+/-15V from +48V Phantom

Pilbromatic · 6th August 2009, 05:35 AM

Quite obvious from the title I hope!

Basically, I'm after some sort of schematic to be able to get a 15-0-15 DC supply from +48V phantom. Heck, is this even possible? I think it is...

I just want a versatile schematic that I can implement into preamps for DI boxes, mic pres, etc...

Thanks!

Nisbeth · 6th August 2009, 03:50 PM

You can get off-shelf DC/DC modules that will do this relatively easily, but I would be concerned that a phantom supply couldn't provide enough current to do this reliably. IIRC a mic requires around 7mA from the phantom supply which isn't exactly a lot of current unless it's a mains voltage and you are standing on a wet floor....

/U.

mobyd · 7th August 2009, 09:38 AM

BSS (who made a couple of types of DIs) used a CMOS 555 (7555) driving a transistor driving a little pulse transformer (amazingly, available at RS components) to generate isolated power. Various condenser mics (AKG etc) have phantom driven DC/DC converters. The maximum available power from a single phantom powered mic line is around 150 milliwatts. You will run into the contradicting op amp requirements of low noise, fast slew and low power (choose any two :-) ).
M

scott wurcer · 7th August 2009, 07:04 PM

You get +48V on two 6.81k resistors so by 10mA (5mA/side) you are down to <14V. If you are not using much Isupply you could make +15V in the conventional way and use one of those flying cap doublers to make -15V. There are a lot of sites with ideas for the classic Schoeps transformerless mic circuit, it's a good start.

Pilbromatic · 9th August 2009, 05:46 AM

Cool, thanks! That's a bit of info to get me thinking, atleast! I didn't put too much thought into the current side of things, but I assumed this wouldn't be an issue, unless I were to be running several ICs off the one line.
Cheers!

6th August 2009, 05:35 AM	#1
Pilbromatic diyAudio Member Join Date: Jun 2009	+/-15V from +48V Phantom Quite obvious from the title I hope! Basically, I'm after some sort of schematic to be able to get a 15-0-15 DC supply from +48V phantom. Heck, is this even possible? I think it is... I just want a versatile schematic that I can implement into preamps for DI boxes, mic pres, etc... Thanks!

7th August 2009, 07:04 PM	#4
scott wurcer diyAudio Member Join Date: Jan 2004 Location: cambridge ma	You get +48V on two 6.81k resistors so by 10mA (5mA/side) you are down to <14V. If you are not using much Isupply you could make +15V in the conventional way and use one of those flying cap doublers to make -15V. There are a lot of sites with ideas for the classic Schoeps transformerless mic circuit, it's a good start. __________________ 2012, our time is running out.

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6th August 2009, 03:50 PM	#2
Nisbeth diyAudio Member Join Date: Jan 2001 Location: Denmark	You can get off-shelf DC/DC modules that will do this relatively easily, but I would be concerned that a phantom supply couldn't provide enough current to do this reliably. IIRC a mic requires around 7mA from the phantom supply which isn't exactly a lot of current unless it's a mains voltage and you are standing on a wet floor.... /U.

7th August 2009, 09:38 AM	#3
mobyd diyAudio Member Join Date: Sep 2004 Location: Auckland	BSS (who made a couple of types of DIs) used a CMOS 555 (7555) driving a transistor driving a little pulse transformer (amazingly, available at RS components) to generate isolated power. Various condenser mics (AKG etc) have phantom driven DC/DC converters. The maximum available power from a single phantom powered mic line is around 150 milliwatts. You will run into the contradicting op amp requirements of low noise, fast slew and low power (choose any two :-) ). M

9th August 2009, 05:46 AM	#5
Pilbromatic diyAudio Member Join Date: Jun 2009	Cool, thanks! That's a bit of info to get me thinking, atleast! I didn't put too much thought into the current side of things, but I assumed this wouldn't be an issue, unless I were to be running several ICs off the one line. Cheers!

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