DIY 20dB pad (help...)

[ulriggribbons]

I typically build it into a DPDT switch (U pad), and place it between the input xlr and the input of the mic pre.

Regards

ju

[Milkmansound]

do a search for "true bypass" it will show you how to use a DPDT to wire a circuit into another and bypass it - in this case you will want to bypass the pad or engage it.

whip out the old pencil and paper and draw a schematic - trust me, you will learn a lot going about it that way as opposed to having someone show you every move.

[ulriggribbons]

Ya,

thinking about how to switch this in and out is a good excercise in understanding circuit flow =).

Here's one way:

[RodC]

See if this answers your question. For low level signals the signal is routed more to ground to attenuate it. Keep in mind if you do this on a mic input you are also affecting the impedance/sound.



If this is a balanced mic cable the in would be your + and the Ground would be your - signal.

[RodC]

I belive you are right, I just thought you needed to know how to wire a pot.

I thought you had the balanced part figured out, the article you pointed to stated:

These configurations may be made adjustable by making the various resistances variable. The non-trivial part is that the resistances have to change according to a particular relationship which is not linear. To get an adjustable T-pad, you must buy it as such. An adjustable L-pad has 2 variable elements, whereas an adjustable T-pad has three. The Bridged-T pad is popular because two of the resistors (R1, R2) are fixed and never change value (they are always equal to the pad impedance), so making this configuration adjustable is just a matter of making R3 and R4 variable. It is possible to buy a ready-made pot that can be used as a bridged-tee attenuator but they are expensive and subject to minimum order quantities. This effectively makes them impossible to purchase. It is easier to make a bridged tee attenuator using a rotary switch but this also makes the attenuation steps discrete.

[ulriggribbons]

wouldn't it be smarter to do it like this?

Whatever flips yur lid =). The other way uses the terminals that are available on the switch, rather than wiring resistors in the air.

Regards

ju

[jv]

i seriously DO NOT understand this.

(ofcourse my picture has a fault, that the top resistor got "blurred out" when i converter it to jpg...)

but yours.. i don't understand.
when flipped one way. the left terminals/signal will go through a resistor each AND split and just go to the output.

when flipped the other way (right on the picture) it'll pass through and connect through the vertical resistor..
what am i NOT getting??

When the switch is in the left position, the 2 horizonal resistors are shorted out, and the signal is passed through directly. When in the right position, the 3 resistors (pad) are put into the circuit.

[ulriggribbons]

thinking about how to switch this in and out is a good excercise in understanding circuit flow =).