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Message |
Mr. DOS
Guest
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 Posted:
Sat Oct 29, 2005 1:49 am Post subject:
48 v phantom power to 9 v circuit |
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I have searched for a while, and all of the phantom power circuits I
have found provide 48v from 9v or other batteries. I'd like to power
an old active DI box I have which uses only a 9v battery from the 48v
phanom power that will already be on pins 2 & 3 of the mic cable.
Thanks!
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Greg Glazier
Guest
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| Posted:
Sat Oct 29, 2005 2:48 am Post subject:
Re: 48 v phantom power to 9 v circuit |
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You probably won't be able to get adequate power from a normal phantom
power supply, since most mics typically only draw between 1 and 5 mA.
That gives you roughly .25 watt, or 25-35mA at 9 volts.
Then you need to be able to properly decouple the DC from the audio
line. You're better off sticking with batteries or an AC adapter.
g2 |
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John L Rice
Guest
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| Posted:
Sat Oct 29, 2005 3:25 am Post subject:
Re: 48 v phantom power to 9 v circuit |
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"Greg Glazier" <glazierg@gmail.com> wrote in message
news:1130536097.914256.68540@z14g2000cwz.googlegroups.com...
| Quote: | You probably won't be able to get adequate power from a normal phantom
power supply, since most mics typically only draw between 1 and 5 mA.
That gives you roughly .25 watt, or 25-35mA at 9 volts.
Then you need to be able to properly decouple the DC from the audio
line. You're better off sticking with batteries or an AC adapter.
g2
|
I'm not sure of the circuit to use but I know my Boss DI-1 can use either 9v
battery or phantom power so it is possible.
http://www.roland.com/products/en/DI-1/
--
John L Rice
www.DeliriumFix.com |
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Scott Dorsey
Guest
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| Posted:
Sat Oct 29, 2005 4:27 am Post subject:
Re: 48 v phantom power to 9 v circuit |
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Mr. DOS <mike@mrdos.com> wrote:
| Quote: | I have searched for a while, and all of the phantom power circuits I
have found provide 48v from 9v or other batteries. I'd like to power
an old active DI box I have which uses only a 9v battery from the 48v
phanom power that will already be on pins 2 & 3 of the mic cable.
|
You're basically better off just replacing all the insides. If you use
phantom power, first of all you can't lift the ground any more, which is
a major disadvantage.
But if that disadvantage is not a serious one for you, call Recording
Magazine and ask for the issue that had the DIY DI article that I did
a few years ago. I don't remember the month, but it's a nice design
that uses two inexpensive switching fets, three caps, a diode, and a
couple resistors. Easy to build into any box. No isolation, sadly.
But a super high input impedance and a very high output level.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis." |
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Agent 86
Guest
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| Posted:
Sat Oct 29, 2005 4:42 am Post subject:
Re: 48 v phantom power to 9 v circuit |
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On Fri, 28 Oct 2005 19:27:35 -0400, Scott Dorsey wrote:
| Quote: | If you use phantom power, first of all you can't lift the ground any
more, which is a major disadvantage.
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So what does the switch that says "Open/Gnd" on a Countryman actually do? |
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Agent 86
Guest
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| Posted:
Sat Oct 29, 2005 4:42 am Post subject:
Re: 48 v phantom power to 9 v circuit |
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On Fri, 28 Oct 2005 15:25:19 -0700, John L Rice wrote:
| Quote: |
"Greg Glazier" <glazierg@gmail.com> wrote in message
news:1130536097.914256.68540@z14g2000cwz.googlegroups.com...
You probably won't be able to get adequate power from a normal phantom
power supply, since most mics typically only draw between 1 and 5 mA.
That gives you roughly .25 watt, or 25-35mA at 9 volts.
Then you need to be able to properly decouple the DC from the audio
line. You're better off sticking with batteries or an AC adapter.
g2
I'm not sure of the circuit to use but I know my Boss DI-1 can use either
9v battery or phantom power so it is possible.
http://www.roland.com/products/en/DI-1/
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As does the Countryman & quite a number of others. |
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Mr. DOS
Guest
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| Posted:
Sat Oct 29, 2005 4:42 am Post subject:
Re: 48 v phantom power to 9 v circuit |
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Thanks for all the help. Rather than replace the guts (!), I think
I'll drill a hole for a power connector!
By the way, its a 1st-generation Sansamp Bass DI. I could not find out
what the current draw is on that guy. |
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Scott Dorsey
Guest
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| Posted:
Sat Oct 29, 2005 4:42 am Post subject:
Re: 48 v phantom power to 9 v circuit |
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Agent 86 <maxwellsmart@control.gov> wrote:
| Quote: | On Fri, 28 Oct 2005 19:27:35 -0400, Scott Dorsey wrote:
If you use phantom power, first of all you can't lift the ground any
more, which is a major disadvantage.
So what does the switch that says "Open/Gnd" on a Countryman actually do?
|
If there's no battery in it, it turns it off.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis." |
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John L Rice
Guest
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| Posted:
Sat Oct 29, 2005 4:42 am Post subject:
Re: 48 v phantom power to 9 v circuit |
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"Mr. DOS" <mike@mrdos.com> wrote in message
news:1130544048.566182.130810@o13g2000cwo.googlegroups.com...
| Quote: | Thanks for all the help. Rather than replace the guts (!), I think
I'll drill a hole for a power connector!
By the way, its a 1st-generation Sansamp Bass DI. I could not find out
what the current draw is on that guy.
|
Contact Tech-21, makers of Sansamp products :
http://www.tech21nyc.com/contact.html
--
John L Rice
www.DeliriumFix.com |
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Richard Crowley
Guest
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| Posted:
Sat Oct 29, 2005 5:56 pm Post subject:
Re: 48 v phantom power to 9 v circuit |
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"Pooh Bear" wrote ...
| Quote: | It's perfectly possible to 'ground lift' with a phantom powered DI.
I.e.
break the common connection between source and destination.
|
You'll have to demonstrate your theory with a real schematic
(or equivalent). I can't see how it is possible to run something
on phantom power without access to the ground node. Assuming
that putting a transformer on the DI box *input* (the high-impedance
side) is even more impractical. |
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Phil Allison
Guest
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| Posted:
Sat Oct 29, 2005 6:49 pm Post subject:
Re: 48 v phantom power to 9 v circuit |
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"Richard Crowley
| Quote: |
You'll have to demonstrate your theory with a real schematic
(or equivalent). I can't see how it is possible to run something
on phantom power without access to the ground node.
|
** No such was ever claimed - fuckhead.
| Quote: | Assuming
that putting a transformer on the DI box *input* (the high-impedance
side) is even more impractical.
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** You are an * ass - umming * ass.
Go figure what a fucking "ground" switch is actually needed for.
........... Phil |
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Scott Dorsey
Guest
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| Posted:
Sat Oct 29, 2005 9:54 pm Post subject:
Re: 48 v phantom power to 9 v circuit |
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Richard Crowley <rcrowley@xpr7t.net> wrote:
| Quote: | "Pooh Bear" wrote ...
It's perfectly possible to 'ground lift' with a phantom powered DI.
I.e.
break the common connection between source and destination.
You'll have to demonstrate your theory with a real schematic
(or equivalent). I can't see how it is possible to run something
on phantom power without access to the ground node. Assuming
that putting a transformer on the DI box *input* (the high-impedance
side) is even more impractical.
|
The guys at Radial actually manage to do with with the J48.... they
have a 555 timer in there that generates a 75 KC square wave that
goes into a little switching transformer. So they get an isolated
+/- 12V output that they regulate and use to power the front end. I
think that is really ingenious as hell. But as far as I know, it is
the only way to isolate the grounds with a phantom powered DI box, and
Radial is the only company doing it.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis." |
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Scott Dorsey
Guest
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| Posted:
Sun Oct 30, 2005 8:11 pm Post subject:
Re: 48 v phantom power to 9 v circuit |
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Pooh Bear <rabbitsfriendsandrelations@hotmail.com> wrote:
| Quote: | Scott Dorsey wrote:
Richard Crowley <rcrowley@xpr7t.net> wrote:
"Pooh Bear" wrote ...
It's perfectly possible to 'ground lift' with a phantom powered DI.
I.e.
break the common connection between source and destination.
You'll have to demonstrate your theory with a real schematic
(or equivalent). I can't see how it is possible to run something
on phantom power without access to the ground node. Assuming
that putting a transformer on the DI box *input* (the high-impedance
side) is even more impractical.
The guys at Radial actually manage to do with with the J48.... they
have a 555 timer in there that generates a 75 KC square wave that
goes into a little switching transformer. So they get an isolated
+/- 12V output that they regulate and use to power the front end. I
think that is really ingenious as hell. But as far as I know, it is
the only way to isolate the grounds with a phantom powered DI box, and
Radial is the only company doing it.
Absolute nonsense Scott.
Stop and think where the ground actually needs to be 'lifted' !
|
The ground can be lifted _anywhere_. But the front end has to be active,
which means even if you have a transformer inside there, you still have to
get power to the active front end somehow.
If you want to break the ground at some point where the front end can still
get phantom power, that would mean breaking the ground _before_ the front
end. Which either means sticking a transformer there and spoiling the whole
idea of an active follower with a super-high-Z input, or it means a
differential front end.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis." |
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Pooh Bear
Guest
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| Posted:
Sun Oct 30, 2005 8:32 pm Post subject:
Re: 48 v phantom power to 9 v circuit |
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Scott Dorsey wrote:
| Quote: | Pooh Bear <rabbitsfriendsandrelations@hotmail.com> wrote:
Scott Dorsey wrote:
Richard Crowley <rcrowley@xpr7t.net> wrote:
"Pooh Bear" wrote ...
It's perfectly possible to 'ground lift' with a phantom powered DI.
I.e.
break the common connection between source and destination.
You'll have to demonstrate your theory with a real schematic
(or equivalent). I can't see how it is possible to run something
on phantom power without access to the ground node. Assuming
that putting a transformer on the DI box *input* (the high-impedance
side) is even more impractical.
The guys at Radial actually manage to do with with the J48.... they
have a 555 timer in there that generates a 75 KC square wave that
goes into a little switching transformer. So they get an isolated
+/- 12V output that they regulate and use to power the front end. I
think that is really ingenious as hell. But as far as I know, it is
the only way to isolate the grounds with a phantom powered DI box, and
Radial is the only company doing it.
Absolute nonsense Scott.
Stop and think where the ground actually needs to be 'lifted' !
The ground can be lifted _anywhere_. But the front end has to be active,
which means even if you have a transformer inside there, you still have to
get power to the active front end somehow.
|
Of course. Currrent sources from Pins 2&3 and returns via Pin 1
| Quote: | If you want to break the ground at some point where the front end can still
get phantom power, that would mean breaking the ground _before_ the front
end. Which either means sticking a transformer there and spoiling the whole
idea of an active follower with a super-high-Z input, or it means a
differential front end.
|
Why would it mean spoiling the idea ?
A DI is by definition ( once ground lifted ) a differential device anyway !
I simply don't get what your problem is !
Graham |
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Richard Crowley
Guest
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| Posted:
Sun Oct 30, 2005 9:04 pm Post subject:
Re: 48 v phantom power to 9 v circuit |
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"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:4364D98F.4D9E29E2@hotmail.com...
| Quote: |
Scott Dorsey wrote:
Pooh Bear <rabbitsfriendsandrelations@hotmail.com> wrote:
Scott Dorsey wrote:
Richard Crowley <rcrowley@xpr7t.net> wrote:
"Pooh Bear" wrote ...
It's perfectly possible to 'ground lift' with a phantom powered
DI.
I.e.
break the common connection between source and destination.
You'll have to demonstrate your theory with a real schematic
(or equivalent). I can't see how it is possible to run something
on phantom power without access to the ground node. Assuming
that putting a transformer on the DI box *input* (the
high-impedance
side) is even more impractical.
The guys at Radial actually manage to do with with the J48....
they
have a 555 timer in there that generates a 75 KC square wave that
goes into a little switching transformer. So they get an isolated
+/- 12V output that they regulate and use to power the front end.
I
think that is really ingenious as hell. But as far as I know, it
is
the only way to isolate the grounds with a phantom powered DI box,
and
Radial is the only company doing it.
Absolute nonsense Scott.
Stop and think where the ground actually needs to be 'lifted' !
The ground can be lifted _anywhere_. But the front end has to be
active,
which means even if you have a transformer inside there, you still
have to
get power to the active front end somehow.
Of course. Currrent sources from Pins 2&3 and returns via Pin 1
If you want to break the ground at some point where the front end can
still
get phantom power, that would mean breaking the ground _before_ the
front
end. Which either means sticking a transformer there and spoiling
the whole
idea of an active follower with a super-high-Z input, or it means a
differential front end.
Why would it mean spoiling the idea ?
A DI is by definition ( once ground lifted ) a differential device
anyway !
I simply don't get what your problem is !
|
And you likely don't have a real-world solution for
your hi-Z transformer scheme, either.
OTOH, the in the medical biz, they like using optical
copling. It was even popular for video back in the days
before even cheap $60 TV receivers had video inputs. |
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