Author Topic: Cartridge experiments  (Read 1250 times)

Consoleman

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Cartridge experiments
« on: November 24, 2015, 01:07:42 PM »
It sure has been dead around here, I guess Thanksgiving week isn't a big one for acquiring or working on consoles!

So to add something new, I just received an EV5632 ceramic cartridge which I plan to try out on my '56 Berkshire with the CR-730AA preamp. I'm currently using a Shure M44-7 magnetic cartridge that goes into a standalone phono preamp, then into the Aux input of the 730.

I'm not sure which cartridge originally came with this console (maybe a crystal?) but it's wired with a 3.3M resistor and 220pf cap in parallel between the cartridge and the 6AV6 phono preamp tube. It also has a 3.3M resistor to ground.

Looking at later Magnavox preamp designs from the 60s when ceramic cartridges were in use, I don't see this resistor and cap in parallel, I see the cartridge going straight into the preamp tube with several megaohms going to ground. So I'll bypass these and see what happens.

I plan to experiment with different configs and compare it to the magnetic cartridge/phono preamp, which sounds excellent. This will also allow me to use the compensator control with 78s and see what effect that has, as opposed to using RIAA compensation for everything.
Mark

Curtis W

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Re: Cartridge experiments
« Reply #1 on: October 13, 2016, 01:08:52 PM »
I know it been awhile, but did you or anyone else, ever try the EV5632 cartridge?  If so, what is your opinion? I'm thinking of trying one on a 1958 Zenith Cobra Matic.  It's basically a VM 1200 series changer.   Thanks. Curt

Consoleman

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Re: Cartridge experiments
« Reply #2 on: October 13, 2016, 01:40:19 PM »
I did try the 5632 and it was fine for a ceramic. No comparison to the Shure I had in it though, so I got rid of it.
Mark

TC Chris

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Re: Cartridge experiments
« Reply #3 on: October 13, 2016, 08:24:17 PM »
While we've returned to the subject of 1956-era devices, can you describe which of the RCA jacks on the preamp is the aux. input?  I've got a 1956 Prov. Serenade with the CR 726AA tuner-preamp.  It has 3 jacks, none well labelled .  When I got the record changer I plugged it into the most likely one but got tuner plus record in the speakers.  That most likely is a tape out.  I found the one that worked, and could probably answer my own question by pulling the chassis, but typing is easier. 

Chris Campbell

Consoleman

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Re: Cartridge experiments
« Reply #4 on: October 14, 2016, 06:57:31 AM »
The phono jack has a "P" next to it and the tape/aux input is unlabeled.
Mark

Curtis W

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Re: Cartridge experiments
« Reply #5 on: October 14, 2016, 02:51:47 PM »
I did try the 5632 and it was fine for a ceramic. No comparison to the Shure I had in it though, so I got rid of it.


Good to know.   Thank.  Curt

TC Chris

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Re: Cartridge experiments
« Reply #6 on: October 14, 2016, 07:21:10 PM »
As I recall, there are three jacks, at least on mine.  One is a stand-alone, and it's labelled P, and that's where my changer is plugged.  The other two are, I assume, a tape in/out.  But which is which?

Chris Campbell

TC Chris

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Re: Cartridge experiments
« Reply #7 on: November 13, 2016, 12:23:09 PM »
How about the experiment with the input capacitor and resistor?  Did you try different values or configurations?

Chris Campbell

Consoleman

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Re: Cartridge experiments
« Reply #8 on: November 14, 2016, 06:43:19 PM »
How about the experiment with the input capacitor and resistor?  Did you try different values or configurations?

Chris Campbell

Unfortunately no, the ceramic sounded bad with any loading so I abandoned the experiment. I'd try it again with something better but pickings are slim. I do like the Astatic 89TX in one of my other players so I should try that.
Mark

TC Chris

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Re: Cartridge experiments
« Reply #9 on: November 14, 2016, 10:13:24 PM »
I just looked at the schematic for my 1956 Magnasonic.  It has a 1m resistor in parallel with a 47 pF cap and 470k resistor.

Chris Campbell