[neobop]

There's an interesting thread going on over at VE. Thought I'd bring it to your attention.
http://www.vinylengine.com/phpBB2/viewtopic.php?t=24367

It started off, about the el cheapo AT-95E and has evolved into potting experiments and modifications. Most of the potting and mods are on the last 4 pages or so. It also involves the Clearaudio MMs. Seems that AT is the OEM for the Clearaudio MMs. A new stylus can be fitted to the Clearaudio carts  by using a slightly filed down plug from a modern AT stylus.
neo

[neobop]

I wound up buying a used Virtuoso with a busted cantilever, a 95E and a Jico bonded shibata stylus. The Clearaudio carts take the same plug as the 95. For those unfamiliar with the stylus assembly of an AT, at the cart end of the cantilever there are 2 small magnets and a little rubber donut. they go into and are held by a small block we call the plug. It is the plug, along with the magnets that are inserted into the body. When used on a Clearaudio body, the rest of the plastic around the plug has to be cut away.

Experiments are underway modifying the 95 for higher performance and I'm doing comparisons with the Virtuoso. The latest development is potting the body (inside) of the AT. It seems to make a dramatic difference. We're also making modifications to the plastic top - using top plates and damping the spaces inside. I'm also getting different styli to modify for these carts.

For anyone so inclined, it's really a lot of fun and inexpensive to get started. The 95 has a less aggressive sound than a 440. Subjectively, it seems to have more of a flat response. Some of the others have special loading requirements for flat response. The 95 has an admirable 400mH inductance. This is one of the lowest of any MM. The potential is great and the rewards can go beyond what you might expect.
neo

[Wayner]

Potting the interior is risky business as the coil wire is virtually smaller in diameter then the human hair. I will suggest using some 1000 centistroke liquid silicone to calm the coils down as this is how the Grado Longhorns are treated. You may get the same results with less risk of damage.

Have fun.

Wayner

[neobop]

Hi Wayner,
Only the back part of the body was potted, nothing got near the coils or the magnet area. I was concerned about the wires going to the output pins, but I used liquid type epoxy without a problem. Another member there has also been potting old ATs without problems.

The top piece of a 95 is held on with a small screw that screws into a receptacle on the back/top of the metal body. I put epoxy in the receptacle and gently pushed it down. It didn't take much, I think only that shaft and some on the bottom got potted. The shaft looks like it goes below any output wires. The modifications to the cart made a hugh difference in performance.
neo

[Letitroll98]

Potting the interior is risky business as the coil wire is virtually smaller in diameter then the human hair. I will suggest using some 1000 centistroke liquid silicone to calm the coils down as this is how the Grado Longhorns are treated. You may get the same results with less risk of damage.

Have fun.

Wayner

Quite right Wayne.  To my dismay I found this out the hard way on a fairly expensive Grado.

[neobop]

I wasn't really thinking about Grados when I posted this. I believe BaMorin over at VE has potted some successfully. I don't know much about it.

Denon 103s are often potted, apparently with great success. Soundsmith offers this as 1 of his mods for this cart. Body replacement and top plates are also used extensively. I have an old 103D, the high compliance version. It came with an old TT I bought. I haven't really used it - just tested it. The stylus is the orig and I don't have a stylus inspection microscope. Not exactly sure what to do with it. Maybe I'll just have it re-tipped and a new cantilever.

I thought maybe someone here might have some experience with potting or have a potted cart.
neo

[Wayner]

Neo,

I didn't mean to turn your thread, but I certainly like the potting idea. What potting will cure is microphonics within the coils, which I believe every cartridge suffers from. I have concerns that injecting potting material will break a coil winding, from the application. I wouldn't know how to go about doing it. The Grados can be accessed thru the metal sides of the cartridge body, exposing the coils. getting it in there, and keeping it there while the potting cures is another story. I'd rather drill a small hole on the top, as you suggested, but where to the plastic shavings go?

I have an old one that has a broken coil wire already, maybe I'll experiment on that one.

Wayner 

[neobop]

I think the major improvement comes from reducing vibrations and having a more rigid structure. Reducing vibrations should have a direct effect on the coils and the rest of the generator. It's the wiggles of the cantilever that actually cause the generator to produce electricity, regardless of generator type. If the generator housing isn't physically stable, then those cantilever wiggles will be interpreted by a vibrating generator. The physical vibrations of the body become part of the signal produced, and the music.

Potting an AT-95, at least the back part, is easy. The metal body looks like a P mount. There is a screw, around 1mm thread, that holds the plastic top on. That screw goes into a threaded receptacle in the top/rear of the body. It's about 6mm long or deep. I just mixed up some Locktite 5 min epoxy and used a dental tool to get it in there. I held the cart nose up cause I didn't want to get any near the hole where the magnets and plug goes in. There were a couple little empty spaces in the top that I filled in with mortite. I used an alum top plate made out of an old headshell. You could just glue the top back on after the epoxy has cured, 24hrs.

Pretty dramatic difference here. Another guy has been potting old AT-11 and a 14. He says the same. But this has been going on for yrs with MCs, I just never really checked it out before. Maybe I never had a cart that seemed like a good candidate. The DL103 crowd has thoroughly embraced mods for that one. Not all include potting though.

I was looking at my other ATs, I have a 440ML and a 15SS. There might be a screw under the model name on top, I don't know. It's a little scary thinking about doing this to more expensive carts, but I have been thinking about that 103D. I wonder if my 304.....I better chill.
neo