Seems like I'm always chasing tone -- but this is a remarkable combo. The Peavy Rock Master was an unpopular guitar amp made only from '83-86. 120 watts, but loud as shit for a 120 watts. 2 gain stages. The "pump" knob provides more distortion.
I use a 1 in, 2 out splitter to send my bass to both amps - I use the TC 450 (which is an amazing 7-pound 450 watt transistor amp, by itself, btw) through an 18" speaker to cover the low end I can't get out of the guitar amp, & the Rock Master through a 15" EV speaker gives me the mid range & the gritty grind I've been trying to find for years.
Tried a couple different Marshalls that belonged to friends, & the low end on them gets farty, so I had to roll off too much of the low on them. Great, but not perfect. My Mesa Boogie D 180 is a great tube amp, but gets buzzy instead of gritty/Grindy when it distorts. Better for a clean tone, but not what I want for what I'm doing now, & the bastard weighs 80 lbs. On this thing, I can turn the bass knob all the way UP & it doesn't fart out, it just bites when I hit the strings hard, & is smooth when I play soft. Warm & unexpectedly deep for a guitar amp, & I'm relying on the TC less, except for some volume on the very low end - it moves air. The pull-bright switch on the pre-gain knob is instant Rick-o-sound, & pushed in, it's perfect for the Precision, so swapping basses mid-set is a snap.
$250.00 on eBay. I know you take your chances on eBay, but this thing showed up a little dusty & with a couple loose screws & in 45 minutes, we were up and going.
It's nice after 40 years of playing, to listen to your instrument & not be able to imagine it sounding any better. It's been a long quest.