common vs. floating ground in retrofurbished Philco car radio

I'm having the original Philco AM radio in my '69 Mustang retrofurbushed to AM/FM, 44 watt RMS amp, line level input for my Discman and pre-amp outs - all to retain to the original look of the radio but give better peformance. Crazy, perhaps, but that's what I did...

I don't have it back yet but the guy doing the work said that he had changed the radio from a floating ground to a common ground system... then he mentioned this affecting how the speakers are hooked up, describing a setup that sounded like wiring them in parallel. I had to run to a meeting so didn't get to prolong the conversation but thought I'd ask if anyone here understands this...

1. what is the difference between a common ground setup versus a floating ground?
2. how would the grounding of the system affect the hookup of the speakers?


He said that there was an incompatability between older and newer car radios and components that had different grounds: in the 1970s when guys would try hooking an eight track up with an incompatible ground it would be a case of "you hooked it and cooked it."

TIA,
Ere

 

I just took out the stereo in my Saturn (getting a new Honda) and there should be a common ground, IE the chassis. Once you disconnect the ground from the chassis screw, all you have left is a hot wire from the battery...

This is just my very recent experience....

 

Gary - that's the funniest thing I've read all day

Must remember to breath out..... can't stop tears from obscuring vision...... pain in chest......

All the best - Andrew

 

Or, perhaps neither of the above
I probably misunderstood him. He probably said that it is still a common ground system, which would make sense seeing as how it's the original 1969 radio.

He is providing install instructions and I will be talking to him again. Unfortunately he is in Ohio and I'm in MD but he will be at the Carlisle All-Ford Nationals next week, where I'm taking the car.... hmmm

I did read up on the difference between common ground and floating ground and it appears that the former was used on most pre-1970s cars and the negative terminal from each speaker was grounded at the speaker location (to the extent there even were multiple speakers). Now most cars use floating ground, that is, where each speaker has +/- wires running all the way to the amp. And that while some common ground systems are still being made, they are the cheap ones and have inherent wattage limitations

We'll see. Part of the problem is that I have a pair of Alpine component speakers with crossovers and I'm not sure how or if they will work if a common ground is required. What may salvage the situation is that I had him also install pre-amp outs so I may be able to pick up a decent amp and truly use the Philco as the head unit and run my new speakers from the modern amp.

Thanks, I hope the execution is as clever as the concept!
Ere