The Quest for a New Cartridge...

As much as I am a believer in keeping antiques (or in this case, mid century modernist pieces) in original, unrestored condition, I want to get the maximum possible sound quality out of this Circa 75 model 703.  Some really great people over at vinylengine.com have been trying to help me out with figuring out what kind of cartridge to get, and how to get the cartridge output to match up with the Circa's input voltages (the thread is here if you're interested).  The original cartridge is branded with the Electrohome symbol, but from what I've been able to piece together, it is an Astatic 183D, which is the original ceramic or crystal cartridge that shipped in the stereo console (photo 

Astatic 183D cartridge - the original cartridge from 1969.

to the right).  The first problem I've run into is that this particular kind of cartridge has rather high output of around 0.1 to 0.3 volts.  The modern, high-fidelity magnetic cartridge that I want to replace it with (Shure M97Xe) has an output that is an order of magnitude less at around 4.0 mV, or 0.004 volts.  However, the sound quality increase that should be achieved by switching out the cartridges means that I'm willing to undertake alterations.  This does mean that I will have to use a small ac powered phono preamp to boost the output from the Shure cartridge to something the Electrohome's amp can handle.  There are several small amps that can accomplish this relatively inexpensively.  And they are small enough that they can be easily concealed within the console, and wiring will be a snap.  The rca outputs from the turntable go into the preamp, rca cables from the preamp go out to the amplifier - couldn't be easier! 

 

Headshell from the Dual 1210 turntable showing the connector.

The second problem is that the Astatic 183D uses an internal clip for the wire connectors.  The Shure, on the other hand, uses the more typical type of connectors where there are male leads coming out the rear side of the cartridge body (see clip on lower photo to right).  This means that I'll either have to: 1) alter the connector to something that the Shure cartridge can take; or 2) use no plastic connector at all.  So all of the tiny little wires you see to the right carry the signal from the stylus to the amplifier, four wires = a positive and a negative for each channel, four wires total.  I may solder new wires into the headshell that just have a female connector on each wire, then I can just push the individual connectors together and mount the cartridge that way.  Waiting to order the new cartridge until I hear back from the people at Vinylengine.com to confirm weather my plan will work first.