Theory

First, some interesting reading about crystal cartridges theory.

The first cartridge used in the rebuilding lessons will be the one shown at the end of the theory document. Read it all, there will be an exam next week….-hehe

Complete document (800K, PDF)

Dismantling

Now here’s a list of what you’ll need to rebuild a cartridge:

• Crazy glue
• A latex glove
• Silicone “rubber” bands and large rubber bands (different thickness(es))
• Brass rivets to fit
• Crystal or Piezo element (the 3 rd class will be divided in two parts)
• A drill with a 7/32″ drill bit
• Small length of multi-strand wire
• Solder
• Low power (25W) soldering pencil type -no gun please-
• Small 1″ metal spring clamp (found at dollar store at 6/1$)
• Patience

Remember: Crystal AND ceramic elements suffer from excessive heat. The key is to work fast using a low power soldering pencil. A Weller gun will instantly kill the element.

Now the fun begins.

First you have to dismantle the phono cartridge. Easy task, all is needed is drilling the rivets off using a 7/32″ drill bit.

I like to use my small two speed battery drill or the small press drill (actually a special press drill made for a dremel tool).

Drill off the rivets, all three of them. Be careful with the one on the back as most often than not you wont’ be able to pull it out until you part the cartridge in two. Cut the back rivet flush inside the cartridge then remove the remaining from the outer shell.

Cartridge seen from back view (top). Always drill rivets from the top of the cartridge, that way, if the drill bit slips, the damage (scratches) won’t be apparent once the cartridge is mounted in the tone arm. Not that it really matters though.

Keep the ground lug and discard the back rivet.

The innards. Keep everything but the rubbers and dampers. Clean the stylus cradle from its “suspension”. Also discard the triangular (torque multiplier) piece holding the old crystal.

Making Dampers

This is what should be on your bench once you are done cleaning the cartridge’s innards.

I like to use one of those cheap padded table mat taped to the bench to keep parts from rolling out of sight. I buy them at the dollar store, 2 for a dollar. They are medium density “foam” mats. Here’s what you need now. (see parts list in – Class 2)

I’m sure you wonder what the latex glove is for by now. It makes a perfect cradle damper/suspension. Cut to size, 5 wraps (or 7 in some cases) around the stylus cradle at front and rear.

Here’s how to proceed to cut the glove. Use a metal ruler and a full size blade from an Olfa cutter (watch those fingers). Work on a perfectly plane area (I use an aluminum panel just for that, I guess a square piece of tempered glass could also be a good option). I also found lately a cutter similar to a pizza cutter, for paper and fabric. Sold in dollar store in the scrapbooking section. Works incredibly well!

Cut to size (see picture). You’ll need two.

Installing Dampers

In the previous lesson, we had to cut two length cut to fit from the latex glove. You can also use the new silicone “rubber” bands available at stationary or dollar stores. Only drawback is it has to be the exact thickness:

Too thick, the low frequencies will suffer as the cradle will be too thight inside the shell AND the records will suffer from the poor compliance, resulting in rapid record wear.

Too thin and the lack of proper compliance, the cradle will be fee to move all around, the high frequencies will suffer, Needle talk, high surface noise and lots of distortion will results.

In the following example, I use strips of latex glove as the damper on the front of the stylus cradle and the silicone at the back only to show how to glue both. Try not to use rubber bands as they dry pretty fast. The latex will last many years although the silicone is best for longevity, it is not the best material as far as resilience is concerned though.

Remember those magic numbers using latex glove: 5 and 7. All the cartridges will use either one of those “turns”. The Astatic L70 series uses 5 and this cartridge (Shure) uses 7 on front and 5 at the back.

To fix the latex on the stylus cradle, put a tiny drop of super glue on the shaft in the recessed area then put the end of the latex strip. Try not to start from the top of the cradle but the side. It will glue instantly (so will your fingers if you aren’t careful…) Now wind 7 turns without stretching the latex. You have to slightly pull to make it taut but not stretched. The trick is in the multiple layers of “damping” and the correct total thickness that will make the cartridge sounds great on bass notes without distorting. You need enough “give” for good bass notes but good damping for loud passage, otherwise the needle will chatter in the groove on loud music passage and damage the records instantly (I’ve rebuilt many cartridges from someone else (another “professional rebuilder”) and the damping material used was a thin foam that gave absolutely no damping. The cartridge sure sounded loud, but extremely distorted, not good). End the last turn exactly where you started. Put a tiny drop of glue, then stretch a bit before letting the latex touch the glue. Cut the excess as close as possible.

What it should look like when finished.

See if the cradle still fit in the cartridge. Both halves should clamp together without putting pressure on the new damper but not have the cradle be loose inside the cartridge. If it’s too tight, you will lose bass, too loose, you will damage records. Insert the thumbscrew and wiggle the cradle while keeping both halves together. You’ll know right away if it’s too loose or too tight.

Do the same to the back recessed area. Or you can use the silicone band like this:

Put a tiny drop of super glue on the ends then clamp together for two minutes. Cut the excess as close to the body as possible. The rear damper is as important as the front one. Be sure the cartridge doesn’t put too much pressure when re-assembling the halves. You may have to readjust at the end. You’ll need a little practice.

In the next lesson, how to fix the crystal to the stylus cradle. Daz gonna be fun !

Cartridge Types

Ok…What makes a cartridge sound so different when they all look alike ?

Well…Not all the same inside. The cartridge I use for this lesson uses a torque multiplier. Using a large crystal and some clever piece of mecahnic engineering allows the use of a smaller and lighter stylus (lighter in a total sense of weight needed for proper output). Compliance is also a bit better on the lighter cartridges.

The ubiquitous Astatic L70 series uses a heavy needle cradle. The frequency response suffers, so does the compliance of the stylus assembly. The better the compliance, the softer the catridge is to the record. The higher the frequency response also, but the lower the output. Hence the use of much larger crystals in cartridges like the one used here, the LQ series (P30 is also similar).

The L24, although similar in shape and size, uses a large crystal AND a lighter assembly. High output and wider frequency response. But if you look at all other models, many cut in the 3-4Khz region…Boy, that is quite low in the highs. Once properly restored, the same cartridge will go beyons 6Khz. A definite improvement. Far from the frequency response of a new ceramic type cartridge, but sometimes it is of no concern since the amplifier and speaker combination will not offer any better. Plus, you would need to preamplify the cartridge and cobble something to remove weight from the tone-arm. Ceramic cartridges are designed for a 3-10g weight as opposed to the older types working under “pressure” at 28g+…Ouch !

I posted a simple preamplifier using a single transistor. No modification to the actual circuitry is needed. Look in the phono section for details.

So the rule of thumb for better restoration is to try to get the stylus the most compliant for a better bass response, be gentler to records and provide a higher output when used with the right crystals.

Best buy would be those stereo Ronette sold by a well known seller on eBay, Ed Saunders. I am not making an ad for the guy, merrely pointing out that he has donor cartridges for a decent price. In fact, his prices took a plunge lately, maybe because he doesn’t sell that many. The ones that look promising are silver/chromed Ronette, stereo and go for less than 20$ a piece. Being stereo, that leaves you with 2 crystals at 10$ a pop. Not bad, considering they are 2V elements, which if used properly, will give out almost 3V simply because there will be a better mechanical contact between the stylus cradle and the crystal element…Don’t tell him that…;o)

Adding the Crystal Element

Ok, now’s the beef…

Mounting the crystal ot the stylus/needle cradle.

I will explain as much as possible the whys and hows so that your first restoration will be a success…Now if you really messup, don’t call me…[grin]

Ok, in a previous lesson, we added the dampers to the cradle. Now we need a way to affix the crystal to the cradle and re-create some sort of torque multiplier. Not that it is really necessary, but it will help the frequency response (using the right material), protect the crystal if the cradle is shifted too far from side to side (like bumping the needle on the side of the platter…NOT good) and also offer a slightly better compliance.

What you need to complete the assembly is a small plastic piece of the type use in CD jewel case. I use side cutters to cut the proper piece. If you look at the pictures, I used some small pieces or metal tabs to mechanically link the cradle to the “torque multiplier” and the latter to the crystal element. You can use the same plastic from the jewl case. I just happen to like these little pieces as they are the right size and are found in my donor cartridges. They don’t rellay add to the weight so I kill two birds with one stone…

You see on the right the needle cradle, center the plastic piece cut to lenght and far left, the crystal element from a Ronette cartridge (500 something). The idea is to have the total lenght of the assembly to fit inside the cartridge like this:

Assemble using cyanoacrylate glue, the plastic extension to the needle cradle using two little reinforcement. If the plastic extension is too thing to tightly fit between the small reinforcement, simply use a tiny piece of card stock. Wedge the whole thing and add a drop of glue. Wait 5 minutes then proceed the same to assemble the crystal. Be careful, the crystal is fragile. Make sure you do not put excessive pressure to the crystal while gluing the assembly. This whole thing may lack points aesthetically, but it works great.

Do NOT add a piece that will secure all the parts together with a single long reinforcement. We want to isolate the cradle from the crystal using a compliant extension that doubles as a torque multiplier so use small pieces to secure both parts to the cradle. Do not use metal or stiffer plastic. I’ve used a lot of material, and this plastic works best. Softer and you will loose the highs, harder and the record’s noise will be amplified by 10 ! There is a point of diminishing return in trying to extract the most from the cartridge.

Shims should always be made of card stock. Again, too soft a material and the damping effect will adversely affect the frequency response. Plus, the card stock take pretty well the glue, a plus…Boy, I’m killing a lot of birds with one stone tonite…

Let the whole assembly dry for another 5 minutes. That is the only part where I suggest using cyanoacryalte glue (super glue). Use a rubber glue (or contact cement) when rubber has to be glued. Super glue hardens and dries rubber, but not silicone.

Next lesson, the final assembly.

NOTE: I usually rivet the metal pieces to the stylus cradle and the plastic piece (where the crystal attaches), but to make things easy I just glued them for this lesson).

You can also use two length of plastic and sandwich the crystal between them. Make them one single piece long enough to replace both the little metal tabs and the center piece. Since you’ll be using plastic for both pieces (one on top and second on bottom) The compliance should still be OK.

Re-Assembling

Ok, final lesson…

Now we need to fit the new assembly into the cartridge. Easy task…somewhat…

First, glue some thick rubber band where the end of the crystal will sit. We need soft rubber, very compliant. This will protect the crystal should too much torque be applied to the cradle for any reason. That is why I said previously NOT to use epoxy to secure the crystal to the cartridge body. First it will make the cartridge microphonic, any mechanical vibration to the cartridge body will be passed directly to the crystal, NOT good and if the needle is bumped on the side of the platter or similar excessive lateral displacement, chances to damage the crystal are minimized. epoxy…..yeeeech…..or ACK like Chuck would say…

A short length of multi strand wire is also needed to complete the crystal wiring to the back connector…

First mount the final assembly to the lower half shell of the cartridge and use the right rubber band (or rubber like material that will not become dust with time or lose it’s compliance too fast) to level the assembly. When the assembly is resting inside the lower half of the shell, it must be level. If it’s in an angle, it will create stress to the crystal. The rest of the “support” for the crystal will be added to the top half of the shell until a slight pressure is put to the rear of the crystal when both halves are put together:

Sliiiiight pressure. Idea is to secure the crystal, not jam it or put any stress on it. Too light a pressure, lower output and distortion. Too heavy and bye-bye crystal…That is why using a very compliant piece of rubber is best here for obvious reasons…

Next soldering the crystal to the back connector.

A low wattage soldering iron (25 watts) is best here as we must work fast. Crystals don’t like heat. The crystals I am using have tiny tabs on the back. I use a clean iron and apply first solder to the tab, quickly (half a second) then wait a minute, then cut one strand from the multi-strands wire, put solder on both ends of the tiny wire, put one end on the crystal’s tab and apply heat, quickly. I do both side, waiting one minute between sides.

Then I fit the final assembly in the cartridge. The dampers must fit right in the recessed are at both ends of the cradle. Actually, the tip of the cradle should barely protrude from the front end of the cartridge by maybe 1/32nd”.

Add a small drop of rubber glue (contact cement) to the far rear rubber and let the glue dry. Next, put back the rear connector, slip in the (cleaned) hollow connector solder, then apply heat at the back of the connector (rear of the cartridge) then punch the solder inside the hollow connector while applying the heat. The whole process should take maybe3-4 seconds per connector. Wait at least one minute between connectors. By applying heat to the outside tip of the connector (where you see the tiny wires coming out) keeps the heat away from the crystal.

Once both connectors are done, snip the excess wire then use 400 sandpaper to clean the contact from excess solder or oxidation.

Riveting the halves together is the last step. But before you do, you must try the cartridge. Simply use masking tape to keep the halves together (this should need very slight pressure to keep both halves together, otherwise it would mean you either have too much rubber on the rear, holding the crystal, or the dampers on the cradle are too thick to fit in the recessed “valleys” inside the cartridge. Too stiff will mean less compliance and less bass, higher distortion and greater chances to wear your records faster.)

Simply hold the cartridge in your hand, keeping it parallel to a test records (test record = not valuable record) and let the cartridge play using it’s own weight. I hold the cartridge from the read connectors/pins. If I am satisfied with the first crude test (listen for bass/highs and distortion) I then finish the assembly, using hollow brass rivets.

Here is a simple way to set rivets on the cheap. Use a large nail punch (bought mine in a dollar store, 3 sizes for a dollar) Then create a flange to the rivet, using a small hammer and working with light raps….

Then use a pair of pliers (you can file the ribs off the pliers to make if smooth) and squeeze the rivets flat. This is not the way I do mine, but I did these in the picture just for you (man am I nice or what?) Results are quite acceptable. I use the nail punch to create the flange, then finish with a tiny brass hammer or squeeze the rivets in a small vise. Does a perfect job everytime.

Do the same with the back longer rivets….

Oh, almost forgot, make sure you clear the rear hole before you solder the wires to the back connector. Just push’em away from the hole then solder…

Rivets can be found from a number of suppliers. I buy them locally. If you have problems finding them, let me know.

For better aesthetic, the factory made flange should be showing from the bottom of the cartridge, the side you see when the cartridge is installed.

Next lesson, differences between steel needles, Osmium and Sapphire styli. How they sound, when to use them etc. Also a recording of this cartridge with different styli and needles. We will also see different cartridges like
the ubiquitous Astatic L70 (L72)…

Hints

If the cartridge sounds distorted and everything looks fine, make sure the cradle doesn’t touch the body. In this example, you can clearly see the gap between the stylus cradle and the cartridge body in the opening. The cradle must rest centered in the opening.

In the lesson, I suggest readily available materials that are cheap to the hobbyists. Of course, I do not always use these materials and select the right dampers (compliance) for every job (butyl is great stuff).

You will have to experiment by yourself to find better dampers, but if you follow the lessons carefully, you will have a much better sounding cartridge than following how-to using cheap rubber bands and epoxy glue to affix the crystal to the cartridge body.

A few no-no’s:

Never use rubber bands. They dry with time and you’ll have to re-do the job in a year or two.

Never use epoxy glue to fix the crystal to the phono cartridge body. The crystal needs “give” and damping (compliance) to isolate the crystal element from the cartridge body to minimize microphonics and noise. It will also minimize possible damage to the crystal should the stylus be bumped on the platter or excessive force applied sideways to the stylus.

Never use silicone glue as dampers then squeeze the cartridges halves together to create a damper. There is no sure way, doing so, of centering the cradle in the phono shell. You may find yourself with a distorting cartridge because the cradle touches the body either on the front or rear. Sure, you may get lucky, but it isn’t much effort to do it right the first time.

Sound Clips

Here are four 15 seconds audio clips (22Khz/8 bits mono sampling) recorded acoustically. Which means I used a microphone a few inches to my test amp using a 3 inch speaker. So what you hear is essentially what you’ll hear from the phono, as opposed to having the sampling done thru a preamp stage. Note: the bass will be much better in a real phono, my test amp using a 3 inch speaker…

Listen carefully to the bass, highs, noise and overall volume. Also note the voice content where the cartridge should start rolling off in an original (3-4Khz) while the restored one goes well beyond that (listen to the clarinet).

Note, each clip is a WAV file of about 380Kb.

steel_needle.wav

Second clip using a Nylon damped “universal” stylus (2 mils). The Nylon is supposed to damp noise from the records, judge by yourself…

nylon_damped_universal_stylus.wav

Next using an Osmium stylus:

osmium_stylus.wav

Last, using the wrong stylus. Either too long, using the wrong “shape” (curve shaped when a straight one is needed etc…)

wrong_stylus.wav

You will note the higher distortion from the wrong stylus. I used a bent shank stylus which is correct for the type of cartridge, but the part that goes into the cartridge is way too long. The mechanical vibration get amplified and creates “ringing” well before reaching the crystal. Easy solution is to simply cut the excess. No biggie but ya have to know it.

The nylon damped stylus does a good work of damping the noise, along with the higher frequencies above human voice….

The steel needle has oompf…But the noise is unbearable. A quick solution would be to use a tiny piece of stiff rubber and slip it over the needle, close to the cartridge body, without it actually touching the cartridge’s body. But changing the needle after a play or two is a real pain in the neck…

The Osmium offers a more laid back and much lower output compared to the steel needle, but it also gives a more uniform frequency response.

All in all, it depends on the type of records you are listening. At least now you know what they sound like. Oh, almost forgot. A Sapphire stylus will sound like an Osmium but with much more volume and slightly more noise. I prefer Osmium then Sapphire. Osmium sounds a bit better because it has more “give”, hence damping excess noise from the record.