Potting and mods to phono cartridges

[norman]

I have decided to upgrade my Audio Technica AT95 cartridge. I have ordered an upgrade stylus, and I have a possibly stupid idea that potting the internals with wax or epoxy will add a bit of sonic magic maybe by stopping coil vibrations. There is a hole closed with a screw on top that allows access to the cartrige insides. Has anyone done this and if so, do you have any guidance? My final step will be to make a wood body. Any ideas would be appreciated.

Edited September 23, 2019 by norman

[Guest Muon N']

Some discussion here on wood bodies and maybe more.

 

There is a seller on that auction site that sells wood bodies for these.

[Wimbo]

@norman

This is my AT95VL. Got the body from Germany and cut back the Stylus so there was only the plug left. No potting unless you want to throw it away later.

Sound is a lot less busier then before. Pretty sure the body and stylus body induced noise. It now has a smooth open sound with more bass then I heard before. Nail clippers were used to cut the stylus body away. Very happy with the result and I would be even more so if it was the only cartridge I had.

Edited September 22, 2019 by Wimbo

[audiofeline]

I've been curious about potting carts.  I've looked at many threads on audio forums, and have read of the reported audio improvements.  It also has a risk factor - it can damage the delicate cart insides, so I wouldn't do it to a MC cart, or a high-end MM (unless you are willing to take the risk).  Despite having read lots of reports of how to do it, I've never seen a detailed description or pics of it actually being done. 

 

A while ago I bought two AT95 carts.  It's my intention to try potting one, so I can make a direct comparison to the unpotted cart (I have a couple of spare and identical headshells to do this comparison).  I thought if I destroy one cart, at worst I would have a spare stylus for the undamaged one! 

Since buying these carts, I've also become aware of the esteem the AT3600L cart has.  Similar to the AT95's design, many feel the AT3600L favourably competes against carts selling for hundreds of dollars.  And this humble cart+stylus can be bought for about $17 on eBay (cheaper than the replacement styli for it without cart!).  It's cheap because it's an OEM model - churned out in the 100's of thousands, so it has an economy of scale.  So I've bought a couple of these to practice with before trying to pot the AT95.  And the AT3600L is a great second cartridge to put on a spare headshell to have on hand to play damaged/dirty op shop records that you don't want to risk your good stylus on.  You can't lose at the price.

 

Beeswax has been suggested to use on other forums for cart potting.  A small bar can be bought in Bunnings for about $6, it's with the furniture finish polish, etc. in the paint section.  Candle-making tutorials on the web have info on melting and using it, double-boiling appears to be the safest. 

[Edit - I wonder if pieces could be put into a syringe, and melted with the syringe in the boiling water?]

 

I would think that some sort of funnel would be needed to pour the wax into the cart's screw hole.  I've thought a block of 5mm plastic with a hole drilled with a countersink bit, that could be taped in position on the cart prior to pouring might work OK.  Maybe with a short straw attached that will insert into the screw hole.  Any slight spillage could be cleared off the outside of the cart later.  And I would test pouring wax through the funnel into a simulated cart before doing an actual potting. 

[Edit - using a syringe would be much better than having a funnel - disregard this paragraph!]

 

I will admit that I haven't tried this yet - I'm still getting my TT's restored, so this is a lower priority.  And I was hoping to find some more detailed how-to info before I started.  One thing I'm not sure about is when the wax is poured in the top screw-hole - will there still be space for the stylus shaft to be inserted? 

 

Please share any info you might find, and report how your experiments work!

 

 

Edited September 30, 2019 by audiofeline

[nkoulban]

I have now added a JICO hyper-elliptical stylus, cut away the excess plastic and epoxied the AT95 body into another wood body.  This combo sounds detailed and organic at the same time and has the lowest surface noise of any of my carts.  I have also loaded it with resistors to smooth out the sound a bit more.  A brilliant cart that I love to bits.

[audiofeline]

Some descriptions on how to pot an AT95 here: https://www.audiocircle.com/index.php?topic=85626.0

It appears that only the back part is potted for a significant improvement.

[nkoulban]

This a needle drop I did with this wooden bodied AT95 running the JICO hyper-elliptical stylus.

 

 

[Wimbo]

37 minutes ago, nkoulban said:

This a needle drop I did with this wooden bodied AT95 running the JICO hyper-elliptical stylus.

 

 

Australia beat the Windies 5-1 in the summer tests and I was riding quadricycles up around Maitland on the railways. Driving home back to Sydney on Friday night (in my Beetle with Board Racks) to play pool and get pissed and love women at the Railway Hotel in Hornsby. Wish you Were Here had just been released as well. Great single.

Sounds clean mate.

Edited September 24, 2019 by Wimbo

[norman]

Great needle drops, impressed.

 

I have read some more about potting the AT95. It seems you remove the screw located on the top of the body, and the black plastic top mount then pulls off. You can then fill the metal body's void through the hole in the metal body itself where the screw fitted.

 

For potting: wax or lip protector; white PVA glue, seems it shrinks on drying, and you then top it up; 30 minute set 2 pack glue; 5 minute set Araldite. I have read it's best to try to keep the potting substance at the rear of the cartridge, needing a tilt backwards while it sets.This suggests you need to assemble the stuff you might need to do this around you before you start the 2 pack mix (I'm going to use 5 minute clear Araldite). EDIT - the filling hole is too small in my opinion for epoxy, so I settled for lip balm wax...

 

You may either then pop the plastic top back on, and glue it for stability, or add a wooden/alloy/ceramic body.

 

The final step is then to fit a stylus and trim off the surplus plastic,leaving only a nude cantilever and enough mount so it stays put.

 

My new stylus is at the Post Office, so I will try my mod tonight if I get the time.

 

 

Edited October 9, 2019 by norman

[audiofeline]

Another description of potting an AT95, post #9 (and there are more later)...

https://forums.stevehoffman.tv/threads/cart-modifiers-budget-hunters-clearaudio-at.683049/

 

Some reflections.  I've wondered about using PVA for potting.  I'd be concerned if it shrinks around the fine internal wires and the shrinkage disconnects them.   The lip protector is popular because it has such a low melting point, which I also think is a disadvantage as there is the potential for it to melt in our high Australian summer heatwaves, and I'd prefer not to run that risk (even though it is admittedly a low risk).  I like the idea of beeswax, as the screwhole can be easily tapped to become useable again.  It may be difficult to keep hot enough to be molten to insert easily (would it solidify in a syringe?). 

 

I'd tend not to use the 5 minute Araldite and use the longer-setting version.  The 5min starts to get viscous quickly and may not run very well into the internal crevices.  Also cover the cart with clear tape (not invisible tape) so any spillages are easily cleaned and seams are covered to prevent any leakage. 

 

 

Edited September 25, 2019 by audiofeline

[norman]

Great ideas. I will give the wax a try instead. My new stylus awaits too having collected it. I am moving in small steps - the new one is the red elliptical AT95EX with smaller elliptical dimensions than the standard green, and it sounds far better than the standard green unit without doing any mods.

 

I will use sticky tape on the seams to make sure it doesn't leak out. I have a couple of small syringes that I have collected for doing oiling on camera repairs, and I wonder if keeping it hot / warm in hot water might help in terms of getting it into the cartridge hole, which is about a 3mm x 4mm oval.

 

I shone a light from under the cartridge stylus location into the body cavity to see if there are any possible leaks, but it seems OK in terms of being sealed to stop wax running out and ruining it.

 

Once done, I will let it solidify, clean it up so it's not not waxy on the outside and then 5 minute Araldite the top body back on. The final bit as I understand is to mount the stylus and then trim it while it is in place.

 

A question - Is a Technics headshell preferable to say a traditional SME style headshell after the mod, or vice-versa?

 

Cheers to all who are interested and helping in this dodgy endeavour..... Norm, Canberra

Edited September 25, 2019 by norman

[audiofeline]

Headshells are another can of worms.  I would steer clear of the thin cheap pressed aluminium headshells that come with record-player turntables, they don't have enough rigidity.  I think it's important to have a rigid headshell, so the thick Al in the Technics, Ortofon sh4, etc. are a step-up from the cheap+nasty ones. 

 

But the weight a headshell contributes is also important.  If your cart's need a heavier tonearm, a heavier headshell can add extra mass.  If you need a lighter headshell, magnesium is strong and light and sonically good.  If your turntable/arm/cart is at the higher end (no offense, better than the AT95), the exotic and expensive headshells can make an improvement that won't show on lower-end systems. 

 

BTW, I'm looking forward to hearing how your potting goes, and a report of the acoustic changes.  Pics would be nice if you can manage it.   :  -)

[aussievintage]

4 hours ago, norman said:

Is a Technics headshell preferable to say a traditional SME style headshell after the mod, or vice-versa?

 

Lots of room for experimentation there too.  I carved a nice wooden one.  Some of the nice solid DJ ones that you can get cheap actually work well too.

[Wimbo]

9 hours ago, aussievintage said:

Lots of room for experimentation there too.  I carved a nice wooden one.  Some of the nice solid DJ ones that you can get cheap actually work well too.

And the better Jelco's.

[norman]

POTTING WITH WAX

 

Tonight I had time to undertake the potting, using lip protector wax.  Here goes:

 

Take off the stylus. Having removed the cartridge from the headshell, unscrew the Phillips head screw on the top of the black plastic upper body and pull off the black plastic body top unit. Set these aside. Boil the kettle for water to heat up the syringe to be used. Pull up the plunger to get some air inside, and put the syringe in a clean mug with the boiling water to heat up. I used a syringe with a small - about 1mm - exit hole. The air will heat up and bubble out, but don't worry, no water will get in, and if it does it is easily expelled.

 

Get a big stainless cooking spoon, set it on the gas stove over a very low (important!) heat. Add about 1 to 1.5 cm of new Nivea lip wax (blue tube, no perfume) and pop it onto the spoon. It will melt quickly, so turn off the heat when about 50% of the solid wax remains and it will continue to melt. (Note that I didn't seal any of the cartridge metal body seams with sticky tape and as it turned out there was no need to do this.)

 

Now work quickly - make sure the cartridge is facing with the small screw hole up, grab the syringe and expel the air and any tiny amount of water that might have seeped in. Suck up the melted wax, and then immediately while still liquid squirt the molten wax into the hole, right to the top. Mine didn't take too much to fill. It overflowed a little bit, but this is easy to clean up. The wax solidified within a few seconds in both the cartridge and the syringe.

Clean off the wax properly - I used a tiny wipe of a solvent to make sure the metal body was clean for the next step.

 

Mix up a really small amount of 2 pack glue - I used Araldite 5 minute clear. With a match or toothpick smear some clue inside the black cartridge boy top, and put this onto the cartridge. It will line up nicely with the screw hole. Screw the fixing screw in reasonably firmly, and the top will make a snug fit. I didn't need to wipe up any glue that squeezed out. I know I filled the cartridge up with wax as it squeezed out around the top body fixing screw while I was doing it up. Wipe off the excess that squeezes out, and then put it aside to set.

 

Remount it properly into a headshell, and you are ready for the final lap which I am yet to do - I want to do a bit more research before I trim off the Stylus.

 

You can see the white wax in the screw hole in the pictures that follow.

 

In my next post I will show the mounted cartridge, and when I get the nerve the stylus excess plastic trim process.

 

I have mounted and played the potted and glued unit, and it sounds really, really good.

 

 

 

 

 

 

 

I have only listened to a couple of tracks so far. Remember I am using just the AT95EX stylus (the red one) with a smaller elliptical profile, nothing too fancy.

 

On My 1980s Melissa Etheridge eponymous album, you can hear the room sound - slight reverb I have never heard before, smooth shimmering cymbal highs, and it is really really clean but not cold. The bass has tightened up - I am a bass player and the bass guitar notes and popping sounded, well, real and musical. I think the background noise has gone down too. I am really impressed.

 

Gravity by John Mayer was, well, mind blowing. New details, sold bass, all sorts of details I haven't heard before.

 

I wonder what cutting away the stylus shroud will do.

 

Remember this is a <$60 cartridge with a $45 replacement stylus - I believe it beats easily my Ortofon 2M Blue ($359) already even with just the AT red elliptical stylus. I will do the stylus mod, and then save my pennies for a much better stylus upgrade. I can't wait. EDIT - It doesn't beat the Blue (as my new one has now just about run in), but it runs it pretty darn close.

 

More adventures to follow.

 

PS I kept the wax-filled syringe as I might do this mod to another more upscale Audio Technica cheapy MM at some point.

 

Cheers, Norm

Edited October 9, 2019 by norman

[norman]

So, now I have done some proper listening, I am definitely going to purchase, fit and cut away a hyper elliptical stylus. The potted cartridge is that good.

 

I have two local options from Soundring for this - a Jico for $155 or a Soundring house brand for $129 for the same profile. Miranda HiFi says buy the Jico, but as I am doing this on a budget is there any reason to spend more for the same profile?

 

If anyone has advice on which to choose it would be nice.

 

I am also going to pot another for the SL-1210 Mk2 kit at our coast house, they really do sound fantastic. More photos of the potting process to come when I get home again as I will be more prepared and less nervous this time around.....

Edited September 28, 2019 by norman

[aussievintage]

Those are just hyperelliptical styluses.  You might consider a microline stylus.     I read that the stylus from a VM95ML will fit by cutting away some plastic which you intend to do anyway.  There's also the Vividline stylus from LPGear.

[audiofeline]

I've had a look at my (unmodified) AT95 and AT3600L.   The area where the stylus is inserted appears to be sealed from the rest of the interior, so I can see how fulling the interior with wax wouldn't affect the stylus insertion/removal. 

 

I also checked out the AT95 screw that goes in the top of the cart and provides the filling port.  For reference, it has a M2 thread, in case anyone needs to re-tap the thread after over-filling the cart.  The screw also appeared to have a loctite substance applied to it. 

 

 

[norman]

So can anyone tell me what the difference sonically may be between hyper elliptical and microline profiles? I have already upgraded the stylus to the EX version, so is the hyper elliptical a waste of money?

Edited September 29, 2019 by norman

[georgesgiralt]

Hello,

What would you think about Shea butter to fill the cart ? It is low temperature melting and very hard when cold. So may seal better ?

 

[norman]

15 hours ago, georgesgiralt said:

Hello,

What would you think about Shea butter to fill the cart ? It is low temperature melting and very hard when cold. So may seal better ?

 

I think it might be OK, assuming it's the cosmetic hand cream stuff. Be careful though of perfumy additives as any  aromatic compound might have enough chemistry happening to dissolve the insulating varnish coating on the coil wires. The lip balm I have used from Nivea (blue tube) works and is low cost and has only had positive effects....

Edited September 30, 2019 by norman

[audiofeline]

I'm not familiar with Shea butter, so I might be wrong with this.  A quick google indicated that it is a food derivative, so I would be concerned about it degrading over time (ie, "going-off").  Otherwise, I would imagine that it would work as well as lip balm.

[georgesgiralt]

Thanks for the reply, the Shea butter I have is an organic product "free from perfumes, chemicals and perfectly organic product"... So I bet it is pure 

As it is pure fat, I think it will oxidize with time and become a little rancid ? But I won't eat it so do not bother.

I've some cheap AT carts I'll try to feed with it and report back.

[norman]

Georges, as you will fill the body completely, and I assume will re-fit the top cover and screw, there is no ingress point for air so any oxidation will be fairly slow.

Edited September 30, 2019 by norman

[aussievintage]

28 minutes ago, georgesgiralt said:

Thanks for the reply, the Shea butter I have is an organic product "free from perfumes, chemicals and perfectly organic product"... So I bet it is pure 

As it is pure fat, I think it will oxidize with time and become a little rancid ? But I won't eat it so do not bother.

I've some cheap AT carts I'll try to feed with it and report back.

Have a look at what is in fat  https://www.britannica.com/topic/fat/Chemical-composition-of-fats     I would not be putting that into anything electrical, especially the acids.