I started out as a jazz bassist in high school. I picked up the bass because I could read bass clef, and it was the only instrument that wasn't filled at the time. So I began lessons the summer before starting out on a Fender Squire that I played into the ground. By my senior year, I had switched to my 1991 P-Bass Lyte.
Anyway, a kid moves to our school from Austin, Texas and is a huge Beatles fans. I start listening to his records, and I became obsessed with McCartney and his melodic basslines. I spent a ton of my free time listening to Beatle and Wings records just to pick out the bass lines. So, there's my story.
Anyway, we know that Paul received his Rickenbacker 4001S in August 1964 while on tour in the United States, but it does not show up on the recordings until Rubber Soul. The apparent difference in the sound between the Help! and Rubber Soul and that difference begins with the bass sound. The bass is much thicker and fuller in Rubber Soul, likely a combination of Paul switching to the Rick as part of the Beatles' continuing experimentation with different instruments and sounds, and George Martin bringing up the bass line in mixing the recordings.
It was a good move. As the Beatles' music was transforming from dance music into introspective musical rock, Paul's basslines became more melodic and complex. If you listen to any album made prior to the Rubber Soul sessions, you will notice first that most of Paul's basslines are still based upon repetitive four bar patterns and, second, that the recordings pick up the bottom notes well but that the Hofner is generally lost at the top of its range. Paul continued to play the Hofner on stage and on promotional videos up until Sgt. Pepper, but the recordings in the studio were all from from the Rick. The only exception may be "Wait", which appeared on Rubber Soul but was recorded as part of the Help! sessions.
Nothing against the Hofner 500/1 Violin Bass. It is iconic and a great bass. It is lightweight, easy to play on stage and has a condensed fretboard, which makes it a great play on high-tempo songs. I have one of the re-issued 500/1's and it will always remain among my instruments.