Transistor stage needed to recombine separately treated non-inverting signals?

[kimelopidaer]

Hi, DIYstompbosses -

Recently I was reading in the archive about intermodulation distortion.
Let's say i want to split an incoming signal into a couple of paths in order to boost/filter a range of frequencies differently.

Each path is fed to a FET or BJT amplifier, and worked over in there,
and then I sum the signals together before the output.

Assuming i use decoupling capacitors on each of the split signals
should i consider anything else before just combining them?
I was thinking, is there any reason why the separately treated signals need to pass through a final transistor stage that would be common to all three, if I already arranged for all the gain to happen during the separate stages?

If i only used a buffer on the output, it would revert the signals, correct?
But is there a need for that either, if i'm not recombining them with anything that's been inverted?

Alright, thankyou
K

[Solidhex]

 Do what you find needs to be done. A recovery stage would only be needed if the signals are too quiet. A buffer would be necessary if you don't want anything behind the pedal loading down either of the signals. I would probably think some series resistance on each signal would be good to prevent them from interacting from each other though.

[kimelopidaer]

Alright.

"...some series resistance on each signal would be good to prevent them from interacting from each other..."

Could you clarify for me what you meant by 'interacting'?
Is it that the series resistance somehow addresses the intermodulation problem?

cheers
K

[Solidhex]

 As a possible example let's say you had a set of hard clipping leds at the end of one signal. If both signals were joined together with no resistance between them the diodes would clip both signals. If you wanted to only clip one signal and not both you would have to isolate them a little bit. Basically doing something like putting 2 resistors in series with the outputs of each signal, connecting the other ends together, and tapping your output signal there. Like a blend control set for 50/50. The value of the resistance would depend on the circuits. Not sure every case would require it but this one, for example would.