Hadcock setup & tweaking

[Big John]

I’ve just got my gramophone back out of its box. NAS Hyperspace TT / Hadcock GH242 arm / AT-VM95ML MM cartridge. The unipivot Hadcock has been a constant source of frustration for me, although it is adjusted correctly I think, such that it should stay that way (PTFE tape and latex glue). Here I exaggerate, it has a mid-rangy, airy sound with little in the way of bass punch.

I thought I’d have a go at adding silicone fluid to the well that contains the pivot spike. The dealer had given me some when I bought it. The bearing housing has a tube that extends down into that fluid, around the spike. There was no indication in the 2006 manual that this could be done and I had no idea what the affect would be.

The sound has now snapped into focus. It is meaty and solid, with bass that punches, but far less air. Other than the “torture track”, it will also now track all of the Hi-Fi News bands with ease, whereas previously it would barely track just the first one. When perturbed, it takes a couple of seconds for the azimuth to return to true and no wobble when lifting the cuing lever. The lateral resonance frequency stayed the same at around 10Hz.

One caveat is that it makes it messy to take off the arm from its bearing, with a string of goop lifting up. I’m not sure if it matters if the fluid gets into the bearing.

i rarely post here these days got vitriolic in some posts though to others not me. i have however written several times on this thread some regarding suggestions to George Hadcock via Len Gregory. which George implemented, I use the much thinner Audio Origami damping fluid fluid from J7. My results were essentially the same as yours. try thinning the well damping fluid a little you may find an audio improvement as well as losing the dog with a bone stringing, if it doesn't work with your set up revert to thicker fluid.

I would also suggest that the XTC underslung counterweight off fleabay makes the arm more stable & easier to set up, also sounds better. John Chong made mine to order some years ago I have no connection to J Chong just a satisfied customer.

 

[Avon]

Thanks for your very welcome feedback John. I’ve gone from being unsure about this arm to loving it, but it’s only for the diehard enthusiast perhaps, which doesn’t include me, at least not to this extent anyway. Why I’ve noticed no one saying damping is absolutely essential for it to even function mystifies me. Not even the instruction manual I have mentions this. Then again, it had been largely fine when set up by the dealer without fluid (*), just not when I changed the cartridge. This explains why it’s nagged at me from its box for many a year.

(*) Azimuth changed very slightly across the record, even though the bias pulley angle was spot on. That stopped when the silicone was added.

The price of silicone oil from hi-fi dealers is incredible, given you can buy it by the litre for the same price as the 10ml tube that’s needed here. Obtaining the correct viscosity is obviously the difficult bit though (for grades see http://turntablebasics.com/silicone.html), as it ranges from being almost like water, to being too thick to spread on a sandwich. A couple of seconds, for the azimuth to settle when using the finger lift, means using the queuing lever is far safer as I have it now. I’ll cogitate yet further.

I’m happy with the main weight. Like the XTC, it has its centre of mass below the mounting hole (is it less than the XTC version?), to adjust azimuth, but like a horse I find the Hadcock to be visually attractive. As in horses for courses.

Now the penny has finally dropped, I’ll just enjoy the music this thing is making. Why do turntables make me turn up the volume, while digital doesn’t do that?

 

[Big John]

Thanks for your very welcome feedback John. I’ve gone from being unsure about this arm to loving it, but it’s only for the diehard enthusiast perhaps, which doesn’t include me, at least not to this extent anyway. Why I’ve noticed no one saying damping is absolutely essential for it to even function mystifies me. Not even the instruction manual I have mentions this. Then again, it had been largely fine when set up by the dealer without fluid (*), just not when I changed the cartridge. This explains why it’s nagged at me from its box for many a year.


(*) Azimuth changed very slightly across the record, even though the bias pulley angle was spot on. That stopped when the silicone was added.

The price of silicone oil from hi-fi dealers is incredible, given you can buy it by the litre for the same price as the 10ml tube that’s needed here. Obtaining the correct viscosity is obviously the difficult bit though (for grades see http://turntablebasics.com/silicone.html), as it ranges from being almost like water, to being too thick to spread on a sandwich. A couple of seconds, for the azimuth to settle when using the finger lift, means using the queuing lever is far safer as I have it now. I’ll cogitate yet further.

I’m happy with the main weight. Like the XTC, it has its centre of mass below the mounting hole (is it less than the XTC version?), to adjust azimuth, but like a horse I find the Hadcock to be visually attractive. As in horses for courses.

Now the penny has finally dropped, I’ll just enjoy the music this thing is making. Why do turntables make me turn up the volume, while digital doesn’t do that?

I don't believe George was a fan of damping per-se the amount of damping ie viscosity of the fluid depends on the cartridge & to an extent turntable, my Cartridgeman MusicMaster prototype (I was one of Len's guinea-pigs) requires minimal damping hence using J7's damping fluid, it requires very little bias either.

As for die-hard enthusiast I just got the last soupcon of performance available...

As for silicone fluid I have bought 100% silicone oil meant for radio controlled car gear boxes & rear diffs "CORE-RC.com" off fleabay available in many viscosities not expensive. I have 300000 cst that was the recommended viscosity fluid I found recommended on a USA HiFi site, Incidentally very thick did not string to thick for my application. The fluid J7 sells he describes as twice as thick as water my well has a little of the 300000cst as I did not fully remove before adding the J7 it works.

My Musicmaster has a Cartridgeman Isolator fitted making the cartridge 5-6 mm deeper. The XTC puts the CG at the stylus tip worked out on J Chong's computer algorithm. In my case it made a considerable difference rather than a disc with an offset hole able to move the XTC locks in place with grub screws there is a short Tungsten? grub screw in the brass weight screwed in and out to set horizontal level. You also need to use your original small counterweight for fine adjustment enables you to get most of the weight close to bearing reducing I think moment of inertia, my XTC has a spacer between clamp and brass weight to allow for deeper cartridge, I believe just under £100

 

[Avon]

Interesting pictures, John. I can recognise the bearing housing and spike pillar as being Hadcock, but little else. I don’t see your arm fixing bolt, atop the bearing housing. How is it held in place? And where do the wires come out?

When I took it to pieces, I noticed the dealer had used blue-tack, to stop the arm wand buzzing in its mount. It’s attached with just the one screw and it doesn’t go very far inside. I used PTFE tape to get a tight fit. I remember wondering why the arm rod didn’t go all the way through and out the back, to hold the counterweights. But then Rega also mount(ed) the counterweight rod loosely, so perhaps there’s a reason for this.

Now I’m wondering how I’m to judge when I’ve got my damping fluid “just right”. Can it be predicted? Have I ended up with the bowl containing daddy bear’s porridge? No, I'll let sleeping bears lie I think, at least for now.

 

[Big John]

Interesting pictures, John. I can recognise the bearing housing and spike pillar as being Hadcock, but little else. I don’t see your arm fixing bolt, atop the bearing housing. How is it held in place? And where do the wires come out?

When I took it to pieces, I noticed the dealer had used blue-tack, to stop the arm wand buzzing in its mount. It’s attached with just the one screw and it doesn’t go very far inside. I used PTFE tape to get a tight fit. I remember wondering why the arm rod didn’t go all the way through and out the back, to hold the counterweights. But then Rega also mount(ed) the counterweight rod loosely, so perhaps there’s a reason for this.

Now I’m wondering how I’m to judge when I’ve got my damping fluid “just right”. Can it be predicted? Have I ended up with the bowl containing daddy bear’s porridge? No, I'll let sleeping bears lie I think, at least for now.

The pictures are off the bay, XTC advertising pictures not an actual arm, I used the pictures to show fitting method as I could not upload pictures of my arm.
The suggestion I made which George adopted was to make the counterweight stub off the rear of the bearing rigid there should not be any need for packing between arm tube & bearing, true it is quite shallow though.
There is no room on my arm for any packing the one grub screw is adequate. the reason it does not go right through is because inside the bearing housing are the four small balls that the vertical pin sits in, in this application four is better than three, I remember reading that larger numbers were tested.

 

[eksiil]

pardon my ignorance, but what would half of the viscosity of water be on the silicone viscosity scale (i e in CST)?

 

[Big John]

pardon my ignorance, but would half of the viscosity of water be on the silicone viscosity scale (i e in CST)?

Simple answer I don't know, I thought water was the base figure J7's fluid is 2x as thick as water.

See below water is base line

https://www.coleparmer.com/tech-art... x specific gravity,weight per gallon x 0.120).

 

[Avon]

there should not be any need for packing between arm tube & bearing.

I’d put that down to differences during manufacture. The mount of the wand into the bearing housing on mine was not tight at all, hence I used PTFE tape, while the dealer had used Blu Tack. Also, different metals might expand / contract differently with temperature.

I had the same problem when I bought a new head-shell from Analogue Seduction. After removing the one screw, the original was extremely difficult to take off, while the new one was just loose. There I used latex adhesive, as it wasn’t easy to get PTFE tape to stay in place. It will make replacing the cartridge difficult of course.

the reason it does not go right through is because ...

The bearing housing could have been designed differently, to allow the arm rod to pass clean through, while keeping enough room for the bearing below it. Just my opinion of course. I don't wish to tread on the wizard's toes.

 

[Vinny]

There are (seemingly) more than countless design variations of the pseudo-unipivot tonearm that is still in production, stretching back a good few years, so anyone reading this thread should proceed with caution. (Before anyone gets upset about "pseudo" - it is NOT a unipivot - the bearing is a round-point chromed pin that sits in a the centre of a "nest" of 4 very small ball-bearings that are held captive in the yoke by a brass sleeve.)

So far as the "damping" acieved by dipping the bearing-retaining sleeve in oil goes......................... I am totally unconvinced and have not seen or heard of it anywhere but in this thread. That said, there are about as many different silicone oils (basically changes in molecular weights, and hence viscocities) as there are Hadcock tonearm variants, probably more.

The current design (available in 3? variants but of the same basic build/design) is not really at all difficult to set up, but it is certainly not something for the terminally kack-handed or impractical.

I have swapped headshells around between 3 arms here and they fit inter-changably, just fine.

 

[Avon]

So far as the "damping" acieved by dipping the bearing-retaining sleeve in oil goes......................... I am totally unconvinced and have not seen or heard of it anywhere but in this thread.

Agreed regarding lack of documentation. It shall remain a mystery. However, the arm is designed that way. It’s not as if I have made any modification to it. I was equally unconvinced until I tried it.

I have swapped headshells around between 3 arms here and they fit inter-changably, just fine.

That was just not my experience unfortunately.

 

[Rico]

@Tony L I recall an article in one of the British hifi mags. It may have been HFNRR? Mid-70's? "Setting up the happy Hadcock". I had a copy years ago, my friend bought a Thorens as did I, his came with a Hadcock. We both bought G707s at same time.

If you still have your archive, perhaps a bit of archiveology (malapropism intended) may net you results. Bloody good arm if I recall correctly. HTH.

 

[Tony L]

If you still have your archive, perhaps a bit of archiveology (malapropism intended) may net you results. Bloody good arm if I recall correctly. HTH.

This is a very old thread, my Hadcock is long, long gone replaced first with a SME M2-10 on a Garrard 301, and now with my current totally retro 3009 on a TD-124/II.

I found the Hadcock a competent performer, but the M2-10 beat it to my ears and was vastly easier to set up precisely. The infuriating part of the Hadcock being the single screw that holds the headshell to the arm-tube which meant one always lost azimuth when attempting to set cartridge alignment. Basically undo that screw and the whole thing falls apart! Reading recent posts on the thread I wish I’d tried damping fluid with it. I only ever used mine dry.

 

[Vinny]

. The infuriating part of the Hadcock being the single screw that holds the headshell to the arm-tube which meant one always lost azimuth when attempting to set cartridge alignment. Basically undo that screw and the whole thing falls apart! Reading recent posts on the thread I wish I’d tried damping fluid with it. I only ever used mine dry.

Apart from ensuring that the tops of headshell and yoke are parallel, and the effective length is correct, I see no reason to touch that screw, and never have.
Once they are set, all other adjustment is achieved via the CBWs, albeit that they vary hugely depending on the tonearm vintage. Current design could not be easier - two CBWs, the larger one being eccentric.

As implied above, I think that oil damping in the pivot "depression" is unlikely to have any effect. Because it is around the pivot, the size of any movement of the bearing retaining bush should be minute and far, far smaller than any movement of conventional damping relying on paddles/troughs - ten time further from the pivot, ten times the distance moved.

Given that I have yet to see any mention of what oil (or anything else) should be used...............................

It is just a way of increasing the effective mass of the arm, at the end of the day - higher effective mass means more resistant to movement (or change from uniform motion in a straight line), the same as adding viscous drag. Given the minute change provided by the proposed damping, it would be equivalent to adding a minute blob of blutak to the headshell.

 

[Avon]

Dear Vinny,

With the arm on its rest (but unclamped), hold the arm tube near the head-shell and push down gently. The bearing will lift upwards very easily from its spike. After adding the oil, it takes greater force to detach the bearing, even though there is no extra weight on it. I believe it may be this that improves the stylus tracking, as it could reduce bearing chatter. Perhaps the oil is forming an airlock within the tube, as in the diagram above? Is the tube fully sealed (air keeps the oil out) or is it slightly leaky (oil gets in slowly)? Even if there’s no airlock, perhaps the high surface tension of the oil resists upwards motion?

It may have changed the lateral resonance slightly, as my before and after recordings have a small difference. Oddly the oil increased it from 9Hz to 10Hz approx. This cannot be responsible for the huge increase in tracking ability though. And certainly not for the difference in sound.

The oil grades were discussed above, but nothing concrete. Again, see

http://turntablebasics.com/silicone.html.

In addition to the annoying stringing, the oil I’m using rides up the spike. So there are definitely weeds among the roses with this particular grade (I do not know its value).

In conclusion, it either works or it doesn’t and it’s hardly rocket science. There is only one way to find out.

Sincerely, Avon

 

[Vinny]

Dear Vinny,

With the arm on its rest (but unclamped), hold the arm tube near the head-shell and push down gently. The bearing will lift upwards very easily from its spike. After adding the oil, it takes greater force to detach the bearing, even though there is no extra weight on it.

That is down to the suction as the yoke lifts. This has nothing at all to do with the tonearm in use, or I hope not, as the yoke/bearing will (certainly ought to) stay very firmly on the pin.
Get a bcuket of water, immerse a glass in it, turn it upside down under the water and remove from water - same effect - far greater load than the glass alone, until air gets under the rim.

The ONLY effect that the oil in the recess has is to produce viscous drag as the bearing retaining bush moves in it, which is verging on nothing.

 

[Avon]

the yoke/bearing will (certainly ought to) stay very firmly on the pin.

How did you get to that perfect world? Any tickets for sale?