Parallel tracking air bearing arm

[Magna Audio]

Well dudes. Long weekend, some bits and pieces I had in the garage and an air pump and my protoype / test version is working.
Won't bore you with the details and at the moment it sounds like a Rega with a cheap Ortofon MM through a Nad 3020 and Mission 700 speakers - that's cos' that's what it is! - My garage system, all-be-it a carpeted and nice cosy garage).

Cut and smooth the air bearing with 600 grade wet and dry. Might try 1200 and see if there is any difference.



Bits and pieces coming together - checking arm length and VTA.
Arm tube is made of an archery alloy arrow - Has tapered inner tube (might be good for resonance but who knows). Carbon tube is also a possibility.
Headshell and all all other brackets made of 3.5mm alloy sheet or ali angle.
vertical bearing is Stanley blade in ali channel.



The air pump - I am using a 1 gallon fuel can as the smoothing reservoir.



In operation






I have tested it on 4 lp sides so far without hitch.
Next step is make an arm lowering mech and install Litz wire when it arrives. Litz wire is supposed to be nice and flexi and of good enough quality.

More DIY tomorrow

Could fairly easily knock up a Terminator style one with an under-slung short tone arm and see how that compares.

[Ali Tait]

Nice one looks great Steve! I've heard a couple of decks with Vic's arm and they were both superb.It's a great arm.

[Sgt.Pepper]

Thats a great result to get it fully working Steve
With using angled ali for the horizontal bearing ,I assume its running at a low pressure,do you get any forward and backward movement of the arm,due to the low pressure ?

[Mike]

made of an archery alloy arrow - Has tapered inner tube (might be good for resonance but who knows).

S'good enough for Naim's Aro... so why not!

[Magna Audio]

Can't see any forward and backward motion.
Both sides of the carriage get continuous supply of air of equal pressure. I suppose a resonance could be set up but there would be quite a damping factor in the air pressure and the total moving mass.
I've read it's much less of a problem then a record that is not round. The duff one I am testing in is a bit out and the whole assembly moves laterally side to side esp on the first track of the disc.
The air goes through a 5L smoothing tank which stays at arm lift pressure for longer than the record takes to slow down should there be a power cut - so no stylus jump even in that situation.

I still need to check I am running the right air gap - 50 micron's or so is the recommendation. That's 0.05mm so out with the feeler gauges...
It's a pretty stable flow and can take an arm load of up to 500grams on the Rena 600 pump I have - could probably get away with a small pump...

Anyway a total load of around 300 grams is good for damping but this needs to be dialled in with the lugs (ears) once I have it on the main system.

It's all so adjustable - Lateral and vertical mass.

I'm working on an arm lift now. Don't fancy hand cueing the lovely new Audio Technica 33PTG I just got
Once that is done I will run it on the Technic's SL-1210 first on duff disc with Ortofon cart and then move up to the AT.

Then I'll let you all know how it sound compared to a O.L modded Rega RB250.

[muffinman]

Then I'll let you all know how it sound compared to a O.L modded Rega RB250.

I've got a quid on it being better (in it's own way)

how are finding the 'air noise' btw ?

[Magna Audio]

Just been making the arm lift. Will have to extend the arm due to the Techy having that sloped platter and also need to change the VTA a fair bit as the platter is lower. Techy will be in the workshop for fitting tomorrow - love this long weekend and fairly carp weather

I've got a quid on it being better (in it's own way)

how are finding the 'air noise' btw ?

There is virtually no air noise from the air bearing. The pump is another matter - it's not bad if on a carpeted floor but it's not silent. I think a wooden sound damping box will be in order. Can hear it when she's playing and I might be less noticeable tucked under a Tannoy and sitting away from it. It is sited right by me in the workshop.

Oh well more fun later today - goodness is that the time...

[jkeny]

Steve, you are speedy! I've followed you here from the Zerogain thread. I hope you do the terminator version - by all accounts it's superior - & give us a comparison against this arm.

The air pump noise seems to be the Achilles heel of the whole affair. You're using a Rena which are supposedly quiet! I've seen reference to this as one of the quietest around because it's a piston system rather than diaphragm! http://www.medousa.com/en/product/de...sp?prd_ln=lpac I wonder has anybody here tried one?

Another one I found in researching is this one - again a piston type, out of production but from the UK so might be easy to find for you. If it turned out to be as quiet as it appears in the video then it would also be good to leave it on display: http://www.youtube.com/watch?v=NdhncxI9rUA

[Magna Audio]

I put the arm on the SL-1210 today. Not had time to swap carts etc so just ran it up with the Ortofon through the Denon surround sound amp in 2 channel mode in to the Tannoy's - sound's better than the Rega/Ortofon/NAD/Mission but miles off what the AT-33PTG/P75/TVC/Valve amp/Tannoy's regardless of arms sounds.

Will wait with the 33 PTG on the arm until I get the Litz tone arm wire as the solution I am using now if a bit stiff and gives some problems lateral loading probs. I played about 4 discs without problems today.

I put the pump under the Tannoy's (they are on low stands - er bricks actually). Even putting it on Foculpods did not help much. Do folk really put up with air pumps in their living space for the quiet hobby of fish?
I will need to make a sound deadening box or use the now defunct Sat dish cable hole in the wall for the air feed and mains cable and put the damn thing outside in a waterproof box (large ice cream container with some fine wire mesh for breathing on the bottom should do it) That would shut the damn thing out/up!
That's probably faster and more effective than all the sensible sized sound proofing boxes I can come up with.
I am lucky in that the exit for the sat cable is down the side of the house we just use for junk storage...

Those pro air-pump jobbies look expensive- quite normal for our hobby I guess:-)
Like the lack of sound with those piston ones - Not so quiet on the other Utube clips though - hard to tell / more investigation yes.

[jkeny]

I too find it amazing that aquarium owners would put up with anything other than a silent pump in their living room. Maybe audiophiles are more discriminating about the intrusiveness of background noise. My wifes' Dell laptop fan drives me to distraction when she has it turned on in the living room. It's quiet but the noise fluctuates & draws attention as a result.

I have a friend also putting one of these together & he has exactly the same issue with the pump noise - tried every sound deadening trick known & ended up locating it outside the listening room.

It's a pity as a lot of people can't do this & as a result are put off by this factor. I'm one of these and as a result am researching pumps to try find a solution.

One suggestion was a refrigerator compressor (which are quiet < 30dB) mounted in a sound box but I wonder if there's enough air flow from one & how long one would last without the lubrication that normally circulates in the fridge coolant liquid.