Passive adder?

[Primus]

I want to try something a little strange I read on one of the dub boards. I want to run an AM radio through my pedal board. However, I also want to be able to play my guitar at the same time. I know that you need to use an active device to split a signal to two amps, but what about combining two signals into one pedal? can this be done by just soldering the inputs together (never cross streams, Ray!). I was thinking of having a switch that switched between just guitar and radio + guitar.

Another question, that might be off topic... I was thinking it'd be cool to take the upper stage of a Leslie speaker using an 8 ohm driver and drive it from the cabinet extension on my amp. However, I am concerned that switching the driver load on and off my amp could damage it. Any thoughts?

[RandomRedLetters]

well there are passive A/B/Y boxes, and in theory you could use it to hook up 2 sources to one amp, its bi-directional. As far being able to mix the 2 signals in the A/B/Y box, im sure you'd need an active one for any signal buffering, boosting, eq etc, basically if you wanted a mixer for the 2 signals.

I would just use a passive A/B/Y box and make sure the level of the AM radio is where you want it before playing.

[RandomRedLetters]

As far as the Leslie amp thing, dont do it. Guitar amps are made so the load (Speaker cabinet) is constantly on, otherwise you can fry your transformers and/or filtering Caps.

[Paul Perry (Frostwave)]

Here's a very nice simple mixer:
http://www.aaroncake.net/circuits/mixer1.htm Thanks, Aron!

Otherwise, just hook up the guitar & run the radio in via a 47K resistor to the same point (to avoid loading the pickup). Oh and put a .1uF cap in series wth the 47K resistor, just for luck (& in case there are any bias problems).