[sdiy] Clipping summing opamp issue..

[Tom Wiltshire]

I love the way this list can always come up with half a dozen  
different ways to perform even the simplest task like this!

T.

On 29 Jan 2010, at 07:25, JH. wrote:

>> If you have switching jacks on the input (and aren't using them for
>> normalization), you could automatically detect when an input was  
>> in use
>> and adjust the gain appropriately.  No big, expensive rotary  
>> switch...
>
> You might as well do *passive* summing: just a resistor for each  
> input, and a buffer stage after the resistors, but *no* virtual GND
> node, and *no* low value shunt resistor. Then, connect each of the  
> resistors to an input jack *without* normalizing to GND. That
> way, each open input won't do anything to the signal, but each  
> input with something plugged in will work as a shunt for the other
> inputs, and attenuate the signal. Sort of automatic gain adjustment  
> wihout any active detection.
>
> JH.
>
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