[rcag_ils]

Does anyone have any experience with the PT-5? I can't seem to find any info on it, vinylengine.com starts with PT-6.

Is it oil damped? The cap seem to be made to come off, but since I don't know, so I don't want to force it. The arm tube has a plastic sleeve over it, sort of like the Sumiko analog survival kit, is there similar product available for other tonearms? This idea must have worked since several manufacturers made them years ago.

Overall, a very high quality arm, counterweight is made out of brass (judged from the little paint chip on it), looks very rugged. I wish mine looked a little better, since I am a perfectionist, it doesn't look too bad now, not all banged up or anything. Everything seems to be working.

The Linn basic plus will go on the Heybrook TT2, and the PT-6 will go on the CJ Walker, the Grace 707 will be on a spare armboard for the CJ Walker. I am in Analog Heaven.

[BobM]

I'm not 100% certain, but I believe all of the AQ PT arms are essentially the same, except that the tonearm wire and interconnect "quality" is updated in the higher number arms like the 6, 7, etc.

[TheChairGuy]

The PT-5 is likely sourced from JELCO...a large specialty manufacturer of tonearms for decades (most famously for Linn...which is why all Linn's and JELCO's share the same armboard mounting and effective length for the 9" arms)

My PT-6 was fluid damped..I suspect you PT-5 is, too.  You shouldn't have to 'force' the cap off if it is...it should screw off easily if it's the same cap as my old PT-6.

You didn't mention the cartridges you intend to pair it with...but fluid damping tends to be most helpful with higher compliance cartridges (which are typically moving magnet or moving iron types)

Lower compliance cartridges (most moving coils) tend not to benefit from fluid damping.

Grado's, which are middle to high compliance...benefit mightily from fluid damping.

Thanks, John

[rcag_ils]

Yes, probably a Grado will go on that arm, but have no idea where to get the fluid though.

I just got the cap off, it looks surprisingly clean inside, doesn't look like the last owner ever put anything in there, no spilled fluid anywhere.

There's only a brass cup there, then there's a built in plunger on the cap that goes in the brass cup when screwed on.

So how is it being damped by the fluid? Where does the fluid go, and how much? I expect to see some sort of shock absorbor type arrangment in there.

Thanks for the inputs.

[TheChairGuy]

Yup, you found it.

You just put in about halfway up the brass cup and the cap locks down on the fluid to provide damping.

You can get them at Turntable Basics....the 30000 and 100000 cst generally best here (http://turntablebasics.com/silicone.html)

Better yet (and cheaper) are hobby shops.  They can sell you 50000 or 60000 cst silicone (they often know it as differential oil used in the transmissions of motorized cars they sell)

You can just order it online thru Tower Hobbies, too (that's where I've gotten it before)

http://www3.towerhobbies.com/cgi-bin/WTI0095P?FVSEARCH=differential+oil&search=Go

Grado's THRIVE on fluid damping...it improves them often dramatically.  A lot of their tweeky nature can be dialed out by use of fluid damping.

Regards, John

[rcag_ils]

Interesting, I dug out all my vintage Audio magazines, what I've found is in 1988, Audioquest had a PT-5, then in 1989 there were a PT-5,and a PT-5+, both had viscous damping as optional, I guess the PT-5+ had a different patch cable. Then in 1990 there were PT-6, 7, and 8, all had viscous damping as optional, maybe different patch cables.

Then of course, there were a PT-9 replacing all of them.

How does the damping work, how does it damp? I know that the SME had a padel mounted on the tonearm which riding in a trough filled with silicone. The PT-5 just had a brass cup inside the bearing housing where the bearing are mounted, the cup doesn't really move. ??????  ????

[TheChairGuy]

I don't know of physics between 'pivot' and 'trough' fluid damping...but, I owned the PT-6 and used silicone in it and I also made a home brew trough for an old JVC once (using aluminum foil, and half a paper clip as paddle).

By far, I found the trough to damp better than whatever effect I found with the pivot damping.

You can see my 'fugly' experiment with damping troughs here: http://www.audiocircle.com/index.php?topic=22938.40

I'm not sure if the reason was arm specific, or cartridge specific as to the outcome(s)...but I felt the trough (like SME's) was the best implementation of the idea.

Nonetheless, it's worth a try for such little outlay as even the pivot damping helped a little with a couple cartridges.

btw, the ABSOLUTE best implementation I have heard of damping is on my current JVC QL-F6 and QL-Y66F tables.  The F6 is permanently damped with an internal fluid reservoir...and the Y66F has electronic damping.  The idea is the same - it damps both vertical and horizontal oscillations. 

Essentially, this means any high compliance cartridge is a match for them...and Grado's sound divine in them

In a situation where a higher compliance cartridge is employed in a medium to high mass tonearm, the ill-effects of the match can be mitigated to some degree if the tonearm offers fluid damping. Here, a small paddle connected to the arm rests in a reservoir filled with viscous silicone fluid. This design feature restricts small, rapid motions of the arm (like the small undulations that would occur in a high-compliance cartridge), while providing unrestricted progress to the arm as it slowly traces across the record. This system also may improve the sound of some phono cartridges that offer little internal damping of their own.

John

[rcag_ils]

John, is your PT-6 has a brass cup in the pivot like my PT-5, and a plunger on the cover which goes into the brass cup? If so, that means it doesn't take much silicone fluid in there, otherwise it'll spill all over inside of the housing when the cap's being screwed on. How much did you put in?

The Sumiko MMT manual says the amount of the fuild can vary depending on the damping.

PS, on my Pro-ject 6.1, the damping trough damps the spindle bearing plinth, Sumiko thinks that damping the tonearm is too hard on the stylus due to the thickness of the fluid.

[TheChairGuy]

John, is your PT-6 has a brass cup in the pivot like my PT-5, and a plunger on the cover which goes into the brass cup? If so, that means it doesn't take much silicone fluid in there, otherwise it'll spill all over inside of the housing when the cap's being screwed on. How much did you put in?

I remember putting about halfway in there (50000 cst I think)...I no longer own the arm.

I remember it had a brass cup, but cannot remember a plunger on the under side of the cap, offhand 

It's probably true that one can vary the damping by varying both the level (ie, level) and thickness of the fluid....I cannot say that my experimentation was that layered or in-depth.  The 50000cst oil worked great in the trough...so I used the same in the pivot in those experiments.

But, orthobiz/Paul owns it now and may be reading this post and can comment - he's always lurking somewhere that guy

John

[drphoto]

rcag. Since you mentioned Grado, do you want a Grado Green for cheap? $20 an it's yours via USPS. I got it for $40 from a fellow AC a few weeks ago. Has probably less than an 2 hours play time.

Reason for selling.....they hum on Thorens (original deck) and Rega (replacement deck)

Heck of a nice sounding cart for so little money. Too bad I couldn't use it and had to spend way more to get something that would work.

It has a bit of blu-tak residue on the front from where I'd stuck on a Longhorn.

[rcag_ils]

The PT-9 instruction says the knurl bearing cap is the damping adjustment. Screwing it all the way down for max damping, screwing it less for less damping, that's something that I didn't know before.

[orthobiz]

 

But, orthobiz/Paul owns it now and may be reading this post and can comment - he's always lurking somewhere that guy

John

I still have it John
I am not using it...
It had oil leaking out when I got it, I believe it was shipped with oil in the reservoir and one channel has fouled wires.

I bought a PT-9 instead but have not damped it yet. I may take the 6 apart and rewire it (yeah, right) someday.

Anyway, the cap has a bump on its undersurface and the bump rides in the reservoir cup. The cap moves and the cup doesn't, thus the damping.

Meanwhile I have not been around, I studied for and passed my recertification boards. Hope to be more active...I have put a new arm, SAMA, dust cover, SDS, Cloud 11 base on your venerable HW-19. Gotta post pics soon!!!!

Paul