sanken cos 11 mic XLR mod

[angelothewolf]

Hi everyone! i got this Sanken COS-11D PT lavalier microphone with TA5F conector to use with a wireless system. I need to replace the TA5F conector with a XLR for studio use (with phantom power). i try diferent wirings but i could not get a good result...
this is the stock wiring, as far as i know this micrphone works with 5V from the transmiter system>


The specs on te manual says> power supply......+48V +/-4V Phantom
i try this wiring and i get the thing to work but there's a background white noise>



Any ideas of how can i get this thing working well with phantom power?

[Jazz P Bass]

Maybe you need to knock down the phantom voltage to 5 volts.

SANKEN MICROPHONE CO .,LTD. | Q & A [ Basic of Wiring Method ]

[angelothewolf]

Maybe you need to knock down the phantom voltage to 5 volts.

SANKEN MICROPHONE CO .,LTD. | Q & A [ Basic of Wiring Method ]

yes i was trying to avoid that, what you think is the best way to do that? Voltage regulator?

Thanks!

[angelothewolf]

Gonna try this....

[Jazz P Bass]

Let us know how it pans out.

[angelothewolf]

Sure!

[angelothewolf]

well i made this circuit with a 5V1 zener and works pretty well, the only issue is that seems to have much lower gain!

[Jazz P Bass]

As it should.

[angelothewolf]

and why is that? do you think that this can ruin the S/n ratio? can i inprove this circuit a little bit to get more output? i try it with a 1073 preamp and have to set it around 60db for a good output, i think is too low isn't?

[Jazz P Bass]

My reasoning for the " As it should" statement is the fact that you where running the mic on 48 Vdc & dropped it down to % Vdc.
That translates to 'less gain'.

[J M Fahey]

No.

1) The camera input is a conventional electret connection: unbalanced, low voltage (in this case 5V) and, most important, the Fet has a drain load of 10k and has gain and it's high impedance.

They say around 10 dB, "not guaranteed/variable" , I think that's minimum gain, I usually get 15 to 20 dB .

2) the XLR connection is balanced and low impedance.

They achieve that by connecting same value resistors at source and drain: instant "gain 1 stage"
Kiss good by to the stage gain.

To boot, the Chinn schematic, although conceptually correct, uses way too low resistors .

Ho probably wanted to be able to drive a "textbook" load impedance of real 600 ohms ... which was correct in the 40's , when "Audio Engineer" usually meant "Telephone Engineer" ; but modern balanced inputs have at least 2K ... and many even more.

Unless the mixing desk is 2 blocks away, I'd rise load resistors to at least 470r each, even 1k wouldn't be crazy.

You may gain a couple dB that way, although the "Fet unity gain" problem remains.

Side note: the Chinn schematic wrongly calls XLR pin 3 "minus voltage".... while in fact both 2 and 3 are positive.

In fact you'd need to add a dual Op Amp, phantom fed balanced stage with gain in your adapter.

[angelothewolf]

alright now im getting there, so the right thing would be a balanced line driver opamp stage! thats it.

i try a 680ohm resistors in there and its better, a couple of db's. im going to try that on the studio to hear the s/n ratio better. the idea is to fit the circuit inside the XLR connector so an opamp stage would be tight, i think i have some SSM balanced line drivers chips somewhere...

thanks for the help!

[J M Fahey]

the idea is to fit the circuit inside the XLR connector so an opamp stage would be tight,

You bet.

I'd put it in the smallest Hammond box, which can be dropped on the floor and kicked with combat boots all day without a problem.

All it needs is a proper mic connector on one end, a male XLR on the other, maybe a tiny Led to show it's getting Phantom power.

And it does NOT need any specialized Line Driver chip, a humble TL072 will be ample.

[angelothewolf]

yes, sure, that would be the right way, but i need this working for today so i think i will stay with the chinn circuit. I put a 1k resistors on it and the gain is ok, but there is a problem with phase i think, it has very bad low freq response. Maybe is because we have the same phase at pins 2 & 3? how can i solve this??

[zaray]

No.

1) The camera input is a conventional electret connection: unbalanced, low voltage (in this case 5V) and, most important, the Fet has a drain load of 10k and has gain and it's high impedance.

They say around 10 dB, "not guaranteed/variable" , I think that's minimum gain, I usually get 15 to 20 dB .

2) the XLR connection is balanced and low impedance.

They achieve that by connecting same value resistors at source and drain: instant "gain 1 stage"
Kiss good by to the stage gain.

To boot, the Chinn schematic, although conceptually correct, uses way too low resistors .

Ho probably wanted to be able to drive a "textbook" load impedance of real 600 ohms ... which was correct in the 40's , when "Audio Engineer" usually meant "Telephone Engineer" ; but modern balanced inputs have at least 2K ... and many even more.

Unless the mixing desk is 2 blocks away, I'd rise load resistors to at least 470r each, even 1k wouldn't be crazy.

You may gain a couple dB that way, although the "Fet unity gain" problem remains.

Side note: the Chinn schematic wrongly calls XLR pin 3 "minus voltage".... while in fact both 2 and 3 are positive.

In fact you'd need to add a dual Op Amp, phantom fed balanced stage with gain in your adapter.

Hi - The Chinn circuit is actually a Balanced 48v to "T power" converter (this method of powering mics was used in some early field mic systems.)