SP B1, phantom power, and pads

[flanneljammies]

Has anyone used an inline pad with a Studio Projects B1? Does the pad mess with the phantom power supply?

 

[dr.colossus]

i use one quite often, hasn't messed mine up. never even occured to me that it might!

 

[Marik]

Flanneljammies,

Usually the inline pads made as H-type attenuator with two
56 Ohm resistors in series and 150 Ohm resistor across the center taps (for -10 attenuation). The 112 Ohm resitance in series with standard 6.81K phantom power current drop resistors has negligibale effect. You are fine.

 

[DJL]

Has anyone used an inline pad with a Studio Projects B1? Does the pad mess with the phantom power supply?

(1) Yes (2) No

 

[bgavin]

Marik, would you please detail that a bit more so I can build one?

Also include the r-values for -20dB

Thanks in advance...

 

[Marik]

Hope it won't screw format:

-----56 Ohm--+--56 Ohm----

...............150 Ohm..............

-----56 Ohm--+--56 Ohm----


For -20db change four 56 Ohm resistors for 82 Ohm, and 150 Ohm (tied between + signs, please disregard dots--I needed them to keep 150 Ohm in the middle) to 39 Ohm.

If it is unclear let me know and I will draw and post schematics.

 

[bgavin]

Marik,

Is this how you intended it to look?

Link to Drawing

I assume the pad is across the two hot leads, and the ground is passed through?

 

[Marik]

<Marik,
Is this how you intended it to look?>

Yes, just replace 150 Ohm resistor with 39 Ohm--this one for
-20db.

<I assume the pad is across the two hot leads, and the ground is passed through?>

Yep!

 

[bgavin]

Marik,

I modified the drawing for the center resistor change. Please use the above link, and verify.

Thanks.

 

[Marik]

Bgavin,

Looks good! The interesting thing is that it works not as a resistance divider, but the 39 Ohm leak resistor connects (+) and (-) of the signal and they cancel each other.

 

[bgavin]

Here are both drawings.

Link to -10dB Pad

Link to -20dB Pad

 

[Marik]

Looks good!