ensure acceptable noise level. And all those 0.1uF...c'mon. Wrap your eyes around the old German stuff and get back to me.

analag

What impact would omitting that have on the G7?

Also, there is no additional 10k resistor in the B+ nor a ~2u2/250v capacitor either on BigUgly's. I'm assuming this is for more B+ filtering on the G7 though.

I'm curious as to using BigUgly's board, for a sort of G7... 

 

[PRR]

> what exactly is the purpose of the teflon standoffs

Condenser capsule is a VERY high impedance. The least little moisture absorbed on or in the insulation will hurt bass and raise hiss level. The capsule "hot" lead(s) are normally air-wired as much as possible, but must land somewhere; Teflon is pretty good stuff.

 

[Blue Jinn]

Thanks!

That explains a few things.....

I've been re-reading the Royer Mod threads  here and may try some of the other mods as well like adding the grid resistor. (I actually found a 2 gig at a surplus place nearby.)