Pioneer PL-50 and Sansui Six - "PHONO MAG" pre-amp needed?

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Verno1978

New Member
Hi friends. First-time poster. I've really enjoyed all your contributions to this site as I've been starting to build my vintage setup. I have a Sansui Six and just acquired a Pioneer PL-50. Both in wonderful shape. Very excited!

I thought I was in the clear with my Six---certain that I wouldn't need to buy a pre-amp to run a TT. I've been reading through the manual for the PL-50, though, which states "The cartridge furnished with the PL-50 is an induced magnet type. Therefore, use the PHONO MAG input jacks of your amplifier for connection with the PL-50. If your amplifier is not provided with the PHONO MAG input jacks, you must purchase a pre-amplifier (such as PIONEER STP-2) separately and use it for matching the PL-50 to your amplifier."

I researched a bit and learned that an amp may have PHONO MAG and PHONO CER labeled input jacks for magnetic cartridges and ceramic cartridges. But I don't quite know what to do where, as in my case, the back of the Six doesn't say one way or the other. The Six has two sets of Phono jacks. Neither says PHONO MAG.

This newb is baffled. Is my Six ready to rock as is? Or am I on the hunt for a pre-amp?

Thanks!

EDITED TO ADD: My Six's manual says, "Note: (1) If using a moving-coil (MC) type cartridge, be sure to employ a step-up transformer or separate head amplifier between the turntable and the SIX. (2) If you wish to use a ceramic or crystal type cartridge, connect the outputs of the turntable to the AUX input terminals" Not sure if that information helps. Thanks again!
 
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Hi, welcome to AK. Forget about prehistoric ceramic and crystal carts, no one uses them these days for hi-fi purposes. You also do not need any specific Pio pre-amp and the turntable
brand has very little to do with it all. Ignore the Pio brand oriented marketing brainwash from back then. What's important is the cart.

MM (moving magnet -> magnetic -> 'MAG') carts and induced magnet (moving iron -> MI) types generate voltage in the the order of 5mV (millivolts) while MC (moving coil) carts generate much lower voltage in the order of fractions of one millivolt. The common receiver's phono input from the early 70's was designed primarily for MM carts with input sensitivity of about 2.5mV. This means you could not plug to the PHONO input a turntable with a cart that generates less voltage than the input sensitivity, such as MC types. Hence, the step-up transformer (SUT) mentioning in the MC context. Most MM/MI carts would do nicely out of the box though.

The good news are that contemporary receivers with PHONO input already include a phono stage that is designed to perform the RIAA equalization necessary to process a signal from a turntable and then amplify it enough for the main amp section to kick in. The SIX does not require a separate head amp or SUT in order to allow you to listen to a turntable with MM/MI type cartridge.

The other inputs such as 'AUX' are considered 'line level' with an input sensitivity of a minimal 150mV. Old ceramic and crystal carts could generate high enough voltage for that, and their impedance and load resistance were tweaked to avoid the need for RIAA equalization. They did not need any pre-amp either and could be plugged directly to line level inputs, but this was done mainly for maintaining low costs and was typical in the 50's and in 60's low and mid-fi. Fast forward to 70's gear and all you really need is an MM or MI type cartridge for your turntable - if you don't already have an intact one. The double PHONO inputs mean you can plug a couple turntables to the receiver and A/B between them with the function switch.

Best consult the turntable forum for recommendations on a suitable cart. Just state the budget and turntable and you'll be over your head in replies. This is really not a brand specific issue.
 
Either of your phono inputs will work just fine with a moving (aka induced) magnet cartridge, commonly referred to as an MM cartridge. That's what they are there for. You would only need a step-up transformer if you mount a moving coil (MC) cartridge on your turntable...and even then, only for low-output moving coil cartridges. There are high-output moving coil cartridges as well, and these can often be used with "regular" phono inputs.

On that note, I'm not clear from your post whether your PL-50 has a cartridge (and stylus) or not? If so, do you believe it to be the original cartridge? While sometimes the original cartridge is with a "vintage" turntable, it may well be a replacement model. Are there any identifying marks on the cartridge? And if it is indeed the original cartridge, you might want to give some thought to replacing its stylus (once you determine that the cartridge itself is in good working order...it is likely to have had quite a bit of wear.
 
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Your PL-50 is a nice older table. You might want to think about replacing the oil in the spindle bearing well, and take a good look at the thrust bearing, upon which the spindle rests and rotates. These can be easily replaced if worn. New oil and a new bearing, if needed, assure quietest possible operation. Also, you can download a free RPM app for your smartphone to check speed. These apps are not the last word in accuracy, but most are good enough for general use. If you decide to replace the belt, finding a replacement with the same thickness as the original is critical to the table's ability to run at the proper speed.

Another easy maintenance item is oiling the motor. A few drops of a light oil (sewing machine oil or similar...make sure no parafin, no detergent, no additives) should be added at the motor lubrication hole, next to the belt capstan.

And of course, if you have not done so, assure that the tracking force is correct and that the cartridge is properly aligned. See the User Manual for instructions; it is available at no cost at vinylengine.com.
 
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If your cartridge really is a PC-35, and you are sure the cartridge is in good working order (both channels working, with equal output), and you like the sound of it, a replacement stylus is pretty cheap:

https://www.turntableneedles.com/PN...neer-PC-35-etc--our-Needle-628-D7_p_1241.html

This seller is quite reliable.

The replacement stylus is is conical, like the original. It tracks pretty heavy (2-3 grams, probably best at 2.5 to 3.0), and will not offer quite as much detail as a finer cut stylus (such as an elliptical), but I, for one, like the sound of the PC-35.
 
Thank you both! Incredibly helpful. I double-checked this evening. The cart is a PC-35. And the gentleman who sold it to me also gave me two styli that he bought ages ago. I'm excited to report that I finally got the opportunity to throw a record on and it's playing and appears to be 100% functional. Sounds lovely to my ears too. Both channels singing nicely. Though, I will replace the stylus with the extra he gave me that is labeled "new" and see if there's a difference. I'm also going to buy one of those off the link you provided, Spark1. The current stylus sounds good to me, but I'm pretty easy to please so who the heck knows what a new one will do. He gave me the original manual too. So I'll dial in the tracking force and alignment.

Spark1, thanks a million for the other tips on giving it a tuneup. I have ordered some supplies, and if you don't mind, I might reply back here if I have any questions.

I can't thank you guys enough. Very helpful. I'm having a blast. We didn't have much when I was a kid, but my parents had records, a Sansui SIX, and a Miracord 45 and this is really taking me back!
 
Glad to hear it. The Six is a well-built receiver...but I am partial to Sansui gear.

Here is a link to an aftermarket thrust bearing, if yours is failing (a common problem, given the age of these tables).

https://www.patsaudioparts.com/single-post/2017/10/15/Pioneer-PL-50-Thrust-Bearing

I've bought some parts from him over the past several years (I have a "hobby" business restoring and repairing older turntables).

You are lucky to have a "new old stock" stylus assembly for the PC-35. While the suspension can "collapse" with age, they are usually good to go. Pop it on and see if it sounds any different (after calibrating and then setting tracking force, and getting the stylus aligned, and making sure the table is level).

The PL-50 has a good, reliable motor. It's weakness is an overly complicated, and somewhat trouble prone, auto-return mechanism. Also, the anti-skate mechanism is fragile. Very attractive table. Good luck with it..
 
Thanks, spark. Is there anything to be done to protect or maintain the auto-return mechanism? Or do I just enjoy it for as long as it lasts and try to fix once it breaks?
 
In my experience, the auto function.works itself out of adjustment, or misbehaves due to gummed up lubricants. You can clean out the old lubricants from the mechanisms and replace it to help avoid future problems. I've not seen a PL50 with aito return problems that could not be corrected (altho I'm sure it happens).
 
spark1 said:
Your PL-50 is a nice older table. You might want to think about replacing the oil in the spindle bearing well, and take a good look at the thrust bearing, upon which the spindle rests and rotates. These can be easily replaced if worn. New oil and a new bearing, if needed, assure quietest possible operation. Also, you can download a free RPM app for your smartphone to check speed. These apps are not the last word in accuracy, but most are good enough for general use. If you decide to replace the belt, finding a replacement with the same thickness as the original is critical to the table's ability to run at the proper speed.

Another easy maintenance item is oiling the motor. A few drops of a light oil (sewing machine oil or similar...make sure no parafin, no detergent, no additives) should be added at the motor lubrication hole, next to the belt capstan.

And of course, if you have not done so, assure that the tracking force is correct and that the cartridge is properly aligned. See the User Manual for instructions; it is available at no cost at vinylengine.com.
Click to expand...

Spark, the shipments have been rolling into my house and I've printed off the service manual. The new stylus from the site ou recommended helped quiet down some sibilance so I think the stylus was probably ready for a change. I have the new thrust bearing ready to install and the sewing machine oil for the motor, so I'll tackle those next. Appreciate the help.

I do need to solve (1) the auto-return isn't working and (2) sometimes when I shift the lever to OFF, the tone arm returns but the platter doesn't stop spinning. Last night, switched the function lever to off, the arm returned, and it spun for several minutes (with the overhead index stand still illuminated). Eventually it shut off. Service manual says this means the microswitch isn't functioning correctly. It instructs me to repeat the auto-return cycle several times and adjust the microswitch spring so that it performs on/off action correctly. I'll pop it open this week and see what I can do. Any lubricant that you recommend for the workings of the auto return mechanism?
 
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