Using his live rig in the studio, with just of hint of compression and EQ in the mastering process.

Also, don't discount the 3 quarts of scotch used while warming up LOL.

whats a good but affordable compression pedal?

If compression is very important in the studio most people don't use it live because the sound will compress naturally at high volume anyway and you lose the dynamic (i.e. if everyone start to play softly on a part, the bass will still be pounding like a mofo and it'll draw at you some bad looks) . Another thing you need to know is, cheap compressors pedals (Ibanez, Boss...) are major tone-suckers so unless you get something like a Demeter/EBS... you may want to save your cash.

Compressor rule of thumb: a compressor is like a baseball umpire, if it's a good one, you should barely notice it. In my studio rack I have a DBX160 XT, it's a classic for bass but I bought an IK Multimedia Fairchild 670 plugin which works fantastic too.

My guess on his tone: It's a combination of his bass skills and his knowledge of equalization, no "magic box" will supersede this. Gear-wise, a P-Bass with Rotosounds and an Ampeg tube amp should take you right there. AzWhoFan should be the authority here though.

Here's some various things that I've read/seen over the years...

He liked incredibly low action and a very straight neck with steel roundwounds and even gold plated strings... it helped him acheive the aggressive "buzz" he was known for.

In addition to this, he played with a pretty percussive style close to the neck... his fingers would almost tap on the strings as he played them, giving each note a percussive slap tone.

I've also heard YouTube clips where's he's using a full-bore overdrive and/or distortion of some kind. Not sure whether it was from an external pedal/preamp or if it was through his head... I know in the old days, before speakers designed specifically for bass were common, some of his grit came from the speakers themselves distorting.

Anyway... other than my personal observations, here's a shitload of info... more than you'd ever need.

http://www.thewho.net/whotabs/gear/bass/bass.html

99 % is his fingers and attack of the bass....Yeh I love his gear but you could stick an Ibanez in his hands in the day and would be unmistakably him. He was a self proclaimed bass guitarist and played as loud as he wanted and as many notes as he wanted and cranked everything up but that entirety aside it’s almost all completely in his hands or sadly said was...just my 2 cents

If compression is very important in the studio most people don't use it live because the sound will compress naturally at high volume anyway and you lose the dynamic (i.e. if everyone start to play softly on a part, the bass will still be pounding like a mofo and it'll draw at you some bad looks) . Another thing you need to know is, cheap compressors pedals (Ibanez, Boss...) are major tone-suckers so unless you get something like a Demeter/EBS... you may want to save your cash. Compressor rule of thumb: a compressor is like a baseball umpire, if it's a good one, you should barely notice it. In my studio rack I have a DBX160 XT, it's a classic for bass but I bought an IK Multimedia Fairchild 670 plugin which works fantastic too.

My guess on his tone: It's a combination of his bass skills and his knowledge of equalization, no "magic box" will supersede this. Gear-wise, a P-Bass with Rotosounds and an Ampeg tube amp should take you right there. AzWhoFan should be the authority here though.