Gefell MV690 12v-48v modification

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ytrehalf

Well-known member
Joined
Jun 4, 2004
Messages
100
Location
NY
Hello,
I bought a Gefell MV690 a while ago intending to build a power supply for it. But now I'm considering converting the microphone to use phantom power, instead. I'd like to switch the 7 pin connector to an XLR as well.

Does anyone have any information on this modification?
 
Brendan,
I've not got round to doing this yet, but here's some info for the 692.

peter

http://www.purpose.freeserve.co.uk/gefell_1.jpg
http://www.purpose.freeserve.co.uk/gefell_2.jpg
http://www.purpose.freeserve.co.uk/gefell_3.jpg
 
Edit: this will NOT work (without internal cutting):

MV690-Phantom.gif
 
I have 2 692s with the Gefell factory 48V phantom change. I will try to draw the mod tonight. I forgot about this I told Peter I would do this some time ago.
 
cool silentarts, now i finally have the 690 schem, too... :thumb:

the gefell people are very nice - when i sent them one of my 691's with UM70 for cleaning of the capsule, they said "oh, this 3rd party p48 mod wasn't done quite right, we'd like to redo it. we're also gonna throw out that russian FET, which is too noisy anyway, and stuff. oh, and while we're at, the old chassis looks so worn, we'll provide a new one so it looks decent when it leaves our house."

they did all this at a remarkably low price... great. :green:
 
I've also had very good experiences with the folks at Gefell.
They once completely cleaned and refurbed a capsule without charging anything for it.

way to go.
 
Gus,
Are you saying that you have a little additional pcb in there similar to this?

Can anyone kindly translate...pretty pretty please.

geffel_2.gif
 
Peter

I don't have a board in my microphones. It looks like a factory mod. I say this because the connector was machined again for the XLR. The machine work is nice. I will take a picture of the inside.
 
Gus, in your drawing I see the 12v zener, but what is the value of the other diode?

0.6v?
 
[quote author="peter purpose"]Can anyone kindly translate...pretty pretty please.
][/quote]

"umbau" = modification
"BE-Seite" = main PCB component side

(below) remove C12 (10nF) and D3/2 (SAY60)
(right) insert 48V PCB. note: use extra isolation for both leg C and the whole PCB
(bottom) main PCB solder side

that's all you gotta know.
 
Guys.....are we going to an awful lot of trouble here?

12V version
gefell_11.jpg


48V version
gefell_31.jpg


Won't the variable resistor just take the voltage down to the desired value?

peter
 
[quote author="ytrehalf"]Gus, in your drawing I see the 12v zener, but what is the value of the other diode?

0.6v?[/quote]

Brendan,
My simulated circuit uses a 1N4007 and all looks pretty good.

peter

gus692.jpg
 
One other thing.......
I made a connector by taking a neutrik face mount and cutting off the flange. Remove the spring jobbie in the gefell original and ream it out about half a mm, then apply a little glue and slip in the neutrik.

conn.jpg
 

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