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Originally Posted by ulysses Sure it would, but it costs at least $750 more than an inline pad. In fact, if you use a single input and a single output of the Folcrom, it IS nothing more than an inline pad.
You can easily build your own pad into a patch cord or XLR cable. You need three resistors and the ability to make your own patch cable (that's a separate thread). Make the cable as you normally would, but at one end (the "source" end) you solder a 7500-ohm resistor in line between the connector and the wire. Do this on both the "hot" pin and the "cold" pin. Then, at the "load" end of the cable (the other connector) you solder the wires directly to the connector just like a regular patch cord but you ALSO connect a 150-ohm "shunt" resistor BETWEEN the hot and cold pins. Connect the cable shield to the connector ground at both ends (or just one end) as you normally would. This will give you a pad that's approximately 40dB (about right for turning a line-level signal into a mike-level signal). It will also load your line-level output with about 15k ohms, which is just fine. And it will present a source impedance to the mike preamp that's very close to 150 ohms, which is what most preamp are expecting. You could screw around with the resistor values a bit if you wanted, but you're limited somewhat by the fact that you need a relatively high input imedance and a specific output impedance. If you want less than 40dB of gain, you could go down to about 4700 ohms for the two series resistors and up to about 250 ohms for the shunt resisor without too much effect on the impedance. Those values would give you approximately 32dB attenuation.
The question of whether a resistive pad will affect the tonality of the source or the preamp. The answer is that any potential change in tone will depend on the specific gear in question and in any case will be proportional to the deviation from the "ideal" source impedances. Keep the input impedance high and the ooutput impedance at 150 ohms and you will have a sonically neutral pad.
Of course the biggest tonal change will come from the fact that the mike preamp will no longer be overloaded and clipping from the line-level input. |
This is how you do it. Do use quality resistors, like Dale RN55's from Mouser. Match the two series resistors with a meter for better than 1/2 % to maintain CMRR. This can be installed into an empty Switchcraft barrel extender. Keep in mind this will affect phantom power so don't try to use it with this pad inserted.
Many low cost consoles do this to pad the inputs as they only have a mic pre in, not a line circuit. Soundcraft 600's come to mind.
Jim Williams
Audio Upgrades