best Amp (not PA) for slim phatty

[A.David.MacKinnon]

A Bassman (depending on the model) makes a great guitar amp but not the greatest bass amp. It can be amazing at lower volumes but if you need to keep up with a loud drummer it won't have the volume you need without getting super fuzzy.
I'd look for something with a fair bit of headroom especially seeing as the phatty puts out a much louder signal than a passive guitar/bass pick-up. I gig with a farfisa organ somewhat regularly and have had the best results with solid state amps for the same reasons listed above. The level is too hot for the preamp stage of most tube amps.
Depends on the sound you're after though. If blown out and fuzzy is what you're after then most tube amps will do the trick and sound great.

I did a record a while back for a band called the Birthday Cakes. They're a trio - synths, guitar and drums. The keyboard player covered most of the bass duties and was running a Moog into a solid state Traynor keyboard amp as well as a tube bass amp. The keyboard amp was clean and the tube amp had some growl to it. We blended the two sounds as needed.

[markjazzbassist]

your most important purchase is your cabinet not the head. the synth will put out frequencies well below and above what a bass does. this requires a super modern full range flat response type cabinet otherwise you're going to blow the speaker. I would journey over to talkbass.com and post there and see what they say (i belong over there too, good people there). There are a number of synth bass players (keyboard synth bass) on there that can help. What is your budget?

on the amp side of things how loud is your band? does your drummer smash? no PA what venue sizes (capacity) are you playing? Depending on that i can give some suggestions.

[kslight]

If you want cleanish volume and something semi practical to carry around I would lean towards solid state. I love the Roland JC120, it’s pretty good at exactly this (well, kind of heavy but oh well). If you want something “bigger,” and sort of self contained...Schecter used to make a “depth charge” 4x12 cab which is a guitar cab with a sub replacing one speaker. I’ve not used one so this isn’t a recommendation, but what you’re asking for made me think of this. You could probably DIY something like this if you wanted, with a crossover. I would stick a solid state head of sorts on that.

On the tube side, my business partner’s old band used to gig their keys through a monster vintage 100 watt Super Bassman + pyramid cabs rig. Then one guitar player with a couple 4x12s, bass player with an 8x10, and a loud ass drummer. You could almost never hear the singer.

My take on that...the problem with this setup is managing stage volume in most venues. If you have a singer...you will never hear them well in the PA if you have a bunch of unnecessary loud amps going on stage. Not to knock your aesthetic, but something to think about. Some bands don’t care about having intelligible vocals...