Help/suggestions, I want to modify a Pro-Ject 9c tonearm

[Mark W.]

I curious about the prospect of modifying a Pro-Ject 9c (carbon fiber tube aluminum headshell) to have a replaceable headshell like the mmt arm I had for a little while.

I have all the machine tools and years of the kinds of skills needed to actually do the work. (I made handmade custom knives including folders and automatics for 14 years)So that side of the effort is well covered.

What I need to know is a source of the little joint these tonearms use. Or is this something I would have to source from another tonearm? I can easily make my own headshell out of just about anything from Titanium to Pink Ivory wood (materials all ready sitting unused in my shop)So I can easily match the slight angle offset the Pro-ject headshell uses.

I would also take the time to upgrade the tone arm wires (maybe it is my understanding they are sourced from Cardas so a measurable upgrade might be hard to justify).

My purpose in doing this would be to add some cartridge flexibility to my beloved RM-5 table.

I'm currently using a not yet broke in Goldring Erocia H and would like to have the ability to run an Ortofon 2M Bronze and my Shure V15 Type III for certain LP's As well as just playing around.

 

[Art K.]

I think I'd leave that arm as the engineer who designed it intended. Perhaps buy another table for changing out cartridges on the fly. I like my cartridge with everything I play with it. If you're not feeling the same way perhaps you haven't arrived at the final destination for a cartridge. You have a nice rig, my advice is don't mess with it.

 

[Mark W.]

Art if I decide to go through with this I would source another arm to do the work to. I would not risk the one arm that came with the table. Which of course then might lead someone to suggest using a different arm that already has a removable headshell.

My answer to that is of all the insane modifications other guys do to TT's this is actually kind of minor. And would have some real advantage.

 

[Art K.]

I've never seen anyone modifying that table...besides changing the cartridge or mat. It's your table...good luck.

 

[Mr. Lin]

Mark, as I understand it, having a non-removable headshell is preferable in terms of sound reproduction quality. I'm not sure if it's resonance or something else, but if you notice, a lot of "high-end" turntables have a single piece tonearm (like all the Rega arms, for example). By the same token there's no finger lift. It's actually one of the things that attracted me to this table.

If you were going to go to all the trouble of designing a tonearm, why don't you just see what the likelihood of successfully installing a different tonearm would be?

 

[Mark W.]

Mark, as I understand it, having a non-removable headshell is preferable in terms of sound reproduction quality. I'm not sure if it's resonance or something else, but if you notice, a lot of "high-end" turntables have a single piece tonearm (like all the Rega arms, for example). By the same token there's no finger lift. It's actually one of the things that attracted me to this table.

If you were going to go to all the trouble of designing a tonearm, why don't you just see what the likelihood of successfully installing a different tonearm would be?

Yes but then other high end tonearms have the connector. This is all in the thinking about stage. As I said in my reply to Art if I decide to do this I will source a new or used 9c tonearm to make the modifications on. So that it ends up being a plug and play setup.

 

[Mr. Lin]

This is why they make turntables with multiple tonearms.

 

[Nat]

If what a tonearm did was simply hold the cartridge in place, your idea might not be a bad one. But arms behavior is complex -- there is all sorts of resonant behavior, not just the simple interaction of the arm mass and the compliance of the cartridge, but the bending and vibrating of every part of the arm -- this is why arms sound different. Taking an arm that was carefully designed to be one way and making it another way is a crapshoot. It might be good, it might be bad. But it would be astonishing (and egg all over the manufacturer's face) if it is better than, or even as good as, the original design.
Obviously its your money, and no one can tell you what to do with it, but the suggestion of buying a different, more adaptable arm makes more sense.
But I suspect that what you really want to do is use those machining skills, and the obvious answer is to build a whole new arm. There are a variety of suggestions out there, unipivots being the most common type, since the bearing issue is minimized, but the air bearing linear arms being also pretty popular.
Keep your current arm as your reference, and see if you can beat it.

 

[Mark W.]

I take from reading the responses no one has found the sentences that explain I would be doing this with a second 9c arm. As to competing with the manufactures design based on what other guys do to Turntables and the set ups I would venture this to be rather minimal.

Guys tear carts apart gluing the guts into home made wood and aluminum blocks. They change from one headshell to the next. The take a table designed for a 8" arm and put a 12 S shaped arm on it. They take a suspended table and anchor it into a 30lb block of wood. Rewires, changing platters, dental floss instead of rubber belts, adding flywheels, changing motor types completely, packing the underside of a plinth with bluetach or some other putty like material. And all other types of mutilation. And in ever case I read the guy thinks it makes the table sound better.

So either you can't really effect the sound of a table or arm by modifying it or you can do almost anything and end up with a better sound then stock.

This question was posted to discuss the modification itself. Not so much the morals behind the idea. I tend to think a LONG time on things before I act. Looking at the engineering of a problem or project from many angles before taking any action.

I just wanted some feedback and to hopefully get a source for the one thing I would need I don't have the tonearm joint.

 

[Nat]

I understood that you planned to use a second arm -- I wasn't concerned that you would deprive yourself of your only arm -- my point was that arms are complex beasts, probably more so than turntables or plinths, and so your chances of getting as good sounding a tonearm after your rather large proposed modification are not great.
The art of tonearm design is even more abstruse than turntable or plinth design, and parts cost and shipping costs figure into the designer's choice less than with turntable or plinths. The limitations and mistakes of turntable and plinth designs are easier to identify and correct than that of tonearms. Certainly the average mass market arm can be improved just as the turntable and plinth can be, but when you get into the higher end arms, it gets much harder to know what will help and what will harm, and what works for one arm won't for another.
I assume that a 9c isn't a dirt cheap arm, and my suggestion was based on the idea that it would be more cost effective to go with another arm. But if the appeal is that it would be a drop in replacement, then I guess its a reasonable choice. I would guess that other arms would be the easiest source of the interchangeable mount and headshells, but I believe the Graham arm uses a mil spec electrical connector for its bayonet for the wand, and that connector might be available from whoever makes it. Grahm makes some very high claims about its rigidity, so it might be a good choice for your purposes. Alternately you could machine a simple split ring collet and use an allen bolt to clamp the headshell, but you'd have to figure out a way to make electrical connections.
If you go ahead with the project, I do hope you post some pictures and comments -- all the theoretical opinions in the world don't hold a candle to actual experience.

 

[Kim G]