Topic: ? on making a -25dB in line pad

[rowjimmytour]

http://www.uneeda-audio.com/pads/
I made one set of cables w/ -20dB built in pad following the "U" schematics w/ R1=680 R2=150 R3=680
Pin 1=680>shield
Pin 2=680>+(blue),150>Pin 3
Pin 3=neutral(white)

I want to make a new cable w/ built in -25dB pad and according to the site above I would use "O" schematics w/ R1=1300 R2=150 R3=1300 R4=3300
Here is where I am a little lost but my guess is two resisters(150,1300) go from pin 2>pin 3 and pin 1>3300&150 and pin 2>1300? Is this correct or am I way off before I make this inline XLR cable for my R4? Or do you split the 3300>pin 1,3 and the 150>pin 2,3? Also could I just make a "U" pad again and use 2 x 1300 and 1x 150 same as my first and get a -25 pad?
Thanks in advance for help.
PEace
Edit pin #'s and resister values
I was looking at some of my diagrams and I believe I can achieve a -25dB pad using a "U" configuration w:
R1=1300
R2=150
R3=1300
XLR cable w/ shield>1300>pin1
XLR cable w/ positive(blue)>1300>pin2
XLR cable w/ neutral(white)>150>pin3>pin2

I believe this will work but please let me know what you think and this time instead of using cheap ratshack 4% resisters of carbon I am going to find 1% metal film 1/4 watt.

[Roger Gustavsson]

Hi,

Do you really need a pad like that? Are you using the equipment in your profile? If yes, it seems unlikely that you will need a pad at all. Even at 131dB at the microphones, there will not be more than about 0dBu (775mV) going to the recorder. You could then use the line input (maybe no phantom power possible then...) Running the mic inputs with minimum gain, would allow about 108dB. If you apply a -25dB pad at the mic input in its minimum gain setting, you are not using any gain from the micamp at all. There are no pad in the microphone? It is normally a better solution to reduce the levels before the built-in electronics.

Roger

[rowjimmytour]

This cable is for sound board patch(line in) not mic in!!
Peace

[Roving Sign]

There are no pad in the microphone? It is normally a better solution to reduce the levels before the built-in electronics.

Roger

Depends on the goal - if you are overloading the mic itself...use the on-mic pads...

If you are overloading your preamp - use a pad before the preamp...(or any built into the preamp) using pads after the microphone keeps the signal to noise ratio the same - Using on-mic pads will raise singal to noise...

If your stuck with NO attenutors on your preamp - you can resort to the on-mic pads...but with the above mentioned penalty...

Back to the original poster: What exactly are you trying to achieve...?

[Roving Sign]

This cable is for sound board patch(line in) not mic in!!
Peace

Shouldnt you be using the 1/4 TRS line inputs for this? Sounds like you are trying to force a pro line level signal down a mic preamp level pipe? Why?

[Roger Gustavsson]

If you are overloading your preamp - use a pad before the preamp...(or any built into the preamp) using pads after the microphone keeps the signal to noise ratio the same - Using on-mic pads will raise singal to noise...

If your stuck with NO attenutors on your preamp - you can resort to the on-mic pads...but with the above mentioned penalty...

Back to the original poster: What exactly are you trying to achieve...?

Yes, it depends on the situation. But if your mics are overloading, it is better to use a built-in pad. But this is off-topic in this thread.

On-topic: Is not this R4 working with normal professional levels? Nominal +4dB (1250mV) according to the specification. What level will a sound board deliver?

[easy jim]

On-topic: Is not this R4 working with normal professional levels? Nominal +4dB (1250mV) according to the specification. What level will a sound board deliver?

I believe the Oade Bros. modifications affect/disable the line inputs if I remember correctly. 

Knowing the local club where he is having the most issues, too, the engineer typically runs really hot out of the +4dB XLR outs since the feed has historically been set for a DAT machine that will accept a much higher input level before clipping.

[rowjimmytour]

On-topic: Is not this R4 working with normal professional levels? Nominal +4dB (1250mV) according to the specification. What level will a sound board deliver?

I believe the Oade Bros. modifications affect/disable the line inputs if I remember correctly. 

Knowing the local club where he is having the most issues, too, the engineer typically runs really hot out of the +4dB XLR outs since the feed has historically been set for a DAT machine that will accept a much higher input level before clipping.

Like easyjim said the signal runs hot out of the SDB at this club but its also happen at a Alejandra Escovedo show at a theater also. I have a patch cord that goes rca(SDB)>XLRM(R4) and I use adapters for different boards but mostly 1/4". Just like mentioned above I made a -20dB pad built into my XLR cable end but I feel like I need a little more pad still and want to make a -25dB pad again built into my XLR cable. This is not for a mic input which on my R4 are channel 3,4 w/ transparent mod while 1,2 are for line in like a SDB patch but can be used for mic also w/ no mod on these channels. The reason for all this is when I first got my R4 I got to do a few matrix shows and I found the SDB feed to be brick walling or very close to it so I built my pad. I don't think I would ever run SDB only so this is for a matrix mix which I like to run more aud in my mix then SDB so even w/ the shows I blew the SDB patch I still had a nice aud source.
Peace

[rowjimmytour]

Here are some pics of the fineal results.





http://s5.photobucket.com/albums/y181/rowjimmytour/-25dBpad/

[yousef]

Nice. I wish I had your dexterity with a soldering iron...