Gyraf G7 polarisation voltage modifications for M7 type Capsules

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useme2305

Well-known member
Joined
Aug 1, 2010
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294
Location
Berlin, Germany
hi,

i posted this in a very old thread in the Lab but got no feedback so here's a fresh thread.

it's about the voltage divider in the G7 circuit and how to mod it to make the circuit work with M7 type capsules.

here's my take on Jakob's and Skylar's suggestions to make the circuit work with M7 type capsules.

as you can see i added a second voltage divider for the rear diaphragm for even polarisation.
i'm just not sure if the total resistance in the little add on voltage divider is correct or if it matters at all? the ratio of the resistors is definitely right though i believe.

am i totally off or will this actually work? i am an absolute beginner.

check out my mods here:
http://i50.tinypic.com/21mg876.jpg

or in the attached pic.
 

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I have done this mod (G7 with M7 capsule) and used this modified schematics.(Dont remember who made the mod)  You also need to change the voltagedivider-resistors for the pattern-switcing.
 

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hey,

that's the mod Skylar suggested in his whitemarket thread.

my mod is basically the same or at least very similar. i however placed the additional voltage divider for the polar pattern switching voltage in the mic instead of the PSU. i also think that my version achieves a better result as far as strict evenness between front and back plate voltage goes if my math is correct.

i'd be glad if someone more experienced than me took a look at my idea.
 
Your idea is probably bether for an other reason as well. It was quite confusing to put more resistors on the patternswtching-part on the power-pcb and get this right. This way you avoid this.
 
jakob, how does the polar-pattern voltage divider in my first post look to you?
i am not sure about the total resistance....does it even matter?

would a voltage divider consisting of a 150k and a 470k resistor be better to bring the 0-160V down to 0-120V?
 
Hi
I'm considering trying a build using two Octavia mk012 capsules set up like a km56 with the g7 electronics. I think the mk12 wants 40v. Is that possible? I won't be using the psu for anything else so modding the microphone or the psu doesn't matter.
/
Emil
 
Hi,

i just had finished a voltage modification in my 2 PSU when i stumbled over this post.  :-\

After a few days of thinking about this way, i decided to re-do my PSU modification and go for this approach.

I put 2 trimmers for both voltage dividers in, so i can adjust both voltages for a best fit.
(Cardiod ~57V, fig.8 ~123V, polarization ~58V)

Great modification!!

ROCK-ON!
 

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I don't get this.  Sure 470/290 gives some 62V, but isn't the 300K adding up to the 290?!  So you will actually get 88V there?
 
Hey, sorry to bring this up again. But is there a "definitive" way to do this?
There seems to be alot of options and everytime someone doubts the mod or says there is a better one... 
I did it like VanGenz but instead of the 10K resistor on the PSU I put in a 33k because my power transformer was spitting out about 148VAC instead of 135VAC (about 193VDC before the "10k" resistor. It should be 180VDC)... With this I got the +160V, about 68V in Cardioid and 136 in Figure of 8. But now I have phase issues...
Does anybody now what could cause that?
If I would get 120V on B+ instead of the 160V, would I than be able to use the "stock" circuit?

Something is really weird. I can see the phase issue only when recording my voice. When I record a guitar it looks good... Any explanation for this?
Here is a picture of what I mean. Left is Voice in Cardioid, middle is voice in figure of 8, spoken from both sides. And right is guitar.
Unbenannt.png
 
yeah, I read about that. but I never really noticed that with the rode nt1000 I used...

do you have any tips for bringing the polarisation voltage down, but keeping the b+ at 160V? somehow I don't have even polarisation between the front and back capsule
 
#1
I wanna do your mod in the the pcb, accord with your maths, the placement of resistors changes could be this?
 

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