Author Topic: 930x Optimisation  (Read 394 times)


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930x Optimisation
« on: February 10, 2018, 04:46:38 PM »

I just picked up another Magnavox this morning (been there anyone?).  It's a Symphony 1-ST657S from 1962.  I also have a 657S from 1961 with a 9302 amp.  It's the Symphony styling that I like.

The tuner on the former '62 says FM Stereo and on the latter '61 FM MPX, which makes sense given the dates and the evolution of the multiplex as option or standard.  The '62 I picked up has the 3-tube multiplex manual (and its own silver-seal cert), so I assume it's inside. 

Unfortunately, I didn't take the back off it before I dropped it, but based on the fact that I have another smaller 1962 Magnavox with 3-tube MPX and 9304 amp, I suspect we're going to find a 9304 (could be wrong, maybe the 9304 is uniquely associated with the series 100 tuner).  I have both a 2-tube and a 3-tube MPX now, and the molex pins are different.

Anyway, my goal is to have 2 657's (930x Symphonys) working super nicely. One for the kitchen, one for the bedroom, and the 233L cranking in the living room.

To get to the point: is there any clear guidance on which 930x flavour is best? 
Additionally, is there any dead-cert 930x circuit improvement that I should do for the Symphony configuration?

Obviously I've read the stuff on other forums where hifi folks are trying to use/modify the 930x amp outside the console, but I have zilch interest in that road.  I just LOVE the vintage consoles and want to make them sound as good as possible.

If anyone knows what I'm burbling on about and wishes to chime in with some solid empirical info that would *definitely* help, much obliged.



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Re: 930x Optimisation
« Reply #1 on: February 10, 2018, 08:58:34 PM »
AHA!  You answered a question I had been looking all winter for the answer to.  THANK YOU!!

My 1963 2ST653 has a different Molex connector than the old two tube MPX adapters have.  Now I know what I need.  The three-tuber!

A 9300 is a 9300 is a 9300.  They made various versions ala 9302-00, 9304-10 and so forth.  It is the same basic amplifier, slightly modified for use is a specific instrument.  Such as the Symphony, the five-knobber Stereo Theaters, the six-knobber Stereo Theaters, Stereo Theaters with remote control,  the little Imperial and so forth.  Like having a 327 Chevy V-8 in an Impala, Impala SS, Caprice, Bel Air, Biscayne, Chevelle or a truck.  Same engine, different motor mounts, different transmission, different radiator.  Still a 327.  And, like the Chevy 327, the Magnavox 9300 series amplifier is among the best 15 WPC stereo amplifiers ever made by anybody.  Like a 327, hearing one in full song will make you grin......

You don't need to change anything on a 9300.  Leave it like it is and enjoy it.  Adding go-fast kiddie add-ons recommended by the folks on "that other forum" is silly and counter-productive.  Fix it right and enjoy it for another 50 years.

IIRC, the 656's and 657's came standard with a MPX adapter.  Starting in mid-1961, there was an "FM AFC" position added to the function switch on Magnavox stereo instruments.  This is in addition to the "stereo FM" position.  AFC goes a long way to cure the drifting common on Magnavox tube FM tuners.
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