Question on ins and outs...

[kiehano]

Ok...I've looked all over and every thread I've found on the internet regarding this winds up spinning wildly out of control and never seems to answer the question. I'll make this as simple as I can.

I play doom/stoner stuff.  I like a lot of bass.  I love the sound of my Ampeg VH140 but it lacks the really deep bass I want. I found a potential solution. 

guitar > ampeg...speaker out > cab
+
preamp output of Ampeg > instrument input of Sunn Concert Bass...into another cab.

So, what I'm doing here is driving one cab with the ampeg while simultaneously running the preamp out into the front end of the Sunn which I drive a 2nd cab with for that extra bass oomph.  I've only done it at low volume levels but it sounds GIGANTIC.  The question is whether or not it would be safe at higher levels when the preamp output of the Ampeg is running a bit hotter or is it going to destroy the Sunn?

preamp out > instrument input...safe?

[kiehano]

I just ran a little test.  I have no way to determine the actual level of the signal coming from the preamp output of the Ampeg, but even when the volume is cranked, it still didn't make my MXR 10 band EQ clip (odd, it does clip sometimes when I have it in the FX loop).  I've never had to turn that amp up past 3 when playing with a band either.  This is leading me to believe that it's safe.  Seems logical enough...right?

[J M Fahey]

Since the Ampeg preamp is SS and Op Amp driven, you will never have more than 10 or 15V Pk ... or *less*, which should kill no musical instrument preamp input (*we* are the tough guys, aren't we?)
If your MXR is 9V powered, you will never get more than 4.5V Peak, even safer.
I doubt you will *burn* something, but be aware that exaggerated EQ curves,  can sound good at low power, where you have huge headroom, but at stage levels it might get farty, buzzy, chopped, etc.
Anyway, good luck.

[Enzo]

You won;t hurt it, if you turn up too far, you wind up clipping.