Author:
Date:
Subject:
Badmuts
2008-07-15 10:23:01
Microtech Gefell 7 pin DIY conversion to phantom power?
Hello,
I got a Microtech Gefell PM 750 thru Ebay and want to get it running.
It has a 7 pin connector of which 4 pins are used: 2 for the signal from the
output transformer of the built-in preamp, 2 for 12V power supply.
As i don't have the original PSU and i want to use the mic with regular
phantom power anyway i'd like to figure out exactly how to do this.
So basically i'm looking for a known-working schematic to derive 12V from
phantom power.
I think of something like 2 resistors for tapping the phantom power (which
value would i need?) and a zener diode, or a 78L12. Should i add some extra
resistor and/or capacitor for decoupling?
Or would the preamp circuitry benefit from applying a voltage higher than
12V (higher dynamic range, no zener diode noise?)
It would be great if i could fit the components into the housing of one of
the plugs.
I'm aware of the fact that Microtech Gefell offers a service to convert the
mic to XLR, but including shipping back and forth to germany it gets too
expensive.
The same with the conversion cables available from Ebay - i really don't
want to pay big bucks for a cable that i could easily solder myself and that
contains only a few electronic components in the housing of one of the
plugs.
Did anyone have the conversion done by Microtech Gefell and could you
comment on how they did it?
Regards,
Theo
Author:
Date:
Subject:
Scott Dorsey
2008-07-15 09:25:51
Re: Microtech Gefell 7 pin DIY conversion to phantom power?
Badmuts <[email protected]> wrote:
>
>I got a Microtech Gefell PM 750 thru Ebay and want to get it running.
>It has a 7 pin connector of which 4 pins are used: 2 for the signal from the
>output transformer of the built-in preamp, 2 for 12V power supply.
>As i don't have the original PSU and i want to use the mic with regular
>phantom power anyway i'd like to figure out exactly how to do this.
>
>So basically i'm looking for a known-working schematic to derive 12V from
>phantom power.
You can't do it effectively with that mike. It requires a lot more
current than you can get with phantom power. That's the downside of the
whole phantom power business.
Make a power supply box with eight AA batteries in it.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Author:
Date:
Subject:
0junk4me@bellsouth.net
2008-07-15 16:59:29
Re: Microtech Gefell 7 pin DIY conversion to phantom power?
On 2008-07-15 kludge@panix.com(ScottDorsey) said:
>Badmuts <[email protected]> wrote:
>>I got a Microtech Gefell PM 750 thru Ebay and want to get it
>>running. It has a 7 pin connector of which 4 pins are used: 2 for
>>the signal from the output transformer of the built-in preamp, 2
>>for 12V power supply. As i don't have the original PSU and i want
>>to use the mic with regular phantom power anyway i'd like to
>figure out exactly how to do this. >
>You can't do it effectively with that mike. It requires a lot more
>current than you can get with phantom power. That's the downside
>of the whole phantom power business.
>Make a power supply box with eight AA batteries in it.
Yep, get you a good metal project box at your favorite
electronic project parts dealers.
get the fittings for the batteries, you'll need eight in
series. IF the mic will take a bit of overovltage I might
even go with 10 giving you 15 vdc. MOst 12 vdc devices are
intended for 13.8, so check the specs on the mic carfully.
IF it'll handle 15 I"d go ahead and do 10 of them.
Richard webb,
replace anything before at with elspider
Author:
Date:
Subject:
Badmuts
2008-07-15 19:16:39
Re: Microtech Gefell 7 pin DIY conversion to phantom power?
"Scott Dorsey" <[email protected]> wrote in message
news:g5i8gv$qjb$1@panix2.panix.com...
> Badmuts <[email protected]> wrote:
> You can't do it effectively with that mike. It requires a lot more
> current than you can get with phantom power. That's the downside of the
> whole phantom power business.
But how do Microtech Gefell do the mod then?
> Make a power supply box with eight AA batteries in it.
I hate batteries, they're always empty at the wrong moment, but i'll just
use a 12V power supply that i built myself years ago.
Author:
Date:
Subject:
Scott Dorsey
2008-07-15 13:23:11
Re: Microtech Gefell 7 pin DIY conversion to phantom power?
Badmuts <[email protected]> wrote:
>"Scott Dorsey" <[email protected]> wrote in message
>news:g5i8gv$qjb$1@panix2.panix.com...
>> Badmuts <[email protected]> wrote:
>> You can't do it effectively with that mike. It requires a lot more
>> current than you can get with phantom power. That's the downside of the
>> whole phantom power business.
>
>But how do Microtech Gefell do the mod then?
They replace the entire output stage with different electronics.
>> Make a power supply box with eight AA batteries in it.
>
>I hate batteries, they're always empty at the wrong moment, but i'll just
>use a 12V power supply that i built myself years ago.
Make sure it's regulated and has good bypassing, and you should be fine.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Author:
Date:
Subject:
Badmuts
2008-07-15 19:33:49
Re: Microtech Gefell 7 pin DIY conversion to phantom power?
> >But how do Microtech Gefell do the mod then?
>
> They replace the entire output stage with different electronics.
Hmm, in that case it might be worth the money. But first i'm going to get
the mic running in it's current state to see if the capsule is functional
and if i like the sound enough to do more mods.
> Make sure it's regulated and has good bypassing, and you should be fine.
It is.
Thanks once again for your valuable input.
Theo
Author:
Date:
Subject:
hank alrich
2008-07-15 12:40:24
Re: Microtech Gefell 7 pin DIY conversion to phantom power?
Badmuts <[email protected]> wrote:
> I got a Microtech Gefell PM 750 thru Ebay and want to get it running.
> It has a 7 pin connector of which 4 pins are used: 2 for the signal from the
> output transformer of the built-in preamp, 2 for 12V power supply.
> As i don't have the original PSU and i want to use the mic with regular
> phantom power anyway i'd like to figure out exactly how to do this.
While not suggesting that your unit is hot, one indicator of stolen tube
condenser mics is the lack of a power supply. Thieves know what they're
looking for from ad photos, but they don't see the rest of the picture.
--
ha
Iraq is Arabic for Vietnam
Author:
Date:
Subject:
Badmuts
2008-07-17 12:48:10
Re: Microtech Gefell 7 pin DIY conversion to phantom power?
> While not suggesting that your unit is hot, one indicator of stolen tube
> condenser mics is the lack of a power supply. Thieves know what they're
> looking for from ad photos, but they don't see the rest of the picture.
It's not a tube condenser. But it is an old mic.
I have no means (or reason) to verify it was obtained legally by the seller.
But you have a point...
Bm
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