G7 Mic - capsule 70volts, not 80

Hello

I am finishing up a pair of G7 mics.  I have capsules that have working voltage of 70, rather than 80 on the G7.  What would be the best way to limit the
voltage to 70 without causing any problems with the capsule and especially the sound quality??  I'm thinking 1 watt resistor, but is there a better option?

Thanks for your input,

Scott

It appears there is an old thread surrounding this topic.  I believe I have an answer.

S

I did this on my G7, if you run into problems. The voltage divider in the mic needs to be changed to lower the capsule voltage. To keep the patterns correct, the voltage divider in the psu needs to be modified as well.

Would it be OK to use a set of zeners to reduce and regulate the polarization voltage? E.g. Mouser has 60v 5w zeners for US$0.33 a piece, so feed the mic 120/60/0? 56v seem even more common.

No, you should use the suggested change in the voltage divider. Otherwise your patterns will be wrong.

Jakob E.

Thanks!

I think I understand now: For Big Ugly's circuit B+ is 120v. :-[

The low voltage thread however from Gus says, "that said, I use another method." Any idea what that method may be?

I'm working a couple more BigUgly/Royer types to get comfortable, before embarking on a G7, but I read all I can!

For measuring B+ do to the calculations, am I correct to assume you can replace the capsule with suitable pair of capacitors and then measure?

Hi ! I don't think you need to do that, just measure at the junction between the two 470k resistors. You have the polarisation voltage here.

What I would do : in the power suply , from B+, insert a 22k res. in serie with two 82k (in serie, in place of the two 100k) that form the voltage divider at the "patern" switch. In the microphone: insert a 120k res. between B+ and the "higher" 470k . This way, you theorically get around 141-70,5-0 volts in the PS and about 71 volts in the mic.
Close enough in my book.
Laurent.