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I think it's all about resonance actually.
The speaker and cabinet resonate at a suitably low note, so you get a really good dance beat out of not a huge amp.
The turntable is actually vertical, and, sorry, really heavy stylus pressure, sprung to resonate at some other frequency.
The preamp is very interesting. It is an oscillator, which is modulated by the coil in the pickup!
Then FM detector.
I feel a new preamp coming on..
What if you could tune in to your turntable on your FM tuner??
Ahem, that's rather complicated, as you meed a crystal on a proper fequency etc. In other words: "Don't try this at home"!
You have to do some research into local regulations and all that.
It's kind of like a remote, but on FM band. Tiny range.
I'm going to experiment with it. It's a tiny transmitter on a designated frequency. At least here. Swotting up local regs would probably be good.
What about a wee box which has the phono preamp valves on top, but beneath is a readily available FM tranmiiter chip with telescopic antenna. Switch from "Phono" to "Line". Wallah!
Remote turntable etc to your transister on the deck.
Here we are in a nutshell!
http://www.digikey.com/us/en/ph/rohm/bh14.html
Totally impractical. The thing to have would be a mini transmitter connected to the "Tape recording out" socket.
It was the 78RPM machine that had the "Cobra" arm with the oscillator. A vane was moved by the stylus to vary the inductance of the coil, which modulated the oscillator preamp. I have one of those pickups here for test purposes, as that is the only way to check if it is operating.
On those 'boxes, the records are each on a tray stacked to the right in the cabinet, and the selected one swings out over the turntable, which spirals up, collecting the record and carrying it up to the top where the arm is. Only plays one side of record.
Here is another jukebox amp in for an overhaul.
This a Row-Ami amp in really mint condition, of the early'60s. Those red, and black wax and paper caps you see are the main thing to replace, but also it's a good idea to do all the plate load resistors, as they are doing a lot of work and are invariably carbon composition types, where the resistance value is got by varying the proportion of carbon granules with the amount of chalk granules. (!).
Nothing like a film type, carbon or whatever to lower the noise heaps.
Stereo amp with separate preamp not shown.
That has conventional magnetic pickup and valve automatic volume control to cope with varying levels on the records.
It's a bit "hard case" really, as the record producers would impress bigger and bigger levels on their records so theirs would sound louder than the other guys. All to be levelled out by the designers of the jukebox.
Dunno why I didn't think of it before, but here in front of me is an 8" speaker connected to sophisticated short-wave radio nobody listens to anymore.
So what I do is take out the old radio type speaker and install a one only 15 ohm Richard Allan CG8T I happen to have.
Above the bench in the workshop I keep a ten watt wee monoblock with sentitive front end and traditional ulta-linear EL84'S.
My YouTube videos rock!
Carefull though, one can overblast the decibels from only a few feet away.
A refinement:
Well this is just a rapid rig-up on a Sunday afternoon.
The speaker is 15 ohm, but the amp happens to be set to 8 ohm.
The amp is overpowered in "ultra-linear" and would be better in triode mode. Easy to set amp to triode and 15 ohm.
Speaker is open baffle.
Can redo cabinet to Helm-Holtz I think.
As is, not in the slightest scientific, but I have to say it certanily rocks on those YouTube videos!
A bit of a blast on this video I made myself I have to say:
http://www.youtube.com/watch?v=6Cwd6Wb69ms
http://www.youtube.com/watch?v=bnwJWOLWBls
Attachment 11180The mini monoblock.
Actually quite a serious wee OPT on that, with 1.75" of Radiometal.
The copper wrapped power transformer prevents transmitting hum into those cables!
This looks better for a quicker broadband:
Attachment 11181