Pan Circuit Loading/ Bus Impedance Math Question...

[mutterd]

Hey guys,

I have a quick question…

I am working on the math to figure out some Panpots and I am unsure of something….

I am trying to determine the load of a pan circuit that is driving busses connected to a virtual ground summing circuit. I have a simple passive pan circuit with a dual pot slugged to create the law, 2.4k bus resistors and 12 channels - so the bus impedance is 200 ohms.

My question is this:

Is the bus resistor of the channel in question in series with the bus, or is it included in the parallel sum of the overall bus impedance.

ie - if i put one probe on one side of the pan pots output before the bus resistor and the other on the input of the virtual ground summing amp will i read 2.6k on the meter or 200 ohms?

I'm sure this is simple, but I'm just not sure and the difference between a 2600 ohm load and a 200 ohm load really changes things for the pan circuit.

thanks guys,
Timothy

 

[ruffrecords]

If you have a virtual earth mixer then the far end of each mix bus resistor is effectively tied to 0V so you have 2.4K in your case from each pan pot output to 0V. It would help if you posted a schematic.


Cheers

Ian

 

[JohnRoberts]

Hey guys,

I have a quick question…

I am working on the math to figure out some Panpots and I am unsure of something….

I am trying to determine the load of a pan circuit that is driving busses connected to a virtual ground summing circuit. I have a simple passive pan circuit with a dual pot slugged to create the law, 2.4k bus resistors and 12 channels - so the bus impedance is 200 ohms.

My question is this:

Is the bus resistor of the channel in question in series with the bus, or is it included in the parallel sum of the overall bus impedance.

Yes.

ie - if i put one probe on one side of the pan pots output before the bus resistor and the other on the input of the virtual ground summing amp will i read 2.6k on the meter or 200 ohms?

If power is turned off and you measure across 2.4k resistor you should get 2.4k

I'm sure this is simple, but I'm just not sure and the difference between a 2600 ohm load and a 200 ohm load really changes things for the pan circuit.

thanks guys,
Timothy

200 ohms is the effective impedance of all the bus feed resistors in parallel, and what it appears like to the sum amp. 2.4k is what it looks like to the channel pan pots.

JR

 

[mutterd]

200 ohms is the effective impedance of all the bus feed resistors in parallel, and what it appears like to the sum amp. 2.4k is what it looks like to the channel pan pots.

JR

Perfect - thanks so much guys.
T.