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anonymous 2 January 2006

Hi Yall
So I Have this great invention in mind.
A phantom powered Buffer for ribbon mics such as the Nady RSM-2 or Oktava ml-52, beyer m130 etc.
It is a preamp circuit (fet + 15 db or so + impedance buffer ( 6kOHMs or better) in the vein of the Royer R 122 but can be used and plugged in between ANY ribbon mic and mixer and, Voila no need For a special preamp or worries about frying your ribbon mic cause you cant disabe phantom power on one channel at a time!
Heres the catch I dont quite have the skills to figure this one out.
( If i could I would be getting a patent and making big $$$$$ cause this is an invention whose time has come.
SO if any of you have an idea how to make such a utility lets put our collective minds together and give it a whirl.
Just think you could run a ribbon right into your Roland VS recorder or Mackie vlz
alongside 7 other pahntom powered condensers with no worries
There is a circuit diagram in "the microphone Book" of the Royer r 122
that would be a good starting point
I am sure ther are a myriad of ways to accomlish this goal with the skills of an average DIY'er
Let the race Begin!
JFLO

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Comments

Kev Tue, 01/03/2006 - 00:42

You mean something like this

Rode D-Power Plug Features:
Instrumentation grade pre-amplifier.
Balanced input and balanced output.
Minimum losses over long cable runs.
P48V phantom powered.
Gain: +20 dB.
Input Level (nominal): 1 mV.
Output Level (nominal): 10 mV.
Frequency Response: 20 Hz~20 kHz (-3 dB)
Input impedance: 100 k ohm balanced/arm.
Output Impedence: 100 ohm balanced.
Noise: -116 dB A-Wt RTI.
Max. Input: 0.8 Vp-p.
Max. Output: +11.4 dBu @ 1% THD (8 Vp-p).
Input Connector: XLR 3 PIN Female.
Output Connector: XLR 3 PIN Male.
Pin Assignment: Pin 1 GND,
Pin 2 Signal (+),
Pin 3 Signal (-).
Current Consumption: 3 mA @ 48V.
Weight approx.: 73.8 grm

there are a few products out there ... some pass phantom and some not
some are switchable

and some are DIY

Kev Tue, 01/03/2006 - 12:49

I hope it works ??

I DON'T HAVE ONE
so I can't check for you
For use with the typical ribbon you will need to check that it doesn't pass phantom
send them an email

what is it for ?

Look at it as if it were a DI box with a little gain.

Input impedance: 100 k ohm balanced/arm.
Output impedance: 100 ohm balanced.
It can impedance covert just like a DI box

Gain: +20 dB.
Increase the level so it should be easy to get overall gains of up to 70dB even with simple typical mic-pres

Noise: -116 dB A-Wt RTI.
potentially it could help you with hiss
but would need to know more about what levels of gain
and your recording methods to know if this will help you specifically

... and as they suggest ,
is also good for very long cable runs

moonbaby Wed, 01/04/2006 - 15:33

They have touted that puppy as a "long cable run" device for DYNAMIC mics. It will be interesting to find out if it does indeed pass the phantom power it uses to power it on to the mic that is connected.
Kev, couldn't some sort of diode arrangement be rigged to keep DC from getting to the pins on a ribbon mic? Kind of like the diodes they use in stomp boxes to prevent a backwards-connected battery from blowing up a fuzzbox? Dumb question, I guess, but just curious...

Kev Wed, 01/04/2006 - 22:22

thanks Eric ... all correct
but even the electronic, amplifier circuit will probably employ the caps method
DC blocking caps is a common used term.

moonbaby is quite right that Rode market this thing as a long run fix-it for dynamic mics

but the basic idea is out there and been recycled a number of times both commercial and DIY
A FET booster sort of thing to suit impedances or Ribbons then with an output to suite the typical 150 to 300 ohm mic pre ... gains of 10 to 20 as stated above.

Shameless plug :shock:
does Joe have one at the JLM Audio site ?
if not ... ring or email him and tell him to get to it
I know he has done this in the past

barnee Fri, 02/10/2006 - 10:13

I've bought some Rode PowerPlugs.

I didnt make a lot of tests on it... My Ribbon seems to still have th hiss being louder...

I have to check again.

The PowerPlug is Powered from the 48V. No power between the powerPlug and the microphone.

The +20db thing...well...hum... I have to check again...

MadMax Mon, 02/13/2006 - 17:46

Funny that I should come along and find this thread right now...

I just got my SF12 back from Royer... some butthead must have (dis)connected the mic with phantom power on... (rat bastard) and then brought the mic back and NEVER told me. As a matter of fact, he said it worked and sounded GREAT!...

At any rate, I talked to a Royer tech who relayed this from one of the engineers...

He suggested that I take two 22uF, 100WVDC axial caps and put them in series with the signal +&-. I get his point, it blocks the phantom and passes the signal. 22uF should give enough bandwidth... As long as it's not a long run, the mic stays protected and minimal signal degeneration.

I found caps that are small enough diameter to fit in a classic XLR gender changer shell at DigiKey... should be here in a few days. I think that the main thing to be concerned with is the polarity of the caps so that they are essentially in series... e.g. (negative)-cap+ Mic -cap+(positive)

Kev, you're the tech's tech... any thoughts?

Thanx,
Max

Kev Mon, 02/13/2006 - 23:05

??
:shock:
I'm doing three things at once here ... but if I have read that right I get

Mic pin2 ... (-) 22uF, 100WVDC (+) ... pin2 Mic-pre
Mic pin3 ... (-) 22uF, 100WVDC (+) ... pin3 Mic-pre

Mic pin1 .............................................. pin3 Mic-pre

Our signals are AC.
HOWEVER the phantom is 48V DC and that's why I have pointed the caps at the source voltage.

Some might prefer to see you use a BIPOLAR capactors
or
use what is known as a Back to Back pair to create the 22uf cap

but I feel the above look fine and is worth the try to save those mics.
I wonder if it is worth have 2 resistors (1meg +) to drain any DC out of the caps ???
I'll think on that.

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