Topic: Stereo mini XLR > Mini Jack with 4.7k Mod

[rsimms3]

So I want to build a cable that incorporates the 4.7k mod to use with my Sound Pros battery box instead of buy a new one.  I have read what I can about the 4.7k mod, but wanted to get very specific about what it would looke like in a connector cable.  Here are two pictures, if someone could point me in the right direction, I would appreciate at.  The picture on the left is putting the 4.7k resistor in the ground line and then tying into the audio line, only two connections to the ground of the mini plug.  The right one is putting the resistor between the two wires on both sides and all wires tying to mini plug.  Or, is there a way to do it with only one reisistor for the whole cable?

[Church-Audio]

So I want to build a cable that incorporates the 4.7k mod to use with my Sound Pros battery box instead of buy a new one.  I have read what I can about the 4.7k mod, but wanted to get very specific about what it would looke like in a connector cable.  Here are two pictures, if someone could point me in the right direction, I would appreciate at.  The picture on the left is putting the 4.7k resistor in the ground line and then tying into the audio line, only two connections to the ground of the mini plug.  The right one is putting the resistor between the two wires on both sides and all wires tying to mini plug.  Or, is there a way to do it with only one reisistor for the whole cable?

Well as the person who invented this mod.. You must use two resistors they MUST be metal film and must be HAND matched to 4.7k exactly if at all possible.. both sets of resistors should always be the same value. You can use 1/8 watt resistors they are very small and easy to work with DIGIKEY.COM sells them for cheap.. I use NTE Flame proof series on my mics.. Not that you have to worry about flame


NICE DRAWING buy the way thanks for taking the time and doing that. Now others can do the mod. I get about 20 mod questions a week I will use this drawing now to explain things.. By the way the 900 series mics do not need my mod only the 800 series but other three wire mics can also use this mod.. I have tried it on naks but it does not seem to improve there performance.

Chris

[rsimms3]

So which drawing is correct?  The one on the left ties 4 wires to the mini plug and the other ties all 6.  I was hoping the left drawing would work so I would have less wires to sodder to the plug.  The one on the left puts the resistor in the middle of the ground wire and then attaches to the audio wire which is the only one attached to the plug where the right drawing shows the resistor in a bridge type connection between the audio and ground wires, all connected to the mini plug.

[Church-Audio]

So which drawing is correct?  The one on the left ties 4 wires to the mini plug and the other ties all 6.  I was hoping the left drawing would work so I would have less wires to sodder to the plug.  The one on the left puts the resistor in the middle of the ground wire and then attaches to the audio wire which is the only one attached to the plug where the right drawing shows the resistor in a bridge type connection between the audio and ground wires, all connected to the mini plug.

Sorry the drawing on the right is correct the one on the left is not. Putting a resistor between ground is not a good idea because it will increase your noise floor and will not work.

[rsimms3]

Are the yellow lines also connections?  Because if you have 1 and 2 going to ground, it doesn't matter if you put a resistor between them.  Did you mean to erase them in the right graph?

I didn't erase anything in the right picture.  These are the connections on a set of AT853s.  I want to incorporate the 4.7k mod into the cable.  In a Sound Pros battery box, the signals are on the Red instead of Yellow.  In the end, both 1 and 2 on both sides go to the ground on the mini plug.  So, should the resistor be between the ground and the actual signal line?  I should have made that more clear that it was going to a Sound Pros battery box. Below is what I based my original drawing on, as outlined by Richard to bring this out to the open with Chris.

I finally did a simple (and obvious) hack on AT853's to prevent overloading.

Normally they are connected like this:
- red wire: + battery box, and audio
- yellow wire and shield: ground for battery and audio
The standard (two-wire) battery box supplies power to the mics through a 10k resistor.

What I did was put a 4.7k resistor between yellow and ground.  (Actually, I put a *tiny* surface mount part right at the capsule, but you could do this anywhere on the cable.)  Now I power the mics with the standard (two-wire) battery box.  This will reduce gain a bit, but it *should* prevent overloading.

I think this idea originates with Dick Campbell, where he used it for WM60A mics for speaker response measurement.

Anyway, I modified a pair of my mics and sold them to Bobcat.  He's going to torture test them at some Tool shows...

  Richard

[Church-Audio]

Are the yellow lines also connections?  Because if you have 1 and 2 going to ground, it doesn't matter if you put a resistor between them.  Did you mean to erase them in the right graph?

I didn't erase anything in the right picture.  These are the connections on a set of AT853s.  I want to incorporate the 4.7k mod into the cable.  In a Sound Pros battery box, the signals are on the Red instead of Yellow.  In the end, both 1 and 2 on both sides go to the ground on the mini plug.  So, should the resistor be between the ground and the actual signal line?  I should have made that more clear that it was going to a Sound Pros battery box. Below is what I based my original drawing on, as outlined by Richard to bring this out to the open with Chris.

I finally did a simple (and obvious) hack on AT853's to prevent overloading.

Normally they are connected like this:
- red wire: + battery box, and audio
- yellow wire and shield: ground for battery and audio
The standard (two-wire) battery box supplies power to the mics through a 10k resistor.

What I did was put a 4.7k resistor between yellow and ground.  (Actually, I put a *tiny* surface mount part right at the capsule, but you could do this anywhere on the cable.)  Now I power the mics with the standard (two-wire) battery box.  This will reduce gain a bit, but it *should* prevent overloading.

I think this idea originates with Dick Campbell, where he used it for WM60A mics for speaker response measurement.

Anyway, I modified a pair of my mics and sold them to Bobcat.  He's going to torture test them at some Tool shows...

  Richard

Sorry Jon is right. here is the updated drawing with the corrections..


Chris

[rsimms3]

I see, same as the left picture in the first post only the ground goes all the way and the audio (yellow) can be joined using the resistor.  Thanks.