One of the great things about my Ultra is its ability to mix signals. Every now and then, it's fun to mix the stereo signal to the rear ERRs. I find I don't like to listen that way often, but now and then, it is quite pleasant. I agree with the low level caveat, and while the ERRs don't fire upward, I think their dispersion lends itself well to the effect. Not sure though the wireless mic/guitar amp combo will be neutral/flat, though.

Look forward to hearing your report.

For home use I used to dangle a mike over the front of my combo and feed it to another practice amp. Having the fuller sound was always more involving.

Back in the 80`s I read about how the atmosphere on Chick Coreas live album could be unlocked by using `out of phase` rear speakers. So I wired up some rear speakers to use with my B&W DM7`s. It was ok, not convincing, and some time later my Naim Nait int had to go back to Naim for repair. God knows what loads the little amp was driving.

Perhaps someone with some technical knowledge can help me here:  

The impedance of the receiver, that is, the unit that is to be plugged directly into the guitar practice amp, is nominal 600 ohms... The plug is an unbalanced 1/4" phone plug as shown above... 600 ohms, I would rate as medium impedance, mic-wise...

However, all guitar amp 1/4" phone plug inputs are usually of high impedance...  They're made to take, well, the output of guitar pickups...

I'm left wondering what that might do to the fidelity, or even the gain level that I might get...

Since I'm not looking for ultra-high fildelity here, it might not be a problem... Also, I'm not looking for too much gain, as the whole thing needs a rather low level to work right...

Bottom line: Does anyone think that plugging the wireless mic receiver unit directly into the guitar amp might not work?...

My guess is that it will be adequate, but not great...

I read somewhere that a mid impedance source into a hi Z input shouldn't be a problem, but...  ???...  (m.)

Well Mark this wont help, but when it comes to plugging instruments into any amount of amps and fx`s, wah wahs, mics I wouldn`t know and dont want to know what impedances they are. I just plug all the 1/4in jacks in and fiddle around till the sound comes out. Some mics use the smaller jacks but they all fit into a 1/4in jack convertor, and v/versa. Everything seems compatible. And why wouldn`t it. What I envisage when you try your experiment is that you will be amplifying not only the sound from your speakers but also the ambience and reflected sound from around the mic. The more you amplify the mic the more `mush` will get heard.
So the closer the mic and the lower its ampflification the cleaner the sound.
It will be like a very fast echo, almost reverb. I sometimes use an echo box that is actually called a delay which can be set to almost instantaneous. That touch of delay gives the guitar a pleasing sound, like, fuller. So playing a Strat with a little delay gets it nearer to a Gibsons  fatter sound.

This is the one I use Mark. I`ve had it around 25yrs. Just looked on e-bay and they are around £400. Unbelievable. I would have thought £50 max.


But....what I was suggesting is that you will get a very fast echo anyway, and you dont really want it, unless you do want to make it sound like you`re sitting in a big venue with it`s delayed reberberations  
ps there are a lot of Boss delay pedals on e-bay at reasonable prices.
They should all have very quick echoes. A check on the manufacturers website should have the specs if the ad doesn`t carry them.

To be honest Mark a direct line out and then through a delay would be better. I`m still debating wheather the CSP2+`s head phone jack would be ok to use as a feed in to my cassette deck for record. If so then the jack could theoretically be used to drive a rear speaker and pass through an echo unit on the way. Micing speakers is in theory ok, but in practice you`ll have to be careful with feedback. Mics to close, or amping them to much......it`s a balancing act. But hey your at home what am I banging on about.  I remember setting speakers up in different rooms once and could have sworn I heard Jimi tuning up in the other room. Have fun.