Bartender, what amp and cabs were you using while searching for the sound?
it's nice of you to ask but as a disclaimer I didn't have a ton of money to spend on gear until the last several years and also I used to be really clueless about gear(pre-internet) .
The first bass I got trying to get a Phil sound was actually a Steinberger XM2-5 with a low B. I had just seen the Dead in Buffalo (1986?) and Phil was dropping low B bombs during Jack Straw that shook the stadium.
My amp at the time was (I am laughing thinking back about this) some sort of Peavey P.A. head (???) running through a 2 x 15 cab. I used to cram that giant cab into pretty small cars.
The sound was pretty muddy.
I got my hands on a Crate head and bought a graphic EQ pedal and that setup through the 2 x 15 was ok.
The I got rid of all of that and used a gallien krueger RB400 head through a nice 15" JBL speaker. I got some aspects of Phil's sound out of that old rig with the Steinberger but it wasn't dynamic enough.
That was all from 1987 till about 2001 when I then joined an all original band playing a totally different kind of music so I put the Steinberger away and used a Fender P-bass for a few years.
About 2003 I discovered the amazing sound of a 4 x 10 cab. The GK head on the 4 x 10 sounded so dynamic and powerful and bright yet warm and great clarity and mid's etc... I could hear the Phil potential in that setup. Eventually I sold my Steinberger after owning it for 20 years and bought a Modulus Q5 from a TB member.
That Q5 with the NTMB Bartolini's through the 4 x 10 cab was pretty awesome.
But alas... I had to start downsizing and I was only playing in my church band.
I sold the 4 x 10 and the GK head actually burned out on me.
I am now playing in a band doing some Dead and playing the Clement 5'r through a Markbass CMD121p. Markbass kicks ass and I get a good Phil sound out of it. The preamp on the Clement is powerful so I can really dial in that sound.
I would love to play the Clement through a 4 x 10 but I also love carrying my bass and amp in one trip from my SUV.
I'd love to hear some others attempts at the Phil sound with various gear.