'50's Webcor Musicale Cartridge Conversion Advice

[skibjr]

Hi guys - I picked up a fairly nice mid-century Webcor Musicale Coronet record player (model MT1655-01) for my boss, who just wanted to play his dad's old records. He's not really an audiophile; he's just looking to do some casual "background" listening. I talked him out of the POS "Crosley" type reproduction players currently out on the market, figuring I could get him a nice good-quality vintage player and fix it up for him to use.

Stupid me. :bash:

After the last several weeks wrestling with this thing, I finally got it to the point where I was able to test it on a few stereo LPs I didn't care too much about - which turned out to be a good thing, because it ripped the **** out of them. You could literally hold the record up to the light and see where the needle had played. And subsequent replays of the same tracks were notably more distorted and noisier, after just one play!

So, I did some research here on AK, and have confirmed what I've already experienced for myself - that an old GE RPX magnetic cartridge, tracking at 10 grams or so, even with a brand new 0.7 mil "microgroove" stylus is a big fat no-no for ANY stereo record - which brings me to my question:

What do you guys recommend as a replacement cartridge for the GE RPX? I obviously need a stereo cartridge with vertical compliance, because about half the bosses records are stereo LPs. However, he also has some old 78s, and I'd like for him to be able to play those as well. I'd need something that puts out the same signal level as the RPX, will mount on and track okay with the big clunky tone arm, and that has switchable styli for 33-45/78. If I have to go with ceramic, than that's what I have to do - I'm thinking much of the improved high-end of a magnetic would be lost on the series-string one-way speakers used in the cabinet anyway. I really appreciate your recommendations!!

Here are a few shots of the beast in question:

 

[skibjr]

Did I stump y'all??

Perhaps a yea or nay for the Shure SC35C? It's designed to track at between 4-6 grams - perhaps a bit on the low end for this arm but maybe doable, and the 5mV output is about the same. I can also get a 78 RPM stylus for it and manually change it out as needed. It even looks like the mounting would be compatible... :scratch2:

 

[KentTeffeteller]

That is what I'd do for this arm. It will play modern records with reasonable safety and has vertical compliance. With this changer in good order, it will serve you fine.

 

[gadget73]

The SC35 ought to do OK. Just wire the two channels together for mono output and you should be fine. Sell the old GE to someone into mono and 78's. They're pretty good sounding in that application actually. The GE is standard 1/2" mount, so you should have no trouble bolting up a different cartridge.

 

[Olorin67]

I second the Shure SC35. Dont toss the RPX, they go for decent $ on ebay. Probably the best cart ever for old 78s. i have 2 musicales, kept one with the mono cart for 78s and mono 45s. You may need to tweak the cartridge loading, the early RPX used a cartridge load around 7k ohms, new ones are mostly 47k.

 

[skibjr]

Regarding cartridge loading, I found the following thread on the Antique Radio Forums site that seems to apply here:

http://www.antiqueradios.com/forums/viewtopic.php?f=9&t=236624

Looking at the schematic for the amp, it appears a 10K phono load resistance is used, so I'll try swapping it out with 47K when I install the SC35C and see which sounds better to me.

Thanks so much for the feedback, guys - this has definitely been a learning experience for me!! :yes:

 

[skibjr]

Well, the SC35C arrived yesterday, and I installed it last night. I had to use some spacers to give the needle body clearance beyond the front lip of the tone arm so I could swap LP and 78 styli, but the screws provided with the new cartridge were long enough to allow the required spacing. I set the tracking pressure to 5 grams, which seemed to work just fine - a little needle-bounce during tone arm set-down in the change cycle, but not too bad.

It sounds pretty good, and I can tell the Shure is a heckuva lot easier on LPs than the old RPX, but there's one issue that's bugging me. No bass. Or at least, much less than with the RPX. I can come up with two possibilities; (1) the old GE VR cartridges are just naturally bass-heavy, and I'm hearing perhaps a more accurate sound with the Shure, or (2) since the RPX was giving me 12mV output and the Shure only puts out 5mV, I have to crank the loudness-compensated volume control higher, which is taking me out of the control's compensation range.

Oh, by the way, the RPX was originally loaded with a 10K resistor (R4, above), which I changed to 47K when I installed the SC35C. I wouldn't think that would have much if anything to do with bass response, though, would it?

The player sounds nice and clean with the new Shure, but I really miss the fullness/fatness it used to have. Does anybody have any ideas regarding how I can get it back??

 

[Aerobat]

Are you using a phono preamp? You'll need one with a magnetic cartridge.

It's funny, I just did this with my Webster 356-1 changer. I used a Shure M44-7 and an ART-DJ phono pre. By removing the hardware from the tonearm I was able to get tracking force down to 3.6g. It tracks and changes records just fine.

 

[KentTeffeteller]

The Webcor has a phono stage, it had a magnetic cartridge to begin with here.

 

[skibjr]

Are you using a phono preamp? You'll need one with a magnetic cartridge.

The built-in amp includes a MM phono stage, as it originally shipped with a magnetic cartridge from the factory. The problem is, the original cartridge kicks out over twice the signal of the new cartridge, so I have to crank the volume a bit to compensate.

I was thinking about picking up an inexpensive phono preamp and using it in place of the initial preamp stage. That would most likely give me back the gain I need, but it seems almost sacrilegious to bypass a perfectly good 12AX7 preamp circuit with cheap solid state.

Pretty amazing that you were able to get down to 3.6g on your Webster. It looks like the 356 has a very similar arm to mine - same dual rubber grommet mounts and pivot assembly, anyway. I'm fairly impressed with the changer in this player (Webster model 141A), and yours is a good 6 or 7 years older then mine. :thmbsp:

 

[gadget73]

How do you have it wired exactly? If the channels are bridged together, but in reverse, it will tend to cancel out the bass.

If you need more gain, try re-working the stock phono stage to the one out of the back of the RCA book. It uses a 12AX7, but has a few different component values. That should give you what you need with minimal bother or modification to the original unit.

 

[Aerobat]

To get the weight down I removed the "rocker" mechanism and the hardware that held it and the wiring in, and replaced the two hardened rubber grommets.

I also wired the cartridge in series and left the original signal wire in place. It only uses one channel of the ART before being hard-wired to the amp input.

Honestly the sound isn't a whole lot better than with the Asiatic 89TX ceramic. There's more detail but the amp can't really use the extra frequency extension. It is definitely easier on the records though.

I was surprised that this ancient arm uses a half-inch mount and the same screw size that the Shure came with.

 

[skibjr]

How do you have it wired exactly? If the channels are bridged together, but in reverse, it will tend to cancel out the bass.

I jumpered the grounds together and the signal pins together as shown:
(BTW - this is how Shure jumpers their "mono" M78S version of the SC35C)

I'm thinking I might try the Shure M44-7 before I get involved with attempting to rewire the phono stage for additional gain. If one can believe the advertising hype, the M44-7 is recommended for its heavy bass response AND, it kicks out 9.5 mV (compared to the SC35C's 5.0 mV). That gets me closer to what the preamp stage is expecting, and perhaps back into the compensated range of the volume control. Only issue is whether or not I can get the stylus pressure anywhere near the recommended 3.0g range - but Aerobat, if you can do it, so can I! :yes:

 

[Aerobat]

I jumpered the grounds together and the signal pins together as shown:
(BTW - this is how Shure jumpers their "mono" M78S version of the SC35C)



I'm thinking I might try the Shure M44-7 before I get involved with attempting to rewire the phono stage for additional gain. If one can believe the advertising hype, the M44-7 is recommended for its heavy bass response AND, it kicks out 9.5 mV (compared to the SC35C's 5.0 mV). That gets me closer to what the preamp stage is expecting, and perhaps back into the compensated range of the volume control. Only issue is whether or not I can get the stylus pressure anywhere near the recommended 3.0g range - but Aerobat, if you can do it, so can I! :yes:

I'm seeing a lot of metal parts in the middle of the arm - what are those for?

 

[skibjr]

I'm seeing a lot of metal parts in the middle of the arm - what are those for?

That's a spring clip to secure the tone arm to its support for transport. Looks like yours has the screws for a similar assembly. Prolly be the first thing to go if I need to lighten up the arm...

 

[gadget73]

just another thought, increasing the loading resistor to 47k from 10k should make the amp stage more sensitive than it was originally. It probably doesn't want to see 12mv now anyway.

 

[Aerobat]

Anyone who has done a magnetic conversion on one of these old players - what do you do to deal with hum? It's present on mine with the changer powered on or off. Running a ground from the phone pre to the changer makes no difference. I also removed the ground strap from the cartridge to no effect.

 

[gadget73]

Are the leads in the arm shielded? If not try that or at least twist them together to see if that helps

 

[Aerobat]

Are the leads in the arm shielded? If not try that or at least twist them together to see if that helps

Check it out above, the signal is shielded with the ground like a coax. The signal wire in the LT-30 is the same.

 

[skibjr]

Anyone who has done a magnetic conversion on one of these old players - what do you do to deal with hum? It's present on mine with the changer powered on or off. Running a ground from the phone pre to the changer makes no difference. I also removed the ground strap from the cartridge to no effect.

I don't see a ground wire connected directly to the metal tone arm on yours. (Note the grounding lug near the pivot on mine) Perhaps ensuring the tone arm is well-grounded would help?