Tube compressor for bass.

what do you mean by thicken the tone? do you want to saturate your sound? do you want to even your peaks? lengthen your sustain? Are you tlaking about something to use on recordings of your bass or to put in an effects loop? A varimu or optical compressor might tickle you but I wouldn't be lugging those around to gigs. What era of Paul's sound interests you? Live or studio?

first amps, later beatles you had fender all tube heads, bassmans of various eras, he defintiely owned a blonde one and a a silverface one, 2 very different amps I might add and mid to alte there was a selmer trebl n bass mk1 or mk2 which is like if a marshall and a blonde bassman had a baby.... wings and beyond you're looking at either fenders early on or the notorious mesa bass 400, a real contender against the all tube SVT although the one he used is very expensive to maintain, imagine a number of bassmans chained up with an optional graphic EQ, less deep sounding than an SVT tube head but more syrupy? hard to describe, I briefly owned one...... there is no compressor in line, the compression would be in the studio across a recorded microphone signal

go read about what a compressor does and the different ways it can do it, there are varous types of 'tube' comrpession but msot are really just tube based line amps in and/or out versus what is called varimu compression which uses sharp cutoff pentodes aand/or the bias point of some of the tubes to change the volume envelope of the signal base don feedback of the inputsignal to the bias circuit etc. the buy in on a good channel of varimu is about 2 grand usually, and up from there... also bass frequencies have more energy electrically than treble therefore a compressor tends to thin bass, yup

compressors that don't include some varimu tube designs, better optical designs like the LA2A and LA3A by urei, the symetrix 501 in peak mode, rms sucks bass... the 1176 but it depends onthe clone if you're going clones... the cheap ones are not as bottom heavy, you would want something like a black lion bluey or their other one, the black one, that's got decent bass...

I somehow deleted the post you were replying to so i forget what i was rambling about.... I have no idea how I did that.... so in answer to your querry, no, all of that gear is expensive. Mixing analog is costly. I don't even know how much money I have tied up in my home post-room and I don't have an varimus. You could try either an art VLA which ahs low plate voltage tubes that sound very thick driving a solid state optical comrpessor. Has an extremely 'cheap vintage' sound like some old AM braodcast gear, the gates stuff for example, that's on the lofi, midrangey side so may give you some of that glop you want, plus opto is slow compression so improper settings are unlikely to destroy your transients or bass. It excels at turning live drums into when the levee breaks for example. Hard to screw up. The VLA is cheap and quality, I have 2, a mk1 and mk2, both are good at what they do. I've never tried them into an amplifier or anything though. Then there's the 1176, perhaps my favorite compressor. Its based loosely on the earlier 176 varimu by Bill Putnam but modernized to use FETs. There were a lot of revisions. There are a lot of clones. I have a number of clones and modded versions and I wouldn't go into the cheap seats for bass, fine for snare etc, not bass. If you're spending under $500US don't bother. I quite like my black lion bluey, they also make a modified version that handles bass well, I think its called the seventeen.... the purple audio is very good and if you want to build one you could buy a hairball audio kit in any revision. I would read up on these guys, I defintiely use it on bass guitar on occassion when I want to have overt compression or use the output amp to really color the sound as none of the revisions are wht you would call transparent, although A and B are the funkiest with a good weight, lots of harmonics and a mid-forward aggression when hitting hard, even at unity gain (later revisions you actually might need to run the amp output hotter than your input to get the thing to give up a really pronounced thickening effect). As a studio rat I also own a lot of getting the job done type gear though. You don't always need to ehar the gear working and in that department there are lots of excellent options. But you don't want that.

all this said, for live purposes that hybrid head you use will be a real limiting factor, I've had so many bad experiences with the non-tube ampegs, and I'm not too sure how well any of this gear is going to do in tis effects loop, plus if you wanted to use it out front you probably want a quality DI box to get your signal in at a nice low impedance, if you're trying to go live you're creating a really goofy use case scenario for all of this dynamics processing as the stuff you like is not intended for this purpose... if you just want something for the old home studio? Well collecting compressors is a rewarding hobby and then you get to play with them all. Long ago I realized that I don't love music so much as I love compressors and EQs, they're so cool... best of luck. If you can swing about $1500US you might look at wes audio's altec clone which is well regarded and half the price of other mono varimu designs, but I ahd an original altec back in the day and I don't get the current hype, in american tube units I vastly prefer the gates stuff.

EDIT: I should also point out that your use case scenario isn't actually abut dynamics control, the raison d'etre of compression, you're actually seeking artifacts.... artifacts are like side effects of the compression circuit or line amps, they're actually design flaws but we happen to like some of them...

anyway, if you're looking for studio use I guess you could send me a recording of your bass nd I could let you hear it through a few of my nicer compressors of various styles which may help you out. It would only take a sec. Although you will also be hearing a little of my mixng desk which has some color of its own. I'm still confused about your use case scenario though I think because you're confused as well.